Biology subjects

Redpath, A. N.

Publications and source records attributed to Redpath, A. N..

6 recordsLinked to original sources

bioRxiv2025

Organ-specific and conserved regulatory logic orchestrates gene expression in the embryonic mesothelium

The embryonic coelomic mesothelium undergoes epithelial-to-mesenchymal transition (EMT) to promote vascular growth and parenchymal development. A prominent example is the epicardium, which plays an essential role during heart development. Little is known about the mechanisms behind gene regulation in the coelomic mesothelium, or the organ-specific enhancer logic that endows specialization. Using gene regulatory network inference via multi-omic analysis, our study reveals trans- and cis-regulatory elements (CREs) that regulate mesothelial gene expression in three organs: heart, lung, and pancreas. We delineate pivotal transcription factors (TFs) and CREs specific to the epicardium, and show, in contrast, that the TF MAF orchestrates pan-mesothelial gene expression via conserved CREs, which are absent in non-mesothelial lineages. MAF may preserve mesothelial identity, evidenced by negative correlation with EMT and mouse-human conservation. Collectively, our work elucidates the regulatory logic behind cell type identity and leverages single-cell integration to gain insights into mammalian organ development. HighlightsO_LICoelomic mesothelia display distinct transcriptome linked to their morphogenic role C_LIO_LIMesothelial markers associate with organ-specific trans- and cis-regulatory logic C_LIO_LIPan-mesothelial gene regulatory mechanisms control canonical marker expression C_LIO_LIIntegrating mouse and human datasets uncovers conserved dynamics of epicardial EMT C_LI

systems biology↗

bioRxiv2025

Essential regulation of heparan sulfate proteoglycan signalling controls cell behaviour to support cardiac development

Heparan sulfate proteoglycan (HSPG)-dependent signalling is essential for cardiac development, yet how HSPGs are regulated in the forming heart is unknown. Here, we show that the extracellular heparan sulfate modifier, SULF1, expressed by the epicardium, dynamically regulates HSPG sulfation to fine-tune the magnitude and duration of signalling to impact cell fate and cardiac morphogenesis. Single cell genomics and lineage tracing studies reveal Sulf1 to be strongly co-expressed with Wt1 in the epicardium, with reduction of both coinciding with epithelial-mesenchymal transition and quiescence. CUT&RUN-seq revealed transcriptional control of Sulf1 by WT1 which directly impacts essential HSPG-dependent downstream signalling. Our study highlights, for the first time, essential fine-tuning of HSPG-dependent signalling to modulate key processes for heart formation.

developmental biology↗

bioRxiv2021

Thymosin β4 preserves vascular smooth muscle phenotype in atherosclerosis via regulation of Low Density Lipoprotein Related Protein 1 (LRP1)

ObjectiveAtherosclerosis is a progressive, degenerative vascular disease and a leading cause of morbidity and mortality. In response to endothelial damage, platelet derived growth factor (PDGF)-BB induced phenotypic modulation of medial smooth muscle cells (VSMCs) promotes atherosclerotic lesion formation and destabilisation of the vessel wall. VSMC sensitivity to PDGF-BB is determined by endocytosis of Low density lipoprotein receptor related protein 1 (LRP1)-PDGFR{beta} complexes to balance receptor recycling with lysosomal degradation. Consequently, LRP1 is implicated in various arterial diseases. Having identified T{beta}4 as a regulator of LRP1-mediated endocytosis to protect against aortic aneurysm, we sought to determine whether T{beta}4 may additionally function to protect against atherosclerosis, by regulating LRP1-mediated growth factor signalling. Approach and ResultsBy single cell transcriptomic analysis, Tmsb4x, encoding T{beta}4, strongly correlated with contractile gene expression and was significantly down-regulated in cells that adopted a modulated phenotype in atherosclerosis. We assessed susceptibility to atherosclerosis of global T{beta}4 knockout mice using the ApoE-/- hypercholesterolaemia model. Inflammation, elastin integrity, VSMC phenotype and signalling were analysed in the aortic root and descending aorta. T{beta}4KO; ApoE-/- mice develop larger atherosclerotic plaques than control mice, with medial layer degeneration characterised by accelerated VSMC phenotypic modulation. Defects in T{beta}4KO; ApoE-/- mice phenocopied those in VSMC-specific LRP1 nulls and, moreover, were underpinned by hyperactivated LRP1-PDGFR{beta} signalling. ConclusionsWe identify an atheroprotective role for endogenous T{beta}4 in maintaining differentiated VSMC phenotype via LRP1-mediated PDGFR{beta} signalling.

pathology↗

bioRxiv2021

SRSF3 is a key regulator of epicardial formation

The epicardium is a fundamental regulator of cardiac development and regeneration, functioning to secrete essential growth factors and to produce epicardium-derived cells (EPDCs) that contribute most coronary mural cells and cardiac fibroblasts. The molecular mechanisms controlling epicardial formation have not been fully elucidated. In this study, we found that the RNA-binding protein SRSF3 is highly expressed in the embryonic proepicardium and epicardial layer. Deletion of Srsf3 from the murine proepicardium led to proliferative arrest, which prevented proper epicardial formation. Induction of Srsf3 deletion after the proepicardial stage resulted in impaired epicardial proliferation and EPDC formation by E13.5. Single-cell RNA-sequencing showed SRSF3-depleted epicardial cells were eliminated, however, the surviving non-recombined cells became hyperproliferative and, remarkably, compensated for the early deficit, via a mechanism that involved Srsf3 up-regulation This unexpected finding attests the importance of SRSF3 in controlling epicardial proliferation, and highlights the significant confounding effect of mosaic recombination on embryonic phenotyping. Mapping the SRSF3-RNA interaction network by endogenous irCLIP identified binding to major cell cycle regulators, such as Ccnd1 and Map4k4, with both splicing and non-splicing roles. This research defines SRSF3 as a key regulator of epicardial cell proliferation.

developmental biology↗

bioRxiv2021

Maternal iron deficiency impacts the placental arterial network.

Placental vascular gene networks in mammals have been largely unexplored due to a lack of well validated molecular markers to identify them. This is required to study how they form in development, and how they are impacted by embryonic or maternal defects, which in-turn adversely affects the forming heart and vasculature. Such defects are known to be a consequence of maternal iron deficiency (ID), the most common nutrient deficiency world-wide. Here we employed marker analysis to characterise the arterial/arteriole and venous/venule endothelial cells (ECs) during normal placental development, and in the context of maternal ID. We reveal for the first time that placental ECs are unique compared with their embryonic counterparts. In the developing embryo, arterial ECs express Neuropilin1 (Nrp1), Delta-like ligand 4 (Dll4) and Notch1, while developing venous ECs express Neuropilin2 (Nrp2), Apj (Aplnr) and Ephrinb4 (Ephb4). However, in the E15.5 placenta, Nrp1 and Notch1 were restricted to arteries, but not continuing arteriole ECs. The arterial tree exclusively expressed Dll4. Nrp2 showed pan-EC expression at E15.5, while Ephb4 was not present at this stage. However, we found the placental venous vascular tree could be distinguished from the arterial tree by high versus low Endomucin (EMCN) and Apj (Aplnr) expression respectively. Using EMCN, we reveal that the placental arterial, but not venous, vascular tree is adversely impacted by maternal ID, with reduced area, total length and number of junctions of all vessels without affecting the EMCN high vessels. Defects to the embryonic cardiovascular system can therefore have a significant impact on blood flow delivery and expansion of the placental arterial tree.

developmental biology↗

bioRxiv2019

Thymosin β4 mediates vascular protection via regulation of Low Density Lipoprotein Related Protein 1 (LRP1)

Vascular stability and tone are maintained by contractile smooth muscle cells (VSMCs). However, injury-induced growth factors stimulate a contractile-synthetic phenotypic switch which promotes atherosclerosis and susceptibility to abdominal aortic aneurysm (AAA). As a regulator of embryonic VSMC differentiation, we hypothesised that Thymosin {beta}4 (T{beta}4) may additionally function to maintain healthy vasculature and protect against disease throughout postnatal life. This was supported by identification of an interaction with Low density lipoprotein receptor related protein 1 (LRP1), an endocytic regulator of PDGF-BB signalling and VSMC proliferation. LRP1 variants have been identified by GWAS as major risk loci for AAA and coronary artery disease. T{beta}4-null mice display aortic VSMC and elastin defects, phenocopying LRP1 mutants and suggesting compromised vascular integrity. We confirmed predisposition to disease in models of atherosclerosis and AAA. Diseased vessels and plaques were characterised by accelerated contractile-synthetic VSMC switching and augmented PDGFR{beta} signalling. In vitro, enhanced sensitivity to PDGF-BB, upon loss of T{beta}4, coincided with dysregulated endocytosis, leading to increased recycling of LRP1-PDGFR{beta} and reduced lysosomal targeting. Our study identifies T{beta}4 as a key regulator of LRP1 for maintaining vascular health, providing insight which may reveal useful therapeutic targets for modulation of VSMC phenotypic switching and disease progression.

cell biology↗