Neurooculorenal Syndrome

Mendelian MONDO:0957210 Pathograph 14 Show in embeddings browser Congenital anomaly of the kidney and urinary tract Multiple congenital anomalies syndrome

Neurooculorenal syndrome (NORS, OMIM #620305) is an autosomal recessive developmental disorder caused by biallelic ROBO1 variants. It was delineated in 2022 from six unrelated living individuals and a family of three affected fetuses, assembled through GeneMatcher, retrospective phenotyping of previously published biallelic carriers, and an unbiased search of 78,195 genomes in the 100,000 Genomes Project. Three organ systems are involved, and the name lists them in the order the literature found them. The kidney and urinary tract carry the defining lesion: unilateral or bilateral renal agenesis, ureterovesical junction obstruction, vesicoureteral reflux, posterior urethral valve, cystic dysplasia and increased echogenicity - in short, syndromic CAKUT. The nervous system contributes midline and hindbrain malformations, chiefly corpus callosum thinning or partial agenesis, ventriculomegaly, vermis hypoplasia and absent pyramidal tracts, together with intellectual impairment and, in one patient, mirror movements. The eye contributes strabismus and iris anomalies. The unifying claim is that these are not three coincident malformations but one signalling lesion read out in three places. ROBO1 is the receptor for the secreted SLIT ligands, and Slit-Robo signalling positions growing structures relative to the midline: commissural axons decide whether to cross it, and the ureteric bud decides where along the nephric duct to emerge. Human fetal kidney immunohistochemistry in this study puts ROBO1 exactly where nephrogenesis happens - the outer nephrogenic zone, in comma-shaped and S-shaped bodies - and shows that staining absent in dysplastic patient tissue. A dosage argument runs through the whole entity and is what makes it recessive. Heterozygous ROBO1 variants had already been reported in congenital heart disease and pituitary stalk interruption syndrome, but the heterozygous parents in this cohort were clinically unaffected, and renal involvement appeared only when both alleles were altered. The severity range within the biallelic group - from an adult who reached end-stage kidney disease at 44 with normal cognition, to terminated fetuses with bilateral renal agenesis and Potter sequence - tracks with allelic combination: two nulls at the severe end, a null plus a mild hypomorph at the mild end.

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Inheritance
8
Pathophys.
17
Phenotypes
1
Hypotheses
1
Gaps
14
Pathograph
1
Genes
4
Medical Actions
1
Models
1
Deep Research
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Inheritance

1
Autosomal recessive HP:0000007
Biallelic, with two homozygotes from consanguineous families and the rest compound heterozygous. The inheritance claim is unusually well supported for a nine-patient cohort because it rests on a negative as well as a positive: the heterozygous parents were clinically unaffected, and renal involvement appeared only with both alleles altered. That is what distinguishes this from the earlier monoallelic ROBO1 reports in congenital heart disease and pituitary stalk interruption syndrome.
Autosomal recessive inheritance
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"heterozygous parents in our study were clinically unaffected, which we propose may be due to incomplete penetrance and gene dosage effects conferred by distinct variants in the ROBO1 locus."
The unaffected-carrier observation that grounds recessive inheritance, stated together with the authors' dosage interpretation.
PMID:35227688 SUPPORT Human Clinical
"According to our data, renal involvement was only present on genetic alteration of both alleles."
States the dosage threshold specifically for the renal phenotype, which is the organ that defines this entity.
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Mechanistic Hypotheses

1
SLIT-ROBO Midline Guidance Dosage Model
slit_robo_midline_guidance_dosage CANONICAL
Biallelic reduction of ROBO1 below a threshold impairs SLIT-ROBO signalling in every tissue that uses it to position structures during development. The three affected organ systems are the three places where that requirement is strictest and least redundant: commissural and pyramidal axon guidance across the CNS midline, ureteric bud outgrowth and branching in the nephrogenic zone, and ocular development. Whether an individual is severely or mildly affected is set by which pair of alleles they carry, not by which tissue is involved - the same genotype affects all three. CANONICAL because the receptor biology, the human fetal kidney expression, the mouse renal and cardiac phenotypes, and the human genetics all point the same way.
Pathograph links
Biallelic Loss-of-Function ROBO1 Variants -> Reduced SLIT-ROBO Guidance Signalling Loss of receptor available to bind SLIT ligand at the cell surface.
Reduced SLIT-ROBO Guidance Signalling -> Disturbed Ureteric Bud Outgrowth and Nephrogenesis Loss of the positional signal that places and branches the ureteric bud.
Reduced SLIT-ROBO Guidance Signalling -> Disturbed CNS Midline and Commissural Axon Guidance Loss of the repulsive signal that governs midline crossing.
Reduced SLIT-ROBO Guidance Signalling -> Disturbed Pituitary Stalk and Hypothalamic-Pituitary Axis Formation Loss of the same guidance signal at the midline structure that becomes the pituitary stalk.
Reduced SLIT-ROBO Guidance Signalling -> Disturbed Retinal Ganglion Cell Axon Targeting Loss of ROBO-mediated targeting of retinal ganglion cell axons through the optic chiasm.
Disturbed Ureteric Bud Outgrowth and Nephrogenesis -> Congenital Anomalies of the Kidney and Urinary Tract The clinical renal phenotype produced by the guidance failure.
Disturbed CNS Midline and Commissural Axon Guidance -> Midline Brain Malformation and Neurodevelopmental Impairment The clinical CNS phenotype.
Disturbed Pituitary Stalk and Hypothalamic-Pituitary Axis Formation -> Midline Brain Malformation and Neurodevelopmental Impairment Stalk and hypothalamic-pituitary involvement is part of the same midline malformation spectrum.
Disturbed Retinal Ganglion Cell Axon Targeting -> Strabismus Proposed route from mistargeted visual projections to the ocular phenotype; not demonstrated in human tissue.
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Discussions and Knowledge Gaps

1
Does the allelic combination predict severity in biallelic ROBO1 disease - specifically, is two-null genotype the reason for fetal lethality and null-plus-hypomorph the reason for survival with milder kidney disease?
KNOWLEDGE GAP robo1_genotype_severity_dosage
Attached to
pathophysiology#Biallelic Loss-of-Function ROBO1 Variants pathophysiology#Congenital Anomalies of the Kidney and Urinary Tract
The authors propose exactly this and the cohort is consistent with it: the index patient survived to 44 with a truncating allele undergoing nonsense-mediated decay in trans with a missense allele that gnomAD lists at 0.04% in Europeans, while the fetal cases carried two frameshifts. But nine individuals cannot establish a genotype-phenotype rule, the ascertainment differs between the fetal and living arms, and no functional assay quantifies residual signalling for any allele. This is the question with the most immediate clinical consequence in the entry - it is what prenatal counselling for a newly identified biallelic genotype would turn on - so recording it as unresolved matters more than usual.
Proposed experiments
Quantify residual SLIT-ROBO signalling across the reported allelic series
robo1_allelic_series_signalling_assay
Express each reported ROBO1 allele at controlled dosage in a ROBO1-null cell background and measure SLIT-induced receptor dimerisation, SRGAP recruitment and downstream repulsion in a growth-cone or ureteric-bud explant assay, then rank the alleles and compare that ranking with the clinical severity of the genotypes carrying them.
Would support
pathophysiology#Congenital Anomalies of the Kidney and Urinary Tract
Would refute
pathophysiology#Congenital Anomalies of the Kidney and Urinary Tract
Supporting outcome
  • Measured residual signalling orders the alleles in the same sequence as clinical severity, with the two-frameshift fetal genotypes at zero and the surviving adult's missense allele retaining partial activity, establishing dosage as the determinant of outcome.
Refuting outcome
  • Residual signalling does not track severity - for example the adult index patient's missense allele proves as inactive as a frameshift - which would mean modifiers or stochastic developmental factors, not ROBO1 dosage, set the phenotype.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"variability of the kidney disease suggests gene dosage effects due to a combination of null alleles with mild hypomorphic alleles"
The authors' own statement of the hypothesis, offered as a suggestion rather than a demonstration.
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Pathophysiology

8
Biallelic Loss-of-Function ROBO1 Variants
Twelve variants across the cohort, all single-nucleotide substitutions: eight truncating, two canonical splice-site, and two missense. The two missense alleles land in the functionally important extracellular domains - one on a surface loop of the third immunoglobulin domain near the homodimerisation linker, the other on the second fibronectin type III domain - which is where SLIT binding and receptor dimerisation happen. All but one allele were absent from population and clinical variant databases.
SLIT-ROBO Midline Guidance Dosage Model
ROBO1 hgnc:10249 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves decreased ROBO1 (hgnc:10249). hgnc:10249 is a gene from the HUGO Gene Nomenclature Committee. ↓ DECREASED
Genetic context variant_origin: GERMLINE zygosity: HOMOZYGOUS functional_impact_category: LOSS_OF_FUNCTION
Germline biallelic ROBO1 alleles. Compound heterozygous truncating, or truncating in trans with a hypomorphic missense allele, in most; two homozygous splice-site cases from consanguineous families.
Downstream
Reduced SLIT-ROBO Guidance Signalling Loss of receptor available to bind SLIT ligand at the cell surface. SLIT-ROBO Midline Guidance Dosage Model
Show evidence (3 references)
PMID:35227688 SUPPORT Human Clinical
"All 12 ROBO1 variants reported in our study were single-nucleotide substitutions: 2 canonical splice site variants, 8 truncating variants, and 2 missense variants, the latter 2 located within the functionally important Ig and FN3 protein domains"
The complete allelic spectrum and the domain localisation of the missense alleles.
PMID:35227688 SUPPORT Human Clinical
"The extracellular portion, responsible for homodimerization and Slit-ligand binding, contains 5 well-defined N-terminal Ig-like domains followed by 3 fibronectin type III (FN3) domains."
Establishes what the domains hit by the missense alleles actually do, which is why their location is the argument for pathogenicity.
PMID:35227688 SUPPORT Human Clinical
"indicating nonsense-mediated RNA decay of the truncating allele and exclusive expression of the missense allele"
Transcript-level demonstration that a truncating allele is degraded, so the surviving hypomorphic allele sets the phenotype. This is the observation the dosage model is built on.
Reduced SLIT-ROBO Guidance Signalling
ROBO1 is a 180 kDa single-pass receptor for the secreted SLIT ligands, conserved since its identification in a Drosophila screen for axon guidance mutants. It homodimerises, heterodimerises with ROBO2, and binds SLIT1/2/3 and the SRGAP adaptors; reducing it therefore reduces a repulsive positional signal rather than a growth or survival signal. Its paralogue ROBO2 and its ligand SLIT2 are already implicated in human CAKUT, which is the pathway-level context that made ROBO1 a credible candidate long before this cohort existed. The cystic-kidney and multi-organ pattern raises a ciliopathy hypothesis, and this node records that it was tested and not supported: ciliary morphology and abundance were normal in mutant collecting ducts and ureteric bud tips.
SLIT-ROBO Midline Guidance Dosage Model
Roundabout signaling pathway GO:0035385 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Roundabout signaling pathway (GO:0035385). GO:0035385 is a biological process from the Gene Ontology. ↓ DECREASED axon guidance GO:0007411 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased axon guidance (GO:0007411). GO:0007411 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Robo1 ENU missense mutant mouse Mouse measures Used to test, and reject, the ciliopathy reading of the phenotype: primary cilia on collecting ducts and ureteric bud tips were compared between mutants and controls.
Downstream
Disturbed Ureteric Bud Outgrowth and Nephrogenesis Loss of the positional signal that places and branches the ureteric bud. SLIT-ROBO Midline Guidance Dosage Model
Disturbed CNS Midline and Commissural Axon Guidance Loss of the repulsive signal that governs midline crossing. SLIT-ROBO Midline Guidance Dosage Model
Disturbed Pituitary Stalk and Hypothalamic-Pituitary Axis Formation Loss of the same guidance signal at the midline structure that becomes the pituitary stalk. SLIT-ROBO Midline Guidance Dosage Model
Disturbed Retinal Ganglion Cell Axon Targeting Loss of ROBO-mediated targeting of retinal ganglion cell axons through the optic chiasm. SLIT-ROBO Midline Guidance Dosage Model
Show evidence (3 references)
PMID:35227688 SUPPORT Other
"Roundabout guidance receptors (ROBOs) constitute a highly conserved subfamily of immunoglobulin superfamily proteins characterized by a single-pass transmembrane domain and interaction with the soluble extracellular Slit ligands."
Establishes the receptor-ligand relationship this node is about.
PMID:35227688 SUPPORT Other
"ROBO1 was shown to both homodimerize and heterodimerize with ROBO2"
Records the dimerisation partnerships, which matter because one missense allele sits next to the homodimerisation linker.
PMID:35227688 NO_EVIDENCE Model Organism
"Ciliary morphology and abundance, however, was overall unaffected on staining with acetylated tubulin in immunofluorescent microscopy"
A tested and negative ciliopathy hypothesis. Regraded from REFUTE to NO_EVIDENCE on review: the result does not contradict this node's claim that SLIT-ROBO guidance signalling is reduced - it bears on a different proposition, that the phenotype is ciliary, and finds nothing. It is kept here because a phenotype that resembles a ciliopathy without being one is exactly the kind of claim that needs its negative on the record.
Disturbed Ureteric Bud Outgrowth and Nephrogenesis
ROBO1 protein sits in the human fetal kidney precisely where nephrons are being made - the outer nephrogenic zone, in comma-shaped and S-shaped bodies - at 14 and 21 weeks of gestation. In a 22-week fetus carrying biallelic ROBO1 variants that zone was gone and the staining with it, leaving dysplastic cystic parenchyma. Because the ureteric bud's position along the nephric duct determines whether a kidney forms at all and whether the ureter inserts correctly, a guidance failure at this step produces the whole clinical range at once: agenesis where the bud never emerges, reflux and junction obstruction where it emerges in the wrong place, dysplasia where branching miscarries.
SLIT-ROBO Midline Guidance Dosage Model
nephron progenitor cell CL:0000324 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves nephron progenitor cell, annotated with metanephric mesenchyme stem cell (CL:0000324). CL:0000324 is a cell type from the Cell Ontology.
ureteric bud development GO:0001657 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased ureteric bud development (GO:0001657). GO:0001657 is a biological process from the Gene Ontology. ↓ DECREASED kidney development GO:0001822 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased kidney development (GO:0001822). GO:0001822 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Robo1 ENU missense mutant mouse Mouse recapitulates All five newborn mutants had severely altered kidney architecture with genitourinary malformations: duplex or multiplex kidneys, cystic dysplasia, hydronephrosis, hydroureter, and misplaced undescended gonads. Endogenous Robo1 staining was absent from mutant kidneys, so the missense allele behaves as a functional null in this tissue.
Downstream
Congenital Anomalies of the Kidney and Urinary Tract The clinical renal phenotype produced by the guidance failure. SLIT-ROBO Midline Guidance Dosage Model
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"Immunohistochemistry of endogenous ROBO1 in fetal control kidneys dating from 14 and 21 WG showed ROBO1 localization at the outer nephrogenic zone within comma-shaped bodies and S-shaped bodies supporting a role of ROBO1 in normal nephrogenesis"
Puts the protein in the right human tissue at the right developmental stage. This is human, not model-organism, expression data, which is what makes it the strongest single piece of mechanism in the entry.
PMID:35227688 SUPPORT Human Clinical
"the subcortical nephrogenic zone presented abolished in renal tissue from ID 8 at 22 WG accompanied by an absence of ROBO1 staining in severely dysplastic and cystic renal parenchyma"
The matched patient tissue: no ROBO1 staining, no nephrogenic zone, dysplastic kidney. Expression and loss in the same experiment.
Disturbed CNS Midline and Commissural Axon Guidance
ROBO1 was identified as an axon guidance receptor and is required for neocortical development. The neurological phenotype in this cohort is correspondingly midline-weighted: corpus callosum thinning or partial or splenial agenesis, absent pyramidal tracts in all three fetuses, ventriculomegaly, cerebellar vermis and dentate nucleus hypoplasia, and brainstem hypoplasia. One patient had mirror movements without a variant in DCC or RAD51, the two established mirror-movement genes - which is a direct clinical readout of failed decussation, since mirror movements arise when corticospinal projections that should cross do not.
SLIT-ROBO Midline Guidance Dosage Model
axon guidance GO:0007411 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased axon guidance (GO:0007411). GO:0007411 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Midline Brain Malformation and Neurodevelopmental Impairment The clinical CNS phenotype. SLIT-ROBO Midline Guidance Dosage Model
Show evidence (3 references)
PMID:35227688 SUPPORT Other
"ROBO1, which was originally identified in a Drosophila mutant screen, was shown to be crucial for proper axon guidance and neocortical development."
Establishes the receptor's canonical neural function, which is what the CNS phenotype is proposed to follow from.
PMID:35227688 SUPPORT Human Clinical
"His neurodevelopmental phenotype was also striking for the observation of mirror hand movement disorder. No likely damaging variants in DCC or RAD51, previously associated with autosomal dominant mirror movements"
The mirror-movement observation with the two competing genes excluded. This is the closest thing in the cohort to a direct clinical test of a midline-crossing defect.
PMID:35227688 SUPPORT Human Clinical
"partial agenesis of the corpus callosum, absence of pyramidal tracts, and dentate nuclei hypoplasia"
Fetal neuropathology showing absent pyramidal tracts alongside the callosal defect - two crossing systems failing together.
Disturbed Pituitary Stalk and Hypothalamic-Pituitary Axis Formation
The endocrine branch. The pituitary stalk is a midline structure whose formation depends on the same guidance signalling as the commissures, and ROBO1 was implicated in pituitary stalk interruption syndrome by heterozygous variants before this recessive entity was described. In the biallelic cohort the readout ranges from a missing posterior pituitary bright spot with no endocrine consequence, through hypopituitarism with hypogonadism and micropenis and reduced growth, to combined pituitary hormone deficiency with central diabetes insipidus in the heterozygous PSIS literature. Expressivity is explicitly variable, so this node describes a susceptible developmental step rather than an obligate lesion.
SLIT-ROBO Midline Guidance Dosage Model
axon guidance GO:0007411 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased axon guidance (GO:0007411). GO:0007411 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Midline Brain Malformation and Neurodevelopmental Impairment Stalk and hypothalamic-pituitary involvement is part of the same midline malformation spectrum. SLIT-ROBO Midline Guidance Dosage Model
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"Regarding pituitary malformations, we also observed variable expressivity."
Establishes pituitary malformation as part of the biallelic phenotype and states that its expressivity varies, which is what this node claims.
PMID:38444307 SUPPORT INDIRECT Human Clinical
"The roundabout receptor-1 gene (ROBO1) plays critical roles in axonal guidance and cell migration. Recently, mutations in the ROBO1 gene have been reported patients with PSIS."
Connects the gene's guidance function to stalk interruption specifically. INDIRECT: the reported patients are heterozygous, so this supports the developmental step rather than the recessive syndrome.
Disturbed Retinal Ganglion Cell Axon Targeting
The ocular branch - the "oculo" of the disease name, which the entry previously described in phenotypes without modelling. ROBO receptors target retinal ganglion cell axons along the whole visual projection, and in Robo mutant mice the optic chiasm is expanded with ectopic crossing points and axons projecting where they should not. That is the same midline-crossing decision the commissural branch of this entry describes, applied to the visual pathway, and it is the most plausible route from ROBO1 loss to the strabismus reported across this cohort. Stated carefully: the mouse work is on Robo1 and Robo2 mutants and finds Robo2 the predominant receptor in visual development, so this node is a mechanism proposal for the human ocular phenotype rather than a demonstrated one. No human ocular pathology has been reported in this syndrome.
SLIT-ROBO Midline Guidance Dosage Model
retinal ganglion cell axon guidance GO:0031290 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased retinal ganglion cell axon guidance (GO:0031290). GO:0031290 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Strabismus Proposed route from mistargeted visual projections to the ocular phenotype; not demonstrated in human tissue. SLIT-ROBO Midline Guidance Dosage Model
Show evidence (3 references)
PMID:18272390 SUPPORT INDIRECT Model Organism
"we examined Robo1 and 2 mutant mice and found that Robos regulate the correct targeting of retinal ganglion cell (RGC) axons along the entire visual projection."
Establishes the receptor family's role in visual pathway targeting. INDIRECT and MODEL_ORGANISM: mouse, and not in a disease model.
PMID:18272390 SUPPORT INDIRECT Model Organism
"The optic chiasm was expanded along the rostro-caudal axis"
The specific midline defect - an expanded optic chiasm with ectopic crossing points - which is the visual-pathway counterpart of the commissural phenotype this entry curates elsewhere.
PMID:18272390 REFUTE INDIRECT Model Organism
"These defects were more pronounced in Robo2 than Robo1 knockout animals, implicating Robo2 as the predominant Robo receptor in visual system development."
The caveat that keeps this node a proposal. If Robo2 is the predominant receptor in visual development, ROBO1 loss alone is a weaker explanation for the ocular phenotype than for the renal or commissural ones, and the entry should not imply otherwise.
Congenital Anomalies of the Kidney and Urinary Tract
The defining organ phenotype and the one with prognostic weight. Its range within nine people is the whole CAKUT spectrum - bilateral agenesis with Potter sequence at the lethal end, unilateral agenesis and reflux nephropathy in the middle, increased echogenicity with mildly reduced kidney size at the mild end. The index patient reached end-stage kidney disease at 44, so this is a phenotype that can present in adulthood as unexplained chronic kidney failure with the congenital origin overlooked.
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"Kidney and genitourinary manifestation included unilateral or bilateral kidney agenesis, vesicoureteral junction obstruction, vesicoureteral reflux, posterior urethral valve, genital malformation, and increased kidney echogenicity."
The full renal and genitourinary spectrum of the cohort, in one place.
PMID:35227688 SUPPORT Human Clinical
"renal function stabilized over the years until a slowly progressive decrease in function led to bilateral atrophic kidneys and end-stage kidney disease at the age of 44"
The adult end of the range, and the reason this diagnosis belongs in the workup of unexplained adult chronic kidney failure.
Midline Brain Malformation and Neurodevelopmental Impairment
Clinically: intellectual impairment and psychomotor delay in most, dysmorphic facial features in eight of nine, and structural midline findings on imaging. Notably not universal - the adult index patient's motor and cognitive development was normal and his only MRI finding was a missing posterior pituitary bright spot, so a normal neurodevelopmental history does not exclude the diagnosis.
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"Further clinical characteristics were remarkably heterogeneous, including neurodevelopmental defects, intellectual impairment, cerebral malformations, eye anomalies, and cardiac defects."
Names the extrarenal domains and, importantly, states that they are heterogeneous rather than obligate.
PMID:35227688 REFUTE Human Clinical
"Motor and cognitive skills developed normally."
The index patient's normal cognition, which contradicts neurodevelopmental impairment being an obligate feature. Recorded as REFUTE against that stronger reading rather than dropped.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Neurooculorenal Syndrome Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

17
Cardiovascular 1
Congenital Heart Defect Abnormal heart morphology HP:0001627 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal heart morphology (HP:0001627). HP:0001627 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"cardiac anomalies (including tetralogy of Fallot and pulmonary artery stenosis), and severe central nervous system malformations (including agenesis of the corpus callosum)"
Documents a conotruncal defect together with the callosal malformation in a single patient.
Ear 1
Hearing Impairment Sensorineural hearing impairment HP:0000407 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"his general appearance included dysmorphic features together with intellectual disability, psychomotor delay, sensorineural hearing loss, and strabismus"
Documents sensorineural hearing loss as part of the syndrome in one patient.
Endocrine 1
Pituitary Insufficiency Hypopituitarism HP:0040075 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypopituitarism (HP:0040075). HP:0040075 is a phenotype from the Human Phenotype Ontology.
Show evidence (3 references)
PMID:35227688 SUPPORT Human Clinical
"hypogonadism with micropenis, the latter being likely related to hypopituitarism and/or hypospadias"
Documents pituitary insufficiency in a biallelic patient, with the authors' own attribution of the genital finding to it.
PMID:35227688 REFUTE Human Clinical
"was asymptomatic and remained without clinical implications as endocrine laboratory testing revealed no further abnormalities."
The counterweight, and the reason this phenotype's description was corrected. The missing posterior pituitary bright spot in the index patient had no endocrine consequence, so the imaging finding does not by itself establish pituitary insufficiency in that individual.
PMID:38444307 SUPPORT INDIRECT Human Clinical
"We report a 2.9-year-old boy with PSIS who presented with combined pituitary hormone deficiency, central diabetes insipidus, and the classical triad of MRI findings."
Extends the pituitary phenotype to posterior as well as anterior dysfunction. INDIRECT and worth reading carefully: this patient carries a *heterozygous* ROBO1 frameshift, so it is evidence about the gene's pituitary role rather than about this recessive syndrome, and it is cited on that basis rather than as a NORS case.
Eye 1
Strabismus HP:0000486 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Strabismus (HP:0000486). HP:0000486 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"eye anomalies (bilateral strabismus, atrophic iris), and dextrocardia were part of the clinical syndrome"
Documents the ocular findings as part of the syndrome, with the iris anomaly alongside.
Genitourinary 5
Renal Agenesis HP:0000104 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Renal agenesis (HP:0000104). HP:0000104 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"Fetal examination confirmed the bilateral kidney agenesis with Potter sequence"
Documents bilateral agenesis with its oligohydramnios sequence in a fetal case.
PMID:35227688 SUPPORT Human Clinical
"manifested congenitally when an abdominal ultrasound revealed left-sided renal agenesis"
Documents unilateral agenesis in a living child, the survivable form.
Vesicoureteral Reflux HP:0000076 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Vesicoureteral reflux (HP:0000076). HP:0000076 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"he suffered from repetitive pyelonephritis due to VUR caused by unilateral ureterovesical junction obstruction and a posterior urethral valve requiring surgical intervention within his first year of life"
Documents reflux with the obstruction and valve, and its clinical consequence.
Cystic Renal Dysplasia HP:0000800 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cystic renal dysplasia (HP:0000800). HP:0000800 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"grade 3 VUR, mild hydronephrosis, and increased renal echogenicity with cystic dysplasia were observed on the right kidney"
Documents cystic dysplasia with reflux and hydronephrosis in one kidney of a patient whose other kidney is absent.
Chronic Kidney Failure Stage 5 chronic kidney disease HP:0003774 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Stage 5 chronic kidney disease (HP:0003774), qualified as course progressive. HP:0003774 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"The 44-year-old index patient (ID 1) was genetically evaluated for chronic kidney failure of unknown etiology while awaiting kidney transplantation."
Documents progression to transplant-requiring kidney failure, and the diagnostic context in which the genotype was found.
Cryptorchidism HP:0000028 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cryptorchidism (HP:0000028). HP:0000028 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"Urorenal manifestation encompassed bilateral renal hyperechogenicity, slightly reduced kidney size, and bilateral cryptorchidism."
Documents bilateral cryptorchidism with the renal findings in the same patient.
Head and Neck 1
Dysmorphic Facial Features Abnormal facial shape HP:0001999 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal facial shape (HP:0001999). HP:0001999 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"with frontal bossing, bitemporal narrowing, medially upslanting eyebrows, and low set, posteriorly rotated ears"
The specific facial gestalt, described in a comparison between two unrelated patients from different populations.
Nervous System 6
Corpus Callosum Anomaly Abnormal corpus callosum morphology HP:0001273 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal corpus callosum morphology (HP:0001273). HP:0001273 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"Morphologically, nervous system anomalies comprised thinning of the corpus callosum and hypoplasia of the pons and midbrain"
Documents callosal thinning with brainstem hypoplasia in one patient.
PMID:35227688 SUPPORT Human Clinical
"corpus callosum splenium agenesis, a small thalamus, and atrophic changes at the mesencephalopontine level"
A partial (splenial) callosal defect in a second patient, showing the graded nature of the finding.
Mirror Movements Bimanual synkinesia HP:0001335 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bimanual synkinesia (HP:0001335). HP:0001335 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"His neurodevelopmental phenotype was also striking for the observation of mirror hand movement disorder. No likely damaging variants in DCC or RAD51, previously associated with autosomal dominant mirror movements"
The observation together with the exclusion of the two competing genes, which is what makes it attributable to ROBO1 here.
Corticospinal Tract Deficiency Corticospinal tract hypoplasia HP:0007016 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Corticospinal tract hypoplasia (HP:0007016). HP:0007016 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"vermis hypoplasia, absence of pyramidal tracts, and dentate nuclei hypoplasia"
Documents absent pyramidal tracts on fetal neuropathological examination, alongside the hindbrain findings.
Ventriculomegaly HP:0002119 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ventriculomegaly (HP:0002119). HP:0002119 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"associated with enlarged cerebral ventricles and vermis hypoplasia"
Documents ventriculomegaly with vermis hypoplasia on antenatal examination.
Cerebellar Vermis Hypoplasia HP:0001320 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cerebellar vermis hypoplasia (HP:0001320). HP:0001320 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"vermis hypoplasia, absence of pyramidal tracts, and dentate nuclei hypoplasia"
Documents vermis and dentate hypoplasia alongside the absent pyramidal tracts in fetal neuropathology.
Intellectual Disability HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249). HP:0001249 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"his general appearance included dysmorphic features together with intellectual disability, psychomotor delay, sensorineural hearing loss, and strabismus"
Documents intellectual disability with the associated delay, hearing and eye findings in one patient.
Growth 1
Growth Restriction Growth delay HP:0001510 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Growth delay (HP:0001510). HP:0001510 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"Furthermore, the patient's growth rate was reduced, and his general appearance included dysmorphic features together with intellectual disability, psychomotor delay, sensorineural hearing loss, and strabismus."
Documents reduced growth rate in the patient who also has documented pituitary insufficiency.
🧬

Genetic Associations

1
ROBO1
Gene: ROBO1 hgnc:10249 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is ROBO1 (hgnc:10249). hgnc:10249 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: GERMLINE
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"we here propose biallelic ROBO1 variants as causing syndromic, but viable CAKUT phenotypes in humans"
The gene-disease assertion, with the authors' own emphasis that biallelic loss is compatible with life - which had been the open question.
PMID:35227688 SUPPORT Human Clinical
"In contrast to our observations in ROBO1, VUR associated with ROBO2 was observed on monoallelic variation and dominant inheritance with incomplete penetrance"
Distinguishes this gene's inheritance pattern from its paralogue's, which is what keeps the two entities separate.
💊

Medical Actions

4
Kidney replacement therapy for established kidney failure
Action: Kidney TransplantationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Kidney Transplantation (NCIT:C15265). NCIT:C15265 is a clinical intervention from the NCI Thesaurus. NCIT:C15265
Platform: Surgery
The end of the renal course for the severe survivors, and the reason this diagnosis has prognostic weight rather than only explanatory value. The index patient reached end-stage kidney disease at 44 and was on the transplant waiting list when the genotype was found. Nothing modifies the underlying malformation; this treats its consequence.
Mechanism Target:
Congenital Anomalies of the Kidney and Urinary Tract — Replaces failed renal function. It does not act on the developmental lesion, which is complete before birth.
Show evidence (1 reference)
PMID:35227688 SUPPORT INDIRECT Human Clinical
"The 44-year-old index patient (ID 1) was genetically evaluated for chronic kidney failure of unknown etiology while awaiting kidney transplantation."
Documents that a patient with this genotype reached transplant candidacy. INDIRECT: the source reports the clinical situation, not an outcome of transplantation in this disease.
Urological correction of obstruction and reflux
Action: Surgical ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Surgical Procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. NCIT:C15329
Platform: Surgery
Where the ureteric-bud lesion produces obstruction rather than agenesis, the consequence is recurrent pyelonephritis and progressive scarring, and it is surgically addressable. The index patient had a posterior urethral valve and ureterovesical junction obstruction corrected in his first year; his renal function then stayed stable for four decades. That sequence is an argument for early urological assessment, though a single course is not evidence of benefit.
Mechanism Target:
Congenital Anomalies of the Kidney and Urinary Tract — Relieves obstruction and reflux, addressing the secondary injury rather than the malformation.
Show evidence (1 reference)
PMID:35227688 SUPPORT INDIRECT Human Clinical
"he suffered from repetitive pyelonephritis due to VUR caused by unilateral ureterovesical junction obstruction and a posterior urethral valve requiring surgical intervention within his first year of life"
Documents the surgical intervention and the lesions it addressed. INDIRECT: one patient, and the subsequent stability is not attributed to the surgery by the source.
Pituitary hormone replacement
Action: Hormone Replacement TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Hormone Replacement Therapy (NCIT:C15599). NCIT:C15599 is a clinical intervention from the NCI Thesaurus. NCIT:C15599
Platform: Protein replacement
Where the pituitary is involved, the deficiencies are replaceable, which makes this the one part of the syndrome with a treatment that restores function rather than managing damage. Reported in the ROBO1-related pituitary literature rather than in the NORS cohort itself, so the link from this entity to this treatment runs through the shared gene.
Mechanism Target:
Disturbed Pituitary Stalk and Hypothalamic-Pituitary Axis Formation — Replaces the hormone output lost when the midline pituitary structures fail to form. It does not act on the malformation itself.
Show evidence (1 reference)
PMID:38444307 SUPPORT INDIRECT Human Clinical
"We conclude and emphasize that ROBO1 should be investigated in patients with PSIS."
Establishes ROBO1 as a cause of the pituitary phenotype that this treatment addresses. INDIRECT twice over: the patient is heterozygous rather than biallelic, and the source recommends genetic testing rather than reporting a treatment outcome.
Reproductive genetic counseling and cascade testing
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Platform: Behavioral / lifestyle
A recessive syndrome with a one-in-four recurrence risk and, at the severe end, a lethal prenatal phenotype - so counselling with prenatal or preimplantation options is a substantive part of care after a first affected pregnancy. Three of the nine reported individuals are fetuses from one family, which is what that risk looks like in practice. The counselling has a second, less obvious use. Two patients in this cohort were found by re-examining the kidneys of people already carrying a ROBO1-related cardiac or neurological diagnosis, so a molecular diagnosis in one organ system should prompt screening of the others.
Show evidence (2 references)
PMID:35227688 SUPPORT INDIRECT Human Clinical
"in patients with already established ROBO1-associated cardiac or neuronal disorders, screening for kidney involvement is indicated."
The cross-organ screening recommendation that a molecular diagnosis enables. INDIRECT: it is a diagnostic recommendation being used to support a counselling and surveillance role.
PMID:35227688 SUPPORT INDIRECT Human Clinical
"Lastly, we describe a previously unreported family with 3 affected fetal cases"
The recurrence this counselling addresses: three affected pregnancies in one family. INDIRECT: it documents the recurrence, not the effect of counselling on it.
🔬

Diagnosis

2
Multi-organ screening after a molecular diagnosis
The defining paper's closing recommendation, and the practical consequence of a syndrome whose organ involvement is heterogeneous and not predictable from any one system. Eye, heart, central nervous system, gonad and kidney each need looking at, because the cohort contains patients whose renal disease was found only by re-examining someone already diagnosed with a ROBO1-related cardiac or neurological disorder - and one adult whose kidney failure went unexplained until 44.
multi-organ screening after molecular diagnosis NCIT:C18020 NCI Thesaurus (NCIT)
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"requires extensive screening for eye, heart, central nervous system, gonad, and kidney involvement"
The surveillance recommendation, naming the five organ systems.
PMID:35227688 SUPPORT Human Clinical
"in patients with already established ROBO1-associated cardiac or neuronal disorders, screening for kidney involvement is indicated."
The specific direction that found two patients in this cohort: looking at the kidneys of people already diagnosed with something else.
Gene-panel or exome sequencing in syndromic CAKUT
The practical recommendation from the defining study runs in both directions. ROBO1 should be included in genetic analysis of CAKUT, including in adults with chronic kidney failure of unknown cause; and conversely, anyone already carrying a ROBO1-associated cardiac or neurodevelopmental diagnosis should be screened for kidney involvement, since two patients in this cohort were found by re-examining the kidneys of people already diagnosed with something else.
exome or gene-panel sequencing NCIT:C18020 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:35227688 SUPPORT Human Clinical
"comprehensive genetic analysis in CAKUT should include ROBO1 as a new cause of recessively inherited disease. Hence, in patients with already established ROBO1-associated cardiac or neuronal disorders, screening for kidney involvement is indicated."
Both halves of the diagnostic recommendation, stated by the authors.
📊

Prevalence

1
Worldwide, published cases
Cases In Literature Ultra Rare
Six unrelated living individuals plus three affected fetuses from one family. An unbiased search of 78,195 genomes in the 100,000 Genomes Project returned exactly one further case, which is the closest thing to a population-scale frequency estimate available.
Show evidence (2 references)
PMID:35227688 SUPPORT Human Clinical
"we identified six unrelated individuals and two non-viable fetuses with biallelic truncating or combined missense and truncating variants in ROBO1"
The published cohort size and composition, which is the denominator for this entry.
PMID:35227688 SUPPORT Human Clinical
"we searched 78,195 germline genomes of participants from the 100,000 Genomes Project"
Establishes that the cohort includes an unbiased population-scale search, not only referral-based ascertainment, which is what makes the rarity statement more than an artefact of who was sequenced.
🐁

Animal Models

1
Robo1 ENU missense mutant mouse
A pre-existing ENU line, not made for this study, carrying a homozygous missense change in the third immunoglobulin domain - the same domain as one of the human missense alleles. That correspondence is what makes it an allele-matched model rather than a generic knockout, and the reason the authors reached for it.
Species
Mouse
Genotype
Robo1 homozygous ENU-induced missense (Ig-3 domain)
Publication
PMID:35227688
Pathograph links
Disturbed Ureteric Bud Outgrowth and Nephrogenesis recapitulates fidelity: moderate All five newborn mutants had severely altered kidney architecture with genitourinary malformations: duplex or multiplex kidneys, cystic dysplasia, hydronephrosis, hydroureter, and misplaced undescended gonads. Endogenous Robo1 staining was absent from mutant kidneys, so the missense allele behaves as a functional null in this tissue.
Limitations: A missense allele rather than the truncating alleles that dominate the human cohort, and the renal phenotype is more uniform than the human one - every mutant is affected, whereas human severity ranges from fetal lethality to adult-onset kidney failure. Duplex and multiplex kidneys are also more prominent in the mouse than in the patients, whose commonest severe finding is agenesis.
Readouts
Renal Robo1 immunostaining
Direction: ABOLISHED
Interpretation: Establishes that the ENU missense allele abolishes detectable renal Robo1, which is what licenses reading the mouse as a loss-of-function model for the human truncating alleles.
Show evidence (1 reference)
PMID:35227688 SUPPORT Model Organism
"we found the complete absence of Robo1 expression in mutant kidneys, in contrast to the postnatal renal tubular expression observed in wild-type controls"
The measurement, against wild-type littermate controls.
Kidney and genitourinary morphology at birth
Direction: ALTERED
Interpretation: Structural readout of the CAKUT phenotype, scored in every newborn mutant by microCT and necropsy.
Show evidence (1 reference)
PMID:35227688 SUPPORT Model Organism
"all newborn mutant mice (n = 5) displayed severely altered kidney architecture and genitourinary tract malformations compatible with CAKUT"
The phenotype with its denominator - five of five.
Show evidence (2 references)
PMID:35227688 SUPPORT Model Organism
"On necropsy, macroscopic renal phenotypes also included duplex or multiplex kidneys with cystic dysplasia and consecutive hydronephrosis"
Establishes that the model produces a CAKUT phenotype, which is what makes it informative for this node.
+ 1 more reference
Reduced SLIT-ROBO Guidance Signalling measures fidelity: moderate Used to test, and reject, the ciliopathy reading of the phenotype: primary cilia on collecting ducts and ureteric bud tips were compared between mutants and controls.
Limitations: Morphology and abundance only, by acetylated-tubulin staining. The authors say explicitly that this does not exclude disturbed ciliary signalling, so the negative result bounds the hypothesis rather than closing it.
Readouts
Primary cilium morphology and abundance in collecting duct and ureteric bud tip
Direction: UNCHANGED
Interpretation: A real negative result: no ciliary difference between mutant and control, which argues against a ciliopathy mechanism for the cystic phenotype.
Show evidence (1 reference)
PMID:35227688 SUPPORT Model Organism
"Ciliary morphology and abundance, however, was overall unaffected on staining with acetylated tubulin in immunofluorescent microscopy"
The negative measurement itself.
Show evidence (1 reference)
PMID:35227688 SUPPORT Model Organism
"As renal cystic dilation and extrarenal manifestations (e.g., heart anomalies) were reminiscent of ciliopathy phenotypes, we compared primary cilia protruding from collecting ducts and ureteric bud tips in control versus"
States why the measurement was made - the ciliopathy resemblance - which is what makes this a MEASURES link rather than a phenotype claim.
{ }

Source YAML

click to show 
name: Neurooculorenal Syndrome
creation_date: "2026-08-31T09:00:00Z"
category: Mendelian
disease_term:
  preferred_term: neurooculorenal syndrome
  term:
    id: MONDO:0957210
    label: neurooculorenal syndrome
description: >
  Neurooculorenal syndrome (NORS, OMIM #620305) is an autosomal recessive
  developmental disorder caused by biallelic ROBO1 variants. It was delineated
  in 2022 from six unrelated living individuals and a family of three affected
  fetuses, assembled through GeneMatcher, retrospective phenotyping of
  previously published biallelic carriers, and an unbiased search of 78,195
  genomes in the 100,000 Genomes Project.

  Three organ systems are involved, and the name lists them in the order the
  literature found them. The kidney and urinary tract carry the defining
  lesion: unilateral or bilateral renal agenesis, ureterovesical junction
  obstruction, vesicoureteral reflux, posterior urethral valve, cystic
  dysplasia and increased echogenicity - in short, syndromic CAKUT. The
  nervous system contributes midline and hindbrain malformations, chiefly
  corpus callosum thinning or partial agenesis, ventriculomegaly, vermis
  hypoplasia and absent pyramidal tracts, together with intellectual
  impairment and, in one patient, mirror movements. The eye contributes
  strabismus and iris anomalies.

  The unifying claim is that these are not three coincident malformations but
  one signalling lesion read out in three places. ROBO1 is the receptor for
  the secreted SLIT ligands, and Slit-Robo signalling positions growing
  structures relative to the midline: commissural axons decide whether to
  cross it, and the ureteric bud decides where along the nephric duct to
  emerge. Human fetal kidney immunohistochemistry in this study puts ROBO1
  exactly where nephrogenesis happens - the outer nephrogenic zone, in
  comma-shaped and S-shaped bodies - and shows that staining absent in
  dysplastic patient tissue.

  A dosage argument runs through the whole entity and is what makes it
  recessive. Heterozygous ROBO1 variants had already been reported in
  congenital heart disease and pituitary stalk interruption syndrome, but the
  heterozygous parents in this cohort were clinically unaffected, and renal
  involvement appeared only when both alleles were altered. The severity range
  within the biallelic group - from an adult who reached end-stage kidney
  disease at 44 with normal cognition, to terminated fetuses with bilateral
  renal agenesis and Potter sequence - tracks with allelic combination:
  two nulls at the severe end, a null plus a mild hypomorph at the mild end.

synonyms:
- NORS
- ROBO1-related syndromic CAKUT
- biallelic ROBO1 deficiency

parents:
- Congenital anomaly of the kidney and urinary tract
- Multiple congenital anomalies syndrome

notes: >
  Identifier correction, recorded because the error was mine and was asserted
  as fact. An earlier draft of this description gave the OMIM number as
  #619976. It is #620305: MONDO:0957210 carries `skos:exactMatch OMIM:620305`
  together with `MEDGEN:1841013` and `UMLS:C5830377`, and the deep-research
  report reached the same cluster independently. Nothing in the validation
  stack catches this, because the schema has no OMIM mapping slot - `mappings`
  offers MONDO, ICD-10-CM, ICD-11-F and NCIT only - so the identifier can only
  live in unvalidated description prose. The MedGen and UMLS cross-references
  are likewise unrepresentable and are recorded here rather than structurally.

  Naming, and a caution for anyone searching the literature. The defining
  paper never uses the phrase "neurooculorenal syndrome" - it calls the
  entity "syndromic CAKUT" associated with biallelic ROBO1. The name comes
  from the OMIM entry created afterwards, and MONDO:0957210 follows OMIM. So
  a text search for the disease name against the primary source returns
  nothing, which is a genuine trap: the entity is real and well-evidenced, but
  its name and its evidence live in different documents. Every snippet in this
  entry is therefore keyed on ROBO1 and on the organ phenotypes, not on the
  syndrome name.

  Zygosity and dosage. The two homozygous patients were born to consanguineous
  parents; the rest are compound heterozygous. This entry sets
  `zygosity: HOMOZYGOUS` on the genetic context node as the modal state, which
  is a lossy summary - the schema takes one value and the cohort contains
  both. The compound-heterozygous configuration is the more common one and is
  described in the node text.

  Counting, and the denominator problem. Nine individuals in total, of whom
  three are fetuses ascertained at termination after antenatal ultrasound and
  six are living. The two ascertainment routes select for opposite ends of the
  severity range, so no `frequency` is set on any phenotype in this entry: a
  percentage pooled across a terminated 17-week fetus and a 44-year-old
  transplant candidate would not describe any population that exists.

  What this entry deliberately does not claim. The cystic kidneys and the
  combination of renal, cardiac, brain and eye involvement look like a
  ciliopathy, and the authors tested that directly - ciliary morphology and
  abundance were normal in mutant mouse collecting ducts and ureteric bud
  tips. The negative result is curated as evidence on the mechanism node
  rather than omitted, because "looks like a ciliopathy, is not one" is
  clinically useful and is the kind of finding that disappears if only
  positive results are curated.

prevalence:
- population: Worldwide, published cases
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Six unrelated living individuals plus three affected fetuses from one
    family. An unbiased search of 78,195 genomes in the 100,000 Genomes
    Project returned exactly one further case, which is the closest thing to a
    population-scale frequency estimate available.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identified six unrelated individuals and two non-viable fetuses with biallelic truncating or combined missense and truncating variants in ROBO1"
    explanation: >-
      The published cohort size and composition, which is the denominator for
      this entry.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we searched 78,195 germline genomes of participants from the 100,000 Genomes Project"
    explanation: >-
      Establishes that the cohort includes an unbiased population-scale
      search, not only referral-based ascertainment, which is what makes the
      rarity statement more than an artefact of who was sequenced.

inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >
    Biallelic, with two homozygotes from consanguineous families and the rest
    compound heterozygous. The inheritance claim is unusually well supported
    for a nine-patient cohort because it rests on a negative as well as a
    positive: the heterozygous parents were clinically unaffected, and renal
    involvement appeared only with both alleles altered. That is what
    distinguishes this from the earlier monoallelic ROBO1 reports in
    congenital heart disease and pituitary stalk interruption syndrome.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "heterozygous parents in our study were clinically unaffected, which we propose may be due to incomplete penetrance and gene dosage effects conferred by distinct variants in the ROBO1 locus."
    explanation: >
      The unaffected-carrier observation that grounds recessive inheritance,
      stated together with the authors' dosage interpretation.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "According to our data, renal involvement was only present on genetic alteration of both alleles."
    explanation: >
      States the dosage threshold specifically for the renal phenotype, which
      is the organ that defines this entity.

mechanistic_hypotheses:
- hypothesis_group_id: slit_robo_midline_guidance_dosage
  hypothesis_label: SLIT-ROBO Midline Guidance Dosage Model
  status: CANONICAL
  description: >-
    Biallelic reduction of ROBO1 below a threshold impairs SLIT-ROBO
    signalling in every tissue that uses it to position structures during
    development. The three affected organ systems are the three places where
    that requirement is strictest and least redundant: commissural and
    pyramidal axon guidance across the CNS midline, ureteric bud outgrowth and
    branching in the nephrogenic zone, and ocular development. Whether an
    individual is severely or mildly affected is set by which pair of alleles
    they carry, not by which tissue is involved - the same genotype affects
    all three. CANONICAL because the receptor biology, the human fetal kidney
    expression, the mouse renal and cardiac phenotypes, and the human genetics
    all point the same way.

pathophysiology:
- name: Biallelic Loss-of-Function ROBO1 Variants
  biological_scale: MOLECULAR
  description: >
    Twelve variants across the cohort, all single-nucleotide substitutions:
    eight truncating, two canonical splice-site, and two missense. The two
    missense alleles land in the functionally important extracellular domains
    - one on a surface loop of the third immunoglobulin domain near the
    homodimerisation linker, the other on the second fibronectin type III
    domain - which is where SLIT binding and receptor dimerisation happen. All
    but one allele were absent from population and clinical variant databases.
  genes:
  - preferred_term: ROBO1
    term:
      id: hgnc:10249
      label: ROBO1
    modifier: DECREASED
  genetic_context:
    description: >-
      Germline biallelic ROBO1 alleles. Compound heterozygous truncating, or
      truncating in trans with a hypomorphic missense allele, in most; two
      homozygous splice-site cases from consanguineous families.
    variant_origin: GERMLINE
    zygosity: HOMOZYGOUS
    functional_impact_category: LOSS_OF_FUNCTION
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All 12 ROBO1 variants reported in our study were single-nucleotide substitutions: 2 canonical splice site variants, 8 truncating variants, and 2 missense variants, the latter 2 located within the functionally important Ig and FN3 protein domains"
    explanation: >
      The complete allelic spectrum and the domain localisation of the
      missense alleles.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The extracellular portion, responsible for homodimerization and Slit-ligand binding, contains 5 well-defined N-terminal Ig-like domains followed by 3 fibronectin type III (FN3) domains."
    explanation: >
      Establishes what the domains hit by the missense alleles actually do,
      which is why their location is the argument for pathogenicity.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "indicating nonsense-mediated RNA decay of the truncating allele and exclusive expression of the missense allele"
    explanation: >
      Transcript-level demonstration that a truncating allele is degraded, so
      the surviving hypomorphic allele sets the phenotype. This is the
      observation the dosage model is built on.
  downstream:
  - target: Reduced SLIT-ROBO Guidance Signalling
    description: Loss of receptor available to bind SLIT ligand at the cell surface.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage

- name: Reduced SLIT-ROBO Guidance Signalling
  biological_scale: MOLECULAR
  description: >
    ROBO1 is a 180 kDa single-pass receptor for the secreted SLIT ligands,
    conserved since its identification in a Drosophila screen for axon
    guidance mutants. It homodimerises, heterodimerises with ROBO2, and binds
    SLIT1/2/3 and the SRGAP adaptors; reducing it therefore reduces a
    repulsive positional signal rather than a growth or survival signal. Its
    paralogue ROBO2 and its ligand SLIT2 are already implicated in human
    CAKUT, which is the pathway-level context that made ROBO1 a credible
    candidate long before this cohort existed.

    The cystic-kidney and multi-organ pattern raises a ciliopathy hypothesis,
    and this node records that it was tested and not supported: ciliary
    morphology and abundance were normal in mutant collecting ducts and
    ureteric bud tips.
  biological_processes:
  - preferred_term: Roundabout signaling pathway
    modifier: DECREASED
    term:
      id: GO:0035385
      label: Roundabout signaling pathway
  - preferred_term: axon guidance
    modifier: DECREASED
    term:
      id: GO:0007411
      label: axon guidance
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Roundabout guidance receptors (ROBOs) constitute a highly conserved subfamily of immunoglobulin superfamily proteins characterized by a single-pass transmembrane domain and interaction with the soluble extracellular Slit ligands."
    explanation: >
      Establishes the receptor-ligand relationship this node is about.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ROBO1 was shown to both homodimerize and heterodimerize with ROBO2"
    explanation: >
      Records the dimerisation partnerships, which matter because one missense
      allele sits next to the homodimerisation linker.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: NO_EVIDENCE
    evidence_source: MODEL_ORGANISM
    snippet: "Ciliary morphology and abundance, however, was overall unaffected on staining with acetylated tubulin in immunofluorescent microscopy"
    explanation: >
      A tested and negative ciliopathy hypothesis. Regraded from REFUTE to
      NO_EVIDENCE on review: the result does not contradict this node's claim
      that SLIT-ROBO guidance signalling is reduced - it bears on a different
      proposition, that the phenotype is ciliary, and finds nothing. It is
      kept here because a phenotype that resembles a ciliopathy without being
      one is exactly the kind of claim that needs its negative on the record.
  downstream:
  - target: Disturbed Ureteric Bud Outgrowth and Nephrogenesis
    description: >-
      Loss of the positional signal that places and branches the ureteric bud.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage
  - target: Disturbed CNS Midline and Commissural Axon Guidance
    description: >-
      Loss of the repulsive signal that governs midline crossing.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage
  - target: Disturbed Pituitary Stalk and Hypothalamic-Pituitary Axis Formation
    description: >-
      Loss of the same guidance signal at the midline structure that becomes
      the pituitary stalk.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage
  - target: Disturbed Retinal Ganglion Cell Axon Targeting
    description: >-
      Loss of ROBO-mediated targeting of retinal ganglion cell axons through
      the optic chiasm.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage

- name: Disturbed Ureteric Bud Outgrowth and Nephrogenesis
  biological_scale: TISSUE
  description: >
    ROBO1 protein sits in the human fetal kidney precisely where nephrons are
    being made - the outer nephrogenic zone, in comma-shaped and S-shaped
    bodies - at 14 and 21 weeks of gestation. In a 22-week fetus carrying
    biallelic ROBO1 variants that zone was gone and the staining with it,
    leaving dysplastic cystic parenchyma. Because the ureteric bud's position
    along the nephric duct determines whether a kidney forms at all and
    whether the ureter inserts correctly, a guidance failure at this step
    produces the whole clinical range at once: agenesis where the bud never
    emerges, reflux and junction obstruction where it emerges in the wrong
    place, dysplasia where branching miscarries.
  cell_types:
  - preferred_term: nephron progenitor cell
    term:
      id: CL:0000324
      label: metanephric mesenchyme stem cell
  biological_processes:
  - preferred_term: ureteric bud development
    modifier: DECREASED
    term:
      id: GO:0001657
      label: ureteric bud development
  - preferred_term: kidney development
    modifier: DECREASED
    term:
      id: GO:0001822
      label: kidney development
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Immunohistochemistry of endogenous ROBO1 in fetal control kidneys dating from 14 and 21 WG showed ROBO1 localization at the outer nephrogenic zone within comma-shaped bodies and S-shaped bodies supporting a role of ROBO1 in normal nephrogenesis"
    explanation: >
      Puts the protein in the right human tissue at the right developmental
      stage. This is human, not model-organism, expression data, which is what
      makes it the strongest single piece of mechanism in the entry.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the subcortical nephrogenic zone presented abolished in renal tissue from ID 8 at 22 WG accompanied by an absence of ROBO1 staining in severely dysplastic and cystic renal parenchyma"
    explanation: >
      The matched patient tissue: no ROBO1 staining, no nephrogenic zone,
      dysplastic kidney. Expression and loss in the same experiment.
  downstream:
  - target: Congenital Anomalies of the Kidney and Urinary Tract
    description: The clinical renal phenotype produced by the guidance failure.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage

- name: Disturbed CNS Midline and Commissural Axon Guidance
  biological_scale: TISSUE
  description: >
    ROBO1 was identified as an axon guidance receptor and is required for
    neocortical development. The neurological phenotype in this cohort is
    correspondingly midline-weighted: corpus callosum thinning or partial or
    splenial agenesis, absent pyramidal tracts in all three fetuses,
    ventriculomegaly, cerebellar vermis and dentate nucleus hypoplasia, and
    brainstem hypoplasia. One patient had mirror movements without a variant
    in DCC or RAD51, the two established mirror-movement genes - which is a
    direct clinical readout of failed decussation, since mirror movements
    arise when corticospinal projections that should cross do not.
  biological_processes:
  - preferred_term: axon guidance
    modifier: DECREASED
    term:
      id: GO:0007411
      label: axon guidance
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ROBO1, which was originally identified in a Drosophila mutant screen, was shown to be crucial for proper axon guidance and neocortical development."
    explanation: >
      Establishes the receptor's canonical neural function, which is what the
      CNS phenotype is proposed to follow from.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "His neurodevelopmental phenotype was also striking for the observation of mirror hand movement disorder. No likely damaging variants in DCC or RAD51, previously associated with autosomal dominant mirror movements"
    explanation: >
      The mirror-movement observation with the two competing genes excluded.
      This is the closest thing in the cohort to a direct clinical test of a
      midline-crossing defect.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "partial agenesis of the corpus callosum, absence of pyramidal tracts, and dentate nuclei hypoplasia"
    explanation: >
      Fetal neuropathology showing absent pyramidal tracts alongside the
      callosal defect - two crossing systems failing together.
  downstream:
  - target: Midline Brain Malformation and Neurodevelopmental Impairment
    description: The clinical CNS phenotype.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage

- name: Disturbed Pituitary Stalk and Hypothalamic-Pituitary Axis Formation
  biological_scale: TISSUE
  description: >
    The endocrine branch. The pituitary stalk is a midline structure whose
    formation depends on the same guidance signalling as the commissures, and
    ROBO1 was implicated in pituitary stalk interruption syndrome by
    heterozygous variants before this recessive entity was described. In the
    biallelic cohort the readout ranges from a missing posterior pituitary
    bright spot with no endocrine consequence, through hypopituitarism with
    hypogonadism and micropenis and reduced growth, to combined pituitary
    hormone deficiency with central diabetes insipidus in the heterozygous
    PSIS literature. Expressivity is explicitly variable, so this node
    describes a susceptible developmental step rather than an obligate lesion.
  biological_processes:
  - preferred_term: axon guidance
    modifier: DECREASED
    term:
      id: GO:0007411
      label: axon guidance
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Regarding pituitary malformations, we also observed variable expressivity."
    explanation: >
      Establishes pituitary malformation as part of the biallelic phenotype
      and states that its expressivity varies, which is what this node claims.
  - reference: PMID:38444307
    reference_title: "Pituitary stalk interruption syndrome due to novel ROBO1 mutation presenting as combined pituitary hormone deficiency and central diabetes insipidus."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "The roundabout receptor-1 gene (ROBO1) plays critical roles in axonal guidance and cell migration. Recently, mutations in the ROBO1 gene have been reported patients with PSIS."
    explanation: >
      Connects the gene's guidance function to stalk interruption
      specifically. INDIRECT: the reported patients are heterozygous, so this
      supports the developmental step rather than the recessive syndrome.
  downstream:
  - target: Midline Brain Malformation and Neurodevelopmental Impairment
    description: >-
      Stalk and hypothalamic-pituitary involvement is part of the same midline
      malformation spectrum.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage

- name: Disturbed Retinal Ganglion Cell Axon Targeting
  biological_scale: TISSUE
  description: >
    The ocular branch - the "oculo" of the disease name, which the entry
    previously described in phenotypes without modelling. ROBO receptors
    target retinal ganglion cell axons along the whole visual projection, and
    in Robo mutant mice the optic chiasm is expanded with ectopic crossing
    points and axons projecting where they should not. That is the same
    midline-crossing decision the commissural branch of this entry describes,
    applied to the visual pathway, and it is the most plausible route from
    ROBO1 loss to the strabismus reported across this cohort.

    Stated carefully: the mouse work is on Robo1 and Robo2 mutants and finds
    Robo2 the predominant receptor in visual development, so this node is a
    mechanism proposal for the human ocular phenotype rather than a
    demonstrated one. No human ocular pathology has been reported in this
    syndrome.
  biological_processes:
  - preferred_term: retinal ganglion cell axon guidance
    modifier: DECREASED
    term:
      id: GO:0031290
      label: retinal ganglion cell axon guidance
  evidence:
  - reference: PMID:18272390
    reference_title: "Robos are required for the correct targeting of retinal ganglion cell axons in the visual pathway of the brain."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: MODEL_ORGANISM
    snippet: "we examined Robo1 and 2 mutant mice and found that Robos regulate the correct targeting of retinal ganglion cell (RGC) axons along the entire visual projection."
    explanation: >
      Establishes the receptor family's role in visual pathway targeting.
      INDIRECT and MODEL_ORGANISM: mouse, and not in a disease model.
  - reference: PMID:18272390
    reference_title: "Robos are required for the correct targeting of retinal ganglion cell axons in the visual pathway of the brain."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: MODEL_ORGANISM
    snippet: "The optic chiasm was expanded along the rostro-caudal axis"
    explanation: >
      The specific midline defect - an expanded optic chiasm with ectopic
      crossing points - which is the visual-pathway counterpart of the
      commissural phenotype this entry curates elsewhere.
  - reference: PMID:18272390
    reference_title: "Robos are required for the correct targeting of retinal ganglion cell axons in the visual pathway of the brain."
    supports: REFUTE
    directness: INDIRECT
    evidence_source: MODEL_ORGANISM
    snippet: "These defects were more pronounced in Robo2 than Robo1 knockout animals, implicating Robo2 as the predominant Robo receptor in visual system development."
    explanation: >
      The caveat that keeps this node a proposal. If Robo2 is the predominant
      receptor in visual development, ROBO1 loss alone is a weaker
      explanation for the ocular phenotype than for the renal or commissural
      ones, and the entry should not imply otherwise.
  downstream:
  - target: Strabismus
    description: >-
      Proposed route from mistargeted visual projections to the ocular
      phenotype; not demonstrated in human tissue.
    hypothesis_groups:
    - slit_robo_midline_guidance_dosage

- name: Congenital Anomalies of the Kidney and Urinary Tract
  biological_scale: ORGANISM
  description: >
    The defining organ phenotype and the one with prognostic weight. Its range
    within nine people is the whole CAKUT spectrum - bilateral agenesis with
    Potter sequence at the lethal end, unilateral agenesis and reflux
    nephropathy in the middle, increased echogenicity with mildly reduced
    kidney size at the mild end. The index patient reached end-stage kidney
    disease at 44, so this is a phenotype that can present in adulthood as
    unexplained chronic kidney failure with the congenital origin overlooked.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Kidney and genitourinary manifestation included unilateral or bilateral kidney agenesis, vesicoureteral junction obstruction, vesicoureteral reflux, posterior urethral valve, genital malformation, and increased kidney echogenicity."
    explanation: >
      The full renal and genitourinary spectrum of the cohort, in one place.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "renal function stabilized over the years until a slowly progressive decrease in function led to bilateral atrophic kidneys and end-stage kidney disease at the age of 44"
    explanation: >
      The adult end of the range, and the reason this diagnosis belongs in the
      workup of unexplained adult chronic kidney failure.

- name: Midline Brain Malformation and Neurodevelopmental Impairment
  biological_scale: ORGANISM
  description: >
    Clinically: intellectual impairment and psychomotor delay in most,
    dysmorphic facial features in eight of nine, and structural midline
    findings on imaging. Notably not universal - the adult index patient's
    motor and cognitive development was normal and his only MRI finding was a
    missing posterior pituitary bright spot, so a normal neurodevelopmental
    history does not exclude the diagnosis.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Further clinical characteristics were remarkably heterogeneous, including neurodevelopmental defects, intellectual impairment, cerebral malformations, eye anomalies, and cardiac defects."
    explanation: >
      Names the extrarenal domains and, importantly, states that they are
      heterogeneous rather than obligate.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Motor and cognitive skills developed normally."
    explanation: >
      The index patient's normal cognition, which contradicts neurodevelopmental
      impairment being an obligate feature. Recorded as REFUTE against that
      stronger reading rather than dropped.

phenotypes:
- category: Renal
  name: Renal Agenesis
  description: >
    Unilateral in the living patients, bilateral with Potter sequence in the
    fetuses. This is the most severe end of the ureteric-bud phenotype - the
    bud never induced a kidney on that side.
  phenotype_term:
    preferred_term: Renal agenesis
    term:
      id: HP:0000104
      label: Renal agenesis
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fetal examination confirmed the bilateral kidney agenesis with Potter sequence"
    explanation: >
      Documents bilateral agenesis with its oligohydramnios sequence in a
      fetal case.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "manifested congenitally when an abdominal ultrasound revealed left-sided renal agenesis"
    explanation: >
      Documents unilateral agenesis in a living child, the survivable form.

- category: Renal
  name: Vesicoureteral Reflux
  phenotype_term:
    preferred_term: Vesicoureteral reflux
    term:
      id: HP:0000076
      label: Vesicoureteral reflux
  description: >
    With ureterovesical junction obstruction and posterior urethral valve in
    the index patient, requiring surgery in his first year. Reflux is the
    signature of a ureteric bud that emerged from the wrong position on the
    nephric duct, so it is mechanistically the same lesion as the agenesis,
    one step less severe.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "he suffered from repetitive pyelonephritis due to VUR caused by unilateral ureterovesical junction obstruction and a posterior urethral valve requiring surgical intervention within his first year of life"
    explanation: >
      Documents reflux with the obstruction and valve, and its clinical
      consequence.

- category: Renal
  name: Cystic Renal Dysplasia
  phenotype_term:
    preferred_term: Cystic renal dysplasia
    term:
      id: HP:0000800
      label: Cystic renal dysplasia
  description: >
    Increased echogenicity with cystic dysplasia, and in the mouse model
    highly cystic collecting ducts with mildly dilated proximal tubules. This
    is the finding that makes the disease look like a ciliopathy on imaging.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "grade 3 VUR, mild hydronephrosis, and increased renal echogenicity with cystic dysplasia were observed on the right kidney"
    explanation: >
      Documents cystic dysplasia with reflux and hydronephrosis in one kidney
      of a patient whose other kidney is absent.

- category: Renal
  name: Chronic Kidney Failure
  phenotype_term:
    preferred_term: Stage 5 chronic kidney disease
    term:
      id: HP:0003774
      label: Stage 5 chronic kidney disease
    clinical_course: PROGRESSIVE
  description: >
    The long-term outcome in the one adult in the cohort, reached at 44 years
    after decades of stability. Since CAKUT is the leading cause of paediatric
    chronic kidney failure, this is the phenotype that gives the diagnosis its
    practical weight.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The 44-year-old index patient (ID 1) was genetically evaluated for chronic kidney failure of unknown etiology while awaiting kidney transplantation."
    explanation: >
      Documents progression to transplant-requiring kidney failure, and the
      diagnostic context in which the genotype was found.

- category: Ocular
  name: Strabismus
  description: >
    The most consistent eye finding, present in at least three patients,
    bilateral. Reported alongside an atrophic iris in one. Strabismus in a
    guidance-receptor disorder is worth taking seriously as a possible
    connectivity phenotype rather than a coincidental refractive one, though
    the cohort does not establish that.
  phenotype_term:
    preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "eye anomalies (bilateral strabismus, atrophic iris), and dextrocardia were part of the clinical syndrome"
    explanation: >
      Documents the ocular findings as part of the syndrome, with the iris
      anomaly alongside.

- category: Endocrine
  name: Pituitary Insufficiency
  description: >
    The fourth organ system, and the one the syndrome's name omits. In this
    cohort it shows as hypogonadism with micropenis attributed to
    hypopituitarism, a missing posterior pituitary bright spot on MRI in an
    otherwise normal adult brain, and growth failure. It is mechanistically of
    a piece with the rest: the pituitary stalk is a midline structure whose
    formation depends on the same guidance signalling, and heterozygous ROBO1
    variants were already established in pituitary stalk interruption syndrome
    before this recessive entity was described.

    The missing bright spot is worth knowing about, but the entry previously
    overstated it and the source is explicit: in that patient it was
    asymptomatic and remained without clinical implications, with endocrine
    laboratory testing normal. So it is a structural marker of the same
    midline process, found on an MRI that was otherwise unremarkable in a man
    with normal cognition - not a functional deficit, and not on its own a
    diagnostic pointer. Pituitary expressivity is variable across the cohort,
    which is why the phenotype is curated at the insufficiency level and this
    imaging finding is described rather than bound.
  phenotype_term:
    preferred_term: Hypopituitarism
    term:
      id: HP:0040075
      label: Hypopituitarism
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "hypogonadism with micropenis, the latter being likely related to hypopituitarism and/or hypospadias"
    explanation: >
      Documents pituitary insufficiency in a biallelic patient, with the
      authors' own attribution of the genital finding to it.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "was asymptomatic and remained without clinical implications as endocrine laboratory testing revealed no further abnormalities."
    explanation: >
      The counterweight, and the reason this phenotype's description was
      corrected. The missing posterior pituitary bright spot in the index
      patient had no endocrine consequence, so the imaging finding does not
      by itself establish pituitary insufficiency in that individual.
  - reference: PMID:38444307
    reference_title: "Pituitary stalk interruption syndrome due to novel ROBO1 mutation presenting as combined pituitary hormone deficiency and central diabetes insipidus."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report a 2.9-year-old boy with PSIS who presented with combined pituitary hormone deficiency, central diabetes insipidus, and the classical triad of MRI findings."
    explanation: >
      Extends the pituitary phenotype to posterior as well as anterior
      dysfunction. INDIRECT and worth reading carefully: this patient carries
      a *heterozygous* ROBO1 frameshift, so it is evidence about the gene's
      pituitary role rather than about this recessive syndrome, and it is
      cited on that basis rather than as a NORS case.

- category: Growth
  name: Growth Restriction
  description: >
    Reduced growth rate is reported across the paediatric patients, with
    heights around the 3rd-10th centile. In at least one it is downstream of
    the pituitary involvement rather than a skeletal phenotype, which matters
    for management: it is potentially treatable in a way the structural
    anomalies are not.
  phenotype_term:
    preferred_term: Growth delay
    term:
      id: HP:0001510
      label: Growth delay
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Furthermore, the patient's growth rate was reduced, and his general appearance included dysmorphic features together with intellectual disability, psychomotor delay, sensorineural hearing loss, and strabismus."
    explanation: >
      Documents reduced growth rate in the patient who also has documented
      pituitary insufficiency.

- category: Neurologic
  name: Corpus Callosum Anomaly
  description: >
    Thinning, splenial agenesis, or partial agenesis depending on the
    individual - a graded midline-crossing defect rather than an all-or-none
    one, which fits a dosage model better than a threshold one.
  phenotype_term:
    preferred_term: Abnormal corpus callosum morphology
    term:
      id: HP:0001273
      label: Abnormal corpus callosum morphology
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Morphologically, nervous system anomalies comprised thinning of the corpus callosum and hypoplasia of the pons and midbrain"
    explanation: >
      Documents callosal thinning with brainstem hypoplasia in one patient.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "corpus callosum splenium agenesis, a small thalamus, and atrophic changes at the mesencephalopontine level"
    explanation: >
      A partial (splenial) callosal defect in a second patient, showing the
      graded nature of the finding.

- category: Neurologic
  name: Mirror Movements
  description: >
    Reported in one patient, and the closest thing in this cohort to a direct
    clinical test of the mechanism: mirror movements arise when corticospinal
    projections that should decussate do not. Its evidential weight comes from
    an exclusion - the two established autosomal dominant mirror-movement
    genes, DCC and RAD51, carried no likely damaging variant on exome
    sequencing in this patient.
  phenotype_term:
    preferred_term: Bimanual synkinesia
    term:
      id: HP:0001335
      label: Bimanual synkinesia
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "His neurodevelopmental phenotype was also striking for the observation of mirror hand movement disorder. No likely damaging variants in DCC or RAD51, previously associated with autosomal dominant mirror movements"
    explanation: >
      The observation together with the exclusion of the two competing genes,
      which is what makes it attributable to ROBO1 here.

- category: Neurologic
  name: Corticospinal Tract Deficiency
  description: >
    Absent pyramidal tracts in all three fetuses examined. The structural
    counterpart of the mirror movements above, and the most direct
    neuropathological evidence in this entry that a crossing system fails.
    Bound to the hypoplasia term rather than to an abnormal-pyramidal-sign
    term, because the finding is a structural absence on fetal examination and
    not a clinical sign.
  phenotype_term:
    preferred_term: Corticospinal tract hypoplasia
    term:
      id: HP:0007016
      label: Corticospinal tract hypoplasia
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "vermis hypoplasia, absence of pyramidal tracts, and dentate nuclei hypoplasia"
    explanation: >
      Documents absent pyramidal tracts on fetal neuropathological
      examination, alongside the hindbrain findings.

- category: Neurologic
  name: Ventriculomegaly
  phenotype_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "associated with enlarged cerebral ventricles and vermis hypoplasia"
    explanation: >
      Documents ventriculomegaly with vermis hypoplasia on antenatal
      examination.

- category: Neurologic
  name: Cerebellar Vermis Hypoplasia
  phenotype_term:
    preferred_term: Cerebellar vermis hypoplasia
    term:
      id: HP:0001320
      label: Cerebellar vermis hypoplasia
  description: >
    Present in all three fetuses, with dentate nucleus hypoplasia. Worth
    separating from the supratentorial findings: it extends the guidance
    phenotype into hindbrain development.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "vermis hypoplasia, absence of pyramidal tracts, and dentate nuclei hypoplasia"
    explanation: >
      Documents vermis and dentate hypoplasia alongside the absent pyramidal
      tracts in fetal neuropathology.

- category: Neurologic
  name: Intellectual Disability
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  description: >
    Present in most of the paediatric patients, with psychomotor delay.
    Explicitly absent in the adult index patient, so the entry does not treat
    it as obligate.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "his general appearance included dysmorphic features together with intellectual disability, psychomotor delay, sensorineural hearing loss, and strabismus"
    explanation: >
      Documents intellectual disability with the associated delay, hearing and
      eye findings in one patient.

- category: Craniofacial
  name: Dysmorphic Facial Features
  description: >
    Reported in eight of nine, and reproducible enough across unrelated
    families to be worth describing: frontal bossing, bitemporal narrowing,
    medially upslanting eyebrows, low-set posteriorly rotated ears. The
    resemblance between a Japanese and a Turkish patient with different
    homozygous splice variants is a real gestalt, not an artefact of shared
    ancestry.
  phenotype_term:
    preferred_term: Abnormal facial shape
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "with frontal bossing, bitemporal narrowing, medially upslanting eyebrows, and low set, posteriorly rotated ears"
    explanation: >
      The specific facial gestalt, described in a comparison between two
      unrelated patients from different populations.

- category: Cardiovascular
  name: Congenital Heart Defect
  description: >
    Heterogeneous across the cohort: mitral valve prolapse, patent foramen
    ovale, tetralogy of Fallot with pulmonary artery stenosis, dextrocardia,
    left heart hypoplasia with pulmonary atresia and ventricular septal
    defect. Heterozygous ROBO1 variants were already known in congenital heart
    disease, so the cardiac limb of this syndrome is the one with independent
    monoallelic support.
  phenotype_term:
    preferred_term: Abnormal heart morphology
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "cardiac anomalies (including tetralogy of Fallot and pulmonary artery stenosis), and severe central nervous system malformations (including agenesis of the corpus callosum)"
    explanation: >
      Documents a conotruncal defect together with the callosal malformation
      in a single patient.

- category: Genitourinary
  name: Cryptorchidism
  phenotype_term:
    preferred_term: Cryptorchidism
    term:
      id: HP:0000028
      label: Cryptorchidism
  description: >
    Bilateral in one patient, and reproduced in the mouse as misplaced
    undescended gonads of both sexes - a gonadal positioning failure, which is
    the same class of defect as the ureteric bud mispositioning.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Urorenal manifestation encompassed bilateral renal hyperechogenicity, slightly reduced kidney size, and bilateral cryptorchidism."
    explanation: >
      Documents bilateral cryptorchidism with the renal findings in the same
      patient.

- category: Auditory
  name: Hearing Impairment
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "his general appearance included dysmorphic features together with intellectual disability, psychomotor delay, sensorineural hearing loss, and strabismus"
    explanation: >
      Documents sensorineural hearing loss as part of the syndrome in one
      patient.

animal_models:
- name: Robo1 ENU missense mutant mouse
  species: Mouse
  genotype: Robo1 homozygous ENU-induced missense (Ig-3 domain)
  publication: PMID:35227688
  description: >
    A pre-existing ENU line, not made for this study, carrying a homozygous
    missense change in the third immunoglobulin domain - the same domain as
    one of the human missense alleles. That correspondence is what makes it an
    allele-matched model rather than a generic knockout, and the reason the
    authors reached for it.
  modeled_mechanisms:
  - target: Disturbed Ureteric Bud Outgrowth and Nephrogenesis
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      All five newborn mutants had severely altered kidney architecture with
      genitourinary malformations: duplex or multiplex kidneys, cystic
      dysplasia, hydronephrosis, hydroureter, and misplaced undescended
      gonads. Endogenous Robo1 staining was absent from mutant kidneys, so the
      missense allele behaves as a functional null in this tissue.
    limitations: >-
      A missense allele rather than the truncating alleles that dominate the
      human cohort, and the renal phenotype is more uniform than the human one
      - every mutant is affected, whereas human severity ranges from fetal
      lethality to adult-onset kidney failure. Duplex and multiplex kidneys
      are also more prominent in the mouse than in the patients, whose
      commonest severe finding is agenesis.
    readouts:
    - name: Renal Robo1 immunostaining
      target: Disturbed Ureteric Bud Outgrowth and Nephrogenesis
      direction: ABOLISHED
      interpretation: >-
        Establishes that the ENU missense allele abolishes detectable renal
        Robo1, which is what licenses reading the mouse as a loss-of-function
        model for the human truncating alleles.
      evidence:
      - reference: PMID:35227688
        reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "we found the complete absence of Robo1 expression in mutant kidneys, in contrast to the postnatal renal tubular expression observed in wild-type controls"
        explanation: >
          The measurement, against wild-type littermate controls.
    - name: Kidney and genitourinary morphology at birth
      target: Disturbed Ureteric Bud Outgrowth and Nephrogenesis
      direction: ALTERED
      interpretation: >-
        Structural readout of the CAKUT phenotype, scored in every newborn
        mutant by microCT and necropsy.
      evidence:
      - reference: PMID:35227688
        reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "all newborn mutant mice (n = 5) displayed severely altered kidney architecture and genitourinary tract malformations compatible with CAKUT"
        explanation: >
          The phenotype with its denominator - five of five.
    evidence:
    - reference: PMID:35227688
      reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "On necropsy, macroscopic renal phenotypes also included duplex or multiplex kidneys with cystic dysplasia and consecutive hydronephrosis"
      explanation: >
        Establishes that the model produces a CAKUT phenotype, which is what
        makes it informative for this node.
    - reference: PMID:35227688
      reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Also observed were misplaced undescended gonads, both ovaries and testes, reminiscent of bilateral cryptorchidism reported in ID 3"
      explanation: >
        A second organ where mouse and human findings correspond, extending
        the model's relevance beyond the kidney proper.
  - target: Reduced SLIT-ROBO Guidance Signalling
    relationship: MEASURES
    fidelity: MODERATE
    description: >-
      Used to test, and reject, the ciliopathy reading of the phenotype:
      primary cilia on collecting ducts and ureteric bud tips were compared
      between mutants and controls.
    limitations: >-
      Morphology and abundance only, by acetylated-tubulin staining. The
      authors say explicitly that this does not exclude disturbed ciliary
      signalling, so the negative result bounds the hypothesis rather than
      closing it.
    readouts:
    - name: Primary cilium morphology and abundance in collecting duct and ureteric bud tip
      target: Reduced SLIT-ROBO Guidance Signalling
      direction: UNCHANGED
      interpretation: >-
        A real negative result: no ciliary difference between mutant and
        control, which argues against a ciliopathy mechanism for the cystic
        phenotype.
      evidence:
      - reference: PMID:35227688
        reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Ciliary morphology and abundance, however, was overall unaffected on staining with acetylated tubulin in immunofluorescent microscopy"
        explanation: >
          The negative measurement itself.
    evidence:
    - reference: PMID:35227688
      reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "As renal cystic dilation and extrarenal manifestations (e.g., heart anomalies) were reminiscent of ciliopathy phenotypes, we compared primary cilia protruding from collecting ducts and ureteric bud tips in control versus"
      explanation: >
        States why the measurement was made - the ciliopathy resemblance -
        which is what makes this a MEASURES link rather than a phenotype
        claim.

discussions:
- discussion_id: robo1_genotype_severity_dosage
  kind: KNOWLEDGE_GAP
  attaches_to:
  - pathophysiology#Biallelic Loss-of-Function ROBO1 Variants
  - pathophysiology#Congenital Anomalies of the Kidney and Urinary Tract
  prompt: >-
    Does the allelic combination predict severity in biallelic ROBO1 disease -
    specifically, is two-null genotype the reason for fetal lethality and
    null-plus-hypomorph the reason for survival with milder kidney disease?
  rationale: >
    The authors propose exactly this and the cohort is consistent with it: the
    index patient survived to 44 with a truncating allele undergoing
    nonsense-mediated decay in trans with a missense allele that gnomAD lists
    at 0.04% in Europeans, while the fetal cases carried two frameshifts. But
    nine individuals cannot establish a genotype-phenotype rule, the
    ascertainment differs between the fetal and living arms, and no functional
    assay quantifies residual signalling for any allele. This is the question
    with the most immediate clinical consequence in the entry - it is what
    prenatal counselling for a newly identified biallelic genotype would turn
    on - so recording it as unresolved matters more than usual.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "variability of the kidney disease suggests gene dosage effects due to a combination of null alleles with mild hypomorphic alleles"
    explanation: >
      The authors' own statement of the hypothesis, offered as a suggestion
      rather than a demonstration.
  proposed_experiments:
  - experiment_id: robo1_allelic_series_signalling_assay
    name: Quantify residual SLIT-ROBO signalling across the reported allelic series
    description: >-
      Express each reported ROBO1 allele at controlled dosage in a
      ROBO1-null cell background and measure SLIT-induced receptor
      dimerisation, SRGAP recruitment and downstream repulsion in a growth-cone
      or ureteric-bud explant assay, then rank the alleles and compare that
      ranking with the clinical severity of the genotypes carrying them.
    would_support:
    - pathophysiology#Congenital Anomalies of the Kidney and Urinary Tract
    supporting_outcome:
    - >-
      Measured residual signalling orders the alleles in the same sequence as
      clinical severity, with the two-frameshift fetal genotypes at zero and
      the surviving adult's missense allele retaining partial activity,
      establishing dosage as the determinant of outcome.
    would_refute:
    - pathophysiology#Congenital Anomalies of the Kidney and Urinary Tract
    refuting_outcome:
    - >-
      Residual signalling does not track severity - for example the adult
      index patient's missense allele proves as inactive as a frameshift -
      which would mean modifiers or stochastic developmental factors, not
      ROBO1 dosage, set the phenotype.

genetic:
- name: ROBO1
  notes: >
    The sole gene for this disorder, at 3p12.3, encoding the 180 kDa
    roundabout guidance receptor 1. Biallelic variants cause this recessive
    syndrome; monoallelic variants have separately been reported in congenital
    heart disease and in pituitary stalk interruption syndrome, and the
    unaffected status of the carrier parents here is the evidence that those
    are a different, lower-penetrance situation rather than the same disease in
    milder form. The paralogue ROBO2 and the ligand SLIT2 are independently
    implicated in CAKUT, but by monoallelic variants with incomplete
    penetrance, which is the contrast that makes ROBO1's recessive pattern
    notable.
  gene_term:
    preferred_term: ROBO1
    term:
      id: hgnc:10249
      label: ROBO1
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we here propose biallelic ROBO1 variants as causing syndromic, but viable CAKUT phenotypes in humans"
    explanation: >
      The gene-disease assertion, with the authors' own emphasis that
      biallelic loss is compatible with life - which had been the open
      question.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In contrast to our observations in ROBO1, VUR associated with ROBO2 was observed on monoallelic variation and dominant inheritance with incomplete penetrance"
    explanation: >
      Distinguishes this gene's inheritance pattern from its paralogue's,
      which is what keeps the two entities separate.

treatments:
- name: Kidney replacement therapy for established kidney failure
  description: >
    The end of the renal course for the severe survivors, and the reason this
    diagnosis has prognostic weight rather than only explanatory value. The
    index patient reached end-stage kidney disease at 44 and was on the
    transplant waiting list when the genotype was found. Nothing modifies the
    underlying malformation; this treats its consequence.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Kidney Transplantation
    term:
      id: NCIT:C15265
      label: Kidney Transplantation
  target_mechanisms:
  - target: Congenital Anomalies of the Kidney and Urinary Tract
    description: >-
      Replaces failed renal function. It does not act on the developmental
      lesion, which is complete before birth.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "The 44-year-old index patient (ID 1) was genetically evaluated for chronic kidney failure of unknown etiology while awaiting kidney transplantation."
    explanation: >
      Documents that a patient with this genotype reached transplant
      candidacy. INDIRECT: the source reports the clinical situation, not an
      outcome of transplantation in this disease.

- name: Urological correction of obstruction and reflux
  description: >
    Where the ureteric-bud lesion produces obstruction rather than agenesis,
    the consequence is recurrent pyelonephritis and progressive scarring, and
    it is surgically addressable. The index patient had a posterior urethral
    valve and ureterovesical junction obstruction corrected in his first year;
    his renal function then stayed stable for four decades. That sequence is
    an argument for early urological assessment, though a single course is not
    evidence of benefit.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Surgical Procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_mechanisms:
  - target: Congenital Anomalies of the Kidney and Urinary Tract
    description: >-
      Relieves obstruction and reflux, addressing the secondary injury rather
      than the malformation.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "he suffered from repetitive pyelonephritis due to VUR caused by unilateral ureterovesical junction obstruction and a posterior urethral valve requiring surgical intervention within his first year of life"
    explanation: >
      Documents the surgical intervention and the lesions it addressed.
      INDIRECT: one patient, and the subsequent stability is not attributed to
      the surgery by the source.

- name: Pituitary hormone replacement
  description: >
    Where the pituitary is involved, the deficiencies are replaceable, which
    makes this the one part of the syndrome with a treatment that restores
    function rather than managing damage. Reported in the ROBO1-related
    pituitary literature rather than in the NORS cohort itself, so the link
    from this entity to this treatment runs through the shared gene.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Hormone Replacement Therapy
    term:
      id: NCIT:C15599
      label: Hormone Replacement Therapy
  target_mechanisms:
  - target: Disturbed Pituitary Stalk and Hypothalamic-Pituitary Axis Formation
    description: >-
      Replaces the hormone output lost when the midline pituitary structures
      fail to form. It does not act on the malformation itself.
  evidence:
  - reference: PMID:38444307
    reference_title: "Pituitary stalk interruption syndrome due to novel ROBO1 mutation presenting as combined pituitary hormone deficiency and central diabetes insipidus."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude and emphasize that ROBO1 should be investigated in patients with PSIS."
    explanation: >
      Establishes ROBO1 as a cause of the pituitary phenotype that this
      treatment addresses. INDIRECT twice over: the patient is heterozygous
      rather than biallelic, and the source recommends genetic testing rather
      than reporting a treatment outcome.

- name: Reproductive genetic counseling and cascade testing
  description: >
    A recessive syndrome with a one-in-four recurrence risk and, at the severe
    end, a lethal prenatal phenotype - so counselling with prenatal or
    preimplantation options is a substantive part of care after a first
    affected pregnancy. Three of the nine reported individuals are fetuses
    from one family, which is what that risk looks like in practice.

    The counselling has a second, less obvious use. Two patients in this
    cohort were found by re-examining the kidneys of people already carrying a
    ROBO1-related cardiac or neurological diagnosis, so a molecular diagnosis
    in one organ system should prompt screening of the others.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "in patients with already established ROBO1-associated cardiac or neuronal disorders, screening for kidney involvement is indicated."
    explanation: >
      The cross-organ screening recommendation that a molecular diagnosis
      enables. INDIRECT: it is a diagnostic recommendation being used to
      support a counselling and surveillance role.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "Lastly, we describe a previously unreported family with 3 affected fetal cases"
    explanation: >
      The recurrence this counselling addresses: three affected pregnancies in
      one family. INDIRECT: it documents the recurrence, not the effect of
      counselling on it.

diagnosis:
- name: Multi-organ screening after a molecular diagnosis
  description: >
    The defining paper's closing recommendation, and the practical
    consequence of a syndrome whose organ involvement is heterogeneous and
    not predictable from any one system. Eye, heart, central nervous system,
    gonad and kidney each need looking at, because the cohort contains
    patients whose renal disease was found only by re-examining someone
    already diagnosed with a ROBO1-related cardiac or neurological disorder -
    and one adult whose kidney failure went unexplained until 44.
  diagnosis_term:
    preferred_term: multi-organ screening after molecular diagnosis
    term:
      id: NCIT:C18020
      label: Diagnostic Procedure
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "requires extensive screening for eye, heart, central nervous system, gonad, and kidney involvement"
    explanation: >
      The surveillance recommendation, naming the five organ systems.
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "in patients with already established ROBO1-associated cardiac or neuronal disorders, screening for kidney involvement is indicated."
    explanation: >
      The specific direction that found two patients in this cohort: looking
      at the kidneys of people already diagnosed with something else.

- name: Gene-panel or exome sequencing in syndromic CAKUT
  diagnosis_term:
    preferred_term: exome or gene-panel sequencing
    term:
      id: NCIT:C18020
      label: Diagnostic Procedure
  description: >
    The practical recommendation from the defining study runs in both
    directions. ROBO1 should be included in genetic analysis of CAKUT,
    including in adults with chronic kidney failure of unknown cause; and
    conversely, anyone already carrying a ROBO1-associated cardiac or
    neurodevelopmental diagnosis should be screened for kidney involvement,
    since two patients in this cohort were found by re-examining the kidneys of
    people already diagnosed with something else.
  evidence:
  - reference: PMID:35227688
    reference_title: "Biallelic pathogenic variants in roundabout guidance receptor 1 associate with syndromic congenital anomalies of the kidney and urinary tract."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "comprehensive genetic analysis in CAKUT should include ROBO1 as a new cause of recessively inherited disease. Hence, in patients with already established ROBO1-associated cardiac or neuronal disorders, screening for kidney involvement is indicated."
    explanation: >
      Both halves of the diagnostic recommendation, stated by the authors.
📚

References & Deep Research

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Record notes

Identifier correction, recorded because the error was mine and was asserted as fact. An earlier draft of this description gave the OMIM number as #619976. It is #620305: MONDO:0957210 carries `skos:exactMatch OMIM:620305` together with `MEDGEN:1841013` and `UMLS:C5830377`, and the deep-research report reached the same cluster independently. Nothing in the validation stack catches this, because the schema has no OMIM mapping slot - `mappings` offers MONDO, ICD-10-CM, ICD-11-F and NCIT only - so the identifier can only live in unvalidated description prose. The MedGen and UMLS cross-references are likewise unrepresentable and are recorded here rather than structurally. Naming, and a caution for anyone searching the literature. The defining paper never uses the phrase "neurooculorenal syndrome" - it calls the entity "syndromic CAKUT" associated with biallelic ROBO1. The name comes from the OMIM entry created afterwards, and MONDO:0957210 follows OMIM. So a text search for the disease name against the primary source returns nothing, which is a genuine trap: the entity is real and well-evidenced, but its name and its evidence live in different documents. Every snippet in this entry is therefore keyed on ROBO1 and on the organ phenotypes, not on the syndrome name. Zygosity and dosage. The two homozygous patients were born to consanguineous parents; the rest are compound heterozygous. This entry sets `zygosity: HOMOZYGOUS` on the genetic context node as the modal state, which is a lossy summary - the schema takes one value and the cohort contains both. The compound-heterozygous configuration is the more common one and is described in the node text. Counting, and the denominator problem. Nine individuals in total, of whom three are fetuses ascertained at termination after antenatal ultrasound and six are living. The two ascertainment routes select for opposite ends of the severity range, so no `frequency` is set on any phenotype in this entry: a percentage pooled across a terminated 17-week fetus and a 44-year-old transplant candidate would not describe any population that exists. What this entry deliberately does not claim. The cystic kidneys and the combination of renal, cardiac, brain and eye involvement look like a ciliopathy, and the authors tested that directly - ciliary morphology and abundance were normal in mutant mouse collecting ducts and ureteric bud tips. The negative result is curated as evidence on the mechanism node rather than omitted, because "looks like a ciliopathy, is not one" is clinically useful and is the kind of finding that disappears if only positive results are curated.

Create: Neurooculorenal Syndrome · 2026-08-31T08:57:41Z · View source

De-novo curation of neurooculorenal syndrome, MONDO:0957210, ROBO1 - the biallelic SLIT-ROBO guidance-receptor disorder. One OpenScientist deep-research run: 11/11 references verified, confabulation_rate 0.0; term_validation needs_review true with one obsolete and two unverifiable terms. No CURIE was taken from the report, and that was the right call again - its NCIT suggestions for the treatment section were wrong in the same way as on the other two entries in this run, proposing NCIT:C15366 as Kidney Transplantation when it is Platelet Transfusion and NCIT:C15431 as Hemodialysis when it is Hematopoietic Cell Transplantation. Correct terms were selected from cache/ncit/terms.csv instead. A naming trap is recorded in the entry notes: the defining paper never uses the phrase neurooculorenal syndrome, calling the entity syndromic CAKUT; the name comes from the OMIM entry created afterwards, so a text search for the disease name against its own primary source returns nothing. Every snippet is therefore keyed on ROBO1 and the organ phenotypes. The report contributed the pituitary dimension, which the syndrome name omits and which the entry now curates as its own phenotype plus a hormone-replacement treatment, with PMID:38444307 graded INDIRECT because that patient is heterozygous rather than biallelic. A tested and negative ciliopathy hypothesis is curated as REFUTE evidence rather than dropped. Validated with just validate - schema, terms, 52/52 snippets verified - plus the ungated whole-KB gates.

OpenScientist ▸
Neurooculorenal Syndrome (NORS): A Comprehensive Disease Characteristics Report
openscientist-autonomous 10 citations 2026-08-31T08:38:59.036894

Neurooculorenal Syndrome (NORS): A Comprehensive Disease Characteristics Report

Disease: Neurooculorenal Syndrome (NORS) Primary identifiers: MONDO:0957210 · OMIM #620305 · MedGen C5830377 (UID 1841013) · UMLS C5830377 Causal gene: ROBO1 (Roundabout Guidance Receptor 1), 3p12.3, NCBI Gene 6091, HGNC:10249, UniProt Q9Y6N7 Category: Mendelian (autosomal recessive)

Summary

Neurooculorenal syndrome (NORS) is an ultra-rare autosomal recessive multisystem congenital developmental disorder caused by biallelic loss-of-function variants in ROBO1, the SLIT-activated axon-guidance and cell-migration receptor located at chromosome 3p12.3. The disorder was delineated as a distinct clinical entity by Münch and colleagues in 2022, who identified six unrelated affected individuals plus two non-viable fetuses carrying biallelic truncating variants, or combined missense-plus-truncating variants, in ROBO1 (PMID: 35227688). The name captures the three cardinal organ domains — neuro (brain midline malformations, developmental delay), oculo (strabismus and optic-pathway anomalies), and renal (congenital anomalies of the kidney and urinary tract, CAKUT) — although the phenotype extends to cardiac defects and pituitary hormone deficiency.

Mechanistically, NORS arises because loss of SLIT-ligand-activated ROBO1 signaling disrupts the repulsive axon-guidance and directed cell-migration cues that pattern the embryonic midline and coordinate ureteric-bud/metanephric positioning during kidney development. The clinical spectrum is strikingly broad and bimodal: at the severe end, bilateral renal agenesis with Potter sequence and lethal brain malformation causes perinatal or in-utero death; at the milder end, affected individuals survive with global developmental delay, unilateral renal anomalies, congenital heart defects, ocular misalignment, and pituitary endocrinopathy. This variable expressivity — even within the same family — is attributed to gene-dosage effects, in which the combination of null alleles with mild hypomorphic alleles produces graded severity.

There is no disease-specific or curative therapy. Management is entirely symptomatic and multidisciplinary (nephrology/urology, endocrinology, cardiology, ophthalmology, neurodevelopmental care), and prevention is reproductive-genetic: genetic counseling with a 25% recurrence risk for carrier couples, carrier and cascade testing, prenatal diagnosis, and preimplantation genetic testing for monogenic disease (PGT-M). Diagnosis is definitively molecular — biallelic ROBO1 variants detected by whole-exome or whole-genome sequencing, or via CAKUT gene panels that should now include ROBO1.

Key Findings

Finding 1 — NORS is an autosomal recessive disorder caused by biallelic ROBO1 variants

NORS is unambiguously mapped to a single gene. The ontology cross-references converge: MONDO:0957210 ≡ OMIM:620305 ≡ MedGen C5830377/1841013 ≡ UMLS C5830377, and the disease gene is NCBI Gene 6091 (ROBO1, cytoband 3p12.3). Gene aliases that appear in the literature and databases include NORS, CPHD8, NYS8, DUTT1, and SAX3, several of which correspond to distinct allelic phenotypes (see Finding 6). The landmark delineation study identified biallelic (recessive) inheritance: Münch et al. reported "six unrelated individuals and two non-viable fetuses with biallelic truncating or combined missense and truncating variants in ROBO1" and concluded that "comprehensive genetic analysis in CAKUT should include ROBO1 as a new cause of recessively inherited disease" (PMID: 35227688). Because both alleles must be disrupted for disease to manifest, heterozygous carriers are unaffected, consistent with the recessive model.

Finding 2 — Phenotype spectrum spans kidney, brain, eye, heart, and pituitary

The syndrome is defined by a heterogeneous but recognizable combination of congenital anomalies. Renal and genitourinary manifestations reported by Münch et al. included "unilateral or bilateral kidney agenesis, vesicoureteral junction obstruction, vesicoureteral reflux, posterior urethral valve, genital malformation, and increased kidney echogenicity." The extrarenal features were "remarkably heterogeneous, including neurodevelopmental defects, intellectual impairment, cerebral malformations, eye anomalies, and cardiac defects" (PMID: 35227688). The OMIM/MedGen clinical description frames the disorder as a continuum: at the severe end, in-utero renal agenesis with lethal brain malformations; at the milder end, infantile global developmental delay, dysmorphism, CAKUT, strabismus, congenital heart defects, pituitary hormone deficiency, and midline brain defects (corpus callosum dysgenesis and hindbrain anomalies). Expressivity is variable even within families.

Suggested phenotype (HPO) terms and organ domains:

Domain Representative phenotypes Suggested HPO terms
Renal / urinary Renal agenesis (uni-/bilateral), VUJ obstruction, vesicoureteral reflux, posterior urethral valve, echogenic kidneys HP:0000104 (Renal agenesis), HP:0000110 (Renal dysplasia), HP:0000076 (Vesicoureteral reflux), HP:0010947 (Ureteropelvic junction obstruction)
Neurologic Corpus callosum dysgenesis, hindbrain anomaly, developmental delay, intellectual disability HP:0001263 (Global developmental delay), HP:0001249 (Intellectual disability), HP:0001274 (Agenesis of corpus callosum)
Ocular Strabismus, optic-pathway/chiasm anomaly, nystagmus HP:0000486 (Strabismus), HP:0000639 (Nystagmus)
Cardiac Ventricular septal defect, tetralogy of Fallot, valve defects HP:0001629 (Ventricular septal defect), HP:0001636 (Tetralogy of Fallot)
Endocrine Combined pituitary hormone deficiency, pituitary stalk interruption, central diabetes insipidus HP:0000871 (Hypopituitarism), HP:0000873 (Diabetes insipidus)

Finding 3 — Mechanism: loss of SLIT-ROBO axon-guidance/cell-migration signaling disrupts midline and renal development

ROBO1 encodes an immunoglobulin-superfamily transmembrane receptor that is activated by secreted SLIT proteins and functions in axon guidance and neuronal precursor migration at the CNS midline. In NORS, biallelic loss of function abolishes this signaling. Münch et al. provided direct functional evidence: they "observed absence of kidney ROBO1 expression in both human and murine mutant tissues" and argued that the "variability of the kidney disease suggests gene dosage effects due to a combination of null alleles with mild hypomorphic alleles" (PMID: 35227688). A dedicated review of SLIT-ROBO in the kidney confirmed the pathway is "extensively involved in various aspects of kidney development and maintenance of structure and function" (PMID: 37497439).

The causal chain branches to explain the multiorgan phenotype:

1. Biallelic ROBO1 loss-of-function variants
│  (result in)
▼
2. Loss of SLIT2–ROBO1 repulsive guidance / directed cell migration
│  (leads to, branching by organ field)
├─▶ Branch A (renal): failed ureteric-bud / metanephric
│        positioning → CAKUT / renal agenesis
│
├─▶ Branch B (neural): defective midline axon crossing →
│        corpus callosum & hindbrain dysgenesis; optic-pathway defects
│
└─▶ Branch C (endocrine): disrupted pituitary/hypothalamic axon
 guidance → stalk interruption → hormone deficiency
▼
3. Clinical manifestation: variable multisystem congenital syndrome

Upstream, the initiating lesion is the biallelic mutation; the loss of SLIT-ROBO signaling is the proximal molecular consequence; the organ-specific morphogenetic failures are downstream and largely inferred from the combination of human genetics, expression data, and animal models rather than demonstrated step-by-step in human embryos.

Suggested ontology terms: GO:0007411 (axon guidance), GO:0016477 (cell migration), GO:0021952 (central nervous system projection neuron axonogenesis), GO:0001822 (kidney development); CL:0000540 (neuron), CL:0000650 (mesangial cell), CL:0002518 (kidney epithelial cell); CHEBI-relevant ligand: SLIT2 (protein, not a small molecule).

Finding 4 — ROBO1 is LoF-constrained but not haploinsufficient, consistent with recessive disease

Population constraint metrics reconcile the recessive inheritance with the gene's biological importance. In gnomAD v4, ROBO1 (ENSG00000169855) shows pLI ≈ 0 (5.99×10⁻³⁸), meaning it is not predicted haploinsufficient, yet the observed/expected loss-of-function ratio is 0.76 (90% CI 0.67–0.87; LOEUF 0.87) with LoF Z = 2.84 (149 observed vs 196 expected LoF variants) — a moderate depletion of truncating variants indicating some selective constraint. Missense constraint is modest (missense Z = 1.27; observed/expected 0.93). ClinVar lists 781 ROBO1 variants total, of which 119 are classified pathogenic or likely pathogenic. The NORS-causing variants are biallelic truncating (nonsense/frameshift) or combined missense-plus-truncating — i.e., a loss-of-function class (PMID: 35227688). This profile — tolerant of a single hit but disease-causing when both alleles are lost — is the genetic signature of an autosomal recessive developmental gene.

Finding 5 — Model organisms recapitulate the ocular, cardiac, and renal components

The SLIT-ROBO system is deeply conserved, and animal models reproduce multiple NORS organ domains, strengthening causal inference:

  • Eye / visual pathway (mouse): Robo1 and Robo2 knockouts show that "Robos regulate the correct targeting of retinal ganglion cell (RGC) axons along the entire visual projection," with retinal axons mistargeting, ectopic midline crossing, and an optic chiasm that "was expanded along the rostro-caudal axis" (PMID: 18272390). This maps onto the "oculo" component (strabismus, optic-pathway anomalies).
  • Heart (Drosophila, zebrafish, mouse): Slit-Robo mutants across species show abnormal cardiac cell migration and alignment, ventricular septum and valve defects; in patients, "loss of function variants in ROBO1 have also been linked to ventricular septal defects and tetralogy of Fallot" (PMID: 29538649).
  • Kidney (mouse): Münch et al. documented absence of kidney Robo1 expression in murine mutant tissue, aligning the renal phenotype with the loss-of-expression mechanism (PMID: 35227688).

Additional heart-development evidence establishes Slit-Robo as "a significant pathway in human heart development and CHD" (PMID: 28592524).

Finding 6 — ROBO1 allelic series: recessive syndromic NORS versus (mostly heterozygous) isolated phenotypes

ROBO1 produces a spectrum of clinical entities depending on zygosity and allele severity. The recessive, syndromic NORS is one pole. Distinct OMIM phenotype tags map to gene aliases: CPHD8 (combined pituitary hormone deficiency), NYS8 (congenital nystagmus), and DUTT1 (a 3p12 tumor-suppressor locus). Heterozygous/monoallelic ROBO1 variants have been reported in pituitary stalk interruption syndrome (PSIS) with combined pituitary hormone deficiency and central diabetes insipidus (PMID: 38444307), congenital hypopituitarism with midline defects (where "ROBO1 variants have been associated with pituitary stalk interruption syndrome and highly variable pituitary-phenotypes, ranging from isolated growth hormone deficiency (IGHD) to combined pituitary hormone deficiency (CPHD)" — PMID: 40884218), and isolated congenital heart disease, where "Slit-Robo [is] a significant pathway in human heart development and CHD" (PMID: 28592524).

Suggested anatomical (UBERON) terms for affected structures: UBERON:0002113 (kidney), UBERON:0000056 (ureter), UBERON:0002336 (corpus callosum), UBERON:0002028 (hindbrain), UBERON:0000959 (optic chiasm), UBERON:0000970 (eye), UBERON:0000948 (heart), UBERON:0000007 (pituitary gland), UBERON:0001898 (hypothalamus).

Finding 7 — Epidemiology and inheritance: ultra-rare, autosomal recessive, consanguinity-associated

NORS is autosomal recessive (MedGen/OMIM 620305). No formal prevalence or incidence has been published; the disorder is known from a small number of families (the 6 unrelated individuals plus 2 fetuses of Münch et al., plus scattered case reports) and it lacks an Orphanet ORPHA code (MONDO cross-references are limited to OMIM/MedGen/UMLS). A genetic-epidemiology estimate derived from gnomAD v4 gives a cumulative putative-LoF allele frequency of q ≈ 0.00191 (440 pLoF variants), implying a carrier frequency 2q(1−q) ≈ 0.38% (~1 in 262) and a predicted random-mating birth prevalence of q² ≈ 3.7×10⁻⁶ (~1 in 274,000) as an upper bound (LOFTEE filtering not applied; assumes full penetrance — the true figure is likely lower). Consanguinity and founder homozygosity elevate risk in affected families. The phenotype shows highly variable severity and intrafamilial variable expressivity; heterozygous carriers are unaffected — consistent with pLI ≈ 0 and the observation that "Dutt1/Robo1 heterozygous mice develop normally" (PMID: 15374951; PMID: 35227688).

Finding 8 — Diagnostics: molecular sequencing is definitive; imaging and endocrine workup characterize organ involvement

Diagnosis rests on identifying biallelic ROBO1 variants by whole-exome (WES) or whole-genome (WGS) sequencing, or via CAKUT/renal-developmental gene panels — and ROBO1 should now be included in such panels (PMID: 35227688). Prenatally, fetal ultrasound detects uni-/bilateral renal agenesis, echogenic or dysplastic kidneys, oligohydramnios (Potter sequence), and brain midline anomalies; molecular autopsy/WES is diagnostic in fetuses with kidney anomalies. The genetic approach is broadly endorsed: "Recent identification of genes responsible for CAKUT allows for genetic testing of affected families" (PMID: 40041231). Postnatal workup is organ-directed: renal ultrasound plus kidney function (creatinine/eGFR, urinalysis); brain MRI (corpus callosum/hindbrain dysgenesis, pituitary stalk); echocardiography (VSD/TOF/valves); ophthalmologic exam (strabismus, optic pathway); and pituitary endocrine testing (GH, TSH/free T4, ACTH/cortisol, gonadotropins, prolactin, and posterior-pituitary/ADH function).

Differential diagnosis for syndromic renal agenesis/CAKUT includes GFRA1, FRAS1/FREM2 (Fraser syndrome), GREB1L, ITGA8, PAX2 (papillorenal syndrome), HNF1B, PBX1, and RET-pathway genes. Note that some ROBO1 callosal-dysgenesis cases have been reported with compound heterozygous variants of uncertain significance (VUS), underscoring the interpretive challenge (PMID: 34193621).

Finding 9 — Treatment is symptomatic/multidisciplinary; prevention is reproductive-genetic

There is no targeted, gene-specific, or curative therapy and no NORS-specific clinical trials. Management is supportive and organ-directed:

Organ system Interventions Suggested NCIT concepts
Renal / urinary CKD care, BP and electrolyte management, dialysis, kidney transplantation; urological surgery for obstruction/reflux/posterior urethral valves NCIT:C15431 (Hemodialysis), NCIT:C15366 (Kidney Transplantation)
Endocrine Lifelong pituitary hormone replacement: recombinant growth hormone, levothyroxine, hydrocortisone, sex-steroid induction, desmopressin/DDAVP for central diabetes insipidus NCIT:C1710 (Growth Hormone), NCIT:C29141 (Levothyroxine), NCIT:C509 (Hydrocortisone), NCIT:C29181 (Desmopressin)
Cardiac Surgical/catheter repair of VSD/TOF/valve lesions NCIT:C51696 (Cardiac Surgery)
Ophthalmologic Strabismus correction, refractive/low-vision support NCIT:C157866 (Strabismus Surgery)
Neurodevelopmental Early intervention, physical/occupational/speech therapy, special education, anti-seizure treatment NCIT:C15304 (Physical Therapy), NCIT:C15321 (Rehabilitation Therapy)

Endocrine replacement mirrors that used in ROBO1-related PSIS/CPHD (PMID: 38444307). Prevention is reproductive-genetic: genetic counseling with a 25% recurrence risk for carrier couples, carrier and cascade testing, prenatal diagnosis, and PGT-M — indeed, "Identification of the genetic etiology of CAKUT cases has multiple benefits including accurate risk assessment and reproductive options" (PMID: 40041231). Prognosis is bimodal: perinatal-lethal at the severe end (bilateral renal agenesis/Potter sequence, lethal brain malformation), versus survival with variable disability (CKD, intellectual disability, endocrinopathy) at the milder end.

Finding 10 — ROBO1/DUTT1 tumor-suppressor and perinatal-lethal mouse biology (relevant background, not a NORS clinical feature)

ROBO1/DUTT1 lies in a 3p12.3 region of nested homozygous deletions in breast and lung tumors and is silenced by tumor-specific promoter methylation in human cancers. Homozygous Dutt1/Robo1-deletion mice "generally die at birth due to incomplete lung development," and "Dutt1/Robo1 is a classic tumor suppressor gene requiring inactivation of both alleles" (PMID: 15374951). Heterozygous mice develop normally but show a ~3-fold increase in spontaneous lymphomas/lung adenocarcinomas with promoter methylation of the retained allele. Importantly, no epigenetic silencing mechanism has been implicated in NORS itself, and no cancer predisposition has been reported in NORS patients. The perinatal lethality of homozygous-null mice does, however, parallel the severe lethal end of the NORS spectrum and supports the loss-of-function mechanism.

Finding 11 — Protein architecture and cross-species conservation

Human ROBO1 (UniProt Q9Y6N7; HGNC:10249) is a 1,651-amino-acid single-pass type I transmembrane receptor with an ectodomain of 5 Ig-like C2-type domains + 3 fibronectin type-III (FN3) repeats and an intracellular signaling tail; it localizes to the plasma membrane and axon/cell projection (GO:0005886 plasma membrane; GO:0030424 axon), trafficking through the ER-Golgi intermediate compartment. It is the vertebrate homolog of the Drosophila axon-guidance receptor Roundabout (robo) — "the homologue (ROBO1) of the Drosophila axonal guidance receptor gene, Roundabout" (PMID: 15374951) — and binds SLIT ligands. Orthologs include mouse Robo1 (NCBI Gene 19876, chr16; Taxon 10090), zebrafish robo1 (Taxon 7955), and Drosophila robo1 (Taxon 7227). NORS pathogenic missense variants map to functional Ig/FN3 domains, while truncating variants remove the transmembrane/signaling regions, consistent with loss of function.

Mechanistic Model / Interpretation

NORS is best understood as a SLIT-ROBO signalopathy of embryonic morphogenesis. The single molecular lesion — biallelic inactivation of the SLIT receptor ROBO1 — removes a repulsive guidance and directed-migration cue that multiple developing organ fields depend on simultaneously. Because the same receptor patterns the CNS midline, the visual projection, cardiac cell migration, pituitary/hypothalamic connectivity, and ureteric-bud/metanephric positioning, a single genetic hit yields a pleiotropic, multiorgan syndrome. This "one gene, many organs" logic explains why the disorder is named for three domains yet reaches beyond them.

The dosage model is the key interpretive insight. ROBO1 is not haploinsufficient (pLI ≈ 0; carriers and heterozygous mice are healthy), so a single functional allele suffices for normal development. Disease requires losing both alleles, and the residual signaling capacity of the two alleles together sets severity: two null alleles → severe/lethal (bilateral renal agenesis, lethal brain malformation), whereas a null allele combined with a mild hypomorph → survivable, milder, and more variable disease. This continuous dose-response neatly accounts for the wide intrafamilial and interfamilial variability observed clinically.

   ALLELE DOSAGE (residual SLIT-ROBO signaling)  →  PHENOTYPE SEVERITY
   ───────────────────────────────────────────────────────────────────
   null / null             |  minimal signaling  →  perinatal-lethal
           |                          (bilateral renal
           |                           agenesis, Potter,
           |                           lethal brain malf.)
   null / strong-hypomorph |  low signaling       →  severe CAKUT + CNS
   null / mild-hypomorph   |  partial signaling   →  survivable syndrome
           |                          (unilat. renal, DD,
           |                           CHD, strabismus,
           |                           hypopituitarism)
   +/- (carrier)           |  ~50% signaling      →  unaffected
   ───────────────────────────────────────────────────────────────────

Cross-species evidence is unusually strong for such a rare disorder: mouse Robo knockouts reproduce the optic-chiasm/visual-pathway phenotype, Slit-Robo mutants across three species reproduce cardiac septation/valve defects, and murine mutants show loss of kidney Robo1 expression. This convergence — human genetics + expression data + conserved animal phenotypes — provides confident causal attribution, even though the precise cell-by-cell morphogenetic steps in the human embryo remain inferred rather than directly observed.

Evidence Base

PMID Title (abbrev.) Role in this report Evidence type
35227688 Biallelic pathogenic variants in ROBO1 associate with syndromic CAKUT Landmark delineation. Biallelic ROBO1 as cause, recessive inheritance, phenotype spectrum, loss of kidney expression, dosage model. Human clinical/genetic + mouse
37497439 SLIT-ROBO signaling in renal pathophysiology and renal diseases Supports SLIT-ROBO role in kidney development underlying the renal phenotype. Pathway review
18272390 Robos required for RGC axon targeting in the visual pathway Mouse model for the ocular/optic-chiasm component. Model organism
29538649 Slit-Robo signalling in heart development Links Slit-Robo (and human ROBO1 LoF) to VSD/TOF and cardiac component. Model organism + human
28592524 Loss of function in ROBO1 [CHD] Establishes isolated cardiac phenotype in the allelic series. Human clinical/genetic
38444307 PSIS due to novel ROBO1 variant Pituitary/endocrine end of the allelic series; endocrine management rationale. Human case report
40884218 Compound heterozygous ROBO1 [pituitary phenotypes] Documents pituitary phenotype range (IGHD → CPHD). Human clinical/genetic
15374951 Targeted disruption of Dutt1/Robo1 in mice Tumor-suppressor biology, perinatal-lethal homozygous mice, healthy heterozygotes, Drosophila homology. Model organism
40041231 Challenges in genetic counseling for CAKUT Supports molecular diagnosis and reproductive-genetic prevention. Clinical review
34193621 Callosal dysgenesis and VUS in ROBO1 Illustrates VUS interpretation challenge in diagnosis. Human case report
39492016 CAKUT: A Continuum of Care Context for CAKUT etiology, course, and management. Clinical review

The core disease-defining claim rests on a single primary cohort (PMID: 35227688), reinforced by convergent mechanistic and allelic-series literature spanning human clinical genetics, three model organisms, and pathway reviews.

Section-by-Section Reference to Research Template

  • §1 Disease Information / §4 Genetic-Molecular / §11 Protein dysfunction — Findings 1, 4, 11.
  • §2 Etiology — Genetic cause = biallelic ROBO1 LoF (Findings 1, 3, 4). No established environmental, infectious, or protective factors; consanguinity is a risk-elevating context (Finding 7). No gene-environment interactions reported.
  • §3 Phenotypes / §7 Anatomical structures — Findings 2, 6 (HPO and UBERON terms provided).
  • §5 Environmental Information — Not applicable; NORS is a Mendelian monogenic disorder with no known environmental, lifestyle, or infectious contributors.
  • §6 Mechanism / Pathophysiology — Finding 3 (ordered causal chain), Findings 5 and 11 (pathway conservation and protein architecture).
  • §8 Temporal Development — Congenital/prenatal onset; bimodal course (perinatal-lethal vs chronic lifelong with disability); critical window is embryonic organogenesis (Findings 2, 9).
  • §9 Inheritance and Population — Finding 7 (autosomal recessive, 25% recurrence, ultra-rare, variable penetrance/expressivity, consanguinity, gnomAD-derived carrier frequency).
  • §10 Diagnostics — Finding 8.
  • §11 Outcome/Prognosis — Finding 9 (bimodal prognosis).
  • §12 Treatment / §13 Prevention — Finding 9 (symptomatic/multidisciplinary; reproductive-genetic prevention).
  • §14 Other Species / §15 Model Organisms — Findings 5, 10, 11 (mouse Robo1 19876, zebrafish, Drosophila Roundabout; knockout and hypomorphic models recapitulate ocular/cardiac/renal/pulmonary phenotypes).

Limitations and Knowledge Gaps

  1. Small ascertained cohort. The disease definition rests principally on 6 unrelated individuals + 2 fetuses plus scattered case reports. Phenotype frequencies, penetrance, and the full severity distribution are therefore imprecise.
  2. No formal epidemiology. No published prevalence/incidence; the ~1 in 274,000 figure is a gnomAD-derived upper-bound estimate assuming full penetrance and random mating, without LOFTEE filtering — likely an overestimate of true birth prevalence. No Orphanet ORPHA code exists.
  3. Genotype–phenotype correlation is qualitative. The dosage model is well-motivated but not yet quantified with functional assays that grade individual hypomorphic alleles against clinical severity.
  4. Mechanistic steps in humans are inferred. The organ-specific morphogenetic failures are extrapolated from expression data and animal models, not directly observed in human embryogenesis.
  5. VUS burden. Some ROBO1 candidate cases carry variants of uncertain significance, complicating diagnosis and possibly leaving the phenotype spectrum incompletely defined.
  6. No natural-history study. Long-term outcomes (CKD progression, cognitive trajectory, endocrine evolution) in survivors are not systematically documented.
  7. No epigenetic or modifier-gene data specific to NORS. Modifier genes and any epigenetic contributions to expressivity are unstudied.

Proposed Follow-up Experiments / Actions

  1. International case registry / GeneMatcher recruitment to expand the cohort, quantify per-phenotype frequencies, penetrance, and the severity distribution, and enable a natural-history study.
  2. Functional grading of hypomorphic alleles (e.g., SLIT-binding and downstream-signaling assays in cell models, or zebrafish/mouse allelic-series rescue) to test the gene-dosage severity model quantitatively.
  3. Formal genotype–phenotype correlation mapping missense position (Ig vs FN3 domain) and truncation location to organ-domain involvement and severity.
  4. Conditional and hypomorphic mouse models (kidney-, forebrain-, and pituitary-specific Robo1 deletion) to dissect organ-autonomous versus non-autonomous mechanisms and define critical developmental windows.
  5. Single-cell/spatial transcriptomics of developing kidney, forebrain, and pituitary in Robo1-mutant models to identify the cell populations (CL terms) and signaling states most sensitive to SLIT-ROBO loss.
  6. Prospective molecular-autopsy studies in fetuses with bilateral renal agenesis + brain malformation to establish the prenatal detection rate and refine prenatal diagnostic criteria.
  7. Orphanet/MONDO curation to assign an ORPHA code and formalize the disease entry, improving discoverability and epidemiological tracking.
  8. Carrier-frequency validation using LOFTEE-filtered, ancestry-stratified gnomAD analysis to refine the birth-prevalence estimate and inform carrier-screening policy in consanguineous populations.

Report compiled from a five-iteration autonomous investigation (11 confirmed findings, 26 papers reviewed). All mechanistic and clinical claims are cited to primary literature with PMIDs; direct abstract quotes are used verbatim where provided. Ontology term suggestions (HPO, GO, CL, UBERON, NCIT) are included to support knowledge-base curation.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 11
Resolved 11
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 11
On topic 6
Off topic 0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome Count
Terms checked 44
Resolved 41
Unresolved (possible confabulation) 0
Obsolete 1
Unverifiable 2
Terms whose name was checked 18
Terms named correctly 16
Terms named as a different term 2

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

  • NCIT:C51696 (1 mention) - the report calls it "Cardiac Surgery"; NCIT calls it Orthotopic Liver Transplantation
  • NCIT:C157866 (1 mention) - the report calls it "Strabismus Surgery"; NCIT calls it Gluten Free Diet

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

  • NCIT:C1710 (Pentetic Acid Calcium) (1 mention)

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: OMIM.