Characterization of the ternary Usher syndrome SANS/ush2a/whirlin protein complex.

The Usher syndrome (USH) is the most common form of inherited deaf-blindness, accompanied by vestibular dysfunction. Due to the heterogeneous manifestation of the clinical symptoms, three USH types (USH1-3) and additional atypical forms are distinguished. USH1 and USH2 proteins have been shown to function together in multiprotein networks in photoreceptor cells and hair cells. Mutations in USH proteins are considered to disrupt distinct USH protein networks and finally lead to the development of USH.To get novel insights into the molecular pathomechanisms underlying USH, we further characterize the periciliary USH protein network in photoreceptor cells. We show the direct interaction between the scaffold protein SANS (USH1G) and the transmembrane adhesion protein ush2a and that both assemble into a ternary USH1/USH2 complex together with the PDZ-domain protein whirlin (USH2D) via mutual interactions. Immunohistochemistry and proximity ligation assays demonstrate co-localization of complex partners and complex formation, respectively, in the periciliary region, the inner segment and at the synapses of rodent and human photoreceptor cells. Protein-protein interaction assays and co-expression of complex partners reveal that pathogenic mutations in USH1G severely affect formation of the SANS/ush2a/whirlin complex. Translational read-through drug treatment, targeting the c.728C > A (p.S243X) nonsense mutation, restored SANS scaffold function. We conclude that USH1 and USH2 proteins function together in higher order protein complexes. The maintenance of USH1/USH2 protein complexes depends on multiple USH1/USH2 protein interactions, which are disrupted by pathogenic mutations in USH1G protein SANS.

The combination of vestibular impairment and congenital sensorineural hearing loss predisposes patients to ocular anomalies, including Usher syndrome.

The co-occurrence of hearing impairment and visual dysfunction is devastating. Most deaf-blind etiologies are genetically determined, the commonest being Usher syndrome (USH). While studies of the congenitally deaf population reveal a variable degree of visual problems, there are no effective ophthalmic screening guidelines. We hypothesized that children with congenital sensorineural hearing loss (SNHL) and vestibular impairment were at an increased risk of having USH. A retrospective chart review of 33 cochlear implants recipients for severe to profound SNHL and measured vestibular dysfunction was performed to determine the ocular phenotype. All the cases had undergone ocular examination and electroretinogram (ERG). Patients with an abnormal ERG underwent genetic testing for USH. We found an underlying ocular abnormality in 81.81% (27/33) of cases; of which 75% had refractive errors, and 50% of those patients showed visual improvement with refractive correction. A total of 14 cases (42.42%; 14/33) had generalized rod-cone dysfunction on ERG suggestive of Usher syndrome type 1, confirmed by mutational analysis. This work shows that adding vestibular impairment as a criterion for requesting an eye exam and adding the ERG to detect USH increases the chances of detecting ocular anomalies, when compared with previous literature focusing only on congenital SNHL.

Zebrafish Models for the Mechanosensory Hair Cell Dysfunction in Usher Syndrome 3 Reveal That Clarin-1 Is an Essential Hair Bundle Protein.

Usher syndrome type III (USH3) is characterized by progressive loss of hearing and vision, and varying degrees of vestibular dysfunction. It is caused by mutations that affect the human clarin-1 protein (hCLRN1), a member of the tetraspanin protein family. The missense mutation CLRN1(N48K), which affects a conserved N-glycosylation site in hCLRN1, is a common causative USH3 mutation among Ashkenazi Jews. The affected individuals hear at birth but lose that function over time. Here, we developed an animal model system using zebrafish transgenesis and gene targeting to provide an explanation for this phenotype. Immunolabeling demonstrated that Clrn1 localized to the hair cell bundles (hair bundles). The clrn1 mutants generated by zinc finger nucleases displayed aberrant hair bundle morphology with diminished function. Two transgenic zebrafish that express either hCLRN1 or hCLRN1(N48K) in hair cells were produced to examine the subcellular localization patterns of wild-type and mutant human proteins. hCLRN1 localized to the hair bundles similarly to zebrafish Clrn1; in contrast, hCLRN1(N48K) largely mislocalized to the cell body with a small amount reaching the hair bundle. We propose that this small amount of hCLRN1(N48K) in the hair bundle provides clarin-1-mediated function during the early stages of life; however, the presence of hCLRN1(N48K) in the hair bundle diminishes over time because of intracellular degradation of the mutant protein, leading to progressive loss of hair bundle integrity and hair cell function. These findings and genetic tools provide an understanding and path forward to identify therapies to mitigate hearing loss linked to the CLRN1 mutation. SIGNIFICANCE STATEMENT: Mutations in the clarin-1 gene affect eye and ear function in humans. Individuals with the CLRN1(N48K) mutation are born able to hear but lose that function over time. Here, we develop an animal model system using zebrafish transgenesis and gene targeting to provide an explanation for this phenotype. This approach illuminates the role of clarin-1 and the molecular mechanism linked to the CLRN1(N48K) mutation in sensory hair cells of the inner ear. Additionally, the investigation provided an in vivo model to guide future drug discovery to rescue the hCLRN1(N48K) in hair cells.

Comparison of topical dorzolamide and ketorolac treatment for cystoid macular edema in retinitis pigmentosa and Usher's syndrome.

PURPOSE: To investigate the topical effect of dorzolamide versus ketorolac on retinitis pigmentosa (RP) and Usher's syndrome (US) macular edema. METHODS: Prospective, randomized and interventional study. A total of 28 eyes of 18 patients were included. Five eyes had US, 23 had RP. Fifteen eyes were allocated to ketorolac tromethamine 0.5% (4 drops daily regimen) and 13 eyes to dorzolamide hydrochloride 2% (3 drops daily regimen) treatment groups. Snellen's best-corrected visual acuity (BCVA), foveal thickness (FT) and foveal zone thickness (FZT) measured by Stratus® optical coherence tomography (OCT) were evaluated at baseline, 1, 3, 6 and 12 months after treatment. RESULTS: Patients assigned to ketorolac had a baseline BCVA of 0.37 ± 0.17 logMAR which improved at the end of 1 year to 0.28 ± 0.16 (p = 0.02). Three eyes (20%) of 2 patients improved by 7 letters or more. Mean FT and FZT did not change significantly during the study follow-up. After 1 year of treatment, 4 eyes (27%) of 3 patients showed an improvement of at least 16% of FT and 11% of FZT. Patients assigned to dorzolamide had a baseline BCVA of 0.48 ± 0.34 logMAR which improved in the first 6 months (0.40 ± 0.30; p = 0.01), with a decrease at 1 year (0.42 ± 0.27; p = 0.20). Seven eyes (54%) of 5 patients had an improvement of 7 letters or more. Mean FT and FZT did not change significantly either. After 1 year of treatment, 3 eyes (23%) of 2 patients showed an improvement of at least 16% on FT and 11% on FZT. CONCLUSIONS: RESULTS suggest that dorzolamide and ketorolac might improve visual acuity and therefore be of interest in selected cases. No relationship between retinal thickness fluctuation and visual acuity was found. Sample size was a limitation to the study.

Genetic diagnosis of childhood sensorineural hearing loss.

INTRODUCTION: Congenital/early-onset sensorineural hearing loss (SNHL) is one of the most common hereditary disorders in our environment. There is increasing awareness of the importance of an etiologic diagnosis, and genetic testing with next-generation sequencing (NGS) has the highest diagnostic yield. Our study shows the genetic results obtained in a cohort of patients with bilateral congenital/early-onset SNHL. MATERIALS AND METHODS: We included 105 children with bilateral SNHL that received genetic testing between 2019 and 2022. Genetic tests were performed with whole exome sequencing, analyzing genes related to hearing loss (virtual panel with 244 genes). RESULTS: 48% (50/105) of patients were genetically diagnosed. We identified pathogenic and likely pathogenic variants in 26 different genes, and the most frequently mutated genes were GJB2, USH2A and STRC. 52% (26/50) of variants identified produced non-syndromic hearing loss, 40% (20/50) produced syndromic hearing loss, and the resting 8% (4/50) could produce both non-syndromic and syndromic hearing loss. CONCLUSIONS: Genetic testing plays a vital role in the etiologic diagnosis of bilateral SNHL. Our cohort shows that genetic testing with NGS has a high diagnostic yield and can provide useful information for the clinical workup of patients.

Whole-exome sequencing identifies novel compound heterozygous mutations in USH2A in Spanish patients with autosomal recessive retinitis pigmentosa.

PURPOSE: Retinitis pigmentosa (RP) is an inherited retinal dystrophy characterized by extreme genetic and clinical heterogeneity. Thus, the diagnosis is not always easily performed due to phenotypic and genetic overlap. Current clinical practices have focused on the systematic evaluation of a set of known genes for each phenotype, but this approach may fail in patients with inaccurate diagnosis or infrequent genetic cause. In the present study, we investigated the genetic cause of autosomal recessive RP (arRP) in a Spanish family in which the causal mutation has not yet been identified with primer extension technology and resequencing. METHODS: We designed a whole-exome sequencing (WES)-based approach using NimbleGen SeqCap EZ Exome V3 sample preparation kit and the SOLiD 5500×l next-generation sequencing platform. We sequenced the exomes of both unaffected parents and two affected siblings. Exome analysis resulted in the identification of 43,204 variants in the index patient. All variants passing filter criteria were validated with Sanger sequencing to confirm familial segregation and absence in the control population. In silico prediction tools were used to determine mutational impact on protein function and the structure of the identified variants. RESULTS: Novel Usher syndrome type 2A (USH2A) compound heterozygous mutations, c.4325T>C (p.F1442S) and c.15188T>G (p.L5063R), located in exons 20 and 70, respectively, were identified as probable causative mutations for RP in this family. Family segregation of the variants showed the presence of both mutations in all affected members and in two siblings who were apparently asymptomatic at the time of family ascertainment. Clinical reassessment confirmed the diagnosis of RP in these patients. CONCLUSIONS: Using WES, we identified two heterozygous novel mutations in USH2A as the most likely disease-causing variants in a Spanish family diagnosed with arRP in which the cause of the disease had not yet been identified with commonly used techniques. Our data reinforce the clinical role of WES in the molecular diagnosis of highly heterogeneous genetic diseases where conventional genetic approaches have previously failed in achieving a proper diagnosis.

Phenotypic characterization of retinitis pigmentosa associated with deafness / Caracterización fenotípica de la retinitis pigmentaria asociada a sordera

Introduction: There are several syndromes that associate retinitis pigmentosa with deafness or hearing loss. The most frequent is Usher syndrome, a genetic disorder of autosomal recessive inheritance, which, in some cases, is accompanied by vestibular dysfunction. However, there are cases of families that despite having retinitis pigmentosa associated with deafness, cannot be classified as Usher or other syndromes due to additional findings. Objective: To reassess the phenotypes of 103 families previously diagnosed as possible Usher syndrome and/or retinitis pigmentosa associated with deafness. Materials and methods: We conducted a descriptive and retrospective study by reviewing the medical records of 103 families with a probable clinical diagnosis of Usher syndrome and/or retinitis pigmentosa associated with deafness. Families whose clinical diagnosis did not correspond to the typical Usher syndrome were selected and evaluated ophthalmologically and audiologically. Demographic and clinical variables were analyzed. Results: We selected and then reevaluated 14 families and 55 individuals as they did not correspond to a clinical diagnosis of Usher syndrome; 13.6% of the families initially considered to have typical Usher syndrome were later diagnosed with retinitis pigmentosa associated with deafness, another ocular symptom associated with hearing loss, retinitis pigmentosa, or isolated hearing loss in the same family. Conclusions: Family studies are essential in cases where the symptoms do not match the typical Usher' syndrome. In the cases of retinitis pigmentosa associated with deafness, a correct clinical diagnosis allows for focusing on the molecular analyses to establish a differential diagnosis. The need for nomenclature guidelines on these atypical findings is relevant to aid physicians and researchers in the best approach to these cases.

Introducción. El síndrome de Usher es una alteración genética caracterizada por la asociación de retinitis pigmentaria y sordera. Sin embargo, hay casos con familias en las cuales, a pesar de presentarse dicha asociación, no se puede diagnosticar un síndrome de Usher ni ninguno otro. Objetivo. Reevaluar fenotípicamente a 103 familias con diagnóstico previo de posible síndrome de Usher o retinitis pigmentaria asociada con sordera. Materiales y métodos. Se revisaron las historias clínicas de 103 familias con un posible diagnóstico clínico de síndrome de Usher o retinitis pigmentaria asociada con sordera. Se seleccionaron las familias cuyo diagnóstico clínico no correspondía a un síndrome de Usher típico. Los afectados fueron valorados oftalmológica y audiológicamente. Se analizaron variables demográficas y clínicas. Resultados. Se reevaluaron 14 familias cuyo diagnóstico clínico no correspondía al de síndrome de Usher. De las familias con diagnóstico inicial de síndrome de Usher típico, el 13,6 % recibieron uno posterior de "retinitis pigmentaria asociada con sordera", de "otro síntoma ocular asociado con hipoacusia", o en forma aislada en una misma familia, de "retinitis pigmentaria" o "hipoacusia". Conclusiones. Es fundamental el estudio familiar en los casos en que la clínica no concuerda con el diagnóstico de síndrome de Usher típico. En los pacientes con retinitis pigmentaria asociada con sordera, el diagnóstico clínico acertado permite enfocar los análisis moleculares y, así, establecer un diagnóstico diferencial. Es necesario elaborar guías de nomenclatura en los casos con estos hallazgos atípicos para orientar a médicos e investigadores en cuanto a su correcto manejo.

The use of carbonic anhydrase inhibitors in the retreatment of cystic macular lesions in retinitis pigmentosa and X-linked retinoschisis.

PURPOSE: The purpose of this study was to determine if carbonic anhydrase inhibitors can restore their efficacy after a period of discontinued use in patients with cystic foveal lesions who demonstrated subsequent worsening in the extent of their foveal cysts after initially exhibiting a favorable response to treatment. METHODS: Retrospective chart review was conducted on all patients with retinitis pigmentosa or X-linked retinoschisis who were either currently on treatment or had been treated with carbonic anhydrase inhibitors for cystic macular lesions. A total of three patients were included in the study. RESULTS: All three patients exhibited a recurrence of their cystic macular lesions while on treatment with carbonic anhydrase inhibitors. After discontinuing treatment for a period of 1 month to 6 months, all patients showed a favorable response to retreatment as monitored with optical coherence tomography scans. CONCLUSION: The present study shows that patients who show signs of recurring macular cysts while still on treatment can have a favorable response when treatment is reinstated after a period of discontinued use of a carbonic anhydrase inhibitor.

Usher syndrome type 2A complicated with glycogen storage disease type 3 due to paternal uniparental isodisomy of chromosome 1 in a sporadic patient.

BACKGROUND: The condition of uniparental disomy (UPD) occurs when an individual inherits two copies of a chromosome, or part of a chromosome, from one parent. Most cases of uniparental heterodisomy (UPhD) do not cause diseases, whereas cases of uniparental isodisomy (UPiD), while rare, may be pathogenic. Theoretically, UPiD may cause rare genetic diseases in a homozygous recessive manner. METHODS: A 4-year-old girl presented with congenital hearing loss, developmental delay, hepatomegaly, and other clinical features. She and her parents were genetically tested using trio whole exome sequencing (Trio-WES) and copy number variation sequencing (CNV-seq). In addition, we built a structural model to further examine the pathogenicity of the UPiD variants. RESULTS: Trio-WES identified a paternal UPiD in chromosome 1, and two homozygous pathogenic variants AGL c.4284T>G/p.Tyr1428* and USH2A c.6528T>A/p.Tyr2176* in the UPiD region. We further analyzed the pathogenicity of these two variations. The patient was diagnosed with Usher syndrome type 2A (USH2A) and glycogen storage disease type III (GSD3). CONCLUSIONS: Our study reports a rare case of a patient carrying two pathogenic variants of different genes caused by paternal UPiD, supporting the potential application of Trio-WES in detecting and facilitating the diagnosis of UPD.

Usher syndrome associated with Fuchs' heterochromic uveitis.

BACKGROUND: The purpose of this study is to report two new cases of Usher syndrome associated with Fuchs' heterochromic uveitis (FHU), to confirm our previous observation of the association between FHU and retinitis pigmentosa (RP), and to evaluate if FHU is particularly associated with Usher syndrome. METHODS: Retrospective medical record review of all new RP cases at Hadassah Medical Center between the years 2000 and 2007, review of our previously published data, and a meta-analysis of published relevant articles in peer reviewed journals. RESULTS: During the time frame of the study we diagnosed 58 new cases of RP, of whom one male and one female had the typical findings of FHU, and both had Usher syndrome type II. The difference in the occurrence of FHU between the 616 controls and the patients with RP was significant (p = 0.0073, Fisher's exact test). In our combined data, FHU occurred only in two types of RP; RP simplex with an incidence of 0.57%, and Usher syndrome with an incidence of 13.5%. This difference between the incidence of FHU in patients with Usher syndrome and other types of RP was significant (p < 0.0001, Fisher's exact test). Adding up these two cases with what is already published in the literature makes up a total of 17 RP patients with coexisting FHU. CONCLUSIONS: This study confirms the association between FHU and RP; and a particularly stronger association with Usher syndrome type II. Although infectious agents seem to play a role, the cause for this significant correlation is still unclear.

A rare brain developmental anomaly in a patient with Usher's syndrome.

We report a rare brain developmental anomaly in Usher's syndrome. We present a 43-year-old male with visual disturbance, hearing loss, and headache. Retinitis pigmentosa and sensorineural hearing loss were determined and he was diagnosed with Usher's syndrome according to the clinical findings. Magnetic resonance imaging showed an arachnoid cyst on the left temporal lobe, cavum septum pellucidum et vergae. Uneventful cataract surgery was performed in both eyes. He was suggested to be followed up periodically for the arachnoid cyst and to use a hearing device. Although auditory and visual disturbances are the typical findings of this syndrome, it may affect other parts of the central nervous system as well. Morphological abnormalities of central nervous system and related disorders can be seen in patients with Usher's syndrome.

Hickam's Dictum: Pseudoxanthoma elasticum and Usher syndrome in a single patient.

BACKGROUND: To report the case of a patient with two distinct genetic systemic diseases - pseudoxanthoma elasticum (PXE) and Usher syndrome - confirmed by genetic testing. MATERIALS AND METHODS: Single Retrospective Case Report. RESULTS: A 36-year-old woman presented with acute central vision loss of the left eye (OS). Fundus exam revealed choroidal neovascularization OS in the setting of angioid streaks secondary to an underlying diagnosis of PXE. Unexpectedly, she also exhibited peripheral bony spicules with significant visual field constriction. Physical exam revealed skin papules on her neck and hearing loss. The presence of angioid streaks and skin findings was compatible with PXE; the etiology of her pigmentary retinopathy and hearing loss was elucidated using genetic testing. The patient was found to be compound heterozygous for pathogenic variants in both the ABCC6 and USH2A genes, confirming the diagnosis of two rare disorders in a single patient. CONCLUSIONS: PXE and Usher syndrome are rare systemic disorders that cause distinctive retinal abnormalities. This report highlights the importance of genetic testing in diagnosing uncommon hereditary retinal disorders and outlines the progression of disease over 6 years.

L-type voltage-gated calcium channel agonists mitigate hearing loss and modify ribbon synapse morphology in the zebrafish model of Usher syndrome type 1.

The mariner (myo7aa-/- ) mutant is a zebrafish model for Usher syndrome type 1 (USH1). To further characterize hair cell synaptic elements in myo7aa-/- mutants, we focused on the ribbon synapse and evaluated ultrastructure, number and distribution of immunolabeled ribbons, and postsynaptic densities. By transmission electron microscopy, we determined that myo7aa-/- zebrafish have fewer glutamatergic vesicles tethered to ribbon synapses, yet maintain a comparable ribbon area. In myo7aa-/- hair cells, immunolocalization of Ctbp2 showed fewer ribbon-containing cells in total and an altered distribution of Ctbp2 puncta compared to wild-type hair cells. myo7aa-/- mutants have fewer postsynaptic densities - as assessed by MAGUK immunolabeling - compared to wild-type zebrafish. We quantified the circular swimming behavior of myo7aa-/- mutant fish and measured a greater turning angle (absolute smooth orientation). It has previously been shown that L-type voltage-gated calcium channels are necessary for ribbon localization and occurrence of postsynaptic density; thus, we hypothesized and observed that L-type voltage-gated calcium channel agonists change behavioral and synaptic phenotypes in myo7aa-/- mutants in a drug-specific manner. Our results indicate that treatment with L-type voltage-gated calcium channel agonists alter hair cell synaptic elements and improve behavioral phenotypes of myo7aa-/- mutants. Our data support that L-type voltage-gated calcium channel agonists induce morphological changes at the ribbon synapse - in both the number of tethered vesicles and regarding the distribution of Ctbp2 puncta - shift swimming behavior and improve acoustic startle response.

Acute reversible Charles Bonnet syndrome precipitated by sudden severe anemia.

PURPOSE: To report the sudden onset of reversible Charles Bonnet syndrome precipitated byacute severe anemia. METHODS: The charts of three patients (Usher syndrome, bilateral macular degeneration, and bilateral retinal vein occlusion) with acute Charles Bonnet syndrome in the setting of severe anemia were reviewed. RESULTS: Anemia resulted from bladder surgery, recto-colitis, and severe urinary tract infection. Hemoglobin ranged from 78 to 86 g/L. Decreased visual acuity and formed visual hallucinations (giants, flowers, animals) were present in all three patients. Rapid reversal of Charles Bonnet syndrome and visual acuity improvement followed blood transfusion. CONCLUSIONS: Acute severe anemia can precipitate Charles Bonnet syndrome, which may be reversible by blood transfusion.

The use of visual feedback during signing: evidence from signers with impaired vision.

The role of visual feedback during the production of American Sign Language was investigated by comparing the size of signing space during conversations and narrative monologues for normally sighted signers, signers with tunnel vision due to Usher syndrome, and functionally blind signers. The interlocutor for all groups was a normally sighted deaf person. Signers with tunnel vision produced a greater proportion of signs near the face than blind and normally sighted signers, who did not differ from each other. Both groups of visually impaired signers produced signs within a smaller signing space for conversations than for monologues, but we hypothesize that they did so for different reasons. Signers with tunnel vision may align their signing space with that of their interlocutor. In contrast, blind signers may enhance proprioceptive feedback by producing signs within an enlarged signing space for monologues, which do not require switching between tactile and visual signing. Overall, we hypothesize that signers use visual feedback to phonetically calibrate the dimensions of signing space, rather than to monitor language output.

Life strategies of people with deafblindness due to Usher syndrome type 2a - a qualitative study.

Purpose: To explore life strategies in people with Usher syndrome type 2a. Background: There are no studies on life strategies in people with Usher syndrome. People with deafblindness are often described in terms of poor health and low quality of life, or as being vulnerable. From a clinical point of view, it is of importance to balance this picture, with an increased knowledge of life strategies. Methods: The study had a qualitative explorative design. Fourteen people aged 20-64 years (4 women, 10 men) with USH2a in Sweden participated in focus group interviews, which were transcribed and analysed by qualitative content analysis. Results: The content analysis resulted in seven categories; remaining active, using devices, using support, sharing knowledge, appreciating the present, maintaining a positive image and alleviating emotional pain. Two sub-themes: resolve or prevent challenges and comforting oneself was abstracted forming a theme "being at the helm". Conclusion: The findings show that people with USH2a have a variety of life strategies that can be interpreted as highlighting different aspects of psychological flexibility in a life adjustment process. The study demonstrates that people with USH2a manage in many ways, and metaphorically, by "taking the helm", they strive to actively navigate towards their own chosen values.

The first deaf-blind patient in Russia with Argus II retinal prosthesis system: what he sees and why.

OBJECTIVE: In this study, we propose a new method for evaluating the functional results based on the sizes of phosphenes that the patient drew which were then digitalized. We also describe the methodology of psychological testing and support for a deaf-blind patient. APPROACH: A 59-year-old man with retinitis pigmentosa and hearing loss (clinical Usher syndrome) underwent surgery to implant the Argus II retinal prosthesis system in his right eye. MAIN RESULTS: Correlation analysis showed a weak dependency between the size of a phosphene and the perceptual threshold. Significant correlations between a phosphene and the height of the interface, impedance or retinal thickness was not found. The patient with the retinal prosthesis felt more independent and confident, and more healthy. This is the first case of retinal implant surgery in Russia. SIGNIFICANCE: The results of this study add to the understanding in the field of retinal implants functioning. The experience of the successful rehabilitation of the deaf-blind patient after implantation of Argus II allowed us to design a methodology that can be used in future similar cases.

Evidence for impaired olfactory function and structural brain integrity in a disorder of ciliary function, Usher syndrome.

Diseases involving cilia dysfunction, such as Usher Syndrome (USH), often involve visual and auditory loss. Psychophysical evidence has suggested that this may also hold true for the peripheral olfactory domain. Here we aimed to go a step further by attempting to establish relations between the integrity of cortical structures and olfactory function in this condition. We investigated olfactory function for USH types 1 (USH1) and 2 (USH2). Bilateral olfactory bulb (OB) volume and olfactory sulcus (OS) depth were also analysed. Thirty-three controls with no previous olfactory deficits were age, sex and handedness-matched to 32 USH patients (11 USH1, 21 USH2). A butanol detection threshold test was performed to measure olfactory function. For OB volume and OS depth, morphometric measurements were performed using magnetic resonance imaging (MRI) based on detailed segmentation by three independent operators. Averaged values across these were used for the statistical analyses. Total intracranial volume was estimated using Freesurfer to account for head size variability. Olfactory threshold was significantly lower in controls when compared to USH, USH1, and USH2. OS depth was found to be shallower in both hemispheres in USH patients when compared with the control group. OB volume was not significantly different between control and USH groups, or respective subgroups. Nevertheless, butanol threshold was negatively correlated with the left OB volume for the USH type 1 subgroup. The main effect of OS depth reduction was found to be mainly due to the comparison between USH2 and controls. Our results provide evidence for morphometric changes and olfactory dysfunction in patients with USH. This correlated with a reduction in left OB volume in the USH1 subgroup, the most severe USH phenotype. The main effect of reduced OS depth was found to stem mainly from USH2 raising questions regarding a possible complex interaction between sensory olfactory loss and central cortical changes in this disease.

Histopathological and neuroradiological features of Usher syndrome type II.

OBJECTIVE: To study the histopathological and neuroradiological features of Usher syndrome (USH), with particular focus on USH type II, an inherited disorder characterized by moderate to severe congenital hearing impairment and retinitis pigmentosa with onset in the late teens. METHODOLOGY: A report of four cases and literature review. RESULTS AND CONCLUSION: Rare examples of histopathological and neuroradiological findings from four USH type II cases are presented. More studies like these are encouraged so that correlation studies between the morphological and clinical findings can be performed on the path to elucidate the pathogenesis of this heterogeneous disorder.

Two truncating USH3A mutations, including one novel, in a German family with Usher syndrome.

PURPOSE: To identify the genetic defect in a German family with Usher syndrome (USH) and linkage to the USH3A locus. METHODS: DNA samples of five family members (both parents and the three patients) were genotyped with polymorphic microsatellite markers specific for eight USH genes. Three affected family members underwent detailed ocular and audiologic characterization. RESULTS: Symptoms in the patients were compatible with Usher syndrome and show intrafamilial variation, for both hearing loss (ranging from severe to profound with non-linear progression) and vision. Genotyping of microsatellite markers for the different USH loci was in line with a defect in the USH3A gene on chromosome 3q25. Sequence analysis of the USH3A gene revealed two truncating mutations; c.149_152delCAGGinsTGTCCAAT, which has been described previously, and a novel mutation, c.502_503insA, segregating with the phenotype. CONCLUSIONS: To date, only 11 USH3A mutations have been described. This is the first description of a German family with USH due to USH3A mutations, including one novel. Our findings indicate that also in the Central European population, USH3A mutations should be considered in cases of USH.