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Exogenous Retinoic Acid and Cytochrome P450 26B1 Inhibitor Modulate Meiosis-Associated Genes Expression in Canine Testis, an In Vitro Model

Authors

  • V Kasimanickam,

    1. Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA, USA
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  • R Kasimanickam

    Corresponding author
    1. Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA, USA
    • Author's address (for correspondence): R Kasimanickam, Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA. E-mail: ramkasi@vetmed.wsu.edu

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Contents

Pharmacological approaches to control spermatogenesis are required to resolve overpopulation in dogs. The objective of the study was to investigate the regulation of meiosis-associated and male germ cell-related genes, stimulated by retinoic acid gene 8 (STRA8), synaptonemal complex protein 3 (SYCP3), dosage suppressor of mck1 (DMC1), doublesex and mab-3 related transcription factor 1 (DMRT1) and deleted in azoospermia-like (DAZL) following exogenous administration of retinoic acid (RA) and after the modulation of endogenous RA by a cytochrome P450, family 26, subfamily B, polypeptide 1 inhibitor (CYP26B1-I; R115866) in an in vitro testis model. Testicles of five healthy, medium-sized and mixed-breed dogs were used for the organotypic cultures. All-trans-RA at 2 μm, CYP26B1-I at 1 μm and the control dimethyl sulphoxide (DMSO) were administered to the testes cultures, and the cultures were maintained for 24 h. Genes STRA8, DAZL and DMRT1 were significantly up-regulated as a result of the direct and indirect increase in the RA levels in the testis, subsequent to the exogenous administration of all-trans-RA and CYP26B1 inhibitor. Up-regulation of STRA8 was very prominent compared to DAZL and DMRT, and the drastic up-regulation of STRA8 was also observed with CY26B1-I than with all-trans-RA. No significant differences were found with the early meiotic markers, SYCP3 and DMC1 with RA, CY26B1-I and vehicle treatments. Because DAZL encodes a germ cell-specific RNA-binding protein, required for the induction of STRA8 and initiation of meiosis, we might see the expression differences temporally with the stage of spermatogenesis. DMRT1 is a unique gonad- and stage-specific transcription factor, directly activates STRA8 and has the temporal influence on its expression. Protein expression of DAZL and STRA8 was greater in RA- and CYP26B1-I-treated testis culture, whereas DMRT1 showed greater protein expression for RA treatment, but not for CYP26B1-I treatment compared to control. Relative protein expression of STRA8 was greatest for the CYP26B1-I treatment compared to DMSO and RA treatments. In conclusion, pharmacological intervention of spermatogenesis pertinent to RA signalling is plausible, and the effect of modulation differs upon the types of molecules and the key stages of signalling being targeted.

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