Megakaryocytopoietic Activity of a Truncated Variant of Mouse Thrombopoietin

Hoshi, Sachi; Yoshitomi, Hideki; Komatsu, Norio; Yoshitake, Shinji; Okada, Mami

doi:10.1006/bbrc.1997.6133

Cited by 9 publications

(4 citation statements)

References 14 publications

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“…To do this, several recombinant TPO proteins have been developed that induce the development of megakaryocytes from early hemopoietic progenitors and stimulate megakaryocyte proliferation in vitro and in vivo (Murray et al, 1998;Hoshi et al, 1997). However, all these proteins are obtained from E. coli or in vitro mammalian cell culture, and we anticipate that production of a functionally active hTPO in the milk of animals in large amounts can be an efficient alternative for the treatment of the disease.…”

Section: Figmentioning

confidence: 99%

Expression and Characterization of Bioactive Human Thrombopoietin in the Milk of Transgenic Mice

Sohn¹,

Kim²,

Park³

et al. 1999

DNA and Cell Biology

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Human thrombopoietin (hTPO) is the primary physiological regulator of platelet production and plays a pivotal role in promoting the proliferation and maturation of megakaryocytic progenitor cells and megakaryocytes. In this study, transgenic mice were produced harboring either full-length or the erythropoietin (EPO)-like amino-terminal domain of hTPO cDNA sequences fused to the regulatory elements of the bovine beta-casein gene. The transgene RNA was expressed exclusively in the mammary glands of eight transgenic mice, and a trace amount of the transgene was also found in the lungs of one mouse. The full-length form induced efficient expression of the protein with the highest expression level of 1500 microg/ml; however, the EPO-like domain alone expressed the protein at <0.1 microg/ml. The proteins from the two recombinant cDNAs have apparent molecular weights of about 74 and 17 kDa, due to glycosylation in the case of the full-length cDNA. Cell proliferation assay in vitro indicated that both of the recombinant forms stimulated proliferation of the TPO-dependent BaF3-Mpl cells. A positive correlation appeared between the amount of TPO in the milk of lactating animals and their blood platelet levels. About a twofold increase in platelet numbers in the blood was observed after direct subcutaneous injection of the recombinant hTPO at the level of 30 microg/kg of body weight. On the basis of these results, we anticipate that the recombinant hTPO produced efficiently in milk of transgenic mice will have the same activities as the native hTPO in a few in vivo as well as in vitro biochemical aspects.

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Section: Figmentioning

confidence: 99%

Expression and Characterization of Bioactive Human Thrombopoietin in the Milk of Transgenic Mice

Sohn¹,

Kim²,

Park³

et al. 1999

DNA and Cell Biology

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show abstract

“…Southern blot analysis indicates the presence of only a single copy of the TPO gene in the human genome. Although splicing variants of TPO mRNA have been detected [37‐39], their specific physiological roles remain unknown.…”

Section: Structure and Expression Of The Tpo Genementioning

confidence: 99%

Native Thrombopoietin: Structure and Function

Kato

Matsumoto²,

Ogami³

et al. 1998

STEM CELLS

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Thrombopoietin (TPO), the c-Mpl ligand, is produced constitutively in liver and other organs, circulates in the bloodstream, and is delivered to bone marrow, where it stimulates the early development of multiple hematopoietic lineages and megakaryocytopoiesis. The concentration of TPO in blood is regulated by c-Mpl mass on platelets and megakaryocytes. In addition to regulation by the number of TPO molecules, including the possible modulation of TPO mRNA abundance in bone marrow, megakaryocytopoiesis and platelet production may be regulated as a result of modulation of TPO activity by proteolytic processing that generates truncated forms of the molecule.Characterization of TPO partially purified from human plasma, however, revealed that the full-length molecule was the predominant form in the blood of both normal individuals and thrombocytopenic patients, although small amounts of truncated species were detected. Thus, truncation of TPO, at least that in the circulation examined, does not appear to contribute to the direct regulation of platelet production in response to increased demand. Given that native TPO isolated from the plasma of thrombocytopenic animals comprises truncated forms, the truncation of TPO is likely of physiological importance in the life history of this molecule.

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“…Southern blot analysis indicates the presence of only a single copy of the TPO gene in the human genome. Although splicing variants of TPO mRNA have been detected [37][38][39], their specific physiological roles remain unknown.…”

Section: Structure and Expression Of The Tpo Genementioning

confidence: 99%

Native thrombopoietin: Structure and function

Kato

Matsumoto²,

Ogami³

et al. 1998

Stem Cells

View full text Add to dashboard Cite

Thrombopoietin (TPO), the c-Mpl ligand, is produced constitutively in liver and other organs, circulates in the bloodstream, and is delivered to bone marrow, where it stimulates the early development of multiple hematopoietic lineages and megakaryocytopoiesis. The concentration of TPO in blood is regulated by c-Mpl mass on platelets and megakaryocytes. In addition to regulation by the number of TPO molecules, including the possible modulation of TPO mRNA abundance in bone marrow, megakaryocytopoiesis and platelet production may be regulated as a result of modulation of TPO activity by proteolytic processing that generates truncated forms of the molecule. Characterization of TPO partially purified from human plasma, however, revealed that the full-length molecule was the predominant form in the blood of both normal individuals and thrombocytopenic patients, although small amounts of truncated species were detected. Thus, truncation of TPO, at least that in the circulation examined, does not appear to contribute to the direct regulation of platelet production in response to increased demand. Given that native TPO isolated from the plasma of thrombocytopenic animals comprises truncated forms, the truncation of TPO is likely of physiological importance in the life history of this molecule.

show abstract

Megakaryocytopoietic Activity of a Truncated Variant of Mouse Thrombopoietin

Cited by 9 publications

References 14 publications

Expression and Characterization of Bioactive Human Thrombopoietin in the Milk of Transgenic Mice

Expression and Characterization of Bioactive Human Thrombopoietin in the Milk of Transgenic Mice

Native Thrombopoietin: Structure and Function

Native thrombopoietin: Structure and function

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