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.

Anaphase

In C. elegans, anaphase is comprised of two separable components, anaphase A, where the chromosomes separate from each other before any chromosome to pole movement, and anaphase B, where the spindle poles move away from each other, with the concomitant movement of the chromosomes to the poles. During anaphase B, the movement of the spindles, which carry the chromosomes, occurs through a combination of pulling and pushing forces. Cortical forces attached at the centrosomes pull the microtubule asters away from one another, while central spindle forces from overlapping microtubule arrays that had formed between separating chromosomes, push the chromosomes away from one another. The holocentric nature of C. elegans chromosomes entails special consideration to ensure the forces at all of the microtubule attachment sites of the chromosome are coordinated so that shearing of the chromosome during segregation does not occur.

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.

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.