BmCAP , a silkmoth gene encoding multiple protein isoforms characterized by SoHo and SH3 domains: Expression analysis during ovarian follicular development q Theodoros Georgomanolis, Kostas Iatrou, Luc Swevers * Insect Molecular Genetics and Biotechnology, Institute of Biology, National Centre for Scientific Research “Demokritos”, Aghia Paraskevi Attikis, Athens, Greece article info Article history: Received 14 September 2009 Received in revised form 20 October 2009 Accepted 21 October 2009 Keywords: 20-Hydroxy-ecdysone 20E Ecdysone regulatory cascade E75 Silkmoth Bombyx mori Bombyx genome Ovary Follicular epithelium Oogenesis Vitellogenesis Choriogenesis Vinexin Ponsin Arg-binding protein c-Cbl-associated protein dCAP SH3 domain SoHo domain abstract CAP/ArgBP2/vinexin family proteins, adaptor proteins characterized by three SH3 domains at their C-termini and a SoHo domain towards their N-termini, are known to regulate cell adhesion, cytoskeletal organization, and growth factor signaling. Here we present the isolation and ovarian expression of the BmCAP gene which encodes CAP/ArgBP2/vinexin family proteins in the silkmoth, Bombyx mori. Screening for full-length cDNA clones identified three mRNA isoforms, BmCAP-A1 , BmCAP-A2 and BmCAP-B, which show expression throughout ovarian follicular development. Using an antibody raised against a unique region between the SoHo and SH3 domains, BmCAP-A protein isoforms were identified that show specific expression in different compartments of the ovarian follicles. Immunofluorescence staining of the cells of the follicular epithelium establishes a dynamic pattern of BmCAP-A protein localization during chorio- genesis. During early choriogenesis, BmCAP-A has a diffuse localization in the cytoplasm but could also be found concentrated at the apical and basal sides at the cellecell junctions. During late choriogenesis, the diffuse cytoplasmic staining of BmCAP-A disappears while the staining pattern at the apical side resembles a blueprint for the eggshell surface structure. We suggest that BmCAP-A isoforms have important functions during ovarian development, which involve not only the traditional roles in actin organization or cellecell adhesion but also the regulation of secretion of chorion proteins and the sculpting of the chorion surface. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction In the domesticated silkmoth Bombyx mori, ovarian follicle development occurs almost exclusively during pupal and pharate adult development (Yamauchi and Yoshitake, 1984). During this period each ovary consists of four ovarioles, in which more than 60 maturing follicles are arranged in a linear array. This linear array corresponds to follicle development from previtellogenesis (follicle formation and early stages of growth) and vitellogenesis (protein uptake and yolk formation by the oocyte) to choriogenesis (eggshell formation). Each follicle is a functional developing unit consisting of three cell types: one oocyte, an anterior cap-forming cluster of seven nurse cells of germ cell origin, and a surrounding monolayer of approximately 5000 epithelial (follicular) cells of mesodermal origin (Yamauchi and Yoshitake, 1984). A numbering system was devised to easily indicate follicle stages in which the first choriogenic follicle and last vitellogenic follicle are designated as þ1 and 1, respec- tively, follicles of later choriogenic stages by increasing positive numbers and follicles of earlier vitellogenic stages by negative numbers (Kafatos et al., 1977; Swevers and Iatrou, 1999). Ovarian development is triggered by the steroid hormone 20-hydroxy-ecdysone (20E; Swevers and Iatrou, 1998). During the transition from vitellogenesis to choriogenesis, the levels of 20E in the hemolymph decline (Tsuchida et al., 1987). The decline in 20E signaling is necessary for the initiation of the cascade that will lead to q Genbank Accession Numbers: GQ428999, GQ429000. * Corresponding author. Tel.: þ30 210 650 3586; fax: þ30 210 651 1767. E-mail address: swevers@bio.demokritos.gr (L. Swevers). Contents lists available at ScienceDirect Insect Biochemistry and Molecular Biology journal homepage: www.elsevier.com/locate/ibmb 0965-1748/$ e see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibmb.2009.10.006 Insect Biochemistry and Molecular Biology 39 (2009) 892e902