title: Gene structure and mutant alleles of PCDH15: nonsyndromic deafness DFNB23 and type 1 Usher syndrome.
abstract: Mutations of PCDH15, encoding protocadherin 15, can cause either combined hearing and vision impairment (type 1 Usher syndrome; USH1F) or nonsyndromic deafness (DFNB23). Human PCDH15 is reported to be composed of 35 exons and encodes a variety of isoforms with 3-11 ectodomains (ECs), a transmembrane domain and a carboxy-terminal cytoplasmic domain (CD). Building on these observations, we describe an updated gene structure that has four additional exons of PCDH15 and isoforms that can be subdivided into four classes. Human PCDH15 encodes three alternative, evolutionarily conserved unique cytoplasmic domains (CD1, CD2 or CD3). Families ascertained on the basis of prelingual hearing loss were screened for linkage of this phenotype to markers for PCDH15 on chromosome 10q21.1. In seven of twelve families segregating USH1, we identified homozygous mutant alleles (one missense, one splice site, three nonsense and two deletion mutations) of which six are novel. One family was segregating nonsyndromic deafness DFNB23 due to a homozygous missense mutation. To date, in our cohort of 557 Pakistani families, we have found 11 different PCDH15 mutations that account for deafness in 13 families. Molecular modeling provided mechanistic insight into the phenotypic variation in severity of the PCDH15 missense mutations. We did not find pathogenic mutations in five of the twelve USH1 families linked to markers for USH1F, which suggest either the presence of mutations of yet additional undiscovered exons of PCDH15, mutations in the introns or regulatory elements of PCDH15, or an additional locus for type I USH at chromosome 10q21.1.
authors: Section on Human Genetics, Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD 20850, USA.
authors: Zubair M
authors: ZM
authors: Ahmed
authors: Saima
authors: S
authors: Riazuddin
authors: Sandar
authors: S
authors: Aye
authors: Rana A
authors: RA
authors: Ali
authors: Hanka
authors: H
authors: Venselaar
authors: Saima
authors: S
authors: Anwar
authors: Polina P
authors: PP
authors: Belyantseva
authors: Muhammad
authors: M
authors: Qasim
authors: Sheikh
authors: S
authors: Riazuddin
authors: Thomas B
authors: TB
authors: Friedman
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000070585:Cadherin Related Proteins; D015820:Cadherins / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D008040:Genetic Linkage; D005819:Genetic Markers; D034381:Hearing Loss / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D017386:Sequence Homology, Amino Acid; D052245:Usher Syndromes / Q000235:genetics*
chemical_list: C498835:CDHR15, human; D000070585:Cadherin Related Proteins; D015820:Cadherins; D005819:Genetic Markers