CD34 and myeloproliferative disorder: Subsequently, the PAR1 cell surface expression analysis of MPN cells with CD34 expression (Fig. 2A) revealed that most of the PAR1+population also express CD34+ (Fig. 2B and C) and still there is a smaller population of PAR1+cells which does not express CD34 in a population that lacks CD45 expression (Fig. 2B).