Vascular Endothelial Growth Factor Receptor Family in Ascidians, Halocynthia roretzi (Sea Squirt). Its High Expression in Circulatory System-Containing Tissues

Saeed Samarghandian,Masabumi Shibuya

doi:10.3390/ijms14034841

Abstract

The vascular endothelial growth factor (VEGF)-VEGF Receptor (VEGFR) system is an important pathway for regulation of angiogenesis. However, its evolutionary development, particularly the step from invertebrates to vertebrates, is still largely unknown. Here, we molecularly cloned the VEGFR-like gene from Halocynthia roretzi, a species belonging to the Tunicata, the chordate subphylum recently considered the sister group of vertebrates. The cDNA encoded a homolog of human VEGFR, including the transmembrane domain, and the tyrosine kinase domain with a kinase-insert region, which was designated S. sq VEGFR (GenBank AB374180). Similar to Tunicates including ascidians in the phylogenetic tree, the Amphioxus, another chordate, is located close to vertebrates. However, S. sq VEGFR has a higher homology than the Amphioxus VEGFR-like molecule (GenBank AB025557) to human VEGFR in the kinase domain-2 region. The S. sq VEGFR mRNA was expressed at highest levels in circulatory system-containing tissues, suggesting that S. sq VEGFR plays an important role in the formation or maintenance of circulatory system in Tunicates, Halocynthia roretzi.

Highlights

By comparing invertebrates’ genomes with those of humans and other animals, we could find new insights into the evolutionary origins of human tissues, as well as a better understanding of chordate and vertebrate development in general
To test for the possible existence of VEGF Receptor (VEGFR) in H. roretzi, we made four degenerated oligonucleotide primers based on the sequence of the tyrosine kinase domain in VEGFR genes highly conserved among various species (Figure 2a)
We showed a higher homology of S. sq VEGFR (KD2 region) to human VEGFR

Summary

Introduction

By comparing invertebrates’ genomes with those of humans and other animals, we could find new insights into the evolutionary origins of human tissues, as well as a better understanding of chordate and vertebrate development in general. Phospholipase Cγ-C-kinase-MAP kinase pathway for cell proliferation via the autophosphorylation of a single tyrosine (Y)-containing motif at the 1175Y site of carboxy terminal region [20,21] Understanding these interactions in details has been complicated by extensive gene multiplication events in vertebrates, and it is difficult to clarify their basal characteristics in circulatory system in the phylogenetic development [9,10,11,14,22,23,24,25]. VEGFR/platelet-derived growth factor receptor (PDGFR)-related tyrosine kinase has been identified in Drosophila and other invertebrates including Cephalochordate (amphioxus) and Tunicates (ascidians) such as B. schlosseri, and. We attempted to molecularly clone a receptor related to mammalian VEGFR from another popular ascidian, H. roretzi

Results and Discussion

Animals

Histological Analysis

Generation of Antibody

3.10. Western Blotting

Conclusions