Identification of mutations in two families with sporadic hemophilia A

Abstract

Direct sequencing of segments of the factor VIII gene in 30 hemophiliacs with sporadic disease (32+ kb of sequence in total) revealed two missense transitions: glutamate 1704 to lysine (E1704----K) in a patient with severe hemophilia A and proline 2300 to serine (P2300----S) in a patient with mild hemophilia. Both transitions are likely to be causative mutations because the amino acids affected were evolutionarily conserved. Haplotype and sequence analysis of the mother and grandparents of patient HA12 (E1704----K) indicate that the mutation arose in the grandfather who was 27 years old when his daughter was conceived. The origin of mutation in patient HA39 (P2300----S) could not be determined. As mutations that cause mild disease can be found in seemingly unrelated families, 96 unrelated hemophiliacs were screened rapidly for the P2300----S mutation with polymerase chain reaction (PCR) amplification of specific alleles (PASA). None of these patients had the mutation. PASA was also used to conveniently assess a polymorphic site in intron 7. The polymorphism is estimated to be informative in 13% of Korean females and in 23% of Western European females.

Factor VIII genotype characterization of haemophilia A affected patients with transient and permanent inhibitors: a comprehensive Argentine study of inhibitor risks

“…Mutation p.Glu1704Lys is a non‐conservative change, acidic negative to basic positive and was once reported in a severe‐HA patient without inhibitors . The molecular basis of the dissimilar phenotype of p.Glu1704Lys found in the HADB remains unclear.…”

Somatic/Germinal Mosaicism of a F8 Promoter Deletion Confounds Clinical Predictions in a Family with Haemophilia A: Key Role of Genotype Quantitation

“…Este cambio aminoacídico, Glu>Lys, corresponde a un cambio de aminoácido ácido con carga negativa a básico con carga positiva, estos cambios de clase fisicoquímica no conservativa han sido asociados a un mayor riesgo de desarrollo de inhibidor (Schwaab et al, 2013). Aunque la variante p.Glu1723Lys ha sido reportada en dos ocasiones en la HADB asociada a HA severa/moderada, en ninguno de los casos se reportó desarrollo de inhibidor (Green et al, 2008;Paynton et al, 1991). El residuo Glu1723 del FVIII se ubica a 15 residuos hacia el extremo amino-terminal de un sitio clave de activación por trombina y FXa (Arg1708) y a 17 residuos hacia el extremo carboxilo-terminal de un sitio de activación adicional por FIXa y FXa (Arg1740) (Orlova et al, 2013), y forma parte de una estructura secundaria tipo hoja plegada beta en el dominio A3, que está parcialmente expuesto sobre la superficie del FVIIIa y cuyo cambio generaría, potencialmente, una modificación importante en el potencial electrostático de la superficie según el análisis in silico realizado (Figura III.8).…”