Lineage-specific defect in gene expression in human platelet phospholipase C-beta2 deficiency.
Phospholipase C (PLC)-beta2 plays a major role in platelet activation. Previous studies have described a unique patient with impaired receptor-mediated platelet aggregation, secretion, calcium mobilization, and phospholipase C (PLC) activation associated with a selective decrease in platelet PLC-beta2 isozyme. To identify the mechanisms leading to the defect, platelet RNA from the patient and healthy subjects was subjected to reverse transcription-polymerase chain reaction (RT-PCR) and the products sequenced. The PLC-beta2 cDNA sequence in the patient showed no abnormalities. Platelet PLC-beta2 and beta-actin (internal control) mRNA levels were assessed by RT-PCR; the ratio of PLC-beta2 to beta-actin mRNA levels was 0.80 to 0.95 in 4 healthy subjects and 0.28 in the patient. PLC-beta2 mRNA levels were similarly reduced compared with GPIIb and Galphaq mRNA levels. PLC-gamma2 and platelet factor 4 mRNA levels were normal. Calcium mobilization was studied in neutrophils upon activation with formyl-Met-Leu-Phe (fMLP), adenosine diphosphate (ADP), platelet-activating factor (PAF), interleukin-8 (IL-8), C5a, and leukotriene B(4) (LTB(4)), and it was normal. Neutrophil elastase secretion upon activation with fMLP, ADP, PAF, IL-8, C5a, and LTB(4) was normal, as were neutrophil PLC-beta2 mRNA and PLC-beta2 on immunoblotting. Thus, responses to activation, PLC-beta2 protein, and PLC-beta2 mRNA are decreased in patient platelets but not in neutrophils, providing evidence for a hitherto undescribed lineage (platelet)-specific defect in PLC-beta2 gene expression. These studies provide a physiologically relevant model to delineate regulation of PLC-beta2 gene and its tissue-specific expression. (Blood. 2002;99:905-911)
Mao
Guang Fen
GF
Sol Sherry Thrombosis Research Center, Temple University School of Medicine, 3400 N Broad St, Philadelphia, PA 19140, USA.
Vaidyula
Vijender R
VR
Kunapuli
Satya P
SP
Rao
A Koneti
AK
D001792:Blood Platelets / Q000201:enzymology* / Q000378:metabolism; D019070:Cell Lineage / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D007527:Isoenzymes / Q000032:analysis / Q000172:deficiency / Q000235:genetics*; D009504:Neutrophils / Q000201:enzymology / Q000378:metabolism; D054799:Phospholipase C beta; D051966:Phospholipase C gamma; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D010738:Type C Phospholipases / Q000032:analysis / Q000172:deficiency / Q000235:genetics*
D007527:Isoenzymes; D012333:RNA, Messenger; D010738:Type C Phospholipases; C518036:PLCB2 protein, human; D054799:Phospholipase C beta; D051966:Phospholipase C gamma