Molecular anatomical research of nuclear membrane in mitotic phase : the ultra structure of the surface and genes regulate it.

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For the first step of investigating the functions of Rag gene family molecules in nuclear division process, we isolated the homologues of Rag gene from African clawed frog, Xenopus laevis (XRag1 and XRag2). A multiple alignment and phylogenetic tree indicated that all eukaryotes carry two closely related genes. Together with binding of these two gene products in human and yeast previously reported, XRag1 and XRag2 could form the minimal functional complex in vivo. However, a level of XRag1 and XRag2 transcripts were not linked revealed by RT-PCR. XRag2 expression showed rapid decrease after Mid Blastula Transition (MBT) in contrast to the almost constant level of XRag2. Then, we confirmed the spatial expression patterns of two genes by in situ hybridization. In early stages before MBT, both XRag1 and XRag2 are expressed in animal hemisphere but XRag2 is decreased after stage 8 and no longer detectable in stage 12. Simultaneous expression of XRag1 and XRag2 was detected again after stage 25, tail bud stage in neuronal tissues (eye and ear primordium). In summary, (1) XRag1 and XRag2 shared incompatible genetic functions. (2) During stage 10-25, only XRag1 is expressed. This suggests XRag1 homodimer (or homooligomer) is the functional unit in these stages. (3) Thus, expression ratio of XRag1 and XRag2 may regulate the switching of the cell division mode at MBT. (4) In later stages, these genes are specifically expressed in neuronal tissues, suggesting new XRag1 and XRag2 roles in the development of peripheral nervous system.