A point mutation in the lariat branch point of intron 6 of NPC1 as the cause of abnormal pre-mRNA splicing in Niemann-Pick type C disease
✍ Scribed by Enza Di Leo; Francesca Panico; Patrizia Tarugi; Carla Battisti; Antonio Federico; Sebastiano Calandra
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 406 KB
- Volume
- 24
- Category
- Article
- ISSN
- 1059-7794
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✦ Synopsis
The lariat branch point sequence (BPS) is crucial for splicing pre-mRNA even if BPS mutations have infrequently been reported in human disease. In two siblings with Niemann-Pick type C (NPC) disease we identified two mutations of the NPC1 gene: i) one in exon 20 (c.2932C>T) (p.R978C) previously reported in NPC patients; ii) the other (c.882-28A>G) unreported, in the highly conserved adenosine of a putative lariat BPS of intron 6. Using RT-PCR we found that, besides the normally spliced mRNA, patients' fibroblasts contained minute amounts of an mRNA devoid of exon 7. The exon 6--exon 8 junction in this mRNA causes a frameshift and a premature stop codon, predicted to result in a truncated protein. To assess the effect of c.882-28A>G mutation we constructed two minigenes (wild type and mutant), spanning from intron 5 to intron 8, which were inserted into a pTarget vector and transfected in COS1 cells. The wild type minigene generated an mRNA of the expected size and sequence; the mutant minigene generated only an mRNA devoid of exon 7. This is the first example of a splicing defect due to a mutation in the lariat BPS in an intron of NPC1 found in NPC patients.