Abstract
BackgroundSerum response factor (SRF), a member of the MADS box family of nuclear transcription factors, plays an important role in cardiovascular development and function. Numerous studies demonstrate a central role for SRF in regulating smooth and cardiac muscle cell gene expression. Consistent with this, loss of SRF function blocks differentiation of coronary vascular smooth muscle cells from proepicardial precursors, indicating SRF is necessary for coronary vasculogenesis. The role of SRF in endothelial cell contribution during early vascular development, however, has not been addressed. To investigate this, we generated transgenic mice lacking expression of SRF in endothelial cells. Mice expressing Cre recombinase (Tie2Cre+) under Tie2 promoter control were bred to mice homozygous for Srf alleles containing loxP recombination sites within the Srf gene (Srff/f). Tie2 is a tyrosine kinase receptor expressed predominantly on endothelial cells that mediates signalling during different stages of blood vessel remodelling. Resulting embryos were harvested at specific ages for observation of physical condition and analysis of genotype.ResultsTie2Cre+/-Srff/f embryos appeared to develop normally compared to wild-type littermates until embryonic day 10.5 (E10.5). Beginning at E11.5, Tie2Cre+/-Srff/f embryos exhibited cerebrovascular hemorrhaging and severely disrupted vascular networks within the yolk sac. Hemorrhaging in mutant embryos became more generalized with age, and by E14.5, most Tie2Cre+/-Srff/f embryos observed were nonviable and grossly necrotic. Hearts of mutant embryos were smaller relative to overall body weight compared to wild-type littermates. Immunohistochemical analysis revealed the presence of vascular endothelial cells; however, vessels failed to undergo appropriate remodelling. Initial analysis by electron microscopy suggested a lack of appropriate cell-cell contacts between endothelial cells. Consistent with this, disrupted E-cadherin staining patterns were observed in mutant embryos.ConclusionThese results provide the first in vivo evidence in support of a role for SRF in endothelial cell function and strongly suggest SRF is required for appropriate vascular remodelling.
Highlights
Serum response factor (SRF), a member of the MADS box family of nuclear transcription factors, plays an important role in cardiovascular development and function
The expression pattern of genes under SRF control is regulated in a combinatorial fashion by SRF's ability to interact with a variety of accessory factors such as Elk-1 and SAP-1 to regulate expression of genes involved in cell growth and proliferation, and myocardin and related family factors to control myogenic gene expression
E-cadherin protein detected by immunofluorescence showed a dramatic decrease in signal along the apical brush-border of endothelial cells in the extraembryonic endodermal layer in yolk sac. These results provide the first in vivo evidence in support of a role for SRF in endothelial cell function and strongly suggest SRF is required for appropriate vascular remodelling
Summary
Serum response factor (SRF), a member of the MADS box family of nuclear transcription factors, plays an important role in cardiovascular development and function. Numerous studies demonstrate a central role for SRF in regulating smooth and cardiac muscle cell gene expression. The role of SRF in endothelial cell contribution during early vascular development, has not been addressed. Serum response factor (SRF) is a nuclear transcription factor of the MADS (MCM1, Agamous, Deficiens, SRF) box family. The SRE sequence is present in a wide variety of genes, including those encoding for immediate early proteins (e.g. Fos, Jun, HSP70), neuronal nuclear receptors (e.g. Nurr, Nur77) and numerous contractile and cytoskeletal proteins Expression of SRF is essential in early development as SRF-null embryos die during gastrulation [3]. The expression pattern of genes under SRF control is regulated in a combinatorial fashion by SRF's ability to interact with a variety of accessory factors such as Elk-1 and SAP-1 to regulate expression of genes involved in cell growth and proliferation, and myocardin and related family factors to control myogenic gene expression (for review see [4])
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
