- 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.
- Response to oxidative stress
Oxidative stress can result from an increase in reactive oxygen species or an inability to detoxify reactive intermediates or repair damage caused by these intermediates. Although C. elegans is quite resilient to high levels of oxygen, disruptions in intracellular respiration, such as mutations in
mev-1 and
gas-1, result in increases in reactive oxygen species (ROS). These increases in ROS result in hypersensitivity to high concentrations of oxygen.
- Glucose metabolism
Glucose metabolism refers to the biochemical processes responsible for the formation, breakdown and interconversion of carbohydrates, which include glucose and its various forms such as the aldohexose glucohexose and D-glucose (dextrose), in living organisms. Glucose species molecules are an important source of energy for living organisms and is found free as well as combined in oligosaccharides and polysaccharides.Processes involving glucose metabolism is conserved in metazoans.
- P granule biogenesis and organization
Germ granule proteins are found among a wide variety of species. In C. elegans, these granules are known as P granules. They are initially seen in the cytoplasm of oocytes and early embryos. In early embryogenesis they are asymmetrically segregated into blastomeres that eventually give rise to the germ line. In adults, P granules are peri-nuclear and cluster with nuclear pore complexes. They are associated with RNA metabolism and appear to play a role in nascent mRNA release from the nucleus.
- Gene silencing
Inactivation of gene expression can occur at both the level of transcription and post-transcription. All silencing mechanisms are identical in that they require a small RNA species to provide the necessary gene sequence specificity and effector molecules that bind to the RNAs to process the RNA and to direct its inhibitory activity. Studies of these mechanisms in C. elegans has elucidated a number of different RNA-mediated post-transcriptional mechanisms. These mechanisms differ in the species of small RNAs involved. The different classes of small RNAs in C. elegans includes, microRNAs (miRNA), small interfering RNAs (siRNAs or rasi's), X-chromosome cluster RNAs (X-cluster), tiny noncoding RNAs (tncRNAs), and Piwi-associated RNAs (piRNAs). Gene silencing is accepted as a defense mechanism that evolved to protect the host from exogenous (foreign) sequence such as viral and transposon sequence. It has also been shown that gene silencing plays a critical role in endogenous gene expression to control the developmental timing of genes require for cell specificity, as well as playing a role in aging.
- Response to toxicity
Exposure to a toxic substance can activate any number of processes that result in a change in state or activity of the organism. As a soil dwelling organism, C. elegans has evolved defenses against damaging substances in the soil environment and as such has proved to be an ideal organism for studying biological responses to toxins. These responses can occur at an organism level, such as invoking an avoidance behavior, or on a cellular level, such as activation of a cellular stress response. Cellular defenses have been shown to be invoked in response to reactive oxygen species, heavy metals, and toxin-induced unfolded proteins.
- Response to stress
A stress response is any physical response to factors that upset the normal balance of a biological event. C. elegans nematodes are susceptible to many different environmental stressors that include changes in temperatures, exposure to high osmolarity, and changes in oxygen levels. Internal stressors include DNA damage, accumulation of unfolded proteins, and accumulation of reactive oxygen species. These stressors have been shown to have a strong impact on the lifespan of C. elegans. The regulation of stress responses in the worm are similar to that in other organisms and include modulations of pathways that control caloric intake, mitochondrial respiration, insulin/IGF-1 (IIS), and JNK (c-Jun N-terminal kinase) signaling.
- Oogenesis
Oogenesis is the process of generating functional oocytes from an undifferentiated germ cell. In most animal species, oocytes arrest during meiotic prophase. The completion of meiosis and the preparation of the oocyte for fertilization are triggered in response to intercellular signaling in a process called meiotic maturation. During meiotic maturation, the oocyte transitions to metaphase of meiosis I, the nuclear envelope breaks down, the cortical cytoskeleton undergoes rearrangement, and the meiotic spindle is assembled. By contrast, in C. elegans, the processes of meiotic maturation, ovulation, and fertilization are temporally coupled. Meiotic maturation is triggered by major sperm protein (MSP), which acts as a hormone. In turn the maturing oocyte signals its own ovulation. During ovulation the oocyte passes through the spermatheca becoming fertilized on the way to the uterus.
- Unfolded protein response
The unfolded protein response (UPR) is a stress response that is critical to maintaining protein homeostasis (proteostasis)- the functional concentration of properly folded protein concentration in an organism. The UPR in entirety involves stress signals in the endoplasmic reticulum the mitochondria and the cytoplasm that are activated by increases in misfolded proteins. The increase in misfolded proteins affect protein concentration and can result in the aggregation of protein species. To restore protein homeostasis, these stress signals up-regulate or down-regulate protein transcription as well as regulate protein translation. These systems also influence protein folding by increasing the concentration of chaperones to aid in the folding process. In addition, these systems can increase the activity of the endoplasmic reticulum-associated degradation (ERAD) pathway, to deal with the increase in misfolded proteins. Eventually, sustained activation of the UPR will lead to cellular apoptosis.
- Mitochondrial DNA maintenance and expression
The mitochondrial genome is a vital component of animal metabolism, physiology, and development. C. elegans mitochondrial DNA (mtDNA) is typical of animal mitochondrial genomes in its size, 13,794 nucleotides in length, and gene content of 32 genes: 2 ribosomal RNAs, 22 transfer RNAs, and 12 protein subunits of the mitochondrial respiratory chain (MRC). Unlike nuclear DNA, mtDNA is maternally inherited and can be present at tens to tens of thousands of copies per cell. Its copy number is developmentally regulated, with mtDNA increasing about 30-fold between the L1 and the adult stages. Blocking mtDNA increase leads to larval arrest. Underlying its essential role in the biology of C. elegans, over 200 nuclear genes are needed to replicate, transcribe, and maintain the mitochondrial genome and to assemble the translation machinery required for expressing mitochondrial proteins. Disruptions in these processes have shown that the mitochondrion plays a critical role in aging, life span determination, reactive oxygen species response, the unfolded protein response, and apoptosis. Oddly, despite the essential role of mtDNA encoded genes in the cellular and organismal biology of C. elegans, mutations in mtDNA have not been reported. By contrast, over 300 lesions in human mtDNA have been described, many associated with neurological, endocrinological or muscle diseases.