Peaking of mDYRK-3 expression at a late stage of erythroid development.

To examine the timing of mDYRK-3 gene expression during erythropoiesis, mice were treated with TAP and phlebotomized to generate an accumulation of early erythroid progenitor cells in spleen.25 26 TAP was then removed, and at 3 days after TAP removal, developmental synchronized erythroid progenitor cells from spleen were prepared and placed in liquid culture in the presence of Epo plus SCF or SCF alone. At days 0, 1, and 3, ³²P–RT-PCR was performed, and levels of mDYRK-3, Epo receptor, beta-major globin, and hgprt transcripts were analyzed. In addition, mDYRK-3 (and GAPDh) transcript levels were assayed directly by Northern blotting (lower left panel). Cell histo-morphologies were also analyzed in cytospin preparations (lower right panel). Note the blastlike appearance of cells maintained in SCF only (vs the apparent enucleated morphology of cells cultured for 3 days in Epo plus SCF [arrows]).