||Many regulators and signaling molecules that control the process of vascular development have been described. However, genetic elements regulate the vein identity and intrasegmental vessels (ISV) patterning are still remained unclear. We previously identified the transcription factors islet2 (Isl2) and coupTFIb required for specification of the vein and ISV growth mediated by notch pathway in zebrafish. In order to understand the molecular mechanisms of how isl2 and coupTFIb promote the vascular development, we performed the microarray experiments to identify the potential downstream targets. |
In this study, we first examined the changes in the transcriptome between isl2 knockdown, coupTF1b knockdown and wild-type embryos. Our microarray data showed highly overlapping downstream targets of coupTFIb and isl2, suggesting that coupTFIb and isl2 cooperatively regulate endothelial cell identity, likely in the same pathway.
We further confirmed the increased expression of several genes, such as cpn1, foxo3b, fst1, lnx1, mmp2 and ftr82, in isl2 and coupTFIb double knockdown morphants by in-situ hybridization. In addition, those genes were spatiotemporally expressed in vessels during early development suggesting their functions in vascular development. Among those genes, ftr82 (finTRIM family, member 82) belongs to a large family of tripartite motif proteins (TRIM) containing a RING-B-box-Coiled Coil motif followed by different C-terminal domains. However, no description related to vascular function so far.
Thus, we then examined the vascular function of ftr82. ftr82 mRNA is expressed in developing vessels and loss of ftr82 by morpholino knockdown impairs the growth of ISV and CVP (caudal vein plexus), suggesting the role of ftr82 in promoting ISV and CVP growth. We further showed the ftr82 MO knockdown worked efficiently. We performed TUNEL assay to address whether the cell death contributes to the decrease of ISV and CVP growth, Morpholino- knockdown ftr82 results in the decrease expression of the vein specific marker flt4 and the artery marker ephrnb2. The data showed no increase cell death in the endothelial cells after morpholino injection, suggesting that cell death is not the cause of the observed vascular phenotype.
Taken together, in this study, We identified several potential vascular-specific targets downstream of isl2 and coupTFIb. We also show ftr82 paly an important role for vascular development in zebrafish.