Activation of multiple cryptic donor splice sites by the common congenital afibrinogenemia mutation, FGA IVS4 + 1 G-->T.
Our recent studies on the molecular basis of the autosomal recessive disorder congenital afibrinogenemia showed that the most common mutation is a donor splice mutation in FGA intron 4, IVS4 + 1 G-->T, accounting for approximately half of disease alleles. The effect of this mutation on messenger RNA (mRNA) splicing, however, remained unproven. COS-7 cells transfected with a normal plasmid construct produced 100% mRNA molecules with correct splicing, whereas cells transfected with a mutant construct produced multiple aberrant mRNAs, due to utilization of cryptic donor splice sites situated in exon 4 and intron 4. One particular site situated 4 base pairs (bp) downstream of the normal site was used in 85% of transcripts causing afibrinogenemia by a 4-bp insertion-frameshift, leading to premature alpha-chain truncation. Our results confirm the utility of transfecting COS-7 cells to study mRNA splice-site mutations and demonstrate that the common FGA IVS4 variant is a null mutation leading to afibrinogenemia.
Attanasio
C
C
Division of Medical Genetics, University Medical School and University Hospital, Geneva, Switzerland.
de Moerloose
P
P
Antonarakis
S E
SE
Morris
M A
MA
Neerman-Arbez
M
M
D000347:Afibrinogenemia / Q000151:congenital / Q000209:etiology / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D005091:Exons / Q000235:genetics; D005340:Fibrinogen / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D017354:Point Mutation; D022821:RNA Splice Sites / Q000235:genetics*; D014162:Transfection
D022821:RNA Splice Sites; D005340:Fibrinogen