Embryonic expression of GINS members in the development of the mammalian nervous system.

The GINS (Go, Ichi, Nii, and San) complex contains four protein subunits (PSF1, PSF2, PSF3, and SLD5) and has been identified as a factor essential for the initiation and elongation stages of the DNA replication process. A previous study indicated that PSF2 participated in the developing central nervous system (CNS) of Xenopus laevis. However, the expression and function of GINS members in the mammalian developing nervous system remains unclear. Here, we examined the expression of GINS members in mice during nervous system development via immunofluorescence staining. At the beginning of neural development, PSF1 and SLD5 were highly expressed in neuroepithelial stem cells (NSCs) of the inner surface of neural tube (NT) and overlapped with proliferation marker Ki67. After entering the mid- and late-phase of neural development, PSF1 and SLD5 changed their regions of expression. These genes were highly expressed in dorsal root ganglion (DRG) progenitors, but they showed no overlap with Ki67 positive cells. Instead, a reduction of SLD5 expression promoted neuronal differentiation and maturation in the late-phase. PSF2 and PSF3 showed no tissue-specificity. PSF2 was constitutively and highly expressed whereas PSF3 was expressed at very low levels during neural development. In this study, we demonstrated variations in proteins and expression regions of the GINS members during mammalian CNS development and revealed a correlation between GINS expression and cell proliferation. Furthermore, we have suggested a novel function of GINS member SLD5, which regulates the differentiation of neural stem/progenitors.