Identification of a homozygous single base pair deletion in the gene coding for the human platelet glycoprotein Ib alpha causing Bernard-Soulier syndrome.
Bernard-Soulier Syndrome (BSS) is a hereditary bleeding disorder which is caused by the absence or the dysfunction of the platelet glycoprotein Ib/IX/V (GP Ib/IX/V) complex, the major receptor for von Willebrand factor (vWf). BSS is characterized by the presence of giant platelets that show a reduced binding of vWf. Although BSS is a well-characterized disease, and many cases have been described in the literature, the molecular genetic basis of this disorder has been studied in only a few patients. We have studied the genetic basis of the defect in a BSS patient. Flow cytometric analysis of the platelet membrane glycoproteins revealed a significant decrease or absence of GP Ib alpha on the platelet surface, and low levels of GP V and GP IX. In subsequent immunoprecipitation experiments, we confirmed the presence of GP V (although in significantly decreased amounts) on the platelet surface. These results indicated a defect in the GP Ib alpha chain. Genomic DNA coding for GP Ib alpha was amplified, using the polymerase chain reaction (PCR). Subsequent direct sequence analysis demonstrated a homozygous deletion of T317 resulting in a frameshift deletion and predicting a substitution of Arg for Leu76. This deletion causes a shift in the reading frame, predicting a premature stop codon after 19 altered amino-acids, leading to a severily truncated molecule. The molecular genetic defect found in this patient differed from the mutations observed in three other BSS patients described in the literature. This points to a marked hetereogeneity of this disease.(ABSTRACT TRUNCATED AT 250 WORDS)
Simsek
S
S
Department of Immunologic Haematology, Central Laboratory of The Netherlands Red Cross Blood Transfusion Service, Amsterdam.
Admiraal
L G
LG
Modderman
P W
PW
van der Schoot
C E
CE
von dem Borne
A E
AE
D000328:Adult; D000483:Alleles; D000595:Amino Acid Sequence; D001482:Base Composition; D001483:Base Sequence; D001606:Bernard-Soulier Syndrome / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D005796:Genes; D006720:Homozygote; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010375:Pedigree; D010980:Platelet Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000172:deficiency / Q000235:genetics*; D016415:Sequence Alignment; D017384:Sequence Deletion; D014841:von Willebrand Factor / Q000378:metabolism
D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D014841:von Willebrand Factor; C028254:von Willebrand factor receptor