Comparative analysis of temporal gene expression patterns in the developing ovary of the embryonic chicken

Abstract

Many genes participate in the process of ovarian germ cell development, while the combined action mechanisms of these molecular regulators still need clarification. The present study was focused on determination of differentially expressed genes and gene functions at four critical time points in chicken ovarian development. Comparative transcriptional profiling of ovaries from embryonic day 5.5 (E5.5), E12.5, E15.5 and E18.5 was performed using an Affymetrix GeneChip chicken genome microarray. Differential expression patterns for genes specifically depleted and enriched in each stage were identified. The results showed that most of the up- and downregulated genes were involved in the metabolism of retinoic acid (RA) and synthesis of hormones. Among them, a higher number of up- and downregulated genes in the E15.5 ovary were identified as being involved in steroid biosynthesis and retinol metabolism, respectively. To validate gene changes, expressions of twelve candidate genes related to germ cell development were examined by real-time PCR and found to be consistent with the of GeneChip data. Moreover, the immunostaining results suggested that ovarian development during different stages was regulated by different genes. Furthermore, a Raldh2 knockdown chicken model was produced to investigate the fundamental role of Raldh2 in meiosis initiation. It was found that meiosis occurred abnormally in Raldh2 knockdown ovaries, but the inhibitory effect on meiosis was reversed by the addition of exogenous RA. This study offers insights into the profile of gene expression and mechanisms regulating ovarian development, especially the notable role of Raldh2 in meiosis initiation in the chicken.

The Synchronized Progression from Mitosis to Meiosis in Female Primordial Germ Cells between Layers and Broilers

“…Furthermore, a RALDH2 knockdown chicken model was produced to investigate the fundamental role of RALDH2 in meiosis initiation. It was found that meiosis occurred abnormally in RALDH2 knockdown ovaries [ 44 ]. Through transcriptome analysis, we found that the meiotic-promoting-related genes STRA8 and RALDH2 began to be significantly up-regulated in the PGCs of both breeds of chicken at the E14 stage.…”

Meiotic initiation in chicken germ cells is regulated by Cyp26b1 and mesonephros

“…From embryonic Day 12.5, Stra8 is expressed in the cortex of the left ovary (Smith et al, ). Retinoic acid and RALDH2 are required for induction of meiosis initiation in ovarian germ cells in the chicken embryo (Yu et al, ), in such a way that addition of exogenous RA can rescue the inhibitory effect on meiosis in Raldh2 knockdown ovaries (Yu, Xu, Yu, Yu, & Du, ). In chicken, unlike mammals, RALDH2 is expressed in the embryonic gonads instead of the mesonephros.…”