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Nail patella syndrome (NPS) or osteo-onychodysplasia, is an autosomal dominant disorder characterised by nail dysplasia, absent or hypoplastic patellae, iliac horns and nephropathy. Previous studies have demonstrated linkage of the nail patella locus to the ABO and adenylate kinase loci on human chromosome 9q34. Recently, informative recombination events placed the NPS locus within a 1–2 cM interval within D9S60 and the AK1 gene. We describe here linkage analysis performed in two large Italian pedigrees with 10 and 11 members affected, respectively. A set of highly informative markers have been analysed and the allele segregation in the two families confirmed the linkage to chromosome 9. The presence of three recombination events allows definition of the critical region with a centrometric boundary between markers D9S1881 and D9S1840 and a telomeric boundary between markers D9S315 and D9S290. [ABSTRACT FROM AUTHOR]

Summary: Nonsyndromic sensorineural hearing impairment is inherited in a predominantly autosomal recessive manner in up to 70% of cases. The gene more often involved is GJB2, encoding the gap junction protein Connexin 26. We report here a novel missense mutation in the GJB2 gene found in a Tunisian family. A homozygous change C/G at nucleotide 263 was detected in the 4-year-old girl of this family, affected by congenital moderate hearing loss. This transversion leads to the replacement of a highly conserved alanine with glycine at codon 88 (A88G). The consanguineous parents of the child are healthy carriers of the mutation. [Copyright &y& Elsevier]

Myosins have been implicated in various motile processes, including organelle translocation, ion-channel gating, and cytoskeleton reorganization. Different members of the myosin superfamily are responsible for syndromic and nonsyndromic hearing impairment in both humans and mice. MYH14 encodes one of the heavy chains of the class II nonmuscle myosins, and it is localized within the autosomal dominant hearing impairment (DFNA4) critical region. After demonstrating that MYH14 is highly expressed in mouse cochlea, we performed a mutational screening in a large series of 300 hearing-impaired patients from Italy, Spain, and Belgium and in a German kindred linked to DFNA4. This study allowed us to identify a nonsense and two missense mutations in large pedigrees, linked to DFNA4, as well as a de novo allele in a sporadic case. Absence of these mutations in healthy individuals was tested in 200 control individuals. These findings clearly demonstrate the role of MYH14 in causing autosomal dominant hearing loss and further confirm the crucial role of the myosin superfamily in auditive functions. [ABSTRACT FROM AUTHOR]