Expression of mPer1 and mPer2, two mammalian clock genes, in murine bone marrow

Although circadian variations in hematopoiesis have been well documented, t he molecular mechanism of the circadian rhythms remains elusive. To determi ne if a clock system exists in bone marrow to mediate the circadian rhythms , we analyzed the expression of mPer1 and mPer2, both mouse homologues of t he Drosophila period gene and known regulators of the clock system, in muri ne bone marrow by relative quantitative reverse transcriptase-polymerase ch ain reaction (RT-PCR), We demonstrated that both genes were expressed in bo ne marrow. Furthermore, the expression patterns of mPer1 and mPer2 in total bone marrow cells exhibited two peaks over a 24-h period. In contrast, the expression patterns of these two genes in the Gr-1-positive cells isolated from bone marrow mainly contributed to one of the two peaks. These results indicate that a clock system exists in bone marrow and suggest that the ci rcadian rhythms in bone marrow are lineage- and/or differentiation stage-de pendent. (C) 2000 Academic Press.