| Domain | Established finding | Evidence type | Confidence or limitation |
|---|---|---|---|
| Human genetic evidence | One four-generation Chinese pedigree with 37 members linked DFNA72 to heterozygous **SLC44A4 c.466A>G (p.Met156Val)**. The variant occurred in all 8 tested affected relatives and none of 13 tested unaffected relatives; it was also absent from 1,000 ethnically matched controls and 500 sporadic hearing-loss cases. (pqac-00000000, pqac-00000002, pqac-00000006) | Human pedigree; whole-exome sequencing; Sanger segregation; case-control screening | Strong within-family segregation and rarity evidence, but only one pedigree and one candidate variant have been reported; independent human replication was not identified through 2024. |
| Clinical phenotype | Postlingual tinnitus and sensorineural hearing loss began at approximately **26–30 years**. Early loss primarily involved **0.5–4 kHz**, especially **1–2 kHz**, with approximately **40–50 dB HL** thresholds and a U-shaped or bowl-shaped audiogram; it progressed to involve all frequencies while generally retaining the mid-frequency configuration. (pqac-00000000, pqac-00000002, pqac-00000007) | Human clinical and audiometric observations | Findings were consistent among reported affected relatives, but phenotype frequencies and severity estimates cannot be generalized beyond the single family. |
| Nonsyndromic classification | Tympanometry and temporal-bone imaging were normal. No retrocochlear disorder, vertigo, ototoxic-drug or sustained-noise exposure, or cardiovascular, diabetic, visual, neurologic, or other syndromic manifestations were reported. (pqac-00000000, pqac-00000003) | Human clinical examination; auditory brainstem response; CT and MRI; exposure history | Supports nonsyndromic sensorineural hearing loss in the original pedigree, although long-term surveillance data are limited. |
| Cellular function | In SH-SY5Y cells, mutant SLC44A4 produced lower **radiolabeled choline uptake** and reduced **acetylcholine synthesis** relative to wild-type SLC44A4. (pqac-00000001, pqac-00000004, pqac-00000010) | In-vitro transfection and biochemical assays | Supports impaired transporter activity, but SH-SY5Y cells are not native human olivocochlear neurons or cochlear cells; the precise dominant mechanism remains unresolved. |
| Proposed pathophysiology | Reduced choline transport is proposed to limit acetylcholine production and release by medial olivocochlear neurons, weakening efferent regulation and protection of outer hair cells and thereby causing progressive hearing loss. (pqac-00000001, pqac-00000005, pqac-00000009) | Mechanistic inference integrating cellular assays and auditory physiology | Biologically plausible but not demonstrated directly in affected human cochleae; haploinsufficiency, dominant-negative activity, and gain of function have not been distinguished. |
| Zebrafish model | Morpholino-mediated **slc44a4** knockdown caused abnormal otoliths, fewer or malformed inner-ear and lateral-line hair cells and neuromasts, abnormal stereocilia, and balance or startle deficits. Human SLC44A4 RNA rescued otolith, hair-cell, stereocilia, and hearing phenotypes. (pqac-00000003, pqac-00000005) | Zebrafish loss-of-function and rescue experiments | Supports conserved auditory function and gene-level causality, but morpholino knockdown is not a p.Met156Val knock-in and may model loss of function rather than the human dominant allele. |
| Epidemiology and replication | No disease-specific prevalence, incidence, carrier-frequency, founder-effect, sex-ratio, or geographic estimates were identified. No additional independently replicated DFNA72 family was found through 2024. | Evidence-gap assessment | DFNA72 appears exceptionally rare, but its population frequency and gene-disease validity cannot be quantified confidently from available evidence. |
| Treatment and trials | No SLC44A4-targeted drug, gene therapy, RNA therapy, or DFNA72-specific clinical trial was identified. Current care is supportive: serial audiometry, hearing aids when beneficial, communication rehabilitation, and cochlear-implant evaluation for severe or profound functional loss. | Standard hearing-loss management extrapolated to DFNA72; clinical-trial evidence gap | No DFNA72-specific response rates or comparative outcomes are available; supportive interventions do not correct the molecular defect. |


*Table: Compact evidence map summarizing the human genetic, clinical, cellular, zebrafish, epidemiologic, and treatment evidence for SLC44A4-associated DFNA72. It emphasizes that the association rests on one pedigree despite supportive functional experiments.*