Expression pattern of meiosis associated SYCP family members during germline development in chickens

Synaptonemal complexes (SCs) are associated with synapsis of homologous chromosomes, chiasmata distribution, recombination and segregation of chromosomes during the extended prophase of meiosis I. Three isoforms of SC proteins, SYCP1, SYCP2 and SYCP3, were identified as the structural proteins of SCs, and may be involved in the assembly and disassembly of SCs. The aim of this present study is to determine the pattern of expression of chicken homologues of SYCP family members during ovarian and testicular development. Protein sequence analysis using CLUSTAL X revealed that the sequences and potential phosphorylation sites of chicken SYCP family proteins were highly conserved with mammalian homologues of SYCP family proteins. Quantitative real-time-PCR and in situ hybridisation analysis revealed that chicken SYCP family members were differentially expressed during ovarian and testicular development. During ovarian development, all chicken SYCP family members were detected in primordial germ cells (PGCs) until embryonic day (E) 8.0; the expression continued in proliferating pre-meiotic oogonia until E15.5 and was upregulated in meiotic prophase I oocytes until hatching. After hatching, all chicken SYCP family members were detected at a low level until 24-weeks-old. During testicular development, all chicken SYCP family members were detected in PGCs until E13.0; the expression continued in pro-spermatogonia and proliferating spermatogonia for up to 8 weeks, and was upregulated in meiotic prophase I spermatocytes in adults. Our data demonstrate the expression pattern of meiosis associated SYCP family members during ovarian and testicular development in chickens.