Morioka Takashi, Sakabe Masahide, Ioka Tomoko, Iguchi Tomoko, Mizuta Ken, Hattammaru Miwa, Sakai Chihiro, Itoh Munehiro, Sato Genki E, Hashimoto Aya, Fujita Masahide, Okumura Kazuki, Araki Mutsumi, Xin Mei, Pedersen Roger A, Utset Manuel F, Kimura Hiroshi, Nakagawa Osamu
Laboratory for Cardiovascular System Research, Nara Medical University Advanced Medical Research Center, Kashihara, Nara, Japan; The Second Department of Internal Medicine, Nara Medical University, Kashihara, Nara, Japan.
Genesis. 2014 Nov;52(11):897-906. doi: 10.1002/dvg.22825. Epub 2014 Oct 10.
The Hairy-related transcription factor family of Notch- and ALK1-downstream transcriptional repressors, called Hrt/Hey/Hesr/Chf/Herp/Gridlock, has complementary and indispensable functions for vascular development. While mouse embryos null for either Hrt1/Hey1 or Hrt2/Hey2 did not show early vascular phenotypes, Hrt1/Hey1; Hrt2/Hey2 double null mice (H1(ko) /H2(ko) ) showed embryonic lethality with severe impairment of vascular morphogenesis. It remained unclear, however, whether Hrt/Hey functions are required in endothelial cells or vascular smooth muscle cells. In this study, we demonstrate that mice with endothelial-specific deletion of Hrt2/Hey2 combined with global Hrt1/Hey1 deletion (H1(ko) /H2(eko) ) show abnormal vascular morphogenesis and embryonic lethality. Their defects were characterized by the failure of vascular network formation in the yolk sac, abnormalities of embryonic vascular structures and impaired smooth muscle cell recruitment, and were virtually identical to the H1(ko) /H2(ko) phenotypes. Among signaling molecules implicated in vascular development, Robo4 expression was significantly increased and activation of Src family kinases was suppressed in endothelial cells of H1(ko) /H2(eko) embryos. The present study indicates an important role of Hrt1/Hey1 and Hrt2/Hey2 in endothelial cells during early vascular development, and further suggests involvement of Robo4 and Src family kinases in the mechanisms of embryonic vascular defects caused by the Hrt/Hey deficiency.
Notch和ALK1下游转录抑制因子的毛发相关转录因子家族，称为Hrt/Hey/Hesr/Chf/Herp/Gridlock，在血管发育中具有互补且不可或缺的功能。虽然Hrt1/Hey1或Hrt2/Hey2基因敲除的小鼠胚胎未表现出早期血管表型，但Hrt1/Hey1;Hrt2/Hey2双基因敲除小鼠（H1(ko)/H2(ko)）表现出胚胎致死性，并伴有严重的血管形态发生受损。然而，尚不清楚Hrt/Hey的功能是在内皮细胞还是血管平滑肌细胞中发挥作用。在本研究中，我们证明，内皮细胞特异性缺失Hrt2/Hey2并结合全身性Hrt1/Hey1缺失的小鼠（H1(ko)/H2(eko)）表现出异常的血管形态发生和胚胎致死性。它们的缺陷特征为卵黄囊中血管网络形成失败、胚胎血管结构异常和平滑肌细胞募集受损，并且与H1(ko)/H2(ko)的表型几乎相同。在涉及血管发育的信号分子中，H1(ko)/H2(eko)胚胎的内皮细胞中Robo4表达显著增加，Src家族激酶的激活受到抑制。本研究表明Hrt1/Hey1和Hrt2/Hey2在早期血管发育过程中的内皮细胞中具有重要作用，并进一步提示Robo4和Src家族激酶参与了由Hrt/Hey缺陷引起的胚胎血管缺陷机制。
