The inner and outer nuclear membranes merge to form nuclear pores, which are the sites of nuclear pore complex (NPC) assembly and nucleo-cytoplasmic transport. In mammals, the pore membrane domain contains two known integral membrane proteins: POM121, which is not apparently conserved in C. elegans , and
gp210, which is conserved among metazoans and plants. The C. elegans
gp210 protein (Ce-
gp210) is 19%, 21% and 25% identical (36%, 40% and 44% similar) to the Arabidopsis , Drosophila and rat
gp210 proteins, respectively. Gp210 is proposed to play a fundamental role during membrane fusion, to generate nuclear pores. However, this proposed role is unproven, and is disputed based on the slow rate of
gp210 re-accumulation during nuclear assembly in mammalian cells. We are testing the function of
gp210 in C. elegans . Antibodies raised against different regions of Ce-
gp210 reveal a 209-kDa protein on immunoblots of total worm lysate proteins. By immunofluorescence, the antigens colocalize with NPCs during interphase, consistent with specificity for Ce-
gp210. During mitosis in Drosophila and mammalian cells,
gp210 disassembles during early prophase, similar to other nucleoporins. In contrast, Ce-
gp210 completely disassembles only during late anaphase, similar to the inner nuclear membrane proteins and lamins, and different from soluble nucleoporins, which disassemble during metaphase. Preliminary results in
gp210-deficient ( RNAi ) embryos show that
gp210 is essential for viability during embryonic and larval development. Further characterization of the
gp210- RNAi phenotype is underway, to determine the essential role of
gp210 during development.