Correct usage of a mutated G+1 splice site and transcript quantitation in a lipoprotein lipase-deficient patient

The consequence on the splice mechanism of a mutation occurring at the donor splice site of intron 1 has been studied. We demonstrate that, in spite of the change at G+1 position, this site is still utilized and can produce correctly spliced transcript. Nevertheless the mRNA is detectable only after an 'in vitro' amplification. A procedure has been developed to reveal and quantify the minute amount present in the patient. The very low mRNA level results in a total lack of enzyme, the cause of the disease. The procedure can be useful in cases of rare transcripts and when the source is limited. Furthermore we analyse the interaction between the splice consensus sequence and the small nuclear RNA, that is the necessary intermediate of the splicing mechanism. We speculate on the reasons why cryptic sites are not utilized and only the authentic site can be used, although significantly destabilized by the mutation.