MRTFA augments megakaryocyte maturation by enhancing the SRF regulatory axis

Area of Science:

• Hematology
• Molecular Biology
• Gene Regulation

Background:

• Serum response factor (SRF) and myocardin-related transcription factor A (MRTFA) are crucial for megakaryocyte (Mk) maturation. Deficiencies in SRF or MRTFA lead to thrombocytopenia.
• The human erythroleukemia (HEL) cell line serves as a model for studying MRTFA's role in megakaryopoiesis.
• Understanding the molecular mechanisms by which MRTFA influences SRF activity is essential for comprehending Mk development.

Purpose of the Study:

• To elucidate the mechanisms by which MRTFA enhances megakaryopoiesis.
• To investigate the integrated effects of MRTFA overexpression (MRTFA^OE) and phorbol ester (TPA) induction on SRF binding and gene expression in HEL cells.
• To identify SRF target genes regulated by MRTFA during megakaryopoiesis.

Main Methods:

• Integrated analysis of anti-SRF chromatin immunoprecipitation (ChIP) and RNA-sequencing data from HEL cells.
• Comparison of gene expression and SRF binding patterns in noninduced, TPA-induced, and MRTFA^OE HEL cells.
• ChIP-polymerase chain reaction (PCR) validation in HEL cells and primary human CD34⁺ cell-derived subpopulations.

Main Results:

• TPA induction upregulated 11% of genes, with MRTFA^OE enhancing this to 25%.
• MRTFA^OE increased SRF genomic binding and expression of SRF target genes, particularly those lacking ETS binding motifs.
• SRF and MRTFA binding increased at upregulated target genes, such as CORO1A, during megakaryopoiesis.

Conclusions:

• MRTFA significantly enhances SRF's genomic association and transcriptional activity.
• MRTFA promotes megakaryopoiesis by upregulating specific SRF target genes.
• These findings provide novel insights into the regulation of megakaryopoiesis by the SRF-MRTFA pathway.