Nervous System Development in Caenorhabditis elegans (Research Paper Sample)

Nervous System Development in Caenorhabditis elegans Author Institutional Affiliation COURSE ####: Course Title Instructor’s Name Date Nervous System Development in Caenorhabditis elegans Introduction Since the 1960s and 1970s, seminal work by Sydney Brenner to adopt the Caenorhabditis elegans, a species of soil nematode (Brenner, 1974), as a referential model for understanding the nervous system has made estimable strides. The pioneering research on C. elegans intended to reconstruct the synaptic wiring network of the nematode using volume electron microscopy (Mulcahy et al., 2018). The decision to use the C. elegans species arose from its size and complexity—it is a cylindrical organism measuring about 1mm in length and 70μm diametrically and consisting of a complex network of 473 and 358 cells in the male and female nervous systems respectively (Aamodt, 2006). The cells vary in function, including sensory, polymodal, motor, and interneuron functions, with about 118 cell subgroups specially adapted for synaptic feedback, special sensory functions, and body positioning (Mulcahy et al., 2018). Although the C. elegans nematode has been used as the reference model in the life sciences faculty, 40% of the organism’s genetic structure has undetermined functionality (Petersen et al., 2015). One reason for this would be the fact that the much of the investigation of this organism has occurred in artificial laboratory environments using the conventional N2 strain (Zhang et al., 2017). The nervous system of C. elegans, discovered using electron microscopy, serves as an ideal model for studying the neurodevelopmental process in higher lifeforms, and has undergone several developments since its inception. What do we know? C. elegans has a nervous structure with 302 neurons organized differently throughout the body of the nematode as ganglia. While the base nervous system for the organism may appear simplified, C. elegans has a sophisticated signal-processing network exhibiting complex neuronal interaction enabled by neurotransmitters (Hobert, 2018). Accordingly, the C. elegans nervous system has a host of sensory modalities, which integrally generate distinct behavioral patterns. The information sharing process takes on both associative and non-associative processes of learning. The physical form of C. elegans is also a derivative of many non-clonally defined lineages so that as one lineage gives rise to neurons only, the neuronal choice is made at a later stage in other lineages—for instance, certain muscle cells are generated within neuron-producing lineages while certain forms of neuronal generation occur within muscle cell lineages. Conceivably, the precursor cell responsible for (non-)neuronal choices remains uncommitted to any fate until cell division has reached a terminal point (Hobert, 2018). Similarly, a committed precursor cell remains reversibly active to allow for post-mitotic transformation from a non-neuronal to neuronal form. The free-living C. elegans nematode has been the only one, to this day, whose connectome has undergone complete reconstruction. Scientists nominate C. elegans as the natural choice for a practical natural model that serves as a base model for understanding nervous system complexities. The manageably small number of cells constituting the nematode, that is 959 somatic cells constituting the complete physical structure of the animal, have provided a tractable model for analysing the genetic behaviour of metazoan nervous system development. Further, the cellular makeup of C. elegans remains preferable because it offers an informative template consisting of all specialized and sophisticated neuronal and cellular connections characterizing higher lifeforms. Knowledge about C. elegans availed primarily via cell lineage information allows the developmental process to be understood as the outcome of genetically modelled instructions obtained from diverse molecular and cellular interactions. The “wiring” problem has left unanswered questions about how neuronal connections in C. elegans lead to various phenomena. Specifically, localized spatiality, synaptic interconnectivity with exact connection topologies, and the governing force behind temporal neuronal sequencing over the course of nematode development remains less known (Pathak et al., 2020). In an attempt to resolve these unknown factors, Pathak et al. (2020) suggested three possibilities. First, for enhanced neuronal interconnectivity, direct inter-neuron contact between significantly spaced cellular bodies applies critically towards reducing communication delays. Reduced delays are especially relevant to C. elegans whose synaptic wiring occurs at the axonal swellings. Secondly, process length homophily, implying communication preferences between neurons containing neurites with equal distances between them, is also a contributing factor. The study reported that neurons exhibiting process length homophily have expectedly more connections based on more synaptic interactions. Process lengths also have an effect on neuronal arrangement so that synaptic neuron connections with short process lengths contribute to cellular bodies positioned close to each other. Third, neuronal connections appear to also happen specifically with other neurons belonging to a similar cohort (birth control homophily). Further, terminal node identity, also called cell fate, depends on intrinsic factors, extrinsic factors, and intercellular interactions, which collectively introduce lineage homophily. This type of homophily converges developmental variability to the cell group level. By fully decoding the C. elegans connectome, it is possible to map out cell fate to create a lineage tree with cell-level specificity. The sexual and physical behaviour of C. elegans nematode also varies in both explicit and subtle ways when considered in the direction of nervous system development. For instance, factors such as egg laying for hermaphroditic C. elegans, male mating, reaction to chemical stimuli, locomotion, and behavioural learning all vary in terms of the organism’s biological sex (Barr et al., 2018). As such, genetically motivated sexual differences in the nervous system of C. elegans occurs at different levels with some variations happening due to cellular lineage characteristics while others are the result of sexual regulation and physiological disparities. A recent study also reported on the variety of roles of neurogenin 1 (ngn-1) in C. elegans, the gene which, in humans, causes neurodevelopmental complications. The relationship between ngn-1 and a wide range of neurodevelopmental complications emphasized the need to understand the functionality of this gene when studied in C. elegans as a model organism (Christensen et al., 2020). The study established the central role of ngn-1 in determining the integrity of embryonic epithelia, specifying cell fate, cellular spatiality, and neuronal morphology at various cell classes in C. elegans neurogenesis. The ngn-1 also finds crucial functionality in establishing nerve ring assembly and facilitating gene expression at the neurodevelopmental cascade. How was the knowledge gained? The reconstruction of the entire nervous system of the C. elegans connectome, obtained us...