Abnormal splicing of ABCA1 pre-mRNA in Tangier disease due to a IVS2 +5G>C mutation in ABCA1 gene.
Two point mutations of ABCA1 gene were found in a patient with Tangier disease (TD): i) G>C in intron 2 (IVS2 +5G>C) and ii) c.844 C>T in exon 9 (R282X). The IVS2 +5G>C mutation was also found in the brother of another deceased TD patient, but not in 78 controls and 33 subjects with low HDL. The IVS2 +5G>C mutation disrupts ABCA1 pre-mRNA splicing in fibroblasts, leading to three abnormal mRNAs: devoid of exon 2 (Ex2-/mRNA), exon 4 (Ex4-/mRNA), or both these exons (Ex2-/Ex4-/mRNA), each containing a translation initiation site. These mRNAs are expected either not to be translated or generate short peptides. To investigate the in vitro effect of IVS2 +5G>C mutation, we constructed two ABCA1 minigenes encompassing Ex1-Ex3 region, one with wild-type (WTgene) and the other with mutant (MTgene) intron 2. These minigenes were transfected into COS1 and NIH3T3, two cell lines with a different ABCA1 gene expression. In COS1 cells, WTgene pre-mRNA was spliced correctly, while the splicing of MTgene pre-mRNA resulted in Ex2-/mRNA. In NIH3T3, no splicing of MTgene pre-mRNA was observed, whereas WTgene pre-mRNA was spliced correctly. These results stress the complexity of ABCA1 pre-mRNA splicing in the presence of splice site mutations.
Altilia
Serena
S
Department of Biomedical Sciences, University of Modena and Reggio Emilia, Rome, Italy.
Pisciotta
Livia
L
Garuti
Rita
R
Tarugi
Patrizia
P
Cantafora
Alfredo
A
Calabresi
Laura
L
Tagliabue
Jacopo
J
Maccari
Sergio
S
Bernini
Franco
F
Zanotti
Ilaria
I
Vergani
Carlo
C
Bertolini
Stefano
S
Calandra
Sebastiano
S
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D000328:Adult; D000368:Aged; D017398:Alternative Splicing; D002478:Cells, Cultured; D002648:Child; D002784:Cholesterol / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006239:Haplotypes; D006801:Humans; D007438:Introns; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D017354:Point Mutation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013631:Tangier Disease / Q000235:genetics* / Q000378:metabolism
C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D012333:RNA, Messenger; D002784:Cholesterol