Molecular basis for type 1 antithrombin deficiency: identification of two
novel point mutations and evidence for a de novo splice site mutation
K Jochmans, W Lissens, T Yin, JJ Michiels, L van der Luit, K Peerlinck, M De Waele and I Liebaers
Department of Hematology, Academic Hospital of the Free University of
Brussels, Belgium.
Inherited type 1 antithrombin (AT) deficiency is characterized by a
reduction in both immunologically and functionally detectable protein. The
disorder is associated with a high risk of thromboembolic disease. We have
investigated the molecular basis of type 1 AT deficiency in three unrelated
families. We have used the polymerase chain reaction single-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 single-base
substitution was found in codon 421 in exon 6 (nucleotide position 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 frameshift mutation and
predicting premature termination of protein translation at codon 251. In a
third family, a previously reported G to A substitution, 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 splice site by ectopic transcript analysis
of lymphocyte mRNA. In all cases, the affected individuals were
heterozygous for the mutation and no variant AT protein was detected.
Volume 84,
Issue 11,
pp. 3742-3748,
12/01/1994
Copyright © 1994 by The American Society of Hematology
