Summary
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 grandmother had a G → C substitution
in the invariant AG dinucleotide at the 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. Semiquantitation of
mRNA for the protein S gene revealed that the amount of the proband’s mRNA was reduced
to 60% of normal. Thus, this mutation impaired the normal processing of mRNA for the
protein S gene, resulting in the subject’s severe protein S deficiency.