Summary
Factor XIII deficiency is a rare autosomal (1:2,000,000) recessive disorder of blood
coagulation usually attributed to mutations in the coagulation factor XIII (FXIII)
A gene. We have studied the molecular basis of FXIII deficiency in eight unrelated
South Indian patients. Their diagnosis was based on clinical history, normal plasma
clotting times and increased solubility of fibrin clot in5 mol/l urea. Genomic DNA
was screened for FXIII A gene defects by a novel PCR and CSGE strategy. Mutations
were identified in all these patients. Five of these were novel mutations occurring
in four patients. These included a novel c.210T>G transversion in homozygosity in
exon 3 predicting a Tyr69X in the beta-sandwich domain in one patient. Another patient
was compound heterozygote for a novel c.791C>T transition predicting a Ser263Phe in
the core domain and a novel c.2045–1G>A transition at the acceptor splice junction
of in tron 14. Two novel frame shifts were also identified in two patients in a homozygous
condition. One of them resulted from a single base ‘G’ duplication (c.892_895dupG)
at codons Ser290/Ala291fs affecting the core domain and the other was due to a single
base ‘A’ duplication (c.1642_1644dupA) and at codonTyr547fs affecting barrel-1 domain.
The remaining four patients had the previously reported Arg260His, Ser413Leu, and
Val414Phe (n = 2) missense mutations in the core domain. The novel mutations identified
were considered to be disease causative by studying the nature of mutation, the degree
of conservation of the mutated aminoacid among transglutaminases of different species
and by molecular modeling. Apart from describing a significant number of novel mutations,
this report is the first study from Southern India to describe FXIII A gene mutations.
Keywords
Factor XIII - mutation - CSGE