SRF and SRF Cofactor mRNA Expression Is Differentially Regulated by BDNF Stimulation in Cortical Neurons

Abstract

Serum response factor (SRF) is a transcription factor that plays essential roles in multiple brain functions in concert with SRF cofactors such as ternary complex factor (TCF) and megakaryoblastic leukemia (MKL)/myocardin-related transcription factor (MRTF), which comprises MKL1/MRTFA and MKL2/MRTFB. Here, we stimulated primary cultured rat cortical neurons with brain-derived neurotrophic factor (BDNF) and investigated the levels of SRF and SRF cofactor mRNA expression. We found that SRF mRNA was transiently induced by BDNF, whereas the levels of SRF cofactors were differentially regulated: mRNA expression of Elk1, a TCF family member, and MKL1/MRTFA were unchanged, while in contrast, mRNA expression of MKL2/MRTFB was transiently decreased. Inhibitor experiments revealed that BDNF-mediated alteration in mRNA levels detected in this study was mainly due to the extracellular signal-regulated protein kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway.Collectively, BDNF mediates the reciprocal regulation of SRF and MKL2/MRTFB at the mRNA expression level through ERK/MAPK, which may fine-tune the transcription of SRF target genes in cortical neurons. Accumulating evidence regarding the alteration of SRF and SRF cofactor levels detected in several neurological disorders suggests that the findings of this study might also provide novel insights into valuable therapeutic strategies for the treatment of brain diseases.

Brain‐derived neurotrophic factor (BDNF) downregulates mRNA levels of suppressor of cancer cell invasion (SCAI) variants in cortical neurons

“…Every 3 days, conditioned medium (0.5 mL) was removed and the same volume of fresh medium was added. In addition, our previous reports show that BDNF drastically induces Arc expression (Kikuchi et al, 2019) and decreases the expression of MRTFB isoforms (Ihara et al, 2023) in neurons at DIV9, suggesting that SRF transcriptional machinery and its target genes are transcriptionally regulated at DIV9. Therefore, BDNF stimulation was performed at 9 days in vitro.…”

“…The RNA extraction and qPCR were performed according to previously reported methods (Ihara et al, 2023). In brief, total RNA was extracted using TRIsure (BIO‐38032; Bioline, London, UK) and subjected to complementary DNA synthesis using SuperScript II (18064‐014; Invitrogen).…”

“…Primary rat cortical neurons, which were derived from embryos at 17 days, were cultured as described previously (Ihara et al, 2023) at a cell density of 8 Â 10 5 cells/well. For primary cultures, 12-well plates were used with neurobasal medium (21103-049; Invitrogen, Carlsbad, CA, USA) supplemented with 1Â B27 supplement (17504-044; Invitrogen), 2 μg/mL gentamicin (15750-060; Invitrogen), and 0.5 mM glutamine (25030-081; Invitrogen).…”