Involved in kinetochore assembly and chromosome segregation during embryonic mitosis. Required for the localization of the NDC80 complex member him-10, the chromosomal passenger complex component air-2 and nuclear pore complex proteins npp-23 and npp-15 to kinetochores during metaphase. Required for npp-23 localization to the nuclear envelope during interphase. Recruits mdf-1, a component of the spindle assembly checkpoint, to the nuclear envelope. Appears dispensable for the assembly of the nuclear pore complex and for nuclear protein import. Part of the nuclear pore complex (NPC) (By similarity). May interact with mdf-1 (PubMed:22238360). Localizes to nuclear membrane periphery during interphase and to kinetochore during mitosis. Highly expressed in embryos (at protein level) (PubMed:19167330, PubMed:22238360). Expression decreases rapidly in larvae and becomes restricted to the germline in adults (PubMed:19167330). Larval lethality with about 9-12 percent of animals reaching adulthood. The few surviving adults are sterile. About 10 percent embryonic lethality. Reduced nuclear growth in P1 embryonic cell and delayed entry into mitosis. 39 percent reduction in him-10 kinetochore association and 34 percent reduction in air-2 chromatin association during metaphase. Loss of npp-5 localization to kinetochores during metaphase. About 10 percent of mutants have chromosome segregation defects. RNAi-mediated knockdown causes a loss of npp-23 localization to kinetochores and reduced localization to the nuclear envelope in interphase. Also results in the accumulation of spindle assembly checkpoint protein mdf-1 on kinetochores during metaphase and reduced mdf-1 localization to the nuclear envelope. Does not affect the expression levels of nuclear pore complex components npp-10, npp-19 and npp-7 or npp-10, npp-2 and mel-28 localization and appears to be dispensable for pie-1 nuclear import and for nuclear protein exclusion. Embryos transiently exposed to a hypoxic environment develop into infertile adults. Simultaneous RNAi-mediated knockdown of mdf-1 causes embryonic lethality and severe chromosome segregation defects. Belongs to the nucleoporin Nup84/Nup107 family.