A POINT MUTATION AND A GENE DELETION OF FVIII GENE IN SEVERE HAEMOPHILIA
XIth International Congress on Thrombosis and Haemostasis
The presence of Factor VIII (FVIII) gene lesions has been investigated in 100 haemophilia A patients using cDNA probes for the 3'part of FVIII gene (exons 14-26 ).In two related severe patients without inhibitor a deletion removesthe exon 26; the gene lesion has been confirmed with several restriction enzymes and has been shown by densitometry of the autoradiographic pattern in a woman of the same family. The complete deletionof the exon 26 has been described by Gitschier et al. in a patient
... al. in a patient with inhibitor. Thus the comparison of the end points of the two deletions could help to define the mechanism originating these gene lesions and the relation between gene lesions and the presence of antibody.In a patient with severe Haemophilia and without inhibitor a mutation removing the TaqI site in the exon 24 and originating an abnormal band of 4.2 Kb has been found. A C→T transition in this TaqI site, originating a nonsense codon and a new Hindlll site, has been reported by Gitschier et al in a patient presenting inhibitor. The DNA from our patient tested with Hindlll shows a normal pattern thus indicating a C→T transition in the antisense strand. This mutation should causean aminoacid change (CGA→CAA, Arg→Gln) possiblyresponsible for the FVIII inactivation but that does not remove theantigenic determinants present in the COOH terminal part of FVIII.In addition the same mutation has been observed in an unrelated (asdemonstrated by RFLPs analysis) Italian haemophilic patient confirming the observation of Youssoufian et al that TaqI sites are mutational hot spots in FVIII gene.