Usher Syndrome Research Articles

Nuclear–Cytoplasmic Shuttling of the Usher Syndrome 1G Protein SANS Differs from Its Paralog ANKS4B

The USH1G protein SANS is a small multifunctional scaffold protein. It is involved in several different cellular processes, such as intracellular transport, in the cytoplasm, or splicing of pre-mRNA, in the cell nucleus. Here, we aimed to gain insight into the regulation of the subcellular localization and the nuclear–cytoplasmic shuttling of SANS and its paralog ANKS4B, not yet reported in the nucleus. We identified karyopherins mediating the nuclear import and export by screening the nuclear interactome of SANS. Sequence analyses predicted in silico evolutionarily conserved nuclear localization sequences (NLSs) and nuclear export sequences (NESs) in SANS, but only NESs in ANKS4B, which are suitable for karyopherin binding. Quantifying the nuclear–cytoplasmic localization of wild-type SANS and NLS/NES mutants, we experimentally confirmed in silico predicted NLS and NES functioning in the nuclear–cytoplasmic shuttling in situ in cells. The comparison of SANS and its paralog ANKS4B revealed substantial differences in the interaction with the nuclear splicing protein PRPF31 and in their nuclear localization. Finally, our results on pathogenic USH1G/SANS mutants suggest that the loss of NLSs and NESs and thereby the ability to control nuclear–cytoplasmic shuttling is disease-relevant.

Fine-scale genetic structure and rare variant frequencies.

In response to the current challenge in genetic studies to make new associations, we advocate for a shift toward leveraging population fine-scale structure. Our exploration brings to light distinct fine-structure within populations having undergone a founder effect such as the Ashkenazi Jews and the population of the Quebec' province. We leverage the fine-scale population structure to explore its impact on the frequency of rare variants. Notably, we observed an 8-fold increase in frequency for a variant associated with the Usher syndrome in one Quebec subpopulation. Our study underscores that smaller cohorts with greater genetic similarity demonstrate an important increase in rare variant frequencies, offering a promising avenue for new genetic variants' discovery.

CRISPR-Mediated Gene Editing Tool Development for Patients with Usher Syndrome Type II

Usher syndrome, a rare genetic disease affecting hearing and vision, is an autosomal recessive condition affecting 4 to 17 per 100,000 people and accounting for about 50 percent of hereditary deaf-blindness cases. Usher syndrome type II is caused by mutations of the USH2A gene, a 15.7 kb gene encoding the protein usherin, which localizes to photoreceptor cilium and cochlear hair cells. This subtype of Usher syndrome includes hearing loss from birth and progressive loss of vision, prompting retinitis pigmentosa (RP). Prime editing is a viable option for addressing USH2A mutations and restoring usherin expression and function. To begin, a HEK293T cell line needs to be established for subsequent testing of prime editors. Since prime editing to make the cell line was unsuccessful, homology-directed repair was done and successfully created a cell population with the mutation of interest (single base-pair deletion). Now that this cell population has been created, prime editors will be tested and optimized to address the mutation in a HEK293T cell line and potentially patient-derived induced pluripotent stem cells that are differentiated into photoreceptor precursor cells.

PCDH15 Dual-AAV Gene Therapy for Deafness and Blindness in Usher Syndrome Type 1F Models.

Usher syndrome type 1F (USH1F), resulting from mutations in the protocadherin-15 (PCDH15) gene, is characterized by congenital lack of hearing and balance, and progressive blindness in the form of retinitis pigmentosa. In this study, we explore an approach for USH1F gene therapy, exceeding the single AAV packaging limit by employing a dual adeno-associated virus (AAV) strategy to deliver the full-length PCDH15 coding sequence. We demonstrate the efficacy of this strategy in mouse USH1F models, effectively restoring hearing and balance in these mice. Importantly, our approach also proves successful in expressing PCDH15 protein in clinically relevant retinal models, including human retinal organoids and non-human primate retina, showing efficient targeting of photoreceptors and proper protein expression in the calyceal processes. This research represents a major step toward advancing gene therapy for USH1F and the multiple challenges of hearing, balance, and vision impairment.

Impact of Usher syndrome on athletic performance - navigating silence and darkness

Usher syndrome (USH) is an autosomal recessive genetic disorder and a leading cause of simultaneous hearing and vision loss. The aim of this paper is to provide a detailed review of Usher syndrome, including its pathogenesis, clinical symptoms, diagnostic methods, the role of sport in the lives of athletes and sportspeople with Usher syndrome and available therapeutic options. Understanding this disease is crucial for early detection and the implementation of appropriate therapeutic interventions. Currently, Usher syndrome is classified into three main types (I, II, and III), differentiated by the degree and progression of hearing and vision loss. Type I is characterized by profound congenital deafness and early-onset retinitis pigmentosa. Type II presents with moderate to severe hearing loss and later onset of visual problems. Type III is the rarest, with progressive hearing and vision loss that occurs later in life. The genetic basis of Usher syndrome is linked to mutations in various genes that affect proteins essential for the proper functioning of the inner ear and retina. Early diagnosis and an interdisciplinary approach to treatment are key to improving the quality of life for those affected by this disease. Ongoing research into the genetic mechanisms and potential therapies offers hope for future successful treatments.

Intestinal Tuft Cells Are Enriched With Protocadherins.

Intestinal tuft cells are rare cells that regulate diverse functions. They harbor chemosensory receptors and signal to the mucosal immune system in response to external stimuli, though their full function and structure remain unclear. Named for their apical "tuft" of long actin-rich microvilli, tuft cells facilitate chemoreception and other physiological responses. In enterocytes, microvilli are stabilized by intermicrovillar adhesion complexes (IMACs) composed of several proteins, including cadherin-related family member-2 (CDHR2) and cadherin-related family member-5 (CDHR5), Myosin 7b, and Usher syndrome type 1 C (USH1C). We hypothesized that IMACs would be enriched in tuft cells to regulate microvillar organization. Immunostaining of murine intestinal tissue revealed that CDHR2 and CDHR5 colocalize with the tuft cell markers, DCLK1, phospho-EGFR, advillin, and cytokeratin 18. CDHR2 was dispersed throughout murine tuft cells, while CDHR5 was concentrated on the apical surface. USH1C and Myosin 7b were present in tuft cells, but at lower levels. Human single-cell RNA sequencing revealed robust CDHR2 and CDHR5 expression in tuft cells in the small intestine and colon. Immunostaining of human intestinal tissue confirmed CDHR2 and CDHR5 localization to the apical surface of tuft cells. Our findings demonstrate that protocadherins are key components of murine and human intestinal tuft cells.

Exploring non-coding variants and evaluation of antisense oligonucleotides for splicing redirection in Usher syndrome

Exploring non-coding variants and evaluation of antisense oligonucleotides for splicing redirection in Usher syndrome

A rare transcript homozygous variants in CLRN1(USH3A) causes Usher syndrome type 3 in a Chinese family

BackgroundUsher syndrome type 3 (USH3) is an autosomal recessive inherited disorder caused by pathogenic variants in the CLRN1 gene.ObjectTo evaluate the genotype-phenotype correlation of Usher syndrome type 3 (USH3) in a deaf-blind Chinese family of 3 generations with 2 patients.MethodsWe collected blood samples and clinical data from all of the pedigree family members. Genomic DNA was isolated from peripheral leukocytes using standard method. Targeted next generation sequencing and Sanger sequencing were performed to find the pathogenic variants in this family. Digital PCR and plasmid overexpression assay were used to verify the pathogenicity of variant sites in different transcripts.ResultsAll patients developed bilateral sensorineural hearing loss (SHL), progressive vision loss and nyctalopia. NGS of genes for Usher syndrome, deafness and retinal dystrophy identified a locus mutation in CLRN1 that caused completely different amino acid changes in different transcripts[CLRN1:c.474T > A(P.Cys158Ter) at NM_001256819.2 or c.302T > A(p.Val101Asp) at NM_174878.3], and plasmid overexpression experiments confirmed that the c.474T > A(P.Cys158Ter, NM_001256819.2) was a pathogenic variant which has never been associated with Usher syndrome in China, and the transcript of this mutation was not the version commonly found worldwide.ConclusionsThe CLRN1c.474T > A(NM_001256819.2) mutation is the causative variant in the Chinese family with USH3. The pathogenicity of different transcripts should be particularly considered in pathogenicity analysis.

Genotype Characterization and MiRNA Expression Profiling in Usher Syndrome Cell Lines.

Usher syndrome (USH) is an inherited disorder characterized by sensorineural hearing loss (SNHL), retinitis pigmentosa (RP)-related vision loss, and vestibular dysfunction. USH presents itself as three distinct clinical types, 1, 2, and 3, with no biomarker for early detection. This study aimed to explore whether microRNA (miRNA) expression in USH cell lines is dysregulated compared to the miRNA expression pattern in a cell line derived from a healthy human subject. Lymphocytes from USH patients and healthy individuals were isolated and transformed into stable cell lines using Epstein-Barr virus (EBV). DNA from these cell lines was sequenced using a targeted panel to identify gene variants associated with USH types 1, 2, and 3. Microarray analysis was performed on RNA from both USH and control cell lines using NanoString miRNA microarray technology. Dysregulated miRNAs identified by the microarray were validated using droplet digital PCR technology. DNA sequencing revealed that two USH patients had USH type 1 with gene variants in USH1B (MYO7A) and USH1D (CDH23), while the other two patients were classified as USH type 2 (USH2A) and USH type 3 (CLRN-1), respectively. The NanoString miRNA microarray detected 92 differentially expressed miRNAs in USH cell lines compared to controls. Significantly altered miRNAs exhibited at least a twofold increase or decrease with a p value below 0.05. Among these miRNAs, 20 were specific to USH1, 14 to USH2, and 5 to USH3. Three miRNAs that are known as miRNA-183 family which are crucial for inner ear and retina development, have been significantly downregulated as compared to control cells. Subsequently, droplet digital PCR assays confirmed the dysregulation of the 12 most prominent miRNAs in USH cell lines. This study identifies several miRNA signatures in USH cell lines which may have potential utility in Usher syndrome identification.

Chronic Psychosis in a Patient with Usher Syndrome

Abstract Usher syndrome refers to a group of inherited disorders characterized by visual and auditory impairment. The risk of psychosis in Usher syndrome is higher than that in the general population and is difficult to approach and treat in light of sensory impairment. We present a case of a male with continuous psychotic symptoms for 20 years, in the setting of undiagnosed progressively deteriorating visual and auditory function, with details of treatment given. Possible underlying mechanisms of psychosis in such cases are discussed in brief.

Identification of novel likely pathogenic variant in CDH23 causing non-syndromic hearing loss, and a novel variant in OTOGL in an extended Iranian family

BackgroundSensorineural hearing loss (SNHL) is a clinically and genetically heterogeneous group of disorders of the auditory system. SNHL can occur as a symptom in more than 400 syndromes, and mutations in more than 150 genes can lead to SNHL. Mutations in the GJB2 and GJB6 genes are among the most common causes of SNHL worldwide. Mutations in Cadherin 23 (CDH23) can cause Usher syndrome and/or non-syndromic hearing loss (NSHL).Material and methodsIn this study, the Whole Exome Sequencing (WES) was used to detect the cause of hearing loss in a large consanguineous Iranian family with two patients. All family members underwent a thorough Genotype–phenotype correlation assessment and co-segregation analysis to understand the inheritance pattern within the family. The candidate variants were further confirmed by Sanger sequencing. In addition, in silico analysis was performed to predict the functional impact of the variants; the interpretation of the variants was performed in accordance with the American College of Medical Genetics (ACMG) guidelines.ResultsWES results identified two novel variants, a homozygous missense variant in CDH23 (c.2961T > G) and a heterozygous splice site variant in OTOGL that was compatible with the autosomal recessive pattern of inheritance. Bioinformatics studies confirmed the pathogenic effects of novel variants. The c.2961T > G variant was classified as likely pathogenic.ConclusionsThe novel identified variant in the CDH23 was the cause of congenital profound progressive form of HL. Samples were not available from the second family to distinguish which variant is responsible for the molecular pathology of the disease. Further studies and functional examinations are suggested for investigating the role of OTOGL: c. 1863-1G > T in deafness.

Cochlear implantation in syndromic patients: difficulties and lessons learnt.

Identify the prevalence of syndromes in a cohort of patients who underwent cochlear implantation, to report on the presence of inner and middle ear malformations and highlight the surgical difficulties encountered. Observational, retrospective study. Tertiary referral children's hospital pediatric cochlear implant program. An IRB-approved retrospective chart review of children undergoing cochlear implantation at a tertiary academic medical center, from 2018 to 2023. Preoperative imaging data of syndromic patients in that cohort with special attention to the presence of inner ear or middle ear malformations were collected. Abnormal intraoperative findings and difficulties reported by the surgeons were also noted. 1024 children were unilaterally implanted for bilateral profound hearing loss. There were 45 cases diagnosed with associated syndromes (4.3%). The commonest syndromes were Jervell and Lange Nielsen (JLN) syndrome followed by Waardenberg syndrome (WS), in a prevalence of 34% and 32% respectively. These syndromes had no associated inner ear malformations (IEM). Less common syndromes included Branchio-oto-renal (BOR) syndrome, CHARGE association and Treacher Collins syndrome, 3 cases each, and keratosis icthyosis deafness syndrome (KID), Usher syndrome and Albino, 2 cases each and an H syndrome case. There were 9 cases (20%) with IEM, with 6 cases of perilymph gusher. Two cases had middle ear anomalies and one case had a facial nerve course abnormality. The outcome of these cases was similar to non-syndromic cases. Children with syndromic HL should be dealt with on a case by case scenario to diagnose inner and middle ear malformations. Additional disabilities can affect the rehabilitation procedures. All children with congenital hearing loss should undergo pediatric, cardiologic, ophthalmologic and nephrologic examination in order to exclude the syndromic etiology of hearing loss.

Expanding the genetic landscape of Usher syndrome type IV caused by pathogenic ARSG variants.

Usher syndrome (USH) is the most common cause of deafblindness. USH is autosomal recessively inherited and characterized by rod-cone dystrophy or retinitis pigmentosa (RP), often accompanied by sensorineural hearing loss. Variants in >15 genes have been identified as causative for clinically and genetically distinct subtypes. Among the ultra-rare and recently discovered genes is ARSG, coding for the lysosomal sulfatase Arylsulfatase G. This subtype was assigned as "USH IV" with a late onset of RP and usually late-onset progressive SNHL without vestibular involvement. Here, we describe nine new subjects and the clinical description of four cases with the USH IV phenotype bearing seven novel and two known pathogenic variants. Functional experiments indicated the complete loss of sulfatase enzymatic activity upon ectopic expression of mutated ARSG cDNA. Interestingly, we identified a homozygous missense variant, p.(Arg99His), previously described in dogs with neuronal ceroid lipofuscinosis. Our study expands the genetic landscape of ARSG-USH IV and the number of known subjects by more than 30%. These findings highlight that USH IV likely has been underdiagnosed and emphasize the need to test molecularly unresolved subjects with deafblindness syndrome. Finally, testing of ARSG should be considered for the genetic work-up of apparent isolated inherited retinal diseases.

MultiBac System-based Purification and Biophysical Characterization of Human Myosin-7a.

Myosin-7a is an actin-based motor protein vital for auditory and visual processes. Mutations in myosin-7a lead to Usher syndrome type 1, the most common and severe form of deaf-blindness in humans. It is hypothesized that myosin-7a forms a transmembrane adhesion complex with other Usher proteins, essential for the structural-functional integrity of photoreceptor and cochlear hair cells. However, due to the challenges in obtaining pure, intact protein, the exact functional mechanisms of human myosin-7a remain elusive, with limited structural and biomechanical studies available. Recent studies have shown that mammalian myosin-7a is a multimeric motor complex consisting of a heavy chain and three types of light chains: regulatory light chain (RLC), calmodulin, and calmodulin-like protein 4 (CALML4). Unlike calmodulin, CALML4 does not bind to calcium ions. Both the calcium-sensitive, and insensitive calmodulins are critical for mammalian myosin-7a for proper fine-tuning of its mechanical properties. Here, we describe a detailed method to produce recombinant human myosin-7a holoenzyme using the MultiBac Baculovirus protein expression system. This yields milligram quantities of high-purity full-length protein, allowing for its biochemical and biophysical characterization. We further present a protocol for assessing its mechanical and motile properties using tailored in vitro motility assays and fluorescence microscopy. The availability of the intact human myosin-7a protein, along with the detailed functional characterization protocol described here, paves the way for further investigations into the molecular aspects of myosin-7a in vision and hearing.

A novel compound heterozygous variant of MYO7A in Usher syndrome type 1

Usher syndrome (USH) is a recessive genetic disorder manifested by congenital sensorineural hearing loss and progressive retinitis pigmentosa, which leads to audiovisual impairment. We report a patient with Usher syndrome type 1 with new compound heterozygous MYO7A variants. A total of four members from the USH family were included. Medical history and retinal examinations were taken and genomic DNA from peripheral blood was extracted in the proband and other members. 381 retinal disease-associated genes were screened using targeted sequence capture array technology and Sanger sequencing was used to confirm the screening results. Scanning laser ophthalmoscope showed bone spicule pigmentary deposits in the mid-peripheral retina and whitish and thin retinal blood vessels especially in the arterioles. Optical coherence tomography showed that the centrality of the macular ellipsoid band disappeared in both eyes, and only remained near the fovea. Visual field examination showed a progressive loss of the visual field in a concentric pattern in both eyes. The electroretinography showed a significant decrease in the amplitudes of a- and b-waves in the scotopic and photopic condition. DNA sequencing identified the compound heterozygous variants including c.1003+1G > A: p. (?) and c.5957_5958del: p.G1987Lfs*50 of MYO7A, with the latter being novel. In this study, we found a novel compound heterozygous variant in MYO7A, which enriched the mutation spectrum and expanded our understanding of the heterogeneity of phenotype and genotype of Usher syndrome type 1.

Mucopolysaccharidosis Type IIIE: A Real Human Disease or a Diagnostic Pitfall?

Mucopolysaccharidoses (MPS) comprise a group of 12 metabolic disorders where defects in specific enzyme activities lead to the accumulation of glycosaminoglycans (GAGs) within lysosomes. This classification expands to 13 when considering MPS IIIE. This type of MPS, associated with pathogenic variants in the ARSG gene, has thus far been described only in the context of animal models. However, pathogenic variants in this gene also occur in humans, but are linked to a different disorder, Usher syndrome (USH) type IV, which is sparking increasing debate. This paper gathers, discusses, and summarizes arguments both for and against classifying dysfunctions of arylsulfatase G (due to pathogenic variants in the ARSG gene) in humans as another subtype of MPS, called MPS IIIE. Specific difficulties in diagnostics and the classification of some inherited metabolic diseases are also highlighted and discussed.

Long-term natural history of ellipsoid zone width in USH2A-retinopathy

AimsTo investigate the long-term natural history of ellipsoid zone (EZ) width in USH2A-retinopathy.MethodsEZ width measurements from optical coherence tomography were retrospectively obtained from 110 eyes of 55 participants with molecularly...

Investigating Splice Defects in USH2A Using Targeted Long-Read Sequencing.

Biallelic variants in USH2A are associated with retinitis pigmentosa (RP) and Type 2 Usher Syndrome (USH2), leading to impaired vision and, additionally, hearing loss in the latter. Although the introduction of next-generation sequencing into clinical diagnostics has led to a significant uplift in molecular diagnostic rates, many patients remain molecularly unsolved. It is thought that non-coding variants or variants of uncertain significance contribute significantly to this diagnostic gap. This study aims to demonstrate the clinical utility of the reverse transcription-polymerase chain reaction (RT-PCR)-Oxford Nanopore Technology (ONT) sequencing of USH2A mRNA transcripts from nasal epithelial cells to determine the splice-altering effect of candidate variants. Five affected individuals with USH2 or non-syndromic RP who had undergone whole genome sequencing were recruited for further investigation. All individuals had uncertain genotypes in USH2A, including deep intronic rare variants, c.8682-654C>G, c.9055+389G>A, and c.9959-2971C>T; a synonymous variant of uncertain significance, c.2139C>T; p.(Gly713=); and a predicted loss of function duplication spanning an intron/exon boundary, c.3812-3_3837dup p.(Met1280Ter). In silico assessment using SpliceAI provided splice-altering predictions for all candidate variants which were investigated using ONT sequencing. All predictions were found to be accurate; however, in the case of c.3812-3_3837dup, the outcome was a complex cryptic splicing pattern with predominant in-frame exon 18 skipping and a low level of exon 18 inclusion leading to the predicted stop gain. This study detected and functionally characterised simple and complex mis-splicing patterns in USH2A arising from previously unknown deep intronic variants and previously reported variants of uncertain significance, confirming the pathogenicity of the variants.

Balance Control Impairments in Usher Syndrome.

To explore postural disability in Usher Syndrome (USH) patients using temporal posturographic analysis to better elucidate sensory compensation strategies of deafblind patients for posture control and correlate the Activities-specific Balance Confidence (ABC) scale with posturographic variables. Thirty-four genetically confirmed USH patients (11 USH1, 21 USH2, 2 USH 4) from the Otolaryngology Outpatient Clinic and 35 controls were prospectively studied using both classical and wavelet temporal analysis of center of pressure (CoP) under different visual conditions on static and dynamic platforms. The functional impact of balance was assessed with the ABC scale. Classical data in the spatial domain, Sensorial Organization Test, and frequency analysis of the CoP were analyzed. On unstable surfaces, USH1 had greater CoP surface area with eyes open (38.51 ± 68.67) and closed (28.14 ± 31.64) versus controls (3.31 ± 4.60), p < 0.001 and (7.37 ± 7.91), p < 0.001, respectively. On an unstable platform, USH consistently showed increased postural sway, with elevated angular velocity versus controls with eyes open (USH1 [44.94 ± 62.54]; USH2 [55.64 ± 38.61]; controls [13.4 ± 8.57]) (p = 0.003; p < 0.001) and closed (USH1 [60.36 ± 49.85], USH2 [57.62 ± 42.36]; controls [27.31 ± 19.79]) (p = 0.002; p = 0.042). USH visual impairment appears to be the primary factor influencing postural deficits, with a statistically significant difference observed in the visual Sensorial Organization Test ratio for USH1 (80.73 ± 40.07, p = 0.04) and a highly significant difference for USH2 (75.48 ± 31.67, p < 0.001) versus controls (100). In contrast, vestibular (p = 0.08) and somatosensory (p = 0.537) factors did not reach statistical significance. USH exhibited lower visual dependence than controls (30.31 ± 30.08) (USH1 [6 ± 11.46], p = 0.004; USH2 [8 ± 14.15], p = 0.005). The postural instability index, that corresponds to the ratio of spectral power index and canceling time, differentiated USH from controls on unstable surface with eyes open USH1 (3.33 ± 1.85) p < 0.001; USH2 (3.87 ± 1.05) p < 0.002; controls (1.91 ± 0.85) and closed USH1 (3.91 ± 1.65) p = 0.005; USH2 (3.92 ± 1.05) p = 0.045; controls (2.74 ± 1.27), but not USH1 from USH2. The canceling time in the anteroposterior direction in lower zone distinguished USH subtypes on stable surface with optokinetic USH1 (0.88 ± 1.03), USH2 (0.29 ± 0.23), p = 0.026 and on unstable surface with eyes open USH1 (0.56 ± 1.26), USH2 (0.072 ± 0.09), p = 0.036. ABC scale could distinguish between USH patients and controls, but not between USH subtypes and it correlated with CoP surface area on unstable surface with eyes open only in USH1(ρ = 0.714, p = 0.047). USH patients, particularly USH1, exhibited poorer balance control than controls on unstable platform with eyes open and appeared to rely more on proprioceptive information while suppressing visual input. USH2 seems to use different multisensory balance strategies that do not align as well with the ABC scale. The advanced analysis provided insights into sensory compensation strategies in USH subtypes.

A large-scale screening identified in USH2A gene the P3272L founder pathogenic variant explaining familial Usher syndrome in Sardinia, Italy

BackgroundUsher syndrome (USH) encompasses a group of disorders characterized by congenital sensorineural hearing loss (SNHL) and retinitis pigmentosa (RP). We described the clinical findings, natural history, and molecular analyses of USH patients identified during a large-scale screening to identify quantitative traits related to ocular disorders in the SardiNIA project cohort.MethodsWe identified 3 USH-affected families out of a cohort of 6,148 healthy subjects. 9 subjects presented a pathological phenotype, with SNHL and RP. All patients and their family members underwent a complete ophthalmic examination including best-corrected visual acuity, slit-lamp biomicroscopy, fundoscopy, fundus autofluorescence, spectral-domain optical coherence tomography, and electrophysiological testing. Audiological evaluation was performed with a clinical audiometer. Genotyping was performed using several arrays integrated with whole genome sequence data providing approximately 22 million markers equally distributed for each subject analyzed. Molecular diagnostics focused on analysis of the following candidate genes: MYO7A, USH1C, CDH23, PCDH15, USH1G, CIB2, USH2A, GPR98, DFNB31, CLRN1, and PDZD7.ResultsA single missense causal variant in USH2A gene was identified in homozygous status in all patients and in heterozygous status in unaffected parents. The presence of multiple homozygous patients with the same phenotypic severity of the syndromic form suggests that the Sardinian USH phenotype is the result of a founder effect on a specific pathogenic variant related haplotype. The frequency of heterozygotes in general Sardinian population is 1.89. Additionally, to provide new insights into the structure of usherin and the pathological mechanisms caused by small pathogenic in-frame variants, like p.Pro3272Leu, molecular dynamics simulations of native and mutant protein–protein and protein–ligand complexes were performed that predicted a destabilization of the protein with a decrease in the free energy change.ConclusionsOur results suggest that our approach is effective for the genetic diagnosis of USH. Based on the heterozygous frequency, targeted screening of this variant in the general population and in families at risk or with familial USH can be suggested. This can lead to more accurate molecular diagnosis, better genetic counseling, and improved molecular epidemiology data that are critical for future intervention plans.Trial registrationWe did not perform any health-related interventions for the participants.