Smith lab Developmental Biology Laboratory
: BMP signalling in vascular development
Introduction
To generate a functioning vascular system, a wide array of blood and endothelial cell types must be generated, and those endothelial cells must assemble into intricate branching networks of tubes.
Figure 1: Vascular effects of BMP inhibition. Top: The caudal vein plexus in the tail of the zebrafish embryo after treatment with DMSO or the BMP inhibitor LDN-193189. The plexus in the embryo treated with the inhibitor has fewer branch points at 32 hours hpf. Bottom: The cranial blood vessels are abnormally expanded in 48 hpf embryos injected with a MO that prevents normal splicing of transcripts for alk1, a type I BMP receptor.
We know of several major signalling pathways that are involved at different stages of this complex process. Among them, the importance of BMP signalling is clear from mouse knockout phenotypes, and from the propensity of heterozygous mutations in BMP pathway components to cause human vascular diseases. With these diseases in mind, our aim is to identify transcriptional targets of BMP signalling in the developing zebrafish vascular system, and to understand the biological functions of these target genes.
Using transgenic zebrafish in which endothelial cells express GFP, we can directly observe the effects of BMP inhibition on vascular development. We use a variety of approaches to manipulate BMP signalling, including inducible expression of modified receptors, application of chemical inhibitors such as LDN193189, and gene knockdown by antisense morpholino oligonucleotides (MOs).
We are using high-throughput sequencing to identify BMP-responsive genes in the zebrafish caudal vein plexus and cranial vessels. We have chosen to look at gene regulation in these structures because we know that BMP signalling is necessary for them to form normally (Figure 1). We can then generate mutants for any gene of interest using CRISPR and TALEN technology, as well overexpressing these factors at particular times and places in the embryo. We are also using similar techniques to discover new functions for genes that are strongly expressed in developing blood and endothelium.
