A novel splice acceptor site mutation which produces multiple splicing abnormalities resulting in protein S deficiency type I

In an attempt to explore the molecular mechanisms for protein S deficiency, a patient with such a deficiency was examined at the DNA, RNA and protein levels. Nucleotide analyses revealed that the proband, the mother and the g randmother had a G --> C substitution in the invariant AG dinucleotide at t he splicing acceptor site of intron A/exon 2. This patient was heterozygous for this substitution and the mutant allele was inherited from the proband 's mother and grandmother. Reverse transcription-polymerase chain reaction analysis demonstrated several kinds of splicing abnormalities such as exon skipping and cryptic splicing, in addition to correct splicing. Semiquantit ation of mRNA fdr the protein S gene revealed that the amount of the proban d's mRNA was reduced to 60% of normal. Thus, this mutation impaired the nor mal processing of mRNA for the protein S gene, resulting in the subject's s evere protein S deficiency.