- 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.
- 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.
- Germline development
During germline development germ cells, or reproductive cells, are specified, proliferated, and maintained for the establishment of a germline in the next generation. In C. elegans, germ cells are specified from somatic cells during early embryogenesis. During larval stages, cells of the germline proliferate, undergo meiotic entry, and the germline undergoes sex determination. Gametogenesis, specifically spermatogenesis, begins in late L4 in the hermaphrodite, and switches to oogenesis after the adult molt. Germline proliferation, meiotic development, and gametogenesis continue throughout adulthood.
- Larval development
During post-embryonic development the temporal and spatial regulation of cellular and molecular mechanisms continue past embryogenesis to give rise to a fully functional adult. Post-embryonic development in C. elegans involves progression of the animal through four larval stages. Post-embryonic development involves further limited somatic cell division and cell death to bring the final total to 959 somatic nuclei in the hermaphrodite and 1031 in the male. Other remarkable processes during this period include cell migrations, neuronal rewiring, and adoption of final cell fates. Under conditions of stress, e.g., starvation, reproductive development ceases and the animal switch to a physiologically distinct developmental program to produce the dauer larva.
- Molting
Under good conditions, C. elegans enters and exits four larval stages before becoming a fertile adult. Each developmental stage is punctuated with a molt that entails the shedding of the larval cuticle and the generation of a completely new one. It has been shown that each cuticle is unique in its composition. Molting is a carefully timed process that needs to be coordinated with development, new cuticle synthesis, and cuticle shedding. Mutations in a set of genes called heterochronic genes regulates the timing development and the molts and result in precocious or retarded development of parts of the animals that aren't synchronized with the animals' life stage.
- Trans-splicing
Trans-splicing is an RNA processing event that fuses together sections of two different pre-mRNA sequences. In C. elegans, ~70% of mRNAs are trans-spliced to one of two 22 nucleotide spliced leaders, SL1 or SL2, with more than half of all transcripts undergoing SL1 splicing. During SL1 splicing, the 5' ends of pre-mRNAs are removed and replaced with SL1 sequence in a process very closely related to cis-splicing (intron/exon processing). SL1 sequence is ~100nt and is donated by small nuclear ribonucleoprotein particles (snRNPs). The remaining genes are trans-spliced by SL2. These genes are all downstream genes in closely spaced gene clusters similar to bacterial operons. They are transcribed from a promoter at the 5' end of the cluster of between 2 and 8 genes. This transcription makes a polycistronic pre-mRNA that is co-transcriptionally processed by cleavage and polyadenylation at the 3' end of each gene, and this event is closely coupled to the SL2 trans-splicing event that occurs only ~100 nt further downstream. Recent studies on the mechanism of SL2 trans-splicing have revealed that one of the 3' end formation proteins, CstF, interacts with the only protein known to be specific to the SL2 snRNP.
- 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.
- Ray development
C. elegans male tail contains four types of male-specific sensilla, the most prominent of which are the rays. These 18 sensory rays convey mechano- and chemosensory information critical to male mating. Each ray is composed of three cells: RnA: A-type sensory neuron; RnB: B-type sensory neuron; and Rnst: ray structural cell, which are derived from one neuroblast, the ray precursor cell called Rn. Each ray is morphologically and molecularly distinct from each other. Most all ray identity follows a determinate cell lineage model where cell identity is established based on the pattern of cell division; ray 5 does require external cues from a TGF-beta signalling pathway to adopt its final fate.
- Aging
Aging in C. elegans involves measurable declines in morphology, reproduction, and behavior. Understanding the cellular and molecular processes leading to senescence in this nematode began in the early 1980s with the targeted identification of mutants with extended life spans (an AGE phenotype). These studies identified at least two key regulators of life span, DAF-2, an insulin/IGF receptor ortholog, and DAF-16, a Forkhead-related transcription factor. Since then many more genes and pathways involved in senescence have been identified. Almost all of these genes play important roles in cellular and organismal-level processes other than aging, such as dauer formation, stress response, feeding, and chemosensation. A common marker for aging in C. elegans is the accumulation of lysosomal deposits of lipofuscin, resulting in an increase in intestinal autofluorescence over time.
- 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.