K. Jochmans et al., MOLECULAR-BASIS FOR TYPE-1 ANTITHROMBIN DEFICIENCY - IDENTIFICATION OF 2 NOVEL POINT MUTATIONS AND EVIDENCE FOR A DE-NOVO SPLICE-SITE MUTATION, Blood, 84(11), 1994, pp. 3742-3748
Inherited type 1 antithrombin (AT) deficiency is characterized by a re
duction in both immunologically and functionally detectable protein. T
he disorder is associated with a high risk of thromboembolic disease.
We have investigated the molecular basis of type 1 AT deficiency in th
ree unrelated families. We have used the polymerase chain reaction sin
gle-strand conformation polymorphism (PCR-SSCP) analysis, followed by
direct sequencing of the seven exons and the intron-exon junctions of
the AT gene. Two novel point mutations were identified. A T to C singl
e-base substitution was found in codon 421 in exon 6 (nucleotide posit
ion 13380), leading to an AT 421 isoleucine to threonine substitution.
In another kindred, one of three Cs at nucleotide (nt) positions 5448
to 5450 in exon 3A (codon 151 or 152) was deleted, resulting in a fra
meshift mutation and predicting premature termination of protein trans
lation at codon 251. In a third family, a previously reported G to A s
ubstitution, at nt position 9788 in intron 4, 14 bp in front of exon 5
, was found. We have demonstrated the creation of a de novo exon 5 spl
ice site by ectopic transcript analysis of lymphocyte mRNA. In all cas
es, the affected individuals were heterozygous for the mutation and no
variant AT protein was detected. (C) 1994 by The American Society of
Hematology.