Irles Paula, Ramos Saray, Piulachs Maria-Dolors
Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta, 37, 08003 Barcelona, Spain; Facultad de Agronomía e Ingeniería Forestal, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul, Santiago de Chile, Chile.
Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta, 37, 08003 Barcelona, Spain.
Dev Biol. 2017 Feb 15;422(2):105-114. doi: 10.1016/j.ydbio.2017.01.005. Epub 2017 Jan 13.
The importance of juvenile hormone regulating insect oogenesis suggests looking for genes whose expression is regulated by this hormone. SPARC is a calcium-binding glycoprotein that forms part of the extracellular membranes, which in vertebrates participates in bones mineralization or regulating cell proliferation in some cancer types. This large number of functions described for SPARC in different species might be related to the significant differences in its structure observed when comparing different species-groups. Indeed, these structural differences allow characterizing the different clades. In the cockroach Blattella germanica, a SPARC homolog emerged from ovarian transcriptomes that were constructed to find genes responding to juvenile hormone. In insects, SPARC functions have been studied in oogenesis and in embryo development of Drosophila melanogaster. In the present work, using RNAi approaches, novel functions for SPARC in the B. germanica panoistic ovaries are described. We found that depletion of SPARC does not allow to the follicular cells to complete mitosis, resulting in giant follicular cells nuclei and in a great alteration of the ovarian follicle cytoskeleton. The SPARC contribution to B. germanica oogenesis occurs stabilizing the follicular cell program and helping to maintain the nuclear divisions. Moreover, SPARC is necessary to maintain the cytoskeleton of the follicular cells. Any modification of these key processes disables females for oviposition.
保幼激素调节昆虫卵子发生的重要性表明，需要寻找其表达受该激素调控的基因。SPARC是一种钙结合糖蛋白，是细胞外膜的组成部分，在脊椎动物中参与骨骼矿化或调节某些癌症类型中的细胞增殖。SPARC在不同物种中所具有的大量功能，可能与在比较不同物种组时观察到的其结构上的显著差异有关。事实上，这些结构差异有助于区分不同的进化枝。在德国小蠊中，一个SPARC同源物从为寻找对保幼激素有反应的基因而构建的卵巢转录组中出现。在昆虫中，已经对SPARC在卵子发生和黑腹果蝇胚胎发育中的功能进行了研究。在本研究中，利用RNA干扰方法，描述了SPARC在德国小蠊无滋式卵巢中的新功能。我们发现，SPARC的缺失使滤泡细胞无法完成有丝分裂，导致巨大的滤泡细胞核以及卵巢滤泡细胞骨架的极大改变。SPARC对德国小蠊卵子发生的作用在于稳定滤泡细胞程序并有助于维持核分裂。此外，SPARC对于维持滤泡细胞的细胞骨架是必需的。这些关键过程的任何改变都会使雌性无法产卵。
