Zhou Ling, Chen Tong, Church Robert L
Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, USA.
Mol Vis. 2002 Jun 12;8:143-8.
Three different lens fiber cell intrinsic membrane proteins, MIP (Major Intrinsic Protein), MP19, and connexin50 (Cx50), have separately been implicated as causative candidates for congenital cataracts. The aim of this study was to determine gene transcript expression of these three proteins during successive stages of mouse embryonic development.
Total RNA was prepared from mouse embryos taken at days 9-10 (E9-E10) of gestation, heads of day 11-13 (E11-E13) embryos, and lenses of adult mice. Coupled reverse transcriptase-polymerase chain reaction (RT-PCR) was used to determine gene transcript expression of MIP, Cx50, and MP19 during embryonic development. The products of RT-PCR were further cloned into the TOPO(TM) TA vector, and further analyzed by double strand nucleotide sequencing.
Cx50 gene expression was observed throughout the developmental period observed (E9-E13). MIP transcripts were first observed at mouse embryonic day 11.5 (E11.5) and synthesis continued throughout the developmental period observed. The gene for MP19 (Lim2) begins to express at mouse embryo day 12 (E12) and synthesis continued throughout the developmental period observed. mRNA levels for all three proteins appear to remain steady from these early embryonic stages through adulthood.
The identified early expression of Cx50, MIP, and Lim2 transcripts in mouse embryonic stages suggests that all three proteins play very important, probably quite different, roles in lens fiber cell differentiation. Variation in the temporal expression of these three genes during the course of development suggests a critical gene-coordinated regulation throughout lens fiber cell development. These three genes clearly play important roles in early normal lens development since it is known that mutations in the sequence of each membrane protein results in cataractogenesis.
三种不同的晶状体纤维细胞内在膜蛋白，即主要内在蛋白（MIP）、MP19和连接蛋白50（Cx50），已分别被认为是先天性白内障的致病候选因素。本研究的目的是确定这三种蛋白在小鼠胚胎发育连续阶段的基因转录表达情况。
从妊娠第9 - 10天（E9 - E10）的小鼠胚胎、第11 - 13天（E11 - E13）胚胎的头部以及成年小鼠的晶状体中提取总RNA。采用逆转录聚合酶链反应（RT-PCR）来确定MIP、Cx50和MP19在胚胎发育过程中的基因转录表达。RT-PCR产物进一步克隆到TOPO(TM) TA载体中，并通过双链核苷酸测序进行进一步分析。
在整个观察的发育时期（E9 - E13）均观察到Cx50基因表达。MIP转录本最早在小鼠胚胎第11.5天（E11.5）被观察到，并且在整个观察的发育时期合成持续进行。MP19（Lim2）基因在小鼠胚胎第12天（E12）开始表达，并且在整个观察的发育时期合成持续进行。从这些早期胚胎阶段到成年期，这三种蛋白的mRNA水平似乎保持稳定。
在小鼠胚胎阶段鉴定出的Cx50、MIP和Lim2转录本的早期表达表明，这三种蛋白在晶状体纤维细胞分化中都起着非常重要的、可能相当不同的作用。这三个基因在发育过程中时间表达的变化表明在整个晶状体纤维细胞发育过程中存在关键的基因协调调控。由于已知每种膜蛋白序列中的突变会导致白内障形成，所以这三个基因显然在早期正常晶状体发育中起重要作用。
