Chromosomal Axis Formation and Meiotic Progression in Chicken Oocytes: A Quantitative Analysis

The assembly and disassembly of the synaptonemal complexes (SCs) correlate with the progression of meiotic prophase I. Using immunostaining of the cohesin component SMC3, which is present in the axial elements of the SC, we characterized the synaptic process in chicken oocytes and quantified the frequency of the different prophase stages at hatching and at 3 different ages after hatching. The analysis provides detailed quantitative data regarding the meiotic stages in the chicken ovary showing that the maximum amount of pachytene oocytes is found around hatching and that oocytes reach the diplotene stage 5 days after entering into meiosis. We confirmed the asynchrony of the meiotic development in the female chicken gonad showing that the ovary has a composite population of cells at different stages from day 17 before hatching and for several days after hatching. The significance of these results is discussed in relationship to functional experimental procedures that involve avian oocytes.