- Metabolism
The chemical reactions, and regulation of these reactions, within an organism that are required for growth, reproduction, maintenance of proper cellular and organ function and structure, and response to the environment. These enzyme-catalyzed processes control all cellular functions including digestion, detoxification, protein synthesis, degradation and modification, and energy production.
- Organogenesis
The formation and development of an organ (a structural part of an organism that performs a specialized function) requires the coordination of many intrinsic and extrinsic cues that control cellular processes such as cell division and specificity, cell movement, cell-cell interaction, and cell polarity. C. elegans has proved to be a model organism for studying key organs, e.g., pharynx, intestine, and vulva, in part due to the small number of traceable cells that make up these specialized group of cells.
- Proteostasis
Proper protein function relies on a balanced system of protein synthesis, folding, trafficking and degradation to ensure a homeostatic concentration of properly processed proteins in the organism. Disruptions in any one of these events can result in alterations in the level of proteins, the accumulation of misfolded proteins, and or the aggregation of proteins. Stress responses in the cytoplasm, mitochondria, and ER keep properly folded protein concentrations in check. These systems maintain proteostasis by up-regulating or down-regulating transcriptional and translational processing of proteins or by increasing protein degradation pathways. Many disease states in humans, such as cystic fibrosis, and Alzheimer's, Parkinson's and Huntington's diseases have been attributed to the breakdown of proteostasis systems in the cell.
- RNA interference
RNA interference (RNAi) refers to the silencing of gene expression by the overexpression of RNA molecules. This process is associated with a cellular and nuclear defense mechanism used to combat molecular parasites such as transposons and viruses. In addition, RNA interference has been shown to play a regulatory role in development. Work in C. elegans and other organisms have identified many key regulators and pathways necessary for this process. Specifically, RNAi has been adapted into a tool for the study of gene function; through the use of RNAi, the expression of a target gene can be inhibited by the reverse engineering of a corresponding dsRNA.
- Innate immune response
The innate immune system is the first line of cellular defense in all classes of plants and animals against infection by other organisms. A number of signaling pathways in the nematode have been identified that act in this host response to microbial and fungal pathogens. Like other invertebrates, C. elegans does not have an adaptive immune system. However, unlike some invertebrates, C. elegans does not have any specialized cells dedicated to immune function. Triggering of the innate immune cellular response can occur in any tissue of the worm, and utilizes the any number of signaling pathways, which normally play roles in cell signaling events used during development or normal cell homeostasis.
- 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.
- ER-associated degradation
Correctly folding proteins is a severely complicated process. Within eukaryotes an optimal environment for protein folding is provided by the endoplasmic reticulum (ER). In addition, proper folding requires the activity of numerous molecular chaperones and folding enzymes. Despite the controlled environment and numerous molecular helpers, misfolded proteins do sometimes occur. ER-associated degradation (ERAD) is a normal cell function that detects and deals with these occurrences. Through the ERAD process, misfolded proteins are recognized, retrotranslocated to the cytosol, ubiquinated, and then degraded by the proteosome.
- Olfaction
Volatile organic molecules are sensed through olfaction. C. elegans can distinguish and respond to many volatile odorants through attractive or repulsive chemotactic behaviors. In some instances volatile compounds can induce both behaviors depending on its concentration. Olfaction studies in C. elegans has revealed a complex sensory system where only three types of neurons (AWC, AWA, and AWB) have been found to be responsible for processing over seven classes of volatile odorants, including alcohols, ketones, organic acids, sulfhydrals, and heterocyclic compounds. Detailed study of the molecular machinery behind odor reception has shown that each neuron controls a particular attractive or repulsive behavioral response, for example, AWC controls attractive chemotaxis responses and AWB controls repulsive chemotaxis responses. One distinguishing feature of C. elegans sensory system is that the sensory neurons are polymodal in their stimulus detecting ablility; that is, individual neurons in C. elegans express multiple odorant receptors allowing multiple sensory functions, whereas vertebrate neurons express a single receptor limiting their function to detecting a single odorant.
- Autophagy
Autophagy is the degradation of cytoplasmic components through an autophagolysosome (autolysosome). Of the many types of autophagy in nature, macroautophagy, which involves the sequestration of cellular material by a double-membrane autophagosome, has been observed in C. elegans. The steps in this degradation process include nucleation of vesicle formation, expansion of the membrane with concomitant capture of cellular components (vesicle elongation), autophagolysosome or autolysosome, formation (autophagosome fusion with lysosome), and completion (vesicle breakdown and the lysis of the captured cytoplasmic material).