LPA₁is essential for lymphatic vessel development in zebrafish

Abstract

Lysophosphatidic acid (LPA) has long been implicated in regulating vascular development via endothelial cell-expressed G protein-coupled receptors. However, because of a lack of notable vascular defects reported in LPA receptor knockout mouse studies, the regulation of vasculature by LPA receptors in vivo is still uncertain. Using zebrafish as a model, we studied the gene expression patterns and functions of an LPA receptor, LPA(1), during embryonic development, in particular, vascular formation. Whole-mount in situ hybridization experiments revealed that zebrafish lpa(1) (zlpa(1)) was ubiquitously expressed early in development, and its expression domains were later localized to the head region and the vicinity of the dorsal aorta. The expression of zlpa(1) surrounding the dorsal aorta suggests its role in vasculature development. Knocking down of zLPA(1) by injecting morpholino (MO) oligonucleotides at 0.625-1.25 ng per embryo resulted in the absence of thoracic duct and edema in pericardial sac and trunk in a dose-dependent manner. These zlpa(1)-MO-resulted defects could be specifically rescued by ectopic expression of zlpa(1). In addition, overexpression of vegf-c, a well-known lymphangiogenic factor, also partially ameliorated the inhibition of thoracic duct development. Taken together, these results demonstrate that LPA(1) is necessary for lymphatic vessel formation during embryonic development in zebrafish.

Identification of Vascular and Hematopoietic Genes Downstream of etsrp by Deep Sequencing in Zebrafish

“…These genes deserve as much attention as those only specific to the vascular lineage, as several studies have shown that the down-regulation of such genes resulted in the disruption of vascular development. For instance, knockdown of nrarp-a and nrarp-b [60], [61], lpa 1 [62], and dep1a / dep1b [63] respectively, resulted in defects in intersegmental vessels, lymphangiogenesis, and arterial specification. We obtained approximately 850 genes that were induced 1.9 fold or more by etsrp expression.…”

Visualization of embryonic lymphangiogenesis advances the use of the zebrafish model for research in cancer and lymphatic pathologies

“…Within only a few years since the formal demonstration that zebrafish have a functional lymphatic system, research using this animal model has already advanced discoveries in lymphatic development and its regulation (Kuchler et al, 2006;Yaniv et al, 2006;Lee et al, 2008;Hogan et al, 2009;Isogai et al, 2009). In vivo observation of lymphatic vessel formation was made possible by confocal or multi-photon imaging of transgenic zebrafish with fluorescently marked developing blood and lymphatic vasculature (Kuchler et al, 2006;Yaniv et al, 2006).…”

“…B: Genomic analysis showed syntenic conservation with the position of the human LYVE1 on human chromosome 11, suggesting orthology. vasculature has allowed examination of the nascent trunk lymphatic vessels, but visualization of lymphangiogenesis has been limited to the thoracic duct and its formation (Kuchler et al, 2006;Yaniv et al, 2006;Lee et al, 2008;Hogan et al, 2009). This approach also requires high-resolution fluorescence microscopy, not practicable for large-scale applications.…”

Regulation of Mammalian Physiology, Development, and Disease by the Sphingosine 1-Phosphate and Lysophosphatidic Acid Receptors

“…No defects in blood or lymph vessel formation were grossly apparent in any of these mutant mice, although a small percentage of Lpa 1 -/- pups demonstrated frontal hematomas, a phenotype that was compounded in double deletants Lpa1 -/- Lpa2 -/- 150,151 . Interestingly, zebrafish with LPA 1 knocked down did not have abnormal blood vessel development, but rather defective embryonic lymphatic vasculogenesis 153 . More recently, it was reported that almost 20% of Lpa 4 -/- embryos at E14.5 demonstrated increased perinatal lethality, with embryos displaying edema and hemorrhage at numerous anatomical sites 154 .…”