Mutations of ESRRB encoding estrogen-related receptor beta cause autosomal-recessive nonsyndromic hearing impairment DFNB35.

In a large consanguineous family of Turkish origin, genome-wide homozygosity mapping revealed a locus for recessive nonsyndromic hearing impairment on chromosome 14q24.3-q34.12. Fine mapping with microsatellite markers defined the critical linkage interval to a 18.7 cM region flanked by markers D14S53 and D14S1015. This region partially overlapped with the DFNB35 locus. Mutation analysis of ESRRB, a candidate gene in the overlapping region, revealed a homozygous 7 bp duplication in exon 8 in all affected individuals. This duplication results in a frame shift and premature stop codon. Sequence analysis of the ESRRB gene in the affected individuals of the original DFNB35 family and in three other DFNB35-linked consanguineous families from Pakistan revealed four missense mutations. ESRRB encodes the estrogen-related receptor beta protein, and one of the substitutions (p.A110V) is located in the DNA-binding domain of ESRRB, whereas the other three are substitutions (p.L320P, p.V342L, and p.L347P) located within the ligand-binding domain. Molecular modeling of this nuclear receptor showed that the missense mutations are likely to affect the structure and stability of these domains. RNA in situ hybridization in mice revealed that Esrrb is expressed during inner-ear development, whereas immunohistochemical analysis showed that ESRRB is present postnatally in the cochlea. Our data indicate that ESRRB is essential for inner-ear development and function. To our knowledge, this is the first report of pathogenic mutations of an estrogen-related receptor gene.

MYO15A (DFNB3) mutations in Turkish hearing loss families and functional modeling of a novel motor domain mutation.

Myosin XVA is an unconventional myosin which has been implicated in autosomal recessive nonsyndromic hearing impairment (ARNSHI) in humans. In Myo15A mouse models, vestibular dysfunction accompanies the autosomal recessive hearing loss. Genomewide homozygosity mapping and subsequent fine mapping in two Turkish families with ARNSHI revealed significant linkage to a critical interval harboring a known deafness gene MYO15A on chromosome 17p13.1-17q11.2. Subsequent sequencing of the MYO15A gene led to the identification of a novel missense mutation, c.5492G-->T (p.Gly1831Val) and a novel splice site mutation, c.8968-1G-->C. These mutations were not detected in additional 64 unrelated ARNSHI index patients and in 230 Turkish control chromosomes. Gly1831 is a conserved residue located in the motor domains of the different classes of myosins of different species. Molecular modeling of the motor head domain of the human myosin XVa protein suggests that the Gly1831Val mutation inhibits the powerstroke by reducing backbone flexibility and weakening the hydrophobic interactions necessary for signal transmission to the converter domain.

Mutations in the lipoma HMGIC fusion partner-like 5 (LHFPL5) gene cause autosomal recessive nonsyndromic hearing loss.

In two large Turkish consanguineous families, a locus for autosomal recessive nonsyndromic hearing loss (ARNSHL) was mapped to chromosome 6p21.3 by genome-wide linkage analysis in an interval overlapping with the loci DFNB53 (COL11A2), DFNB66, and DFNB67. Fine mapping excluded DFNB53 and subsequently homozygous mutations were identified in the lipoma HMGIC fusion partner-like 5 (LHFPL5) gene, also named tetraspan membrane protein of hair cell stereocilia (TMHS) gene, which was recently shown to be mutated in the "hurry scurry" mouse and in two DFNB67-linked families from Pakistan. In one family, we found a homozygous one-base pair deletion, c.649delG (p.Glu216ArgfsX26) and in the other family we identified a homozygous transition c.494C>T (p.Thr165Met). Further screening of index patients from 96 Turkish ARNSHL families and 90 Dutch ARNSHL patients identified one additional Turkish family carrying the c.649delG mutation. Haplotype analysis revealed that the c.649delG mutation was located on a common haplotype in both families. Mutation screening of the LHFPL5 homologs LHFPL3 and LHFPL4 did not reveal any disease causing mutation. Our findings indicate that LHFPL5 is essential for normal function of the human cochlea.

A novel TMPRSS3 missense mutation in a DFNB8/10 family prevents proteolytic activation of the protein.

Pathogenic mutations in TMPRSS3, which encodes a transmembrane serine protease, cause non-syndromic deafness DFNB8/10. Missense mutations map in the low density-lipoprotein receptor A (LDLRA), scavenger-receptor cysteine-rich (SRCR), and protease domains of the protein, indicating that all domains are important for its function. TMPRSS3 undergoes proteolytic cleavage and activates the ENaC sodium channel in a Xenopus oocyte model system. To assess the importance of this gene in non-syndromic childhood or congenital deafness in Turkey, we screened for mutations affected members of 25 unrelated Turkish families. The three families with the highest LOD score for linkage to chromosome 21q22.3 were shown to harbor P404L, R216L, or Q398X mutations, suggesting that mutations in TMPRSS3 are a considerable contributor to non-syndromic deafness in the Turkish population. The mutant TMPRSS3 harboring the novel R216L missense mutation within the predicted cleavage site of the protein fails to undergo proteolytic cleavage and is unable to activate ENaC, thus providing evidence that pre-cleavage of TMPRSS3 is mandatory for normal function.

Ocular myasthenia gravis associated with x-linked recessive spinal and bulbar muscular atrophy.

We describe a 34-year-old patient who was admitted with episodic diplopia, ptosis, and swallowing difficulties of 6 months duration. He also had some muscle cramps aggravated by exercise since the age of 20. Bilateral ptosis of the eyelids, normal gaze, rare fasciculations of the tongue, easy fatigability of ocular and bilateral proximal limb muscles, atrophy of the testes, and gynecomastia were found on neurologic examination. Repetitive nerve stimulation studies and jitter measurement disclosed the defect of neuromuscular junction transmission. Acetylcholine receptor binding antibody was not detected. Acetylcholine esterase inhibitors relieved these episodic symptoms. A genetic study that showed an expansion of cytosine-adenine-guanine (CAG) repeat in the first exon of the androgen receptor (AR) confirmed the diagnosis of X-linked recessive spinal and bulbar muscular atrophy (X-SBMA). Thus, this case shows a rare association of ocular myasthenia gravis with X-SBMA.

Detection of chromosomal aberrations in prostate cancer by fluorescence in situ hybridization (FISH).

PURPOSE: Fluorescence in situ hybridization (FISH) is a powerful tool for quantitative analysis of chromosomes and genes and can be applied in a variety of specimens, including cell cultures, isolated nuclei from fresh and fixed tissues, and histological tissue sections. For detection of numerical chromosome aberrations, we examined prostatic cancer samples at our department. In addition, we also observed primary and secondary aberrations taking part in the initiation and progression of tumours. MATERIALS AND METHODS: FISH using chromosome-specific alpha-satellite DNA probes for chromosomes 7, 8, 9, 10, 17, X and Y was performed on 19 prostatic cancer and 19 benign prostatic hyperplasia (BPH) samples obtained from transurethral resection (TUR) and archival paraffin-embedded blocks. RESULTS: Numerical aberrations were observed in 41% of the tumours studied. A range of aberrant copy numbers of chromosome 9 (68%), 7 (63%), 8 (58%), 17 (37%), Y (32%) and 10 (26%) was observed. We did not observe significant aberrations in BPH samples. In prostate cancer patients, chromosomes 7 (47%), 8 (58%) and 9 (63%) were monosomic by FISH. Monosomy 8 and 9 were significant differences (p>0.05) between prostate cancer and BPH patients. CONCLUSIONS: FISH analysis could be observed an one of strongest methods of analysis in detecting numerical aberrations of individual chromosomes with application to paraffin-block samples, metaphase and, interphase nuclei. To our knowledge, this analysis is firstly studied in Turkish patients. Therefore, results of this analysis may be important for Turkish patients.