An intronic mutation in a lariat branchpoint sequence is a direct cause of an inherited human disorder (fish-eye disease).
The first step in the splicing of an intron from nuclear precursors of mRNA results in the formation of a lariat structure. A distinct intronic nucleotide sequence, known as the branchpoint region, plays a central role in this process. We here describe a point mutation in such a sequence. Three sisters were shown to suffer from fish-eye disease (FED), a disorder which is caused by mutations in the gene coding for lecithin:cholesterol acyltransferase (LCAT). Sequencing of the LCAT gene of all three probands revealed compound heterozygosity for a missense mutation in exon 4 which is reported to underlie the FED phenotype, and a point mutation located in intron 4 (IVS4:T-22C). By performing in vitro expression of LCAT minigenes and reverse transcriptase PCR on mRNA isolated from leukocytes of the patient, this gene defect was shown to cause a null allele as the result of complete intron retention. In conclusion, we demonstrated that a point mutation in a lariat branchpoint consensus sequence causes a null allele in a patient with FED. In addition, our finding illustrates the importance of this sequence for normal human mRNA processing. Finally, this report provides a widely applicable strategy which ensures fast and effective screening for intronic defects that underlie differential gene expression.
Kuivenhoven
J A
JA
Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, The Netherlands.
Weibusch
H
H
Pritchard
P H
PH
Funke
H
H
Benne
R
R
Assmann
G
G
Kastelein
J J
JJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D017124:Conserved Sequence; D003316:Corneal Diseases / Q000201:enzymology / Q000235:genetics*; D017931:DNA Primers; D005091:Exons; D005260:Female; D006580:Genetic Carrier Screening; D006801:Humans; D007438:Introns; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D010375:Pedigree; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012322:RNA Precursors / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis
D017931:DNA Primers; D012322:RNA Precursors; D012333:RNA, Messenger; D007862:Phosphatidylcholine-Sterol O-Acyltransferase