Podocalyxin in human haematopoietic cells.
Podocalyxin-like protein (PCLP) is a sialomucin-type membrane protein structurally related to CD34 and endoglycan. It was first described in glomerular podocytes and endothelial cells. In mice, PCLP is present in haemangioblasts, and in both chicken and mice it is a marker of early haematopoietic stem cells and lineage-restricted haematopoietic progenitors. Its expression decreases during differentiation of haematopoietic cells. Of mature blood cells, only chicken and rat thrombocytes express PCLP protein. PCLP expression in human haematopoietic cells has not been studied. Here we demonstrate PCLP mRNA in human CD34+ cells, in lineage committed erythroid, megakaryocyte and myeloid progenitors, in K562 leukaemia cells, and in peripheral blood leucocytes. The mRNA expression level was higher in developing cells than in mature leucocytes. By Northern blotting and cDNA sequencing, the haematopoietic and renal PCLP mRNAs were identical. Of the mobilized CD34+ cells, 28% (mean; range 14-61%) expressed PCLP protein and the majority of PCLP+ cells were CD117+. Almost all of the K562 cells expressed PCLP protein. Surprisingly, PCLP protein was not detected in any mature blood cells. These results suggest that human PCLP may be a valuable marker for a subset of haematopoietic stem cells.
Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Finland.
Laura
L
Kerosuo
Eeva
E
Juvonen
Riitta
R
Alitalo
Mikhail
M
Gylling
Dontscho
D
Kerjaschki
Aaro
A
Miettinen
D018952:Antigens, CD34 / Q000032:analysis; D015415:Biomarkers / Q000032:analysis; D002454:Cell Differentiation / Q000502:physiology; D015870:Gene Expression; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics
D018952:Antigens, CD34; D015415:Biomarkers; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012795:Sialoglycoproteins; C001643:podocalyxin