Genetic Variation in Complex Traits in Transgenic α-Synuclein Strains of Caenorhabditis elegans

Abstract

Different genetic backgrounds can modify the effect of mutated genes. Human α-synuclein (SNCA) gene encodes α-synuclein, and its oligomeric complexes accumulate with age and mediate the disruption of cellular homeostasis, resulting in the neuronal death that is characteristic of Parkinson’s Disease. Polymorphic variants modulate this complex pathologic mechanism. Previously, we constructed five transgenic introgression lines of a Caenorhabditis elegans model of α-synuclein using genetic backgrounds that are genetically diverse from the canonical wild-type Bristol N2. A gene expression analysis revealed that the α-synuclein transgene differentially affects genome-wide transcription due to background modifiers. To further investigate how complex traits are affected in these transgenic lines, we measured the α-synuclein transgene expression, the overall accumulation of the fusion protein of α-synuclein and yellow fluorescent protein (YFP), the lysosome-related organelles, and the body size. By using quantitative PCR (qPCR), we demonstrated stable and similar expression levels of the α-synuclein transgene in different genetic backgrounds. Strikingly, we observed that the levels of the a-synuclein:YFP fusion protein vary in different genetic backgrounds by using the COPAS™ biosorter. The quantification of the Nile Red staining assay demonstrates that α-synuclein also affects lysosome-related organelles and body size. Our results show that the same α-synuclein introgression in different C. elegans backgrounds can produces differing effects on complex traits due to background modifiers.

Innovative fluorescent probes for in vivo visualization of biomolecules in living Caenorhabditis elegans

“…Indeed, it has become common practice for tracking single cells or even molecules in live C. elegans by using fully automated whole-animal imaging and quantitative analysis (33). Large C. elegans populations with target biomolecules marked by fluorescent probes can be subjected to highthroughput quantitative analysis with the Complex Object Parametric Analyzer and Sorter (COPAS) equipment (34)(35)(36)(37). These advances in quantitative C. elegans studies rely heavily on development of genetically encoded fluorescent probes or engineered chemical and nanoprobes.…”

“…Taking advantage of their transparent body and small body sizes, C. elegans can be analyzed by flow cytometry and subjected to worm sorting using large-particle biosorter platforms(25). High-throughput quantitative single-cell analysis can therefore be performed on large C. elegans populations with target biomolecules marked by fluorescent probes(34)(35)(36)(37). In vivo fluorescent labeling techniques have shown great progress over the last decade and overcome limitations such as low sensitivity, low photostability, low brightness, high-background signal and incapacity to be utilized in vivo.…”

Biotic, abiotic and genetic perturbations in genetically variant Caenorhabditis elegans

“…In a previous study, we observed differences in protein expression of α-synuclein between strains NL5901 and SCH4856 while not for mRNA expression in C. elegans [161]. To visualize the α-syn::YFP expression in the N2 and CB4856 background, the YFP signal was observed in NL5901 and SCH4856 under a microscope, which represented the allocation of α-synuclein.…”

“…Importantly, the replicability of pathological hallmarks in C. elegans provides a platform for studying disease [160]. For example, the expression of human α-synuclein in C. elegans caused inclusions containing α-synuclein aggregates, similar with the pathological phenotype of α-synuclein in human [43,161,162]. Together these traits made C. elegans to become a widely applied model organism for genetic variation PD research [26].…”

“…To study PD in C. elegans, transgene pkls2386 encoding human α-synuclein was fused with YFP and introgressed into the N2 and CB4856 genetic background, and the obtained α-synuclein lines were named NL5901 and SCH4856, respectively [43,166]. Previous studies found that the mRNA expression of α-synuclein did not differ between NL5901 and SCH4856, whereas the protein expression of these two strains displayed a significant difference [161].…”