Gene Expression of Chicken Gonads Is Sex- and Side-Specific

Abstract

In chicken, the left and right female gonads undergo a completely different program during development. To learn more about the molecular factors underlying side-specific development and to identify potential sex- and side-specific genes in developing gonads, we separately performed next-generation sequencing-based deepSuperSAGE transcription profiling from left and right, female and male gonads of 19-day-old chicken embryos. A total of 836 transcript variants were significantly differentially expressed (p < 10^-5) between combined male and female gonads. Left-right comparison revealed 1,056 and 822 differentially (p < 10^-5) expressed transcript variants for male and female gonads, respectively, of which 72 are side-specific in both sexes. At least some of these may represent key players for lateral development in birds. Additionally, several genes with laterally differential expression in the ovaries seem to determine female gonads for growth or regression, whereas right-left differences in testes are mostly limited to the differentially expressed genes present in both sexes. With a few exceptions, side-specific genes are not located on the sex chromosomes. The large differences in lateral gene expression in the ovaries in almost all metabolic pathways suggest that the regressing right gonad might have undergone a change of function during evolution.

Gene expression profiling in embryonic chicken ovary during asymmetric development

“…; Scheider et al . ; Lim & Song ). Recently, the mRNA expression of leptin has been identified in ovaries as well as in the limb buds at stages 22–26 (E4.5) of embryonic development in chicken (Seroussi et al .…”

“…This result is inconsistent with observations using transcriptome analysis that stated expression of CYP19A1 varies between sexes but not between left and right ovaries (Scheider et al . ). However, as described above, only a medulla is present from E8 in the right ovary of chicken embryos (Smith & Sinclair ; Smith ; González‐Morán ) and CYP19A1 mRNA is preferentially expressed in the ovarian medulla (González‐Morán ).…”

“…; Scheider et al . ; Lim & Song ). PITX2 , a member of the RIEG/PITX homeobox family, is involved in asymmetric development of gonads, and PITX2 messenger RNA (mRNA) is exclusively expressed in the left ovary at stage 27 (E5–5.5).…”

“…, ; Scheider et al . ). The role of FSHR , CYP19A1 and apoptotic genes might have effects on asymmetrical development of ovaries as they are involved in folliculogenesis and cell proliferation (Pedernera et al .…”

Gene Expression Profiling Reveals Potential Players of Left-Right Asymmetry in Female Chicken Gonads

“…What are the molecular factors underlying side-specific development in female chicken gonads? With the advent of next-generation sequencing (NGS), RNA-seq has been used to assess chicken gonadal sex- and side-biased genes at different developmental stages [ 13 , 14 , 15 ].…”