Hirose Kentaro, Shimoda Nobuyoshi, Kikuchi Yutaka
Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima, Japan.
Gene Expr Patterns. 2011 Oct;11(7):378-83. doi: 10.1016/j.gep.2011.04.002. Epub 2011 May 5.
Leucine-rich repeat (LRR)-containing G protein-coupled receptors (LGRs) belong to the superfamily of G protein-coupled receptors, and are characterized by the presence of seven transmembrane domains and an extracellular domain that contains a series of LRR motifs. Three Lgr proteins - Lgr4, Lgr5, and Lgr6 - were identified as members of the LGR subfamily. Mouse Lgr4 has been implicated in the formation of various organs through regulation of cell proliferation during development, and Lgr5 and Lgr6 are stem cell markers in the intestine or skin. Although the expression of these three genes has already been characterized in adult mice, their expression profiles during the embryonic and larval development of the organism have not yet been defined. We cloned two zebrafish lgr genes using the zebrafish genomic database. Phylogenetic analyses showed that these two genes are orthologs of mammalian Lgr4 and Lgr6. Zebrafish lgr4 is expressed in the neural plate border, Kupffer's vesicle, neural tube, otic vesicles, midbrain, eyes, forebrain, and brain ventricular zone by 24h post-fertilization (hpf). From 36 to 96hpf, lgr4 expression is detected in the midbrain-hindbrain boundary, otic vesicles, pharyngeal arches, cranial cartilages such as Meckel's cartilages, palatoquadrates, and ceratohyals, cranial cavity, pectoral fin buds, brain ventricular zone, ciliary marginal zone, and digestive organs such as the intestine, liver, and pancreas. In contrast, zebrafish lgr6 is expressed in the notochord, Kupffer's vesicle, the most anterior region of diencephalon, otic vesicles, and the anterior and posterior lateral line primordia by 24hpf. From 48 to 72hpf, lgr6 expression is confined to the anterior and posterior neuromasts, otic vesicles, pharyngeal arches, pectoral fin buds, and cranial cartilages such as Meckel's cartilages, ceratohyals, and trabeculae. Our results provide a basis for future studies aimed at analyzing the functions of zebrafish Lgr4 and Lgr6 in cell differentiation and proliferation during organ development.
富含亮氨酸重复序列（LRR）的G蛋白偶联受体（LGR）属于G蛋白偶联受体超家族，其特征在于具有七个跨膜结构域和一个包含一系列LRR基序的细胞外结构域。三种Lgr蛋白——Lgr4、Lgr5和Lgr6——被鉴定为LGR亚家族的成员。小鼠Lgr4已被证明通过在发育过程中调节细胞增殖参与各种器官的形成，而Lgr5和Lgr6是肠道或皮肤中的干细胞标志物。尽管这三个基因在成年小鼠中的表达已经得到了表征，但它们在生物体胚胎和幼体发育过程中的表达谱尚未确定。我们利用斑马鱼基因组数据库克隆了两个斑马鱼lgr基因。系统发育分析表明，这两个基因是哺乳动物Lgr4和Lgr6的直系同源基因。斑马鱼lgr4在受精后24小时（hpf）时在神经板边界、库普弗囊泡、神经管、耳泡、中脑、眼睛、前脑和脑室区表达。在36至96hpf期间，lgr4在中脑-后脑边界、耳泡、咽弓、颅软骨如梅克尔软骨、腭方软骨和角舌骨、颅腔、胸鳍芽、脑室区、睫状边缘区以及消化器官如肠道、肝脏和胰腺中被检测到。相比之下，斑马鱼lgr6在受精后24hpf时在脊索、库普弗囊泡、间脑最前部区域、耳泡以及前后侧线原基中表达。从48至72hpf，lgr6的表达局限于前后神经丘、耳泡、咽弓、胸鳍芽以及颅软骨如梅克尔软骨、角舌骨和小梁。我们的结果为未来旨在分析斑马鱼Lgr4和Lgr6在器官发育过程中细胞分化和增殖功能的研究提供了基础。
