Mutation analysis of HPS1, the gene mutated in Hermansky-Pudlak syndrome, in patients with isolated platelet dense-granule deficiency.
OBJECTIVE
Isolated platelet dense granule (PDG) deficiency is a heterogeneous disorder frequently found among patients with mild to moderate bleeding diatheses. However, the molecular basis of this disorder is unknown. Genes involved in other rare bleeding disorders with associated reduction in the numbers of platelet dense-granules may play a role in isolated PDG deficiency. Among such genes, HPS1 is known to play a key role in the genesis of PDG and as many as 18 different HPS1 mutations have been identified in patients with Hermansky-Pudlak syndrome. Recently, we have identified subjects with one HPS1 heterozygous mutation displaying significant reductions in PDG without the clinical phenotype of Hermansky-Pudlak syndrome. This suggested that HPS1 mutations could be involved in isolated PDG deficiency.


METHODS
We sequenced all coding exons, and flanking intron regions of HPS1 in 16 patients with mild to severe PDG deficiency, most of whom had mild bleeding episodes. Nine patients reported a familial history of bleeding diathesis with PDG deficiency. We also evaluated the prevalence of HPS1 variations in 215 controls. Transmission electron microscopy was used to evaluate the number and morphology of PDG from patients and selected controls.


RESULTS
No patient with PDG deficiency carried severe mutations of the HPS1 gene. We identified 6 previously described and 5 new polymorphisms in the HPS1 gene. Platelet electron microscopy in controls carrying these polymorphisms revealed that they did not significantly modify the number or morphology of PDG.


CONCLUSIONS
Mutations affecting the HPS1 gene play a minor role in isolated PDG deficiency. These results support a molecular heterogeneity responsible for the number and morphology of PDG.
Corral
Javier
J
Universidad de Murcia, Centro Regional de Hemodo-nación, Spain. javier.corral@carm.es
González-Conejero
Rocio
R
Pujol-Moix
Nuria
N
Domenech
Pere
P
Vicente
Vicente
V
D000328:Adult; D001792:Blood Platelets / Q000648:ultrastructure; D002648:Child; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D004252:DNA Mutational Analysis; D005260:Female; D005787:Gene Frequency; D022861:Hermanski-Pudlak Syndrome / Q000235:genetics*; D006801:Humans; D008297:Male; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D010981:Platelet Storage Pool Deficiency / Q000235:genetics*; D011110:Polymorphism, Genetic; D011479:Protamines / Q000235:genetics*
D011479:Protamines; C068621:protamine 2