Summary
The abnormal prothrombin gene of an Italian patient with a severe bleeding tendency
and hypoprothrombinemia was selected for study and compared with the prothrombin genes
of healthy controls. All the coding and their flanking regions and the 5ʹ- and 3ʹ-UT
regions of the prothrombin gene were screened by analyzing the nucleotide sequence
of the corresponding PCR products. The patient was found to be heterozygous for two
novel point mutations: one at nucleotide 4251 in exon 6, which changes the codon for
cysteine-138 (TGC) in the kringle 1 domain to that for tyrosine (TAC), and one at
nucleotide 8812 in exon 10, which results in the replacement of tryptophan-357 (TGG)
by cysteine (TGT) in the catalytic domain. Her mother was heterozygous for the Cys-138
Tyr mutation and her father heterozygous for the Trp-357 Cys mutation. Several other
sequence variations were identified in the prothrombin genes from control individuals.
Only the variations at nucleotide 4203 and 10253 could be established as polymorphisms.