Detection of somatic mutations of the PIG-A gene in Brazilian patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal syndrome ch aracterized by intravascular hemolysis mediated by complement, thrombotic e vents and alterations in hematopoiesis. Basically, the molecular events whi ch underlie the complexity of the syndrome consist of the absence of the gl ycosylphosphatidylinositol (GPI) anchor as a consequence of somatic mutatio ns in the PIG-A gene, located on the X chromosome. The GPI group is respons ible for the attachment of many proteins to the cytoplasmic membrane. Two o f them, CD55 and CD59, have a major role in the inhibition of the action of complement on the cellular membrane of blood cells. The absence of GPI bio synthesis can lead to PNH. Since mutations in the PIG-A gene are always pre sent in patients with PNH, the aim of this study was to characterize the mu tations in the PIG-A gene in Brazilian patients. The analysis of the PIG-A gene was performed using DNA samples derived from bone marrow and periphera l blood. Conformation-sensitive gel electrophoresis was used for screening the mutation and sequencing methods were used to identify the mutations. Mo lecular analysis permitted the identification of three point mutations in t hree patients: one G -->A transition in the 5 ' portion of the second intro n, one T -->A substitution in the second base of codon 430 (Leu430 --> stop ), and one deletion DeltaA in the third base of codon 63. This study repres ents the first description of mutations in the PIG-A gene in a Brazilian po pulation.