title: The Arabic allele: a single base pair substitution activates a 10-base downstream cryptic splice acceptor site in exon 12 of LDLR and severely decreases LDLR expression in two unrelated Arab families with familial hypercholesterolemia.
abstract: Familial hypercholesterolemia (FH) is a monogenic autosomal dominant disorder caused by defects in LDLR. Few reports describe FH mutations among Arabs. We describe a mutation in LDLR of two unrelated Arab families. We investigated 19 patients using DNA sequencing, RFLP, and real-time (RT) PCR. DNA sequencing showed a base pair substitution (c.1706-2 A>T) in the splice acceptor site of LDLR intron 11. Our results were confirmed by RFLP on 2% agarose gel. In silico analysis predicted a new cryptic splice site downstream of the original position generating a 10-base deletion from the beginning of exon 12; (c.1706-1715del.ATCTCCTCAG). cDNA sequencing of exon 12 confirmed the computational analysis. The deletion was visualized on 4% agarose gel. The deletion generates a frameshift and a premature termination codon (c.1991-1993; p.(Asp569Valfs*93). RT-PCR revealed that LDLR mRNA is 9.3%±6.5 and 17.9%±8.0 for FH homozygote and heterozygote individuals respectively, compared to a healthy family control. We predict a class II LDLR mutation that leads to a truncated receptor missing exons 14-18. We called this mutation "the Arabic allele". We expect a significant contribution of this mutation to the prevalence of FH among Arabs. Also, we propose that the severe down regulation of LDLR mRNA expression is due to nonsense-mediated-decay.
authors: Biotechnology Program, Arabian Gulf University, Manama, Bahrain. Shawar@pol.net
authors: Said M
authors: SM
authors: Shawar
authors: Mohammad A
authors: MA
authors: Al-Drees
authors: Ahmad R
authors: AR
authors: Ramadan
authors: Najat H
authors: NH
authors: Ali
authors: Suad M
authors: SM
authors: Alfadhli
mesh_terms: D000293:Adolescent; D000328:Adult; D018912:Arabs / Q000235:genetics*; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D015536:Down-Regulation; D004587:Electrophoresis, Agar Gel; D005091:Exons; D005260:Female; D016368:Frameshift Mutation; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000208:ethnology / Q000235:genetics* / Q000378:metabolism; D007438:Introns; D008297:Male; D008875:Middle Aged; D008877:Middle East / Q000453:epidemiology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010375:Pedigree; D010641:Phenotype; D022821:RNA Splice Sites; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D011973:Receptors, LDL / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion; D055815:Young Adult
chemical_list: D022821:RNA Splice Sites; D012333:RNA, Messenger; D011973:Receptors, LDL