Cuticle biogenesis

The C. elegans cuticle is a protective exoskeleton of specialized extracellular matrix (ECM) consisting primarily of collagen, lipids, and glycoproteins and is required for viability. (Chisholm and Hardin 2005; Page and Johnstone 2007). The cuticle determines the shape of the body and, through connection from the epidermis to muscle, provides anchoring points for muscle contraction. The cuticle also serves as a model for ECM formation and function with molecules and pathways involved in cuticle biogenesis conserved in vertebrates (Page and Johnstone 2007). The outer epithelial layer, the epidermis, of the embryo undergoes a series of cell fusions to make large multinucleate, or syncytial, epidermal cells, which secrete the materials needed to make up the cuticle. This protective layer is produced five times during C. elegans development, with each molt ending with an entirely new cuticle.

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.