NCBI Summary:
In 1990 an oncogene, v-mpl, was identified from the murine myeloproliferative leukemia virus that was capable of immortalizing bone marrow hematopoietic cells from different lineages. In 1992 the human homologue, named, c-mpl, was cloned. Sequence data revealed that c-mpl encoded a protein that was homologous with members of the hematopoietic receptor superfamily. Presence of anti-sense oligodeoxynucleotides of c-mpl inhibited megakaryocyte colony formation. The ligand for c-mpl, thrombopoietin, was cloned in 1994. Thrombopoietin was shown to be the major regulator of megakaryocytopoiesis and platelet formation. The protein encoded by the c-mpl gene, CD110, is a 635 amino acid transmembrane domain, with two extracellular cytokine receptor domains and two intracellular cytokine receptor box motifs . TPO-R deficient mice were severely thrombocytopenic, emphasizing the important role of CD110 and thrombopoietin in megakaryocyte and platelet formation. Upon binding of thrombopoietin CD110 is dimerized and the JAK family of non-receptor tyrosine kinases, as well as the STAT family, the MAPK family, the adaptor protein Shc and the receptors themselves become tyrosine phosphorylated. [provided by RefSeq]
General function
Receptor
Comment
Cellular localization
Plasma membrane
Comment
Ovarian function
Comment
Expression regulated by
Comment
Ovarian localization
Granulosa, Theca, Luteal cells
Comment
The Expression of Thrombopoietin and its Receptor During Different Physiological Stages in the Bovine Ovary. Sarkar M et al. Thrombopoietin (TPO) is known to be involved in megakaryocytopoiesis, but its role in the control of ovarian function is unknown in cattle. The aims of this study were to demonstrate the expression of TPO and its receptor (c-MPL) in detail in bovine corpus luteum (CL) obtained from different stages of the oestrous cycle and during pregnancy - and to demonstrate that TPO/c-MPL system is expressed clearly in bovine follicles. Real-time RT-PCR (qPCR) and ELISA were applied to investigate mRNA expression of examined factors and TPO protein, respectively. In this investigation, increases in the concentrations of TPO protein and the mRNA expression of TPO and c-MPL were noticed during both early luteal stage and late luteal stage of the oestrous cycle. Furthermore, the expression of TPO/c-MPL system does not show any significant regulation in the CL throughout pregnancy. Highest co-expression of TPO/c-MPL system in both theca interna (TI) and granulosa cells (GC) in small follicles (<10 mm in diameter) was observed in this study that may suggest the possible role of TPO/c-MPL system in proliferation of TI and GC cells. To conclude, the results demonstrate the possible involvement of locally produced TPO/c-MPL system as a 'physiological filter' in bovine ovary where they may promote cell selection by inducing proliferation of viable cells and scavenging non-viable cells and thereby may play an important role in modulation of ovarian function.