| domain | best-supported finding | evidence type/strength | suggested ontology terms |
|---|---|---|---|
| Disease / gene / inheritance | Taurine transporter deficiency is a Mendelian disorder caused by biallelic loss-of-function or severe hypomorphic variants in **SLC6A6** (TauT), with autosomal recessive segregation in all reported families. Human evidence currently includes 2 affected siblings in one consanguineous family and 7 affected individuals from 4 unrelated families. (pqac-00000025, pqac-00000029) | Direct human genetic and clinical evidence; strongest available but based on very small case series | SLC6A6; taurine transporter deficiency; autosomal recessive inheritance; MONDO term label if added in future |
| Retinal phenotype | Core phenotype is early-onset retinal degeneration spanning **Leber congenital amaurosis / early-onset retinal dystrophy** with poor vision or nystagmus from birth or early childhood, extinguished or severely depressed ERG, macular atrophy, pigmentary degeneration, and photoreceptor loss on OCT. (pqac-00000024, pqac-00000027, pqac-00000029) | Direct human clinical evidence; consistent across all known cases | HP: Nystagmus; HP: Visual impairment; HP: Night blindness; HP: Abnormal electroretinogram; HP: Macular atrophy; HP: Retinal degeneration; Leber congenital amaurosis; early-onset retinal dystrophy |
| Cardiac phenotype | Cardiomyopathy was prominent in the 2020 family, with mild hypokinetic cardiomyopathy, systolic dysfunction, and LV dilation; in the expanded cohort, a shared structural cardiomyopathy phenotype was **not** consistently present, though short PR intervals were recurrent and cardiology follow-up was advised. (pqac-00000024, pqac-00000023, pqac-00000020, pqac-00000021) | Direct human evidence; variable expressivity, small numbers | HP: Cardiomyopathy; HP: Left ventricular dilatation; HP: Systolic dysfunction; HP: Short PR interval; cardiovascular system |
| Biochemical marker | Fasting plasma taurine is markedly reduced in affected individuals; the index family had nearly undetectable levels (**6–7 μmol/L**), and the multicenter cohort showed significantly lower taurine versus carriers and controls. (pqac-00000025, pqac-00000029) | Direct human biochemical evidence; strong disease biomarker | taurine (CHEBI:15891); HP: Abnormal circulating amino acid concentration; low plasma taurine |
| Pathogenic variants | Reported disease-associated variants include **NM_003043.5:c.1196G>T p.(Gly399Val)** with ~15% residual transport, **NM_003043.6:c.746C>T p.(Thr249Ile)**, **c.880G>A p.(Ala294Thr)**, **c.1210-2389_1348-331del p.(Phe404_Glu449del)**, and **c.338G>A p.(Trp113Ter)**. Missense variants showed severe to complete transport loss; truncating/deletion alleles support loss of function. (pqac-00000025, pqac-00000026, pqac-00000027, pqac-00000029) | Direct human molecular evidence with functional validation for key alleles | SLC6A6 missense variant; nonsense variant; exon deletion; loss of function; hypomorphic allele |
| Diagnosis | Best-supported diagnostic approach is **molecular testing of SLC6A6** in patients with LCA/EORD plus **fasting plasma taurine measurement**, retinal phenotyping (visual acuity, full-field ERG, multimodal imaging/OCT), and where possible functional transport or membrane-trafficking assays in HEK-293 cells or patient fibroblasts. (pqac-00000024, pqac-00000029) | Direct human evidence; practical but not yet standardized by guidelines | whole-exome sequencing; genome sequencing; Sanger confirmation; electroretinography; optical coherence tomography; plasma taurine assay |
| Treatment | **Oral taurine supplementation** is the only disease-directed intervention reported. In the index family, **100 mg/kg/day** normalized blood taurine, reversed systolic cardiomyopathy after 24 months, and arrested retinal degeneration with clinical visual improvement in the younger child; a later retinal-only case normalized plasma taurine on **1–2 g/day** but had no short-term ophthalmic improvement. No side effects were reported in the treated family. (pqac-00000025, pqac-00000023, pqac-00000028) | Direct human therapeutic evidence; promising but limited to anecdotal/case evidence | taurine supplementation; oral administration; NCIT term label: Dietary Supplementation; investigational therapy |
| Mechanism / pathophysiology | Disease mechanism is impaired TauT-mediated taurine uptake from biallelic **SLC6A6** dysfunction, causing cellular taurine deficiency. Human functional work shows markedly reduced or absent transport; modeling places pathogenic residues in transmembrane regions important for ligand recognition, folding, trafficking, and transport cycling. Review/model literature supports downstream osmotic, mitochondrial, oxidative-stress, calcium-handling, and anti-apoptotic defects. (pqac-00000024, pqac-00000026, pqac-00000013, pqac-00000016) | Mixed evidence: direct human functional evidence for transport loss; broader downstream mechanisms mainly model/review inference | sodium/chloride-dependent taurine transport; plasma membrane; mitochondrial dysfunction; oxidative stress; apoptosis; osmoregulation |
| Affected anatomy / cells | Highest-confidence affected structures are **retina** and **heart**. Within retina, human OCT/ERG data and model literature support major involvement of **photoreceptors**; retinal ganglion cell vulnerability is supported mainly by depletion models. Cardiac myocytes are implicated by the cardiomyopathy phenotype. (pqac-00000024, pqac-00000023, pqac-00000014) | Retina/heart: direct human evidence; specific cell-type detail partly inferred from models | UBERON: retina; UBERON: heart; photoreceptor cell; retinal ganglion cell; cardiomyocyte |
| Animal models | **Slc6a6/TauT knockout mice** develop retinal degeneration, cardiomyopathy/cardiac atrophy, skeletal muscle abnormalities, reproductive defects, and age-related multi-organ manifestations; chemically induced taurine depletion also causes photoreceptor and retinal ganglion cell loss. Taurine-deficient cats and dogs provide natural/comparative evidence for retinal degeneration and reversible cardiomyopathy. (pqac-00000023, pqac-00000009, pqac-00000011, pqac-00000010) | Model and veterinary evidence; strong biologic support but indirect for human disease spectrum | knockout mouse model; taurine depletion model; retinal degeneration; dilated cardiomyopathy |
| Epidemiology / gaps | Prevalence, incidence, carrier frequency, penetrance, genotype-phenotype correlations, long-term natural history, and formal management guidelines are **not established**. No disease-specific registered interventional trial was identified in the tool search; current evidence remains based on rare case reports/series. (pqac-00000019, pqac-00000021) | Evidence gap / absence of data | rare disease; unknown prevalence; unknown penetrance; research gap |
| Recent developments | The key recent advance is the expanded multicenter cohort published online in **2025** showing 7 affected individuals from 4 families, broader allelic heterogeneity, consistent retinal phenotype, and functional confirmation of complete taurine transport loss for missense variants. No disease-specific 2023–2024 primary human expansion was identified in the retrieved evidence. (pqac-00000029, pqac-00000026) | Direct human evidence for 2025 expansion; explicit 2023–2024 evidence gap | cohort expansion; variant spectrum; functional validation |


*Table: This table summarizes the best-supported knowledge for SLC6A6-related taurine transporter deficiency across clinical, molecular, mechanistic, and translational domains. It is designed for knowledge-base use and clearly separates direct human evidence from model-based inference and current evidence gaps.*