Mutation analysis in the long isoform of USH2A in American patients with Usher Syndrome type II.
Usher syndrome type II (USH2) is an autosomal recessive disorder characterized by moderate to severe hearing impairment and progressive visual loss due to retinitis pigmentosa (RP). To identify novel mutations and determine the frequency of USH2A mutations as a cause of USH2, we have carried out mutation screening of all 72 coding exons and exon-intron splice sites of the USH2A gene. A total of 20 USH2 American probands of European descent were analyzed using single strand conformational polymorphism (SSCP) and direct sequencing methods. Ten different USH2A mutations were identified in 55% of the probands, five of which were novel mutations. The detected mutations include three missense, three frameshifts and four nonsense mutations, with c.2299delG/p.E767fs mutation, accounting for 38.9% of the pathological alleles. Two cases were homozygotes, two cases were compound heterozygotes and one case had complex allele with three variants. In seven probands, only one USH2A mutation was detected and no pathological mutation was found in the remaining eight individuals. Altogether, our data support the fact that c.2299delG/p.E767fs is indeed the most common USH2A mutation found in USH2 patients of European Caucasian background. Thus, if screening for mutations in USH2A is considered, it is reasonable to screen for the c.2299delG mutation first.
Yan
Denise
D
Department of Otolaryngology, University of Miami, Miami, FL 33136, USA.
Ouyang
Xiaomei
X
Patterson
D Michael
DM
Du
Li Lin
LL
Jacobson
Samuel G
SG
Liu
Xue-Zhong
XZ
D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D018389:Codon, Nonsense; D004252:DNA Mutational Analysis / Q000379:methods*; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D005260:Female; D016368:Frameshift Mutation; D005787:Gene Frequency; D005820:Genetic Testing; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D020125:Mutation, Missense; D018807:Polymorphism, Single-Stranded Conformational; D020033:Protein Isoforms / Q000235:genetics; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014481:United States; D052245:Usher Syndromes / Q000175:diagnosis / Q000235:genetics*; D044465:White People / Q000235:genetics
D018389:Codon, Nonsense; D016326:Extracellular Matrix Proteins; D020033:Protein Isoforms; C112735:USH2A protein, human