Mutations in TMC1 contribute significantly to nonsyndromic autosomal recessive sensorineural hearing loss: a report of five novel mutations.

Genome wide homozygosity mapping using Affymetrix 10K arrays revealed the DFNB7/11 locus including the TMC1 gene in 5 of 35 Turkish families with autosomal recessive nonsyndromic severe to profound congenital or prelingual-onset sensorineural hearing loss (SNHL). Additional 51 families were later screened for co-segregation of the locus with the phenotype using microsatellite markers. GJB2 and mtDNA A1555G mutations were negative in probands from each family. Mutation analysis was performed in families showing co-segregation of autosomal recessive SNHL with haplotypes at the DFNB7/11 locus. A total of six different mutations in seven families were identified, including novel missense alterations, p.G444R (c.1330G>A), p.R445C (c.1333C>T), and p.I677T (c.2030T>C), one novel splice site mutation IVS6+2 T>A (c.64+2T>A), and a novel large deletion of approximately 31kb at the 3' region of the gene including exons 19-24, as well as a previously reported nonsense mutation, p.R34X (c.100C>T). All identified mutations co-segregated with autosomal recessive SNHL in all families and were not found in Turkish hearing controls. These results expand the mutation spectrum of TMC1 with five novel mutations and provide data for the significant contribution of TMC1 mutations in hearing loss.

Rubinstein-Taybi syndrome with normal FISH result and CREBBP gene analysis: a case report.

We report on a six-year-old boy with typical Rubinstein-Taybi syndrome (RSTS) phenotype. Clinical findings included mental and motor retardation, patent ductus arteriosus (PDA), undescended testes, hirsutism, broad thumbs with radial angulation and broad toes, and inguinal hernia. His karyotype was normal (46, XY) and fluorescence in situ hybridization (FISH) showed no deletion of the CREBBP [cAMP response element-binding (CREB) binding protein] gene on chromosome 16p13.3. CREBBP gene sequencing also revealed normal results. We wish to present this case because this patient had typical RSTS phenotype, but normal FISH and CREBBP gene sequencing results. It could be possible that genetic heterogeneity is related with novel mutations in other genes. With the publication of such cases, their significance will be brought to the attention of researchers in this field.

Homozygous mutations in fibroblast growth factor 3 are associated with a new form of syndromic deafness characterized by inner ear agenesis, microtia, and microdontia.

We identified nine individuals from three unrelated Turkish families with a unique autosomal recessive syndrome characterized by type I microtia, microdontia, and profound congenital deafness associated with a complete absence of inner ear structures (Michel aplasia). We later demonstrated three different homozygous mutations (p.S156P, p.R104X, and p.V206SfsX117) in the fibroblast growth factor 3 (FGF3) gene in affected members of these families, cosegregating with the autosomal recessive transmission as a completely penetrant phenotype. These findings demonstrate the involvement of FGF3 mutations in a human malformation syndrome for the first time and contribute to our understanding of the role this gene plays in embryonic development. Of particular interest is that the development of the inner ear is completely disturbed at a very early stage--or the otic vesicle is not induced at all--in all of the affected individuals who carried two mutant FGF3 alleles.