| Summary: | Background The reproductive physiology of canines is unique from other mammals because oocyte maturation occurs about 48–72 hours after ovulation. This study aimed to evaluate the blood serum protein profile in canines during the periovulatory period by using shotgun proteomics to identify potential biomarkers of oocyte maturation. Method Anestrus female dogs (n = 9) were implanted subcutaneously with 4.7 mg of deslorelin to induce estrus and ovulation. After implantation, ovariectomy was performed based on the level of progesterone and vaginal cytology evaluations conducted every 48 hours. Simultaneously, serum samples were collected for proteomic analysis. The oocytes were flushed from the oviduct, and the oocyte maturation stage was identified. Based on oocyte staging, all samples were categorized into three groups (n = 3 dogs per group): pre-ovulation, ovulation with immature oocytes, and ovulation with mature oocytes. All serum samples were analyzed in triplicate (27 independent injections) using liquid chromatography-tandem mass spectrometry to investigate the protein profile. Results Proteomics analysis showed 11 proteins upregulated from three different groups: tubulin-specific chaperone D (TBCD); coiled-coil domain-containing protein 93 (CCDC93); WDFY family member 4 (WDFY4); calcium and integrin-binding protein 1 (CIB1); IQ motif containing E (IQCE); large ribosomal subunit protein uL23 N-terminal domain-containing protein (RPL23A); neuraminidase 4 (NEU4); G protein-coupled receptor kinase (GRK3); NF-keppaB inhibitor delta (NFKBID); leucine rich repeat containing 4B (LRRC4B); and Rho family-interacting cell polarization regulator 2 (RIPOR2). Among these proteins, NFKDIB, which are oocyte maturation markers in other mammalian species, was upregulated in the ovulation with mature oocyte group (P < 0.01). Therefore, NFKBID is a possible to be an oocyte maturation marker in canines, but further studies on larger populations are needed to confirm its potential.
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