IMPC:Characterisation of 4933427D14Rik, an Lhx1 regulated gene, and specification of the left-right body axis

IMPC：Lhx1 调控基因 4933427D14Rik 的表征以及左右身体轴的规范

• 批准号: MR/P026133/1
• 负责人: Elizabeth Robertson
• 金额: $ 4.13万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FP026133%2F1
• 关键词: IMPC; Characterisation; 4933427D14Rik; Lhx1; regulated

Externally humans, and other mammals, appear bilaterally symmetrical. However internally they display an invariant left-right asymmetry. For example, the heart is tilted towards the left while the liver is placed on the right side of the abdomen. How this asymmetry is established is of great interest, both biologically and medically. Defects in human left-right (L-R) pattern formation cause birth defects affecting the heart, vasculature, lungs and gastrointestinal tract that can be life threatening. To understand how these L-R axis defects develop, it is important to more fully understand the molecular and cellular mechanisms by which L-R patterning is established. Cilia are important cellular organelles that can have sensory or motile roles and are critical in setting up the L-R axis. Cilia resemble small hair-like projections on the surface membrane of the cell and inside the cilia is a microtubule-based cytoskeleton. Cilia originate from centrosomes, a cell organelle that serves as the main microtubule organising centre, and consists of a mother and a daughter centriole. The formation of cilia, termed ciliogenesis, initiates when the mother centriole docks at the membrane forming the basal body of the cilia and from which the microtubule cytoskeleton of the cilia extends. In early mammalian development, a transient and architecturally distinct structure, the node, is formed and is essential for establishing the L-R axis. Morphologically the node is formed of a pit of cells, with each cell possessing a motile cilium. Stereotyped rotation of the cilia generates a unidirectional flow of fluid across the node from right to left, leading to asymmetric expression of a handful of genes, including Nodal. Asymmetric Nodal signalling is essential for specifying the L-R body axis as perturbations in Nodal signalling can lead to defects in L-R axis patterning. Lhx1 is a homeobox domain transcription factor whose expression is dependent on Nodal signalling. Embryos lacking Lhx1 display, among a plethora of faults, defects in node morphogenesis and in correct L-R axis patterning. We have recently identified Lhx1 regulated genes through transcriptional profiling experiments, among which was a relatively uncharacterised gene 4933427D14Rik. Exploiting the IMPC resource, our work will establish the role 4933427D14Rik plays in early development in setting up the L-R axis. Preliminary studies suggest that 4933427D14Rik is a centriolar satellite protein that may function in both centriole duplication and ciliogenesis. Preliminary phenotyping of 4933427D14Rik mutant embryos revealed problems in embryonic development that can be attributed to defects in ciliogenesis and L-R establishment. Medically, the recent finding that 4933427D14Rik is mutated in a ciliopathy patient with oral-facial-digital syndrome (OFDS) highlights the importance of this gene. Hence, 4933427D14Rik may play a key role in setting up the L-R axis downstream of Lhx1/Nodal signalling and characterisation of this centriolar satellite protein will ultimately provide insight into the mechanism underlying OFDS and related human birth defects.

从外表上看，人类和其他哺乳动物都是左右对称的。然而，在内部，它们显示出不变的左右不对称性。例如，心脏向左倾斜，而肝脏位于腹部的右侧。这种不对称性是如何建立的，在生物学和医学上都有很大的意义。人类左-右（L-R）模式形成的缺陷导致影响心脏、脉管系统、肺和胃肠道的出生缺陷，这些缺陷可能危及生命。为了了解这些L-R轴缺陷是如何发展的，更全面地了解L-R模式建立的分子和细胞机制是很重要的。纤毛是重要的细胞器，可具有感觉或运动作用，并且在建立L-R轴中至关重要。纤毛类似于细胞表面膜上的小毛发状突起，纤毛内部是基于微管的细胞骨架。纤毛起源于中心体，中心体是一种细胞器，作为主要的微管组织中心，由母亲和女儿中心粒组成。纤毛的形成，称为纤毛发生，起始于母中心粒停靠在形成纤毛基体的膜上，纤毛的微管细胞骨架从该膜延伸。在哺乳动物的早期发育过程中，形成了一个短暂的、结构上独特的结构，即淋巴结，它对建立L-R轴至关重要。在形态学上，节是由一个小坑的细胞，每个细胞拥有一个能动的纤毛。纤毛的定型旋转产生了从右到左穿过淋巴结的单向流体流动，导致少数基因的不对称表达，包括Nodal。不对称的Nodal信号传导对于指定L-R体轴是必不可少的，因为Nodal信号传导中的扰动可能导致L-R轴模式中的缺陷。Lhx 1是一种同源异型框结构域转录因子，其表达依赖于Nodal信号传导。胚胎缺乏Lhx 1显示，在众多的故障，缺陷节点形态发生和正确的L-R轴图案。我们最近通过转录谱实验鉴定了Lhx 1调控基因，其中有一个相对未表征的基因4933427 D14 Rik。利用IMPC资源，我们的工作将确定4933427 D14 Rik在建立L-R轴的早期开发中所起的作用。初步研究表明，4933427 D14 Rik是一个中心粒卫星蛋白，可能在中心粒复制和纤毛发生中发挥作用。4933427 D14 Rik突变胚胎的初步表型分析揭示了胚胎发育中的问题，这些问题可归因于纤毛发生和L-R建立的缺陷。在医学上，最近发现4933427 D14 Rik在患有口面指综合征（OFDS）的纤毛病患者中发生突变，突出了该基因的重要性。因此，4933427 D14 Rik可能在建立Lhx 1/Nodal信号下游的L-R轴中发挥关键作用，并且该中心粒卫星蛋白的表征将最终提供对OFDS和相关人类出生缺陷的潜在机制的深入了解。