The role of SRF coactivators MRTF-A and MRTF-B in adipogenesis in vitro

• Main Author: Al-Sayegh, Mohamed
• Published: St George's, University of London 2012
• Subjects: 571.65072
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589960

This thesis comprises the work undertaken to investigate the role of the family of myocardin- related transcription factors, MRTF-A and MRTF-B, at regulating adipogenesis using the well- established in vitro model of 3T3-LI preadipocyte cells. Serum response factor (SRF) is an essential transcription factor that activates the expression of early immediate genes via recruitment of the family ternary complex factors or the transcription of cytoskeleton and muscle-specific genes via MRTF-A and MRTF-B recruitment. It has been shown that SRF depletion is sufficient to promote adipocyte differentiation in the absence of adipogenic stimuli though the mechanisms responsible for this are unknown. The work presented in this thesis shows that MRTF activity is abrogated at the onset of adipogenesis by two mechanisms: relocation of MRTF protiens to the cytoplasm and downregulation of both MRTF-A and MRTF- B protein and mRNA expression levels. These results suggest that inhibition of MRTF activity might be a pre-requisite for adipogenesis to proceed. In agreement with this, depletion of MRTF- A and MRTF-B protein levels via lentiviral mediated RNA interference was shown to promote adipogenesis in the absence of adipogenic cues where overexpression of a dominant positive MRTF-A form inhibited adipocyte differentiation. Several potential endogenous MRTF target genes that could mediate the effects of MR TFs on adipogenesis were identified using a combination of genome-wide RNA expression analysis of MRTF-depleted cells, quantitative PCR and chromatin immunoprecipitation assays. •