Expression of SRG3, a chromatin-remodelling factor, in the mouse oocyte and early preimplantation embryos.

SRG3 (Smarcc1) is a core subunit of the SWI/SNF complex. In the absence of SRG3, embryonic development ceases during peri-implantation stages, indicating that SRG3, as well as the chromatin-remodelling process, plays an essential role in early mouse development. To gain a better understanding of chromatin remodelling during the early stages of development, we examined SRG3 expression during oogenesis and preimplantation stages using immunofluorescence and western blot assays. SRG3 was detected in nuclei of oocytes during growth and maturation. Following fertilization, SRG3 was detected in pronuclei shortly after their formation. Nuclear concentrations of SRG3 increased in a time-dependent fashion and were found to be greater in the male pronucleus than in the female pronucleus. The increase in nuclear SRG3 was partially inhibited by a protein synthesis inhibitor, but not by a transcriptional inhibitor. Expression of SRG3 is accompanied by expression of Brg1 and Ini1, two other core subunits of the SWI/SNF complex. The expression of these three remodelling factors parallels that of SP1 and TBP, both spatially and temporally, in the mouse embryo, suggesting a role for remodelling factors in chromatin structure and function during early development.