Eeva-Marja Sankila

Mutation in the follicle-stimulating hormone receptor gene causes hereditary hypergonadotropic ovarian failure

Hypergonadotropic ovarian dysgenesis (ODG) with normal karyotype is a heterogeneous condition that in some cases displays Mendelian recessive inheritance. By systematically searching for linkage in multiplex affected families, we mapped a locus for ODG to chromosome 2p. As the previously cloned follicle-stimulating hormone receptor (FSHR) gene had been assigned to 2p, we searched it for mutations. A C566T transition in exon 7 of FSHR predicting an Ala to Val substitution at residue 189 in the extracellular ligand-binding domain segregated perfectly with the disease phenotype. Expression of the gene in transfected cells demonstrated a dramatic reduction of binding capacity and signal transduction, but apparently normal ligand-binding affinity of the mutated receptor. We conclude that the mutation causes ODG in these families.

Mutations in a Novel Gene with Transmembrane Domains Underlie Usher Syndrome Type 3

Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterized by progressive hearing loss, severe retinal degeneration, and variably present vestibular dysfunction, assigned to 3q21-q25. Here, we report on the positional cloning of the USH3 gene. By haplotype and linkage-disequilibrium analyses in Finnish carriers of a putative founder mutation, the critical region was narrowed to 250 kb, of which we sequenced, assembled, and annotated 207 kb. Two novel genes-NOPAR and UCRP-and one previously identified gene-H963-were excluded as USH3, on the basis of mutational analysis. USH3, the candidate gene that we identified, encodes a 120-amino-acid protein. Fifty-two Finnish patients were homozygous for a termination mutation, Y100X; patients in two Finnish families were compound heterozygous for Y100X and for a missense mutation, M44K, whereas patients in an Italian family were homozygous for a 3-bp deletion leading to an amino acid deletion and substitution. USH3 has two predicted transmembrane domains, and it shows no homology to known genes. As revealed by northern blotting and reverse-transcriptase PCR, it is expressed in many tissues, including the retina.

USH3A transcripts encode clarin-1, a four-transmembrane-domain protein with a possible role in sensory synapses

Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterised by the association of post-lingual progressive hearing loss, progressive visual loss due to retinitis pigmentosa and variable presence of vestibular dysfunction. Because the previously defined transcripts do not account for all USH3 cases, we performed further analysis and revealed the presence of additional exons embedded in longer human and mouse USH3A transcripts and three novel USH3A mutations. Expression of Ush3a transcripts was localised by whole mount in situ hybridisation to cochlear hair cells and spiral ganglion cells. The full length USH3A transcript encodes clarin-1, a four-transmembrane-domain protein, which defines a novel vertebrate-specific family of three paralogues. Limited sequence homology to stargazin, a cerebellar synapse four-transmembrane-domain protein, suggests a role for clarin-1 in hair cell and photoreceptor cell synapses, as well as a common pathophysiological pathway for different Usher syndromes.

Norrie disease caused by a gene deletion allowing carrier detection and prenatal diagnosis

Carrier determination and prenatal diagnosis in Norrie disease (ND) has so far not been reported. We describe a kindred with 4 members affected by ND in which a deletion comprising gene locus DXS7 on the short arm of the X chromosome defined by probe L1.28 causes the disorder. This allowed us to predict via chorion villus biopsy that a male foetus of a carrier woman is unaffected.

In vivo confocal microscopy of a family with Schnyder crystalline corneal dystrophy.

OBJECTIVE To analyze corneal morphology in Schnyder crystalline corneal dystrophy (SCCD) in vivo. DESIGN Observational case series. PARTICIPANTS Five eyes of four patients of various belonging to the same family were examined. METHODS The eyes were examined using in vivo confocal microscopy (CM). MAIN OUTCOME MEASURES The corneal morphology including keratocytes and stromal extracellular matrix, as well as basal epithelial/subepithelial nerves is, described. RESULTS The right eye of a 48-year-old male patient had been treated with anterior keratectomy and the left eye with phototherapeutic keratectomy (PTK). The right eye presented with increased stromal reflectivity owing to accumulation of extracellular matrix and large subepithelial crystalline deposits. Far fewer crystals could be observed in the left eye. The haze, however, was increased, either because of the dystrophy or the excimer laser treatment. The anterior keratocytes appeared irregular, and the subepithelial nerves were undetectable in both eyes. His 78-year-old mother showed more advanced changes with dense crystals, highly fibrotic stroma, and severely damaged corneal innervation. The partly irregular anterior keratocytes of the 9- and 7-year-old children contained intracellular deposits, although the corneas were clinically clear with only subtle subepithelial crystalline formation. Accumulation of similar reflective material was also observed in association with the prominent subepithelial nerves. CONCLUSIONS In the early stages of SCCD, highly reflective deposits accumulate intracellularly and around anterior keratocytes and along subepithelial nerves. With time, the normal corneal architecture becomes disturbed by large extracellular crystalline deposits and accumulation of highly reflective extracellular matrix resulting in central opacity and disruption of the subepithelial nerve plexus. Furthermore, neural regeneration after keratectomy appears delayed in SCCD.

Cone structure in patients with usher syndrome type III and mutations in the Clarin 1 gene.

OBJECTIVE To study macular structure and function in patients with Usher syndrome type III (USH3) caused by mutations in the Clarin 1 gene (CLRN1). METHODS High-resolution macular images were obtained by adaptive optics scanning laser ophthalmoscopy and spectral domain optical coherence tomography in 3 patients with USH3 and were compared with those of age-similar control subjects. Vision function measures included best-corrected visual acuity, kinetic and static perimetry, and full-field electroretinography. Coding regions of the CLRN1 gene were sequenced. RESULTS CLRN1 mutations were present in all the patients; a 20-year-old man showed compound heterozygous mutations (p.N48K and p.S188X), and 2 unrelated women aged 25 and 32 years had homozygous mutations (p.N48K). Best-corrected visual acuity ranged from 20/16 to 20/40, with scotomas beginning at 3° eccentricity. The inner segment-outer segment junction or the inner segment ellipsoid band was disrupted within 1° to 4° of the fovea, and the foveal inner and outer segment layers were significantly thinner than normal. Cones near the fovea in patients 1 and 2 showed normal spacing, and the preserved region ended abruptly. Retinal pigment epithelial cells were visible in patient 3 where cones were lost. CONCLUSIONS Cones were observed centrally but not in regions with scotomas, and retinal pigment epithelial cells were visible in regions without cones in patients with CLRN1 mutations. High-resolution measures of retinal structure demonstrate patterns of cone loss associated with CLRN1 mutations. CLINICAL RELEVANCE These findings provide insight into the effect of CLRN1 mutations on macular cone structure, which has implications for the development of treatments for USH3. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00254605.

Penetrance and Phenotype of the Thr377Met Myocilin Mutation in a Large Finnish Family with Juvenile- and Adult-Onset Primary Open-Angle Glaucoma

Purpose: To study the role of myocilin (MYOC) as a susceptibility gene for juvenile- and adult-onset open-angle glaucoma (JOAG and POAG, respectively). Methods: In a six-generation Finnish family with JOAG and POAG, we performed thorough ophthalmologic characterization (including assessment of the visual fields by Octopus perimetry, nerve-fiber layer thickness by photography, and disc size by Heidelberg tomography) of 51 individuals. The coding region of MYOC was screened for mutations by PCR amplification and direct sequencing. Results:We detected a C > T transition at codon 377 resulting in a substitution of a threonine residue for methionine (Thr377Met) in the olfactomedin-like domain of myocilin, segregating in the family. Of the 20 individuals heterozygous for the mutation, nine (45%) were glaucomatous and two (10%) had ocular hypertension (OHT). The mean age at diagnosis of glaucoma in these individuals was 34.3 years (range: 14-66 years). Moreover, three of these individuals suffered retinal vein occlusion (RVO) in one eye, while one individual without the mutation had RVO. Conclusion:Our results further support the evidence that the Thr377Met mutation in MYOC may represent a susceptibility allele for glaucoma. These findings may facilitate genetic counseling, and early diagnosis and treatment of glaucoma. The possible interaction of factors contributing to RVO in conjunction with the Thr377Met mutation warrants further investigation.

The cone-dominant retina and the inner ear of zebrafish express the ortholog of CLRN1, the causative gene of human Usher syndrome type 3A.

Clarin-1 (CLRN1) is the causative gene in Usher syndrome type 3A, an autosomal recessive disorder characterized by progressive vision and hearing loss. CLRN1 encodes Clarin-1, a glycoprotein with homology to the tetraspanin family of proteins. Previous cell culture studies suggest that Clarin-1 localizes to the plasma membrane and interacts with the cytoskeleton. Mouse models demonstrate a role for the protein in mechanosensory hair bundle integrity, but the function of Clarin-1 in hearing remains unclear. Even less is known of its role in vision, because the Clrn1 knockout mouse does not exhibit a retinal phenotype and expression studies in murine retinas have provided conflicting results. Here, we describe cloning and expression analysis of the zebrafish clrn1 gene, and report protein localization of Clarin-1 in auditory and visual cells from embryonic through adult stages. We detect clrn1 transcripts as early as 24h post-fertilization, and expression is maintained through adulthood. In situ hybridization experiments show clrn1 transcripts enriched in mechanosensory hair cells and supporting cells of the inner ear and lateral line organ, photoreceptors, and cells of the inner retina. In mechanosensory hair cells, Clarin-1 is polarized to the apical cell body and the synapses. In the retina, Clarin-1 localizes to lateral cell contacts between photoreceptors and is associated with the outer limiting membrane and subapical processes emanating from Müller glial cells. We also find Clarin-1 protein in the outer plexiform, inner nuclear and ganglion cell layers of the retina. Given the importance of Clarin-1 function in the human retina, it is imperative to find an animal model with a comparable requirement. Our data provide a foundation for exploring the role of Clarin-1 in retinal cell function and survival in a diurnal, cone-dominant species.

Alternative splice variants of the USH3A gene Clarin 1 (CLRN1)

Clarin 1 (CLRN1) is a four-transmembrane protein expressed in cochlear hair cells and neural retina, and when mutated it causes Usher syndrome type 3 (USH3). The main human splice variant of CLRN1 is composed of three exons that code for a 232-aa protein. In this study, we aimed to refine the structure of CLRN1 by an examination of transcript splice variants and promoter regions. Analysis of human retinal cDNA revealed 11 CLRN1 splice variants, of which 5 have not been previously reported. We studied the regulation of gene expression by several promoter domains using a luciferase assay, and identified 1000 nt upstream of the translation start site of the primary CLRN1 splice variant as the principal promoter region. Our results suggest that the CLRN1 gene is significantly more complex than previously described. The complexity of the CLRN1 gene and the identification of multiple splice variants may partially explain why mutations in CLRN1 result in substantial variation in clinical phenotype.

Speech recognition and communication outcomes with cochlear implantation in Usher syndrome type 3.

Background Usher syndrome Type 3 (USH3) is an autosomal recessive disorder characterized by variable type and degree of progressive sensorineural hearing loss and retinitis pigmentosa. Cochlear implants are widely used among these patients. Objectives To evaluate the results and benefits of cochlear implantation in patients with USH3. Study Design A nationwide multicenter retrospective review. Materials and Methods During the years 1995–2005, in 5 Finnish university hospitals, 19 patients with USH3 received a cochlear implant. Saliva samples were collected to verify the USH3 genotype. Patients answered to 3 questionnaires: Glasgow Benefit Inventory, Glasgow Health Status Inventory, and a self-made questionnaire. Audiological data were collected from patient records. Results All the patients with USH3 in the study were homozygous for the Finnish major mutation (p.Y176X). Either they had severe sensorineural hearing loss or they were profoundly deaf. The mean preoperative hearing level (pure-tone average, 0.5–4 kHz) was 110 ± 8 dB hearing loss (HL) and the mean aided hearing level was 58 ± 11 dB HL. The postoperative hearing level (34 ± 9 dB HL) and word recognition scores were significantly better than before surgery. According to the Glasgow Benefit Inventory scores and Glasgow Health Status Inventory data related to hearing, the cochlear implantation was beneficial to patients with USH3. Conclusion Cochlear implantation is beneficial to patients with USH3, and patients learn to use the implant without assistance.