Generation of hypomorphic model mice utilizing an mRNA instability element

点击翻译按钮获取中文摘要

We identified the genes associated with cataract formation in Shumiya cataract rat (SCR) by positional cloning. Mutations of the gene for lanosterol synthase (Lss) were identified. Cataract onset in SCR was uniquely regulated by a specific combination of different mutant (Lss^l) and polymorphic alleles (Lss^s) on the Lss locus. Lss^s was a hypomorphic allele with a G to A nucleotide substitution in exon 4. The G to A nucleotide substitution also caused instability of the Lss mRNA transcripts.When a luciferase reporter gene was linked to the exon 4 sequence of Lss^s, which contain the mRNA instability element and expressed in the COS cells, luciferase activity was significantly reduced. This result indicated that the mRNA instability element functions regardless of the gene, in which it is located. We then examined the possibility that the change of an exonic splicing enhancer (ESE) element by the G to A substitution is the cause of instability of the Lss^s mRNA precursor. Analysis by the computer program ESEfinder identified a novel SRp40 binding motif, with a score of 4.15, in the Lss^s allele. SRp40 has previously been studied for its role in alternative splicing and has been shown to select both proximal and distal 5' splice sites in a substrate-specific manner. It was suggested that the Lss^s mRNA precursor becomes unstable if SRp40 splicing factor is bound to irrelevant sites in the precursor.