KINSSHIP Syndrome

Mendelian MONDO:0851095 Pathograph 12 Show in embeddings browser Skeletal Dysplasia Mesomelic Dysplasia Syndromic intellectual disability

KINSSHIP syndrome is an autosomal dominant multisystem disorder caused by de novo missense variants in — or de novo deletions of — the nine-amino-acid degron of AFF3, the motif through which the protein is handed to a ubiquitin ligase for destruction. Removing the degron stabilizes AFF3 rather than abolishing it, so the disorder is a gain of protein dosage in a transcription elongation factor, not a haploinsufficiency. The acronym enumerates the recognizable pattern: horseshoe KIdney, Nievergelt/Savarirayan-type mesomelic dySplasia, Seizures, Hypertrichosis, Intellectual disability, and Pulmonary involvement. It sits in the mesomelic dysplasia group of the skeletal nosology on the strength of the limb phenotype, but is a developmental-disorder syndrome in which the skeletal finding is one component among several.

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1
Inheritance
3
Pathophys.
6
Phenotypes
2
Gaps
12
Pathograph
1
Genes
3
Differentials
2
Models
2
References
🏷

Classifications

Harrison's Part
GENETICS ENVIRONMENT DISEASE
ISDS Skeletal Nosology
mesomelic and rhizomesomelic dysplasias
👪

Inheritance

1
Autosomal dominant, de novo HP:0000006
Every reported causal allele is de novo — either a missense substitution within the degron or a deletion removing it. The recurrence risk for parents of an affected child is therefore low, subject to the usual caveat of parental gonadal mosaicism.
Autosomal dominant inheritance De novo rate: all reported cases
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"We describe an autosomal dominant disorder associated with de novo missense variants in the degron of AFF3, a nine amino acid sequence important for its binding to ubiquitin ligase, or with de novo deletions of this region."
States the inheritance mode and both classes of de novo allele.
?

Discussions and Knowledge Gaps

2
Is KINSSHIP syndrome caused by increased AFF3 protein dosage, and if so is the excess protein acting through the super elongation complex or through some degradation-independent function?
KNOWLEDGE GAP aff3_dosage_direction
Attached to
pathophysiology#Degron Disruption Stabilizing AFF3
The degron mechanism predicts stabilization, and zebrafish overexpression produces a phenotype, but the delineating paper describes that as "some support" rather than proof, and no measurement of AFF3 protein level in patient cells is reported. The distinction is actionable: if the disease is a dosage excess of an otherwise normal protein, lowering AFF3 is a coherent therapeutic hypothesis, whereas if the stabilized protein has acquired a neomorphic activity it is not.
Why is the mouse knockin of the most common human KINSSHIP missense variant lethal when the human variant is compatible with survival into childhood and beyond?
HUMAN MODEL MISMATCH kinsship_missense_knockin_lethality
Attached to
animal_models#Aff3 degron knockin mouse
Allele-matched knockins are the strongest model design available, and here the closest-matched allele produces early lethality rather than the human syndrome, while the less-matched microdeletion allele produces the limb phenotype. Something — species difference in AFF3 dosage tolerance, paralog compensation, or genetic background — separates the mouse from the human response to the same substitution. Until that is understood, the mouse cannot be used to test interventions against the multisystem phenotype, which is the use a model of this disease would most be wanted for.
⚙

Pathophysiology

3
Degron Disruption Stabilizing AFF3
A degron is a short sequence that marks a protein for destruction. AFF3's is nine amino acids long and binds a ubiquitin ligase. Missense variants within it, and microdeletions removing it, both prevent that hand-off. The consequence is not loss of AFF3 but persistence of it: the variant classes converge on the same endpoint precisely because the motif's only job is to be recognized, so disrupting it by substitution or by excision is equivalent.
AFF3 hgnc:6473 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves AFF3 (hgnc:6473). hgnc:6473 is a gene from the HUGO Gene Nomenclature Committee.
Genetic context AFF3 hgnc:6473 HUGO Gene Nomenclature Committee (hgnc) Relation: this genetic context concerns this gene This genetic context concerns AFF3 (hgnc:6473). hgnc:6473 is a gene from the HUGO Gene Nomenclature Committee. allele_type: degron missense substitution or degron-spanning microdeletion variant_origin: DE_NOVO zygosity: HETEROZYGOUS
Ubiquitin-dependent degradation of AFF3 GO:0043161 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Ubiquitin-dependent degradation of AFF3, annotated with proteasome-mediated ubiquitin-dependent protein catabolic process (GO:0043161). GO:0043161 is a biological process from the Gene Ontology. ↓ DECREASED
AFF3 degron binding to ubiquitin ligase GO:0031625 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves AFF3 degron binding to ubiquitin ligase, annotated with ubiquitin protein ligase binding (GO:0031625), qualified as loss of function. GO:0031625 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION
Animal models
AFF3-overexpressing zebrafish Zebrafish partially recapitulates Supports the inference that the disease arises from increased AFF3 amount rather than from loss of it.
Downstream
Dysregulated Super Elongation Complex Activity An undegraded AFF3 persists in the complex it is a component of.
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"de novo missense variants in the degron of AFF3, a nine amino acid sequence important for its binding to ubiquitin ligase, or with de novo deletions of this region"
Identifies the motif, its function, and the two allele classes that disrupt it — the whole content of this node.
Dysregulated Super Elongation Complex Activity
AFF3 is one of four ALF paralogs (AFF1-AFF4) in the transcriptional super elongation complex, which releases paused RNA polymerase II at genes governing neurogenesis and development. Excess AFF3 therefore acts on transcriptional output rather than on any single structural protein, which is why the phenotype is multisystem. The paralogs are not interchangeable: AFF4 variants cause CHOPS syndrome, which overlaps KINSSHIP only partially, and the published transcriptome work argues each ALF factor contributes something distinct.
transcription elongation by RNA polymerase II GO:0006368 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated transcription elongation by RNA polymerase II (GO:0006368). GO:0006368 is a biological process from the Gene Ontology. ↕ DYSREGULATED
Downstream
Multisystem Developmental Patterning Failure The intermediate targets through which altered elongation produces each organ phenotype are not identified.
Show evidence (2 references)
PMID:33961779 SUPPORT Human Clinical
"The ALF transcription factor paralogs, AFF1, AFF2, AFF3, and AFF4, are components of the transcriptional super elongation complex that regulates expression of genes involved in neurogenesis and development."
Establishes the complex AFF3 belongs to and the class of genes it regulates.
PMID:33961779 SUPPORT Human Clinical
"The only partial phenotypic overlap of AFF3- and AFF4-associated syndromes and the previously published transcriptome analyses of ALF transcription factors suggest that these factors are not redundant and each contributes uniquely to proper development."
Supports the non-redundancy claim that makes a paralog-specific phenotype expected rather than surprising.
Multisystem Developmental Patterning Failure
The convergent endpoint: mesomelic limb deformity, horseshoe kidney, brain malformation and seizures, hypertrichosis, and pulmonary involvement. The Aff3 knockout mouse develops skeletal anomalies, kidney defects, brain malformations, and neurological anomalies — the same organ set — which is the strongest available argument that these are one pleiotropy rather than coincidence.
Animal models
Aff3 degron knockin mouse Mouse partially recapitulates The microdeletion knockin reproduces the lower mesomelic limb deformity seen in affected individuals.
Downstream
Mesomelic Limb Deformity The limb component, and the one the microdeletion knockin mouse reproduces directly.
Horseshoe Kidney Renal fusion is part of the same organ set the Aff3 knockout mouse develops.
Seizures Seizures follow the brain malformations that both the knockout mouse and affected individuals develop.
Intellectual Disability Cognitive impairment follows from the same neurodevelopmental lesion, compounded by the seizure burden where an epileptic encephalopathy is present.
Hypertrichosis Part of the recognizable pattern. No route from altered transcriptional elongation to the hair phenotype has been established.
Pulmonary Involvement Named in the syndrome acronym; neither the specific pulmonary lesion nor its mechanism is characterized in the delineating series.
Show evidence (1 reference)
PMID:33961779 SUPPORT Model Organism
"Whereas homozygous Aff3 knockout mice display skeletal anomalies, kidney defects, brain malformations, and neurological anomalies, knockin animals modeling one of the microdeletions and the most common of the missense variants identified in affected individuals presented with lower mesomelic..."
Reports both the knockout organ set and the allele-specific knockin phenotypes, which together support treating the human features as one pleiotropic consequence.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for KINSSHIP 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.
●

Phenotypes

6
Genitourinary 1
Horseshoe Kidney FREQUENT HP:0000085 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Horseshoe kidney (HP:0000085). HP:0000085 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for seizures, H for hypertrichosis, I for intellectual disability, and P for pulmonary involvement)"
Horseshoe kidney is the first component of the syndrome-defining acronym quoted here in full.
Integument 1
Hypertrichosis FREQUENT HP:0000998 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypertrichosis (HP:0000998). HP:0000998 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for seizures, H for hypertrichosis, I for intellectual disability, and P for pulmonary involvement)"
Hypertrichosis is a named component of the syndrome-defining acronym quoted here in full.
Nervous System 2
Seizures FREQUENT HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for seizures, H for hypertrichosis, I for intellectual disability, and P for pulmonary involvement)"
Seizures are a named component of the syndrome-defining acronym quoted here in full; the paper title additionally names epileptic encephalopathy.
Intellectual Disability VERY_FREQUENT 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:33961779 SUPPORT Human Clinical
"present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for seizures, H for hypertrichosis, I for intellectual disability, and P for pulmonary involvement)"
Intellectual disability is a named component of the syndrome-defining acronym quoted here in full, and of the paper title.
Other 2
Mesomelic Limb Deformity VERY_FREQUENT Mesomelia HP:0003027 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Mesomelia (HP:0003027). HP:0003027 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for seizures, H for hypertrichosis, I for intellectual disability, and P for pulmonary involvement)"
The acronym expansion in the delineating paper, which identifies the limb phenotype as a mesomelic dysplasia of Nievergelt/Savarirayan appearance.
Pulmonary Involvement OCCASIONAL Abnormal lung morphology HP:0002088 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal lung morphology (HP:0002088). HP:0002088 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for seizures, H for hypertrichosis, I for intellectual disability, and P for pulmonary involvement)"
Pulmonary involvement is a named component of the syndrome-defining acronym quoted here in full. The abstract does not specify which pulmonary abnormality, so the HP binding is deliberately general and this is PARTIAL.
🧬

Genetic Associations

1
AFF3
Gene: AFF3 hgnc:6473 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is AFF3 (hgnc:6473). hgnc:6473 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"We describe an autosomal dominant disorder associated with de novo missense variants in the degron of AFF3, a nine amino acid sequence important for its binding to ubiquitin ligase, or with de novo deletions of this region."
Establishes AFF3 as causative and localizes the pathogenic alleles to the degron.
🔬

Diagnosis

2
Recognition of the KINSSHIP Pattern
Suspected from the co-occurrence of mesomelic limb shortening with horseshoe kidney and a developmental/epilepsy phenotype — a combination that no other mesomelic dysplasia produces. Renal imaging is therefore the cheap discriminator: a horseshoe kidney alongside mesomelia effectively excludes the SHOX and HOXD mesomelic dysplasias.
physical examination NCIT:C20989 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome"
Supports the claim that the combination is clinically recognizable as a pattern.
Molecular Confirmation of a Degron Variant
Confirmed by a de novo missense variant within, or a deletion spanning, the AFF3 degron. Because the causal alleles occupy nine codons, variant interpretation should weight location heavily; exome or genome sequencing with copy-number analysis is needed, since the deletion class will be missed by sequence calling alone.
genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"de novo missense variants in the degron of AFF3, a nine amino acid sequence important for its binding to ubiquitin ligase, or with de novo deletions of this region"
Names both allele classes that establish the diagnosis, including the deletion class that sequence-only analysis would miss.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
Eighteen individuals in the delineating series (sixteen newly identified plus two previously reported). No denominator-based estimate exists, so the count is recorded rather than a rate.
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"The sixteen affected individuals we identified, along with two previously reported individuals, present with a recognizable pattern of anomalies"
Gives the cohort size on which the entity was delineated, the basis for the rarity band recorded here.
🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from KINSSHIP Syndrome:

CHOPS syndrome
Overlapping Features Caused by variants in the paralog AFF4, also a super elongation complex component. The overlap with KINSSHIP is explicitly partial, which is itself evidence that the ALF paralogs are not functionally redundant.
Show evidence (1 reference)
PMID:33961779 SUPPORT Human Clinical
"partially overlapping the AFF4-associated CHOPS syndrome"
States the relationship between the two paralog syndromes.
Mesomelic dysplasia, Nievergelt type
Overlapping Features Named in the KINSSHIP acronym for radiographic resemblance, but a separate row of the same nosology group and, per the nosology's own comment, quite a different condition. Nievergelt type has no renal or neurodevelopmental component.
Mesomelic dysplasia, Savarirayan type
Overlapping Features The other type named in the acronym; an ID4-related 6p22.3 microdeletion disorder, again a separate row of group 15 and without the KINSSHIP multisystem pattern.
🐁

Animal Models

2
Aff3 degron knockin mouse
Two allele-matched knockin lines, one modelling a patient microdeletion and one the most common patient missense variant. They separate cleanly: the microdeletion line shows the limb phenotype, the missense line dies early.
Species
Mouse
Genotype
Aff3 degron microdeletion knockin; Aff3 recurrent degron missense knockin
Publication
PMID:33961779
Pathograph links
Multisystem Developmental Patterning Failure partially recapitulates fidelity: moderate The microdeletion knockin reproduces the lower mesomelic limb deformity seen in affected individuals.
Limitations: Only the lower-limb component is reported as recapitulated, and the missense knockin's early lethality means the allele closest to the common human variant cannot be phenotyped for the multisystem pattern at all — the more severe model is the less informative one.
Readouts
Lower limb mesomelic deformity
Direction: ALTERED
Interpretation: The limb deformity is the measured point of correspondence between mouse and human.
Show evidence (1 reference)
PMID:33961779 SUPPORT Model Organism
"knockin animals modeling one of the microdeletions and the most common of the missense variants identified in affected individuals presented with lower mesomelic limb deformities like KINSSHIP-affected individuals and early lethality, respectively"
Reports the limb phenotype in the microdeletion knockin and the early lethality of the missense knockin.
Show evidence (1 reference)
PMID:33961779 SUPPORT Model Organism
"knockin animals modeling one of the microdeletions and the most common of the missense variants identified in affected individuals presented with lower mesomelic limb deformities like KINSSHIP-affected individuals and early lethality, respectively"
Allele-matched knockins are the strongest available argument that the degron alleles cause the human phenotype.
AFF3-overexpressing zebrafish
A dosage experiment rather than an allele model: human AFF3 overexpressed in zebrafish produces body axis anomalies, testing whether more AFF3 is pathogenic at all.
Species
Zebrafish
Genotype
AFF3 mRNA overexpression
Publication
PMID:33961779
Pathograph links
Degron Disruption Stabilizing AFF3 partially recapitulates fidelity: low Supports the inference that the disease arises from increased AFF3 amount rather than from loss of it.
Limitations: Overexpression is not the same perturbation as impaired degradation, the readout is a body-axis anomaly rather than any KINSSHIP feature, and the paper's own wording ("providing some support") is deliberately weak.
Show evidence (1 reference)
PMID:33961779 SUPPORT Model Organism
"Overexpression of AFF3 in zebrafish resulted in body axis anomalies, providing some support for the pathological effect of increased amount of AFF3."
The source states both the result and its limited evidential weight; this link records it at that strength.
{ }

Source YAML

click to show 
name: KINSSHIP Syndrome
synonyms:
- Mesomelic dysplasia with digital anomalies and intellectual disability, AFF3-related
- AFF3-related KINSSHIP syndrome
- mesomelic dysplasia-digital anomalies-intellectual disability syndrome
creation_date: "2026-08-27T00:00:00Z"
category: Mendelian
description: >-
  KINSSHIP syndrome is an autosomal dominant multisystem disorder caused by de
  novo missense variants in — or de novo deletions of — the nine-amino-acid
  degron of AFF3, the motif through which the protein is handed to a ubiquitin
  ligase for destruction. Removing the degron stabilizes AFF3 rather than
  abolishing it, so the disorder is a gain of protein dosage in a transcription
  elongation factor, not a haploinsufficiency. The acronym enumerates the
  recognizable pattern: horseshoe KIdney, Nievergelt/Savarirayan-type mesomelic
  dySplasia, Seizures, Hypertrichosis, Intellectual disability, and Pulmonary
  involvement. It sits in the mesomelic dysplasia group of the skeletal nosology
  on the strength of the limb phenotype, but is a developmental-disorder
  syndrome in which the skeletal finding is one component among several.
disease_term:
  preferred_term: KINSSHIP syndrome
  term:
    id: MONDO:0851095
    label: KINSSHIP syndrome
parents:
- Skeletal Dysplasia
- Mesomelic Dysplasia
- Syndromic intellectual disability
notes: >-
  Naming. The ISDS 2023 table lists this entity as "Mesomelic dysplasia with
  digital anomalies and intellectual disability (KINSSHIP syndrome),
  AFF3-related" and adds an explicit warning in its own comment column that
  despite the acronym's reference to Nievergelt and Savarirayan, the condition
  is quite different from both of those mesomelic dysplasias. The acronym names
  a radiographic resemblance, not a nosologic relationship, and the two named
  types remain separate rows in the same group.

  Dosage direction. This entry treats KINSSHIP as an AFF3 gain-of-dosage
  disorder. That reading rests on the degron mechanism plus two model results
  pointing in the same direction, and is stated as such rather than as settled;
  the ``aff3_dosage_direction`` discussion records what would resolve it.
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    notes: >-
      A de novo Mendelian multisystem developmental disorder; tagged on the
      genetics axis.
  isds_skeletal_category:
  - classification_value: mesomelic_and_rhizomesomelic_dysplasias
    notes: >-
      ISDS Nosology of Genetic Skeletal Disorders, 2023 revision (Unger et al.,
      PMID:36779427), group 15 "Mesomelic and rhizo-mesomelic dysplasias", row
      NOS 15-0160, listed as "Mesomelic dysplasia with digital anomalies and
      intellectual disability (KINSSHIP syndrome), AFF3-related" (MIM 619297,
      AD). The row is new in the 2023 revision — the 2019 revision predates the
      2021 delineation of the syndrome, so there is no 2019 provenance to
      record. The row's own comment states that despite the acronym the
      condition is quite different from both the Nievergelt and Savarirayan
      mesomelic dysplasias, which occupy rows NOS 15-0120 and NOS 15-0150 of the
      same group.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Eighteen individuals in the delineating series (sixteen newly identified
    plus two previously reported). No denominator-based estimate exists, so the
    count is recorded rather than a rate.
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The sixteen affected individuals we identified, along with two previously
      reported individuals, present with a recognizable pattern of anomalies
    explanation: >-
      Gives the cohort size on which the entity was delineated, the basis for
      the rarity band recorded here.
inheritance:
- name: Autosomal dominant, de novo
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  de_novo_rate: "all reported cases"
  description: >-
    Every reported causal allele is de novo — either a missense substitution
    within the degron or a deletion removing it. The recurrence risk for parents
    of an affected child is therefore low, subject to the usual caveat of
    parental gonadal mosaicism.
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We describe an autosomal dominant disorder associated with de novo
      missense variants in the degron of AFF3, a nine amino acid sequence
      important for its binding to ubiquitin ligase, or with de novo deletions
      of this region.
    explanation: >-
      States the inheritance mode and both classes of de novo allele.
pathophysiology:
- name: Degron Disruption Stabilizing AFF3
  biological_scale: MOLECULAR
  genes:
  - preferred_term: AFF3
    term:
      id: hgnc:6473
      label: AFF3
  genetic_context:
    gene:
      preferred_term: AFF3
      term:
        id: hgnc:6473
        label: AFF3
    allele_type: degron missense substitution or degron-spanning microdeletion
    zygosity: HETEROZYGOUS
    variant_origin: DE_NOVO
  description: >-
    A degron is a short sequence that marks a protein for destruction. AFF3's is
    nine amino acids long and binds a ubiquitin ligase. Missense variants within
    it, and microdeletions removing it, both prevent that hand-off. The
    consequence is not loss of AFF3 but persistence of it: the variant classes
    converge on the same endpoint precisely because the motif's only job is to
    be recognized, so disrupting it by substitution or by excision is
    equivalent.
  molecular_functions:
  - preferred_term: AFF3 degron binding to ubiquitin ligase
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0031625
      label: ubiquitin protein ligase binding
  biological_processes:
  - preferred_term: Ubiquitin-dependent degradation of AFF3
    modifier: DECREASED
    term:
      id: GO:0043161
      label: proteasome-mediated ubiquitin-dependent protein catabolic process
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      de novo missense variants in the degron of AFF3, a nine amino acid
      sequence important for its binding to ubiquitin ligase, or with de novo
      deletions of this region
    explanation: >-
      Identifies the motif, its function, and the two allele classes that
      disrupt it — the whole content of this node.
  downstream:
  - target: Dysregulated Super Elongation Complex Activity
    causal_link_type: DIRECT
    description: >-
      An undegraded AFF3 persists in the complex it is a component of.
- name: Dysregulated Super Elongation Complex Activity
  biological_scale: CELLULAR
  description: >-
    AFF3 is one of four ALF paralogs (AFF1-AFF4) in the transcriptional super
    elongation complex, which releases paused RNA polymerase II at genes
    governing neurogenesis and development. Excess AFF3 therefore acts on
    transcriptional output rather than on any single structural protein, which
    is why the phenotype is multisystem. The paralogs are not interchangeable:
    AFF4 variants cause CHOPS syndrome, which overlaps KINSSHIP only partially,
    and the published transcriptome work argues each ALF factor contributes
    something distinct.
  biological_processes:
  - preferred_term: transcription elongation by RNA polymerase II
    modifier: DYSREGULATED
    term:
      id: GO:0006368
      label: transcription elongation by RNA polymerase II
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The ALF transcription factor paralogs, AFF1, AFF2, AFF3, and AFF4, are
      components of the transcriptional super elongation complex that regulates
      expression of genes involved in neurogenesis and development.
    explanation: >-
      Establishes the complex AFF3 belongs to and the class of genes it
      regulates.
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The only partial phenotypic overlap of AFF3- and AFF4-associated syndromes
      and the previously published transcriptome analyses of ALF transcription
      factors suggest that these factors are not redundant and each contributes
      uniquely to proper development.
    explanation: >-
      Supports the non-redundancy claim that makes a paralog-specific phenotype
      expected rather than surprising.
  downstream:
  - target: Multisystem Developmental Patterning Failure
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The intermediate targets through which altered elongation produces each
      organ phenotype are not identified.
- name: Multisystem Developmental Patterning Failure
  biological_scale: ORGANISM
  description: >-
    The convergent endpoint: mesomelic limb deformity, horseshoe kidney, brain
    malformation and seizures, hypertrichosis, and pulmonary involvement. The
    Aff3 knockout mouse develops skeletal anomalies, kidney defects, brain
    malformations, and neurological anomalies — the same organ set — which is
    the strongest available argument that these are one pleiotropy rather than
    coincidence.
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Whereas homozygous Aff3 knockout mice display skeletal anomalies, kidney
      defects, brain malformations, and neurological anomalies, knockin animals
      modeling one of the microdeletions and the most common of the missense
      variants identified in affected individuals presented with lower mesomelic
      limb deformities like KINSSHIP-affected individuals and early lethality,
      respectively.
    explanation: >-
      Reports both the knockout organ set and the allele-specific knockin
      phenotypes, which together support treating the human features as one
      pleiotropic consequence.
  downstream:
  - target: Mesomelic Limb Deformity
    causal_link_type: DIRECT
    description: >-
      The limb component, and the one the microdeletion knockin mouse
      reproduces directly.
  - target: Horseshoe Kidney
    causal_link_type: DIRECT
    description: >-
      Renal fusion is part of the same organ set the Aff3 knockout mouse
      develops.
  - target: Seizures
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Seizures follow the brain malformations that both the knockout mouse and
      affected individuals develop.
  - target: Intellectual Disability
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Cognitive impairment follows from the same neurodevelopmental lesion,
      compounded by the seizure burden where an epileptic encephalopathy is
      present.
  - target: Hypertrichosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Part of the recognizable pattern. No route from altered transcriptional
      elongation to the hair phenotype has been established.
  - target: Pulmonary Involvement
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Named in the syndrome acronym; neither the specific pulmonary lesion nor
      its mechanism is characterized in the delineating series.
phenotypes:
- category: Skeletal
  name: Mesomelic Limb Deformity
  description: >-
    Mesomelic shortening, radiographically likened to the Nievergelt and
    Savarirayan types but, per the nosology's own comment, not the same entity
    as either. The knockin mouse reproduces the lower-limb component.
  phenotype_term:
    preferred_term: Mesomelia
    term:
      id: HP:0003027
      label: Mesomelia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      present with a recognizable pattern of anomalies, which we named KINSSHIP
      syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of
      mesomelic dysplasia, S for seizures, H for hypertrichosis, I for
      intellectual disability, and P for pulmonary involvement)
    explanation: >-
      The acronym expansion in the delineating paper, which identifies the limb
      phenotype as a mesomelic dysplasia of Nievergelt/Savarirayan appearance.
- category: Renal
  name: Horseshoe Kidney
  phenotype_term:
    preferred_term: Horseshoe kidney
    term:
      id: HP:0000085
      label: Horseshoe kidney
  frequency: FREQUENT
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      present with a recognizable pattern of anomalies, which we named KINSSHIP
      syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of
      mesomelic dysplasia, S for seizures, H for hypertrichosis, I for
      intellectual disability, and P for pulmonary involvement)
    explanation: >-
      Horseshoe kidney is the first component of the syndrome-defining acronym
      quoted here in full.
- category: Neurologic
  name: Seizures
  description: >-
    Seizures are part of the core pattern and can take the form of an epileptic
    encephalopathy, which is named in the delineating paper's title and is the
    feature with the greatest bearing on developmental outcome.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  frequency: FREQUENT
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      present with a recognizable pattern of anomalies, which we named KINSSHIP
      syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of
      mesomelic dysplasia, S for seizures, H for hypertrichosis, I for
      intellectual disability, and P for pulmonary involvement)
    explanation: >-
      Seizures are a named component of the syndrome-defining acronym quoted here
      in full; the paper title additionally names epileptic encephalopathy.
- category: Neurologic
  name: Intellectual Disability
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      present with a recognizable pattern of anomalies, which we named KINSSHIP
      syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of
      mesomelic dysplasia, S for seizures, H for hypertrichosis, I for
      intellectual disability, and P for pulmonary involvement)
    explanation: >-
      Intellectual disability is a named component of the syndrome-defining
      acronym quoted here in full, and of the paper title.
- category: Integumentary
  name: Hypertrichosis
  phenotype_term:
    preferred_term: Hypertrichosis
    term:
      id: HP:0000998
      label: Hypertrichosis
  frequency: FREQUENT
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      present with a recognizable pattern of anomalies, which we named KINSSHIP
      syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of
      mesomelic dysplasia, S for seizures, H for hypertrichosis, I for
      intellectual disability, and P for pulmonary involvement)
    explanation: >-
      Hypertrichosis is a named component of the syndrome-defining acronym quoted
      here in full.
- category: Respiratory
  name: Pulmonary Involvement
  phenotype_term:
    preferred_term: Abnormal lung morphology
    term:
      id: HP:0002088
      label: Abnormal lung morphology
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      present with a recognizable pattern of anomalies, which we named KINSSHIP
      syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of
      mesomelic dysplasia, S for seizures, H for hypertrichosis, I for
      intellectual disability, and P for pulmonary involvement)
    explanation: >-
      Pulmonary involvement is a named component of the syndrome-defining acronym
      quoted here in full. The abstract does not specify which pulmonary
      abnormality, so the HP binding is deliberately general and this is PARTIAL.
genetic:
- name: AFF3
  gene_term:
    preferred_term: AFF3
    term:
      id: hgnc:6473
      label: AFF3
  relationship_type: CAUSATIVE
  notes: >-
    AF4/FMR2 family member 3, an ALF-family component of the transcriptional
    super elongation complex. The pathogenic alleles are confined to a
    nine-residue degron — an unusually tight variant-location constraint, which
    is diagnostically useful: a missense variant elsewhere in AFF3 should not be
    called causal for KINSSHIP on the strength of the gene alone. Note also that
    a GCC repeat expansion in AFF3 has been separately associated with disease;
    that is a different allele class and is not curated here.
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We describe an autosomal dominant disorder associated with de novo
      missense variants in the degron of AFF3, a nine amino acid sequence
      important for its binding to ubiquitin ligase, or with de novo deletions
      of this region.
    explanation: >-
      Establishes AFF3 as causative and localizes the pathogenic alleles to the
      degron.
animal_models:
- name: Aff3 degron knockin mouse
  species: Mouse
  genotype: Aff3 degron microdeletion knockin; Aff3 recurrent degron missense knockin
  publication: PMID:33961779
  description: >-
    Two allele-matched knockin lines, one modelling a patient microdeletion and
    one the most common patient missense variant. They separate cleanly: the
    microdeletion line shows the limb phenotype, the missense line dies early.
  modeled_mechanisms:
  - target: Multisystem Developmental Patterning Failure
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      The microdeletion knockin reproduces the lower mesomelic limb deformity
      seen in affected individuals.
    limitations: >-
      Only the lower-limb component is reported as recapitulated, and the
      missense knockin's early lethality means the allele closest to the common
      human variant cannot be phenotyped for the multisystem pattern at all —
      the more severe model is the less informative one.
    readouts:
    - name: Lower limb mesomelic deformity
      target: Multisystem Developmental Patterning Failure
      direction: ALTERED
      interpretation: >-
        The limb deformity is the measured point of correspondence between mouse
        and human.
      evidence:
      - reference: PMID:33961779
        reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          knockin animals modeling one of the microdeletions and the most common
          of the missense variants identified in affected individuals presented
          with lower mesomelic limb deformities like KINSSHIP-affected
          individuals and early lethality, respectively
        explanation: >-
          Reports the limb phenotype in the microdeletion knockin and the early
          lethality of the missense knockin.
    evidence:
    - reference: PMID:33961779
      reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        knockin animals modeling one of the microdeletions and the most common
        of the missense variants identified in affected individuals presented
        with lower mesomelic limb deformities like KINSSHIP-affected
        individuals and early lethality, respectively
      explanation: >-
        Allele-matched knockins are the strongest available argument that the
        degron alleles cause the human phenotype.
- name: AFF3-overexpressing zebrafish
  species: Zebrafish
  genotype: AFF3 mRNA overexpression
  publication: PMID:33961779
  description: >-
    A dosage experiment rather than an allele model: human AFF3 overexpressed in
    zebrafish produces body axis anomalies, testing whether more AFF3 is
    pathogenic at all.
  modeled_mechanisms:
  - target: Degron Disruption Stabilizing AFF3
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      Supports the inference that the disease arises from increased AFF3 amount
      rather than from loss of it.
    limitations: >-
      Overexpression is not the same perturbation as impaired degradation, the
      readout is a body-axis anomaly rather than any KINSSHIP feature, and the
      paper's own wording ("providing some support") is deliberately weak.
    evidence:
    - reference: PMID:33961779
      reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Overexpression of AFF3 in zebrafish resulted in body axis anomalies,
        providing some support for the pathological effect of increased amount
        of AFF3.
      explanation: >-
        The source states both the result and its limited evidential weight;
        this link records it at that strength.
diagnosis:
- name: Recognition of the KINSSHIP Pattern
  description: >-
    Suspected from the co-occurrence of mesomelic limb shortening with horseshoe
    kidney and a developmental/epilepsy phenotype — a combination that no other
    mesomelic dysplasia produces. Renal imaging is therefore the cheap
    discriminator: a horseshoe kidney alongside mesomelia effectively excludes
    the SHOX and HOXD mesomelic dysplasias.
  diagnosis_term:
    preferred_term: physical examination
    term:
      id: NCIT:C20989
      label: Physical Examination
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      present with a recognizable pattern of anomalies, which we named KINSSHIP
      syndrome
    explanation: >-
      Supports the claim that the combination is clinically recognizable as a
      pattern.
- name: Molecular Confirmation of a Degron Variant
  description: >-
    Confirmed by a de novo missense variant within, or a deletion spanning, the
    AFF3 degron. Because the causal alleles occupy nine codons, variant
    interpretation should weight location heavily; exome or genome sequencing
    with copy-number analysis is needed, since the deletion class will be missed
    by sequence calling alone.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      de novo missense variants in the degron of AFF3, a nine amino acid
      sequence important for its binding to ubiquitin ligase, or with de novo
      deletions of this region
    explanation: >-
      Names both allele classes that establish the diagnosis, including the
      deletion class that sequence-only analysis would miss.
differential_diagnoses:
- name: CHOPS syndrome
  description: >-
    Caused by variants in the paralog AFF4, also a super elongation complex
    component. The overlap with KINSSHIP is explicitly partial, which is itself
    evidence that the ALF paralogs are not functionally redundant.
  evidence:
  - reference: PMID:33961779
    reference_title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      partially overlapping the AFF4-associated CHOPS syndrome
    explanation: >-
      States the relationship between the two paralog syndromes.
- name: Mesomelic dysplasia, Nievergelt type
  description: >-
    Named in the KINSSHIP acronym for radiographic resemblance, but a separate
    row of the same nosology group and, per the nosology's own comment, quite a
    different condition. Nievergelt type has no renal or neurodevelopmental
    component.
- name: Mesomelic dysplasia, Savarirayan type
  description: >-
    The other type named in the acronym; an ID4-related 6p22.3 microdeletion
    disorder, again a separate row of group 15 and without the KINSSHIP
    multisystem pattern.
discussions:
- discussion_id: aff3_dosage_direction
  kind: KNOWLEDGE_GAP
  prompt: >-
    Is KINSSHIP syndrome caused by increased AFF3 protein dosage, and if so is
    the excess protein acting through the super elongation complex or through
    some degradation-independent function?
  attaches_to:
  - pathophysiology#Degron Disruption Stabilizing AFF3
  rationale: >-
    The degron mechanism predicts stabilization, and zebrafish overexpression
    produces a phenotype, but the delineating paper describes that as "some
    support" rather than proof, and no measurement of AFF3 protein level in
    patient cells is reported. The distinction is actionable: if the disease is
    a dosage excess of an otherwise normal protein, lowering AFF3 is a coherent
    therapeutic hypothesis, whereas if the stabilized protein has acquired a
    neomorphic activity it is not.
- discussion_id: kinsship_missense_knockin_lethality
  kind: HUMAN_MODEL_MISMATCH
  prompt: >-
    Why is the mouse knockin of the most common human KINSSHIP missense variant
    lethal when the human variant is compatible with survival into childhood and
    beyond?
  attaches_to:
  - animal_models#Aff3 degron knockin mouse
  rationale: >-
    Allele-matched knockins are the strongest model design available, and here
    the closest-matched allele produces early lethality rather than the human
    syndrome, while the less-matched microdeletion allele produces the limb
    phenotype. Something — species difference in AFF3 dosage tolerance, paralog
    compensation, or genetic background — separates the mouse from the human
    response to the same substitution. Until that is understood, the mouse
    cannot be used to test interventions against the multisystem phenotype,
    which is the use a model of this disease would most be wanted for.
references:
- reference: PMID:33961779
  title: "Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy."
- reference: PMID:36779427
  title: "Nosology of genetic skeletal disorders: 2023 revision."
📚

References & Deep Research

References

2
PMID:33961779
Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy.
No top-level findings curated for this source.
PMID:36779427
Nosology of genetic skeletal disorders: 2023 revision.
No top-level findings curated for this source.