Identification of wnt2 in the pearl mussel Hyriopsis cumingii and its role in innate immunity and gonadal development.

Wnt2 is a significant factor in the Wnt signaling pathway, which is associated with a variety of physiological activities, including inflammatory response, cell apoptosis, reproductive system development, and cell differentiation. Hyriopsis cumingii is the main pearl breeding mussel in China. However, the role of wnt2 in this species remains unclear. In this study, wnt2 from H. cumingii was cloned and identified. The full-length cDNA of wnt2 is 1524 bp, containing a 963 bp open reading frame (ORF), encoding 320 amino acid residues. The tissue distribution of H. cumingii indicated that wnt2 was predominantly highly expressed in the ovary and gill. And the expression profile after Aeromonas hydrophila or LPS injection indicated that wnt2 was up-regulated in gill, suggesting its role in the innate immune response. The expression of wnt2 was high at 4-month-old of early gonadal development and throughout ovarian development. In situ hybridization (ISH) showed significant hybridization signals on the gills and mature eggs of female gonads. In addition, miR-1988b-5p was found to negatively regulate wnt2 to affect the expression of key genes (frizzled-5, ctnnb1, and tcf7l) in the Wnt signaling pathway. Thus, these findings suggest a key role for wnt2 in immune regulation and gonadal development in H. cumingii.

Identification and functional analysis of Tex11 and Meig1 in spermatogenesis of Hyriopsis cumingii.

The process of spermatogenesis is complex and controlled by many genes. In mammals, Testis-expressed gene 11 (Tex11) and meiosis expressed gene 1 (Meig1) are typical spermatogenesis-related genes. In this study, we obtained the full length cDNAs for Tex11 (3143bp) and Meig1 (1649bp) in Hyriopsis cumingii by cloning. Among them, Hc-Tex11 contains 930 amino acids and Hc-Meig1 contains 91 amino acids. The protein molecular masses (MW) of Hc-Tex11 and Hc-Meig1 were 105.63 kDa and 10.95 kDa, respectively. Protein secondary structure analysis showed that Hc-TEX11 protein has three TPR domains. The expression of Hc-Tex11 and Hc-Meig1 in different tissues showed higher levels in testes. At different ages, the expression of Hc-Tex11 and Hc-Meig1 was higher levels in 3-year-old male mussels. During spermatogenesis, the mRNA levels of Hc-Tex11, Hc-Meig1 gradually increased with the development of spermatogonia and reached a peak during sperm maturation. Hc-Tex11 and Hc-Meig1 mRNA signals were detected on spermatogonia and spermatocytes by in situ hybridization. In addition, RNA interference (RNAi) experiments of Hc-Tex11 caused a down-regulated of Dmrt1, KinaseX, Tra-2 and Klhl10 genes and an up-regulated of ß-catenin gene. Based on the above experimental results, it can be speculated that Hc-Tex11 and Hc-Meig1 are important in the development of the male gonadal and spermatogenesis in H. cumingii, which can provide important clues to better comprehend the molecular mechanism of Tex11 and Meig1 in regulating spermatogenesis of bivalves.