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Roads to polyploidy: the megakaryocyte example
Katya Ravid1, Jun Lu, Jeffrey M Zimmet
1Department of Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118, USA. ravid@med-biochem.bu.edu
Abstract:
Polyploidy, recognized by multiple copies of the haploid chromosome number, has been described in plants, insects, and in mammalian cells such as, the platelet precursors, the megakaryocytes. Several of these cell types reach high ploidy via a different cell cycle. Megakaryocytes undergo an endomitotic cell cycle, which consists of an S phase interrupted by a gap, during which the cells enter mitosis but skip anaphase B and cytokinesis. Here, we review the mechanisms that lead to this cell cycle and to polyploidy in megakaryocytes, while also comparing them to those described for other systems in which high ploidy is achieved. Overall, polyploidy is associated with an orchestrated change in expression of several genes, of which, some may be a result of high ploidy and hence a determinant of a new cell physiology, while others are inducers of polyploidization. Future studies will aim to further explore these two groups of genes.
Insights
Polyploidy, having multiple chromosome sets, occurs in various organisms. Megakaryocytes achieve high ploidy through a unique endomitotic cell cycle, involving specific gene expression changes.
Area of Science:
- Cell Biology
- Genetics
- Developmental Biology
Background:
- Polyploidy, the state of having more than two sets of chromosomes, is observed across diverse taxa, including plants, insects, and mammalian cells.
- Megakaryocytes, the precursors to platelets, are a key example of mammalian cells that achieve high ploidy levels.
Purpose of the Study:
- To review the mechanisms driving the unique endomitotic cell cycle in megakaryocytes.
- To compare these mechanisms to those in other systems achieving high ploidy.
- To explore the role of gene expression changes in polyploidization and its consequences.
Main Methods:
- Literature review of studies on polyploidy and endomitosis.
- Comparative analysis of cell cycle regulation in megakaryocytes and other polyploid systems.
- Examination of gene expression patterns associated with polyploidy.
Main Results:
- Megakaryocytes utilize an endomitotic cell cycle, characterized by DNA replication (S phase) followed by a gap, mitosis entry, and skipping of anaphase B and cytokinesis.
- This process results in high ploidy, distinct from typical cell division.
- Polyploidy is linked to coordinated alterations in gene expression, with some genes inducing polyploidization and others reflecting its physiological impact.
Conclusions:
- The endomitotic cell cycle is a specialized mechanism for achieving high ploidy in megakaryocytes.
- Gene expression changes are integral to both the induction and the functional outcomes of polyploidy.
- Further research is needed to elucidate the specific roles of these gene groups.