Department of Neurobiology and Anatomy, University of Utah School of Medicine, USA.
Dev Biol. 2012 Mar 1;363(1):166-78. doi: 10.1016/j.ydbio.2011.12.030. Epub 2011 Dec 29.
Motile cilia create asymmetric fluid flow in the evolutionarily conserved ciliated organ of asymmetry (COA) and play a fundamental role in establishing the left-right (LR) axis in vertebrate embryos. The transcriptional control of the large group of genes that encode proteins that contribute to ciliary structure and function remains poorly understood. In this study we find that the winged helix transcription factor Rfx2 is expressed in motile cilia in mouse and zebrafish embryos. Morpholino knockdown of Rfx2 function in the whole embryo or specifically in cells of the zebrafish COA (Kupffer's Vesicle, KV) leads to reduced KV cilia length and perturbations in LR asymmetry. LR patterning defects include randomization of the early asymmetric Nodal signaling pathway genes southpaw, lefty1 and lefty2 and subsequent reversals in the organ primordia of the heart and gut. Rfx2 is also required for ciliogenesis in zebrafish pronephric duct. We further show that by restoring Left-Right dynein (LRD) expression and motility specifically in a subset of ciliated cells of the mouse COA (posterior notochord, PNC), we can restore fluid flow, asymmetric expression of Pitx2 and partially rescue situs defects.
纤毛在进化保守的不对称纤毛器官（COA）中产生不对称的流体流动，在脊椎动物胚胎中建立左右（LR）轴方面发挥着重要作用。对编码参与纤毛结构和功能的蛋白质的大量基因的转录控制仍然知之甚少。在这项研究中，我们发现翼状螺旋转录因子 Rfx2 在小鼠和斑马鱼胚胎的运动纤毛中表达。Rfx2 功能的整体胚胎或特异性在斑马鱼 COA（Kupffer's Vesicle，KV）中的细胞中的形态发生抑制导致 KV 纤毛长度减少和 LR 不对称性紊乱。LR 模式缺陷包括早期不对称 Nodal 信号通路基因 southpaw、lefty1 和 lefty2 的随机化，以及随后心脏和肠道器官原基的反转。Rfx2 也需要斑马鱼肾单位导管的纤毛发生。我们进一步表明，通过特异性地在小鼠 COA（后脊索，PNC）的一组纤毛细胞中恢复左-右动力蛋白（LRD）的表达和运动，我们可以恢复流体流动、Pitx2 的不对称表达，并部分挽救 situs 缺陷。
