Regulation of 22q11 orthologous genes during mouse development

22q11-deletion syndrome (22q11DS) is a developmental anomaly caused by a microdeletion on human chromosome 22q11. Although mouse models indicated Tbx1 as the gene responsible of the syndrome, the phenotypic spectrum of del22q11 patients is complex suggesting that gene-gene and gene-environment interactions, probably during embryonic development, are crucial in delineating the pathogenesis of 22q11DS. In order to define cis-acting regulatory effects of 22q11Ds haploinsufficiency during development we analysed the expression pattern of MM16 mouse genes, that is the syntenic region to 22q11, in RNA from total embryos at different stages (from 4.5 dpc to 14.5 dpc; corresponding to pharyngeal development) by a low density microarray (22q11DS-chip). Keywords: time-course Deletion of 22q11.2 chromosomal region causes the most common microdeletion syndrome in man with an incidence of approximately 1:4000 live births (Scambler, 2000). The major malformations include congenital heart defects such as truncus arteriosus (TA) and interrupted aortic arch type B (IAA-B), hypo/aplasia of the parathyroid glands, hypo/aplasia of the thymus gland, and craniofacial dysmorphism. However more than 180 clinical symptoms are due to 22q11 microdeletion (Ryan et al, 1997); in particular the psychiatric disorders are one of the more prevalent phenotype in adult patients (Basset et al., 2003). An unsolved question regarding 22q11 deletions is whether the associated congenital defects are caused by a single dose-dependent 22q11 gene or rather by the combined loss of multiple linked genes that may act in a common pathway or in parallel during a critical period of pharyngeal development. In order to answer to this question we have turned out our attention at analysing the expression level of 68 murine genes, 39 hortologues to human 22q11 genes and 29 mapping outside. The expression level of these 68 genes was analysed in mouse embryos at different stages (from 4.5 dpc to 14.5 dpc), corresponding to the pharyngeal development. The RNA reference used in this study was obtained by pooling different CD1 mouse embryos at 18.5 dpc; total RNA was isolated by the TRIZOL standard protocol (Invitrogen).22q11缺失综合征（22q11-deletion syndrome, 22q11DS）是由人类22号染色体22q11区域微缺失引发的发育异常性疾病。尽管小鼠模型提示Tbx1是该综合征的致病基因，但22q11缺失患者的表型谱较为复杂，这提示基因-基因、基因-环境间的互作（大概率发生于胚胎发育阶段）在阐明22q11DS的发病机制中发挥关键作用。为明确发育过程中22q11DS单倍剂量不足的顺式调控效应，本研究通过低密度微阵列（22q11DS-chip）分析了与人类22q11区域同线的MM16小鼠基因在不同发育阶段（4.5天胚胎日龄至14.5天胚胎日龄，对应咽发育阶段）全胚胎RNA中的表达模式。关键词：时程分析。22q11.2染色体区域缺失是人类最常见的微缺失综合征，活产儿发病率约为1:4000（Scambler, 2000）。其主要畸形包括先天性心脏缺损，如永存动脉干（truncus arteriosus, TA）和B型主动脉弓中断（interrupted aortic arch type B, IAA-B）、甲状旁腺功能减退/发育不全、胸腺发育不全/发育不良，以及颅面畸形。然而22q11微缺失可引发超过180种临床症状（Ryan等, 1997），其中精神类疾病是成年患者中较为普遍的表型之一（Basset等, 2003）。目前针对22q11缺失的未解问题在于：其相关先天性缺损是由单个剂量依赖性22q11基因导致，还是由多个连锁基因的联合缺失所引起——这些基因可能在咽发育的关键时期通过共同通路或平行通路发挥功能。为解答这一问题，本研究将分析重点转向68个小鼠基因的表达水平：其中39个为人类22q11基因的同源基因，其余29个则定位在该区域之外。本研究分析了这68个基因在不同发育阶段（4.5 dpc至14.5 dpc，对应咽发育阶段）小鼠胚胎中的表达水平。本研究使用的RNA参照样本取自18.5 dpc的不同CD1品系小鼠胚胎的混合样本，总RNA提取按照TRIZOL标准流程（Invitrogen公司）完成。