Biology subjects

Burns, M. C.

Publications and source records attributed to Burns, M. C..

4 recordsLinked to original sources

bioRxiv2021

Anatomy and Development of the Pectoral Fin Vascular Network in the Zebrafish

The pectoral fins of teleost fish are analogous structures to human forelimbs, and the developmental mechanisms directing their initial growth and patterning are conserved between fish and tetrapods. The forelimb vasculature is critical for limb function, and it appears to play important roles during development by promoting development of other limb structures, but the steps leading to its formation are poorly understood. In this study, we use high-resolution imaging to document the stepwise assembly of the zebrafish pectoral fin vasculature. We show that fin vascular network formation is a stereotyped, choreographed process that begins with the growth of an initial vascular loop around the pectoral fin. This loop connects to the dorsal aorta to initiate pectoral vascular circulation. Pectoral fin vascular development continues with concurrent formation of three elaborate vascular plexuses, one in the distal fin that develops into the fin ray vasculature and two near the base of the fin in association with the developing fin musculature. Our findings detail a complex yet highly choreographed series of steps involved in the development of a complete, functional organ-specific vascular network. SUMMARY STATEMENTThe stereotyped assembly of the pectoral fin vasculature is documented from first migratory sprout into the limb bud, to the adult-like form of the four week old larva.

developmental biology↗

bioRxiv2020

Pseudouridine synthases modify human pre-mRNA co-transcriptionally and affect splicing

Eukaryotic messenger RNAs are extensively decorated with modified nucleotides and the resulting epitranscriptome plays important regulatory roles in cells 1. Pseudouridine ({Psi}) is a modified nucleotide that is prevalent in human mRNAs and can be dynamically regulated 2-5. However, it is unclear when in their life cycle RNAs become pseudouridylated and what the endogenous functions of mRNA pseudouridylation are. To determine if pseudouridine is added co-transcriptionally, we conducted pseudouridine profiling 2 on chromatin-associated RNA to reveal thousands of intronic pseudouridines in nascent pre-mRNA at locations that are significantly associated with alternatively spliced exons, enriched near splice sites, and overlap hundreds of binding sites for regulatory RNA binding proteins. Multiple distinct pseudouridine synthases with tissue-specific expression pseudouridylate pre-mRNA sites, and genetic manipulation of the predominant pre-mRNA modifying pseudouridine synthases PUS1, PUS7 and RPUSD4 induced widespread changes in alternative splicing in cells, supporting a role for pre-mRNA pseudouridylation in alternative splicing regulation. Consistently, we find that individual pseudouridines identified in cells are sufficient to directly affect splicing in vitro. Together with previously observed effects of artificial pseudouridylation on RNA-RNA6-8 and RNA-protein 9-11 interactions that are relevant for splicing, our results demonstrate widespread co-transcriptional pre-mRNA pseudouridylation and establish the enormous potential for this RNA modification to control human gene expression.

molecular biology↗

bioRxiv2019

A Molecular Pathway for Arterial-Specific Association of Vascular Smooth Muscle Cells

The preferential accumulation of vascular smooth muscle cells on arteries versus veins during early development is a well-described phenomenon, but the molecular pathways underlying this polarization are not well understood. During zebrafish embryogenesis the cxcr4a receptor (mammalian CXCR4) and its ligand cxcl12b (mammalian CXCL12) are both preferentially expressed on arteries at time points consistent with the arrival and differentiation of the first vascular smooth muscle cells (vSMCs). We show that autocrine cxcl12b/cxcr4 activity leads to increased production of the vSMC chemoattractant ligand pdgfb by endothelial cells in vitro and increased expression of pdgfb by arteries in vivo. Additionally, we demonstrate that expression of the well-characterized blood flow-regulated transcription factor klf2a in primitive veins negatively regulates cxcr4/cxcl12 and pdgfb expression, restricting vSMC recruitment to the arterial vasculature. Together, this signaling axis leads to the differential acquisition of smooth muscle cells at sites where klf2a expression is low and both cxcr4a and pdgfb are co-expressed, i.e. arteries during early development.

cell biology↗

bioRxiv2018

Anti-angiogenic effects of VEGF stimulation on endothelium deficient in phosphoinositide recycling

Anti-angiogenic therapies have generated significant interest for their potential to combat tumor growth (1-6). However, the ability of tumors to overproduce pro-angiogenic ligands and overcome targeted inhibitory therapies has hampered this approach (7, 8). A novel way to circumvent this problem might be to target the resynthesis of critical substrates consumed during intracellular transduction of pro-angiogenic signals in endothelial cells, thus harnessing the tumors own production of excess stimulatory ligands to deplete adjacent host endothelial cells of the capacity to respond to these signals (9-12). Here we show using zebrafish and human endothelial cells in vitro that endothelial cells deficient in CDP-diacylglycerol synthase 2 are uniquely sensitive to increased VEGF stimulation due to a reduced capacity to re-synthesize phosphoinositides, including phosphatidylinositol 4,5-bisphosphate (PIP2) a key substrate for VEGF signal transduction, resulting in VEGF-exacerbated defects in angiogenesis and angiogenic signaling (9-22). Using murine tumor allograft models (23) we show that either systemic or endothelial cell specific suppression of phosphoinositide recycling results in reduced tumor growth and reduced tumor angiogenesis. Our results suggest that inhibition of phosphoinositide recycling may provide a useful anti-angiogenic approach, and highlights the general potential of targeting the resynthesis of rate limiting signaling substrates as a valuable therapeutic strategy.\n\nSUMMARY STATEMENTTargeting phosphoinositide recycling during tumor angiogenesis provides a potentially uniquely effective anti-cancer therapy.

cell biology↗