Koziol Uriel, Costábile Alicia, Domínguez María Fernanda, Iriarte Andrés, Alvite Gabriela, Kun Alejandra, Castillo Estela
Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
Mol Biochem Parasitol. 2011 Feb;175(2):181-91. doi: 10.1016/j.molbiopara.2010.11.009. Epub 2010 Nov 17.
Tropomyosins are a family of actin-binding proteins with diverse roles in actin filament function. One of the best characterized roles is the regulation of muscle contraction. Tropomyosin isoforms can be generated from different genes, and from alternative promoters and alternative splicing from the same gene. In this work, we have isolated sequences for tropomyosin isoforms from the cestode Mesocestoides corti, and searched for tropomyosin genes and isoforms in other flatworms. Two genes are conserved in the cestodes M. corti and Echinococcus multilocularis, and in the trematode Schistosoma mansoni. Both genes have the same structure, and each gene gives rise to at least two different isoforms, a high molecular weight (HMW) and a low molecular weight (LMW) one. Because most exons are duplicated and spliced in a mutually exclusive fashion, isoforms from one gene only share one exon and are highly divergent. The gene duplication preceded the divergence of neodermatans and the planarian Schmidtea mediterranea. Further duplications occurred in Schmidtea, coupled to the selective loss of duplicated exons, resulting in genes that only code for HMW or LMW isoforms. A polyclonal antibody raised against a HMW tropomyosin from Echinococcus granulosus was demonstrated to specifically recognize HMW tropomyosin isoforms of M. corti, and used to study their expression during segmentation. HMW tropomyosins are expressed in muscle layers, with very low or absent levels in other tissues. No expression of HMW tropomyosins is present in early or late genital primordia, and expression only begins once muscle fibers develop in the genital ducts. Therefore, HMW tropomyosins are markers for the development of muscles during the final differentiation of genital primordia.
原肌球蛋白是一类肌动蛋白结合蛋白家族，在肌动蛋白丝功能中具有多种作用。其中一个最具特征的作用是调节肌肉收缩。原肌球蛋白同工型可由不同基因产生，也可由同一基因的不同启动子和可变剪接产生。在这项研究中，我们从绦虫中肠膜绦虫分离出原肌球蛋白同工型的序列，并在其他扁形动物中寻找原肌球蛋白基因和同工型。在绦虫中肠膜绦虫和多房棘球绦虫以及吸虫曼氏血吸虫中，有两个基因是保守的。这两个基因具有相同的结构，每个基因至少产生两种不同的同工型，一种高分子量（HMW）和一种低分子量（LMW）同工型。由于大多数外显子以互斥方式复制和剪接，来自一个基因的同工型仅共享一个外显子，并且高度不同。基因复制发生在新皮动物和涡虫地中海涡虫分化之前。在涡虫中发生了进一步的复制，伴随着复制外显子的选择性丢失，导致只编码HMW或LMW同工型的基因。针对来自细粒棘球绦虫的HMW原肌球蛋白产生的多克隆抗体被证明能特异性识别中肠膜绦虫的HMW原肌球蛋白同工型，并用于研究它们在节段化过程中的表达。HMW原肌球蛋白在肌肉层中表达，在其他组织中的水平非常低或不存在。在早期或晚期生殖原基中不存在HMW原肌球蛋白的表达，只有在生殖管道中的肌纤维发育后才开始表达。因此，HMW原肌球蛋白是生殖原基最终分化过程中肌肉发育的标志物。
