Liang, J. J. | bioRxiv Science

bioRxiv2025

The Challenge of Choosing a Negative Control: A Behavioural and Morphological Characterization of Various unc-43 LOF Alleles in the Model Organism C. elegans

Loss-of-Function (LOF) analyses have been pivotal in the discovery of genetic function in biological processes. However, phenotypic variation can occur between different supposedly LOF alleles of the same gene. We investigated the body of research surrounding the nematode ortholog of the Calcium/Calmodulin-dependent protein Kinase II (CAMKII), unc-43, because of its relevance in a large range of biological functions. Our analysis shows that published findings on unc-43 function were obtained from studies using numerous loss-of-function alleles, leading to potential challenges in aligning research findings. We investigated the similarity of these putative loss-of-function (LOF) mutations by using the Multi-Worm Tracker (Swierczek et al., 2011) to phenotype nine LOF alleles across 27 phenotypes, spanning morphology, baseline locomotion and habituation learning and memory. Interestingly, our study reveals significant differences in phenotypes for these LOF alleles. From our data, we have identified the three putative LOF alleles with the most severe and similar phenotypes propose for two of them (n498n1186 and js125) to be regarded as reference alleles to streamline future research on unc-43 function. This data will help future researchers optimise their research of unc-43 function and determine how to choose a strain/strains to use as a negative control.

genetics↗

bioRxiv2023

A Familial Alzheimers Disease Associated Mutation in Presenilin-1 Mediates Amyloid-Beta Independent Cell Specific Neurodegeneration

Mutations in the presenilin (PS) genes are a predominant cause of familial Alzheimers disease (fAD). An ortholog of PS in the genetic model organism Caenorhabditis elegans (C. elegans) is sel-12. Mutations in the presenilin genes are commonly thought to lead to fAD by upregulating the expression of amyloid beta (A{beta}), however this hypothesis has been challenged by recent evidence. As C. elegans lack amyloid beta (A{beta}), the goal of this work was to examine A{beta}-independent effects of mutations in sel-12 and PS1/PS2 on behaviour and sensory neuron morphology across the lifespan in a C. elegans model. Olfactory chemotaxis experiments were conducted on sel-12(ok2078) loss-of-function mutant worms. Adult sel-12 mutant worms showed significantly lower levels of chemotaxis to odorants compared to wild-type worms throughout their lifespan, and this deficit increased with age. The chemotaxis phenotype in sel-12 mutant worms is rescued by transgenic over-expression of human wild-type PS1, but not the classic fAD-associated variant PS1C410Y, when expression was driven by either the endogenous sel-12 promoter (Psel-12), a pan-neuronal promoter (Primb-1), or by a promoter whose primary expression was in the sensory neurons responsible for the chemotaxis behavior (Psra-6, Podr-10). The behavioural phenotype was also rescued by over-expressing an atypical fAD-linked mutation in PS1 (PS1{Delta}S169) that has been reported to leave the Notch pathway intact. An examination of the morphology of polymodal nociceptive (ASH) neurons responsible for the chemotaxis behavior also showed increased neurodegeneration over time in sel-12 mutant worms that could be rescued by the same transgenes that rescued the behaviour, demonstrating a parallel with the observed behavioral deficits. Thus, we report an A{beta}-independent neurodegeneration in C. elegans that was rescued by cell specific over-expression of wild-type human presenilin.

neuroscience↗