Gene expression Difference in oocytes derived from adult and prepubertal Cattle

Developmental competences of oocytes derived from prepubertal heifers are lower than those derived from adult counterparts. The objective of this study was to identify a range of genes associated with reduced oocyte competence that are differentially expressed between adult versus prepubertal donors. Microarray experiments were conducted using total RNA isolated from GV and MII stages oocytes collected from adult and prepubertal animals using Affymetrix GeneChip Bovine Genome Array containing 24,072 probe sets representing over 23,000 transcripts. A total of 549 and 333 genes were differentially expressed between prepubertal versus adult bovine MII and GV stages oocytes respectively. Out of these, 312 and 176 genes were up-regulated, while 237 and 157 were down-regulated in prepubertal when compared with adult MII and GV oocytes respectively. Ontological classification of the differentially expressed genes revealed that up-regulated genes in adult oocytes were involved in signal transduction, regulation of transcription DNA-dependent, and transport. Results from the present study indicated that significant number of genes were differentially expressed (>2-fold, p<0.01) between the two groups. Thus the decreased developmental competence of oocytes from prepubertal heifers may be induced due to difference in gene expression abundance as observed in our study. In conclusion, transcript abundance analyses of oocytes using microarray approach have been carried out in bovine and several other species. However, to our knowledge, this is the first study carried out to examine genes expression differential abundance in oocytes derived from perpubertal versus adult Japanese Black Cattle.

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