COMPARATIVE PROTEOMIC ANALYSIS OF IMMATURE BUFFALO OOCYTES OF HIGH AND LOW DEVELOPMENTAL COMPETENCE
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Date
2020
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ICAR-NDRI, KARNAL
Abstract
Selecting oocytes of high developmental competence is essential for the success of
several reproductive technologies. The objectives of the present study were i)
identification of proteins differentially expressed in immature oocytes of high and low
developmental competence, selected by brilliant cresyl blue (BCB) staining, ii) to study
the functional relevance of the differentially expressed proteins using bioinformatics tools
and iii) validation of important differentially expressed proteins associated with the
developmental competence of oocyte. Immature oocytes obtained from abattoir buffalo
ovaries were classified into usable and unusable categories based on morphological
criteria, and those of usable category were further classified into oocytes of high (BCB+)
and low (BCB-) developmental competence after staining them with BCB. The oocytes of
both the groups were denuded of their cumulus mass and lysed. Proteins were isolated and
subjected to iTRAQ for proteome analysis. The data obtained was subjected to
bioinformatics analysis using PANTHER, KEGG, DAVID, STRING, CYTOSCAPE
and METSCAPE. A total of 692 proteins were found to be differentially expressed
between BCB+ and BCB- oocytes. Following analysis focused on only three related
species i.e., Bos taurus, Bubalus bubalis and Bos grunniens, 296 proteins were found to
be differentially expressed between the two groups. Among these, 67 proteins were upregulated
(FC≥1.2, FDR ≤ 1%) and 9 down-regulated (FC≤0.83, FDR ≤ 1%) in BCB+
compared to BCB- oocytes. The top ten up-regulated proteins were PFKL, MVP, GLRX,
PGK1, TUBA1D, APMAP, LDHA, HMGN1, ENO1 and YWHAE whereas, the downregulated
proteins included, A1BG, AHSG, APOC3, COX7A2, FETUB, GC, HBA,
NDUFS6 and SERPINA1. Through bioinformatics analysis we found proteins from
metabolic pathways, ribosomes, thermeogenesis, spliceosome, oxidative phosphorylation,
glycolysis/ gluconeogenesis, endoplasmic reticulum protein processing (redox
homeostasis) and from oocyte meiosis. The significantly differentially expressed proteins
were involved in 121 pathways out of which mostly were metabolic pathways suggesting
that the metabolic pathways may be playing an important role in determining the
developmental competence of oocytes. The results indicated that the developmental
competence of immature oocytes may be associated with regulation of translation
including initiation, elongation and termination steps and that compromised carbohydrate
metabolism may contribute to low developmental competence. MVP, LDHA, RPL23A,
RPS11 and PDIA4 were found to be candidate biomarkers of developmental competence
which need to be studied further to identify the best biomarker among them.