Podocalyxin is expressed by all primitive hematopoietic cells and then declines with development. (A) FACS profiles showing expression of PCLP1 by hematopoietic tissues at various stages of development (1 of 3 independent experiments). Mean relative fluorescence intensity (RFI) for each population is indicated numerically above each peak. (B) Graph showing the percentage of PCLP1⁺ cells in tissues during development. DAC indicates days after coitus. (C) Expression of CD34-related transcripts in YS, PB, and FTL of E15 embryos; podxl, endgl, cd34, and hprt indicate RT-PCR–amplified products for podocalyxin, endoglycan, CD34, and hypoxanthine-guanine phosphoribosyl transferase, respectively. The RT-PCR products are shown in a negative image of an agarose gel stained with ethidium bromide. M indicates molecular weight marker.