Related Experiment Video
Updated: Jul 3, 2026
Transduction-Transplantation Mouse Model of Myeloproliferative Neoplasm
Published on: December 22, 2016
Point mutation in the gene encoding p300 suppresses thrombocytopenia in Mpl-/- mice
Maria Kauppi1, James M Murphy, Carolyn A de Graaf
1Cancer and Haematology, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.
Abstract:
In an N-nitroso-N-ethylurea (ENU) mutagenesis screen using Mpl(-/-) mice, we isolated a semidominant suppressor of thrombocytopenia, termed Plt6. The gene mutated in Plt6 mice encodes the transcriptional coregulator p300, and the mutation, a tyrosine to asparagine substitution at amino acid 630 (Y630N), disrupts the interaction between p300 and c-Myb. Mpl(-/-) p300(Plt6/+) mice displayed elevated platelet counts relative to Mpl(-/-) p300(+/+) controls, whereas mice homozygous for the Plt6 mutation produced supraphysiological levels of circulating platelets. On a wild-type genetic background, mice homozygous for the p300(Plt6) mutation, or recipients of Mpl(+/+) p300(Plt6/Plt6) bone marrow, also exhibited thrombocytosis as well as deficiencies in B-lymphoid cells. Increased platelet numbers in Plt6 mutant mice were accompanied by significant increases in megakaryocyte progenitor cells within the bone marrow and spleen with concomitantly elevated numbers of megakaryocytes. The expansion of megakaryocytopoiesis and suppression of Mpl(-/-) thrombocytopenia in Plt6 mutants is highly reminiscent of that observed in mice with mutations affecting the p300 partner protein c-Myb, suggesting an indispensable repressive role for the c-Myb/p300 transcriptional regulatory complex in megakaryocyte development, the inhibition of which allows substantial thrombopoietin (TPO)-independent platelet production.
Insights
A mutation in the p300 gene (Plt6) suppresses low platelet counts and causes thrombocytosis by disrupting the p300/c-Myb interaction, leading to increased megakaryocytes and TPO-independent platelet production.
Area of Science:
- Hematology
- Molecular Biology
- Genetics
Background:
- Thrombocytopenia is a condition characterized by low platelet counts.
- The thrombopoietin (TPO) receptor, Mpl, plays a crucial role in megakaryopoiesis and platelet production.
- Transcriptional coregulators like p300 and transcription factors such as c-Myb are vital for hematopoietic cell development.
Purpose of the Study:
- To identify genetic suppressors of thrombocytopenia in Mpl(-/-) mice.
- To investigate the role of the transcriptional coregulator p300 in megakaryocyte development and platelet production.
- To elucidate the functional interaction between p300 and c-Myb in regulating hematopoiesis.
Main Methods:
- N-nitroso-N-ethylurea (ENU) mutagenesis screen in Mpl(-/-) mice.
- Genetic analysis of the identified Plt6 mutation in the p300 gene.
- Biochemical assays to assess the interaction between p300 and c-Myb.
- Hematological analysis and bone marrow/spleen cell profiling in mutant mice.
Main Results:
- A semidominant mutation in the p300 gene (Plt6, Y630N) was identified as a suppressor of thrombocytopenia.
- The Plt6 mutation disrupts the interaction between p300 and c-Myb.
- Mice with the Plt6 mutation exhibited elevated platelet counts (thrombocytosis), increased megakaryocyte progenitors, and deficiencies in B-lymphoid cells.
- Homozygous Plt6 mutation led to supraphysiological platelet levels and TPO-independent platelet production.
Conclusions:
- The c-Myb/p300 transcriptional complex plays a critical repressive role in megakaryocyte development.
- Inhibition of the c-Myb/p300 complex promotes substantial TPO-independent platelet production.
- The Plt6 mutation provides a novel tool to study the regulation of megakaryopoiesis and platelet production.
