| |
| author |
Karishma S. Patel
| | title |
Modeling and Manipulating Mutant Neurexins in Caenorhabditis elegans
| | abstract |
To understand mechanisms that produce the human conscious experience, including
sensation, perception, cognition, and behavior, researchers have focused on studying the
functional unit of the nervous system, the neuron, and the primary location at which
neurons communicate with each other, the synapse. Since their discovery, neurexins and
neuroligins have been studied as important regulators of the synapse, expressed in species
across the eukaryotic evolutionary tree, from Homo sapiens — where mutations in each
protein have been implicated in human neuropsychological disease — to the nematode
Caenorhabditis elegans. While expressed in a myriad of subtypes and isoforms in humans,
this complexity is vastly reduced in C. elegans, giving researchers a simpler context to
elucidate function and the consequences of mutant alleles. After reviewing what is known
about neurexin and neuroligin structure, function, and binding in humans and C. elegans,
wild type (WT) human neurexin NRXN1, WT C. elegans nrx1, and C. elegans ok1649 and
ds1 nrx1 alleles were further characterized. The longest human isoform, αNRXN1, and the
longest C. elegans isoform, αnrx1, both share 28% sequence identity and 47% similarity
through BLAST analysis. Protein domain analysis using NCBI's Conserved Domain
Search Tool identified 6 functional laminin-neurexin-sex-hormone binding (LNS) sites in
the protein sequences of αNRXN1 and αnrx1, one LNS site in βNRXN1, and no LNS sites
in γNRXN1 as predicted in the literature; no such sites were recognized in the smaller nrx1
isoform initially described as βnrx1. These findings suggest that the shorter C. elegans
isoforms may actually be a γ isoforms, due to the lack of extracellular LNS domains, as in
γNRXN1. Structural models generated by the C-I-TASSER program of WT NRXN1, nrx1,
and ok1649 and ds1 nrx1 alleles from VC1416 and SG1 strains largely suggest retention
of conformation and function, with severe disturbances observed only in the ds1 truncation.
Both alleles of nrx1 appear to retain the ability to express functional γnrx1 forms.
Therefore, methods to generate three novel nrx1-KO models - total nrx1-KO, an αnrx1-
and a γnrx1-KO – using CRISPR-Cas9 technology, microinjection, and selection strategies
were developed to further study the roles neurexins may play in the C. elegans synapse.
Finally, strategies for behavioral characterizations of the three novel C. elegans models
were discussed. The protein models, proposed neurexin manipulations, and suggested
behavioral measures of WT and mutant alleles in C. elegans will further current
understanding of neurexins and neurexin-neuroligin interactions in the C. elegans system.
Ultimately, this work may have potential applications in understanding human neuronal
communication and disease pathways in neuropsychological conditions.
| | school |
The College of Liberal Arts, Drew University
| | degree |
B.S. (2021)
|
| advisor |
Marvin Bayne
|
| committee |
Adam Cassano
Joanna Miller
|
| full text | KPatel.pdf |
| |
