Mitosis

Mitosis is part of the eukaryotic cell cycle and results in the production of two daughter cells each with a copy of the genome. The cell cycle itself is comprised of an interphase (made up of three stages G1, S, and G2) and the M (mitotic) phase. Cell growth, active transcription and translation, and DNA replication occur during interphase. During M phase duplicated DNA (chromatin) condense into sister chromatids (prophase); the nuclear envelop breaks down, kinetochore microtubles attach to the chromosomes and centrosomes are pushed to the poles of the growing spindle (prometaphase); the chromosomes are lined up on the metaphase plate (metaphase); sister chromatids are pulled to spindle poles at opposite ends of the cell (anaphase); the nuclear envelop is reformed and the chromatids decondense to chromatin (telophase); and the cell is cleaved into two by a contractile ring and the resolution of a cleavage furrow (cytokinesis). In some variant cell cycles nuclear division may not be followed by cell division, or G1 and G2 phases may be absent.

Vulval development

The C. elegans vulva connects the hermaphrodite uterus to the outside of the nematode. The development of this organ is an intensively studied biological process making it a useful model for animal organogenesis. C. elegans vulval development involves the temporal and spatial coordination of intercellular signaling, evolutionarily conserved signal transduction pathways, and transcriptional regulation. Among the pathways involved in vulval development are the WNT, epidermal growth factor (EGF), and LIN-12/NOTCH signaling pathways. These pathways work in temporal succession to prime epidermal cells to first be competent to take on vulva cell fates and later to solidify their vulval cell specification. These pathways also work antagonistically to specify the precise pattern of cell fates needed to form the vulva. A key cell in vulval development is the anchor cell. Signals from this cell initiate the transition from epidermal to vulval precursor cell. This cell also influences the specification of surrounding uterine cells, which is required to connect the uterus to the vulva. The development of the final vulval organ requires the anchor cell to invade between terminally differentiated vulval cells in a behavior analogous to that of metastatic tumor cells.