A nonsense mutation in exon 8 of the APC gene (Arg283Ter) causes clinically variable FAP in a Malaysian Chinese family.
The present study was carried out to characterize the causative genetic mutation in a medium-sized Malaysian Chinese pedigree of three generations affected with familial adenomatous polyposis (FAP). Clinical data and genetic studies revealed considerable phenotypic variability in affected individuals in this family. Blood was obtained from members of the FAP-01 family and genomic DNA was extracted. Mutation screening of the adenomatous polyposis coli (APC) gene was carried out using the single strand conformation polymorphism (SSCP) technique. The possibility of exon skipping was predicted by splicing motif recognition software (ESEfinder release2.0). SSCP results showed mobility shifts in exon 8 of the APC gene which segregated with affected members of the family. Sequence analysis revealed that the affected individuals are heterozygous for a C847T transition, whilst all the unaffected family members and control individuals are homozygous C at the same position. This nucleotide substitution generates a stop codon at amino acid position 283, in place of the usual arginine (Arg283Ter). We conclude that an Arg283Ter mutation in the APC gene is causative of the FAP phenotype in this family, although there is considerable variation in the presentation of this disease among affected individuals. Computational analysis predicts that this mutation occurs within sequences that may function as splicing signals, so that the sequence change may affect normal splicing.
Mohamed
Zulqarnain
Z
Department of Biochemistry, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia. zulq@um.edu.my
Ahmad
Rahimah
R
Yoke
Ng Sau
NS
Zakaria
Zubaidah
Z
Ahmad
Harun
H
Yew
Tong Hung
TH
D011125:Adenomatous Polyposis Coli / Q000235:genetics*; D019943:Amino Acid Substitution; D001120:Arginine; D044466:Asian People; D001483:Base Sequence; D018389:Codon, Nonsense / Q000235:genetics*; D005091:Exons / Q000235:genetics*; D005260:Female; D017491:Genes, APC; D006801:Humans; D008296:Malaysia; D008297:Male; D010375:Pedigree; D018807:Polymorphism, Single-Stranded Conformational; D012842:Sarcoma Virus, Woolly Monkey
D018389:Codon, Nonsense; D001120:Arginine