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Differential expression and localization of four connexins in the ovary of the ayu ( Plecoglossus Altivelis )
Author(s) -
Yamamoto Yoji,
Yoshizaki Goro,
Takeuchi Toshio,
Soyano Kiyoshi,
Itoh Fuminari,
Patiño Reynaldo
Publication year - 2007
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.20562
Subject(s) - biology , vitellogenesis , plecoglossus altivelis , oocyte , heterologous , connexin , in situ hybridization , ovary , follicle , microbiology and biotechnology , endocrinology , medicine , messenger rna , gap junction , gene , genetics , embryo , intracellular , fishery , fish <actinopterygii>
Abstract The post‐vitellogenic oocytes of teleost fish are generally unresponsive to maturation‐inducing hormone (MIH) until a luteinizing hormone (LH) surge stimulates sensitivity via the acquisition of oocyte‐maturational competence (OMC). Heterologous gap junctions (GJs) between granulosa cells and the oocyte have been previously implicated in the regulation of oocyte maturation in various vertebrate species. Although heterologous GJ are present in ovarian follicles of ayu ( Plecoglossus altivelis ), their role in maturation remains unclear. In the present study, we cloned and characterized complementary DNAs for GJ protein connexin (Cx), and examined the expression pattern of Cx messenger RNAs in the ayu ovary. Four Cx cDNAs with predicted molecular masses of 32.1 (Cx32.1), 34.9 (Cx34.9), 44.1 (Cx44.1), and 44.2 (Cx44.2) kDa, respectively, were cloned. Northern blot analysis revealed that the levels of Cx44.1 and Cx44.2 transcripts were similar during the vitellogenic and ovulatory stages. Cx32.1 transcripts were more abundant during the vitellogenic stage, but their levels declined thereafter. Cx34.9 transcript levels increased during the vitellogenic stage and remained high during the acquisition of OMC. In situ hybridization revealed that Cx44.1 and Cx44.2 signals were restricted to the oocyte, whereas the Cx32.1 and Cx34.9 signals were detected in both cellular fractions. Furthermore, a dye‐transfer assay revealed the presence of functional GJs between the oocytes and follicle cells. These results suggest that Cx34.9 contributes to the formation of heterologous GJs between oocytes and granulosa cells. Moreover, GJs formed by Cx34.9 may function during the LH‐dependent acquisition of OMC and the MIH‐dependent resumption of meiosis in ayu. Mol. Reprod. Dev. 74: 1113–1123, 2007. © 2007 Wiley‐Liss, Inc.