Reproduction

A fundamental biological process resulting in the production of offspring. In C. elegans, reproduction can result from self-fertilization within a hermaphrodite or by fertilization by mating of a male and hermaphrodite. In C. elegans, during the fourth larval stage of hermaphrodite development, the germline undergoes spermatogenesis to make functional sperm that are stored in the the gonad. In the adult stage, the germline ceases spermatogenesis and switches to oogenesis to produce oocytes that are fertilized by the previously generated spermatozoa or by spermatozoa deposited into the spermatheca during mating with a male. The embryos produced by self-fertilization are encased in an eggshell and initiate development within the uterus of the hermaphrodite. When they reach about the 30-cell stage, the egg-embryos are laid by the hermaphrodite through a vulva.

Ceramide biosynthesis

Ceramides are essential to animal development. Depletion of ceramides by completely eliminating the key enzymes in the ceramide synthesis pathway results in larval lethality.

Cell specification and differentiation

Developmental decisions on the cellular level include choosing between continued proliferation or specifying a fate by differentiating from their sister cells. In C. elegans, many cell fates are a direct outcome of their cell lineage; however, there are cases where cell specification is controlled by extrinsic signals from surrounding cells or tissues that activate intracellular differentiation programs.

Male sexual development

The establishment of the sex of a male organism by physical and physiological differentiation through sex-specific developmental pathways leading to a fully fertile male of the species.

Tail development

Development of the tail in C. elegans follows distinct sex-specific programs. Upon hatching there is very little morphological distinction between the hermaphrodite and the male C. elegans L1. By the adult stage, the hermaphrodite tail is a tapered whip of hypodermis. By contrast the adult male tale is a complex mating structure that stemmed from sex-specific cell lineages as well as reprogrammed cell fates.

Necrosis

Necrosis and apoptosis are contrasting modes of cell death. Whereas apoptotic cell death is associated with development and characterised by distinct stages of cell disassembly and engulfment, necrotic cell death is not a programmed cell fate and is characterised by an catastrophic disruption of the plasma membrane. Necrotic cell death is an important response to and in some cases, defense mechanism of, environmental or viral/bacterial pathogen assault.

Quiescence

A reversible sleep-like state, characterized by inactivity, increased arousal threshold to elicit sensory responses, and homeostasis. In C. elegans these quiescent periods punctuate the start of each larval molt.

Defecation

In C. elegans the expulsion of intestinal contents occurs every 45-50 seconds. This cycle is characterized by a pattern of muscle contractions under both muscle and neuronal control. The steps of the defecation cycle are a posterior body contraction (pBoc), an anterior body contraction (aBoc), and the final expulsion step (Exp) where the enteric muscles contract, opening the anus and allowing the intestinal contents to be released. Each step is independently controlled as mutations exist that affect one step but do not alter the timing or occurrence of the other. Further, Ca++ oscillations in the intestine, rather than neuronal stimulation, have been shown to control the initiating pBoc step. The contractions of the enteric muscles are controlled by GABA motor neurons AVL and DVB through an excitatory GABA-gated cation channel. The periodicity of the cycle is influenced by the presence of food, is temperature compensated, and can be reset by mechanosensory input.

Feeding

Identification of and response to a potential food source is a life-critical process. C. elegans has proved to be a model organism for studying the molecular and cellular mechanisms involved in seeking a food source and discriminating its value. These studies have shown that C. elegans is capable of forming a memory of particular foods and is capable of modifying its eating behavior upon subsequent exposure to the familiar food. In addition, research has shown that this modification in behavior is mediated by extrinsic, such as C. elegans pheromone and bacterial molecules, and intrinsic chemical cues, such as serotonin levels. In C. elegans feeding can be observed by watching pharyngeal pumping, which is composed of a posterior-directed contraction of the grinder followed by an anterior-directed relaxation.

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.