Distinct mechanoreceptor pezo-1 isoforms modulate food intake in the nematode Caenorhabditis elegans

Two PIEZO mechanosensitive cation channels, PIEZO1 and PIEZO2, have been identified in mammals, where they are involved in numerous sensory processes. While structurally similar, PIEZO channels are expressed in distinct tissues and exhibit unique properties. How different PIEZOs transduce force, how their transduction mechanism varies, and how their unique properties match the functional needs of the tissues they are expressed in remain all-important unanswered questions. The nematode Caenorhabditis elegans has a single PIEZO ortholog (pezo-1) predicted to have twelve isoforms. These isoforms share many transmembrane domains but differ in those that distinguish PIEZO1 and PIEZO2 in mammals. We used transcriptional and translational reporters to show that putative promoter sequences immediately upstream of the start codon of long pezo-1 isoforms predominantly drive GFP expression in mesodermally derived tissues (such as muscle and glands). In contrast, sequences upstream of shorter pezo-1 isoforms resulted in GFP expression primarily in neurons. Putative promoters upstream of different isoforms drove GFP expression in different cells of the same organs of the digestive system. The observed unique pattern of complementary expression suggests that different isoforms could possess distinct functions within these organs. We used mutant analysis to show that pharyngeal muscles and glands require long pezo-1 isoforms to respond appropriately to the presence of food. The number of pezo-1 isoforms in C. elegans, their putative differential pattern of expression, and roles in experimentally tractable processes make this an attractive system to investigate the molecular basis for functional differences between members of the PIEZO family of mechanoreceptors.

Immobilization of C. elegans on cultivation plates by thermoelectric cooling for high-throughput subcellular-resolution microscopy

Imaging, visual screens, and optical surgery are frequently applied to the nematode Caenorhabditis elegans at subcellular resolution for in vivo biological research. However, these approaches remain low-throughput and require significant manual effort. To improve throughput and enable automation in these techniques, we implement a novel cooling method to immobilize C. elegans directly on their cultivation plate. Previous studies cooled animals in microfluidics or flooded wells to 1-4 C. Counterintuitively, we find that cooling to 5-7 C immobilizes animals more effectively than lower temperatures. At 6 C, animal movement consists of bouts of submicron nose tip movement occurring at a sufficiently low magnitude and frequency to permit clear imaging. We demonstrate the ability to perform subcellular-resolution fluorescence imaging, including 64x magnification 3D image stacks and 2-min long timelapse recordings of the ASJ neuron without blurring from animal motion. We also observe no long-term side effects from cooling immobilization on animal lifespan or fecundity. We believe our cooling method enables high-throughput and high-resolution microscopy with no chemical or mechanical interventions.

A Deep Learning Analysis Reveals Nitrogen-Doped Graphene Quantum Dots Damage Neurons of Nematode Caenorhabditis elegans

Along with the rapidly increasing applications of nitrogen-doped graphene quantum dots (N-GQDs) in the field of biomedicine, the exposure of N-GQDs undoubtedly pose a risk to the health of human beings, especially in the nervous system. In view of the lack of data from in vivo studies, this study used the nematode Caenorhabditis elegans (C. elegans), which has become a valuable animal model in nanotoxicological studies due to its multiple advantages, to undertake a bio-safety assessment of N-GQDs in the nervous system with the assistance of a deep learning model. The findings suggested that accumulated N-GQDs in the nematodes’ bodies damaged their normal behavior in a dose- and time-dependent manner, and the impairments of the nervous system were obviously severe when the exposure dosages were above 100 μg/mL. When assessing the morphological changes of neurons caused by N-GQDs, a quantitative image-based analysis based on a deep neural network algorithm (YOLACT) was used because traditional image-based analysis is labor-intensive and limited to qualitative evaluation. The quantitative results indicated that N-GQDs damaged dopaminergic and glutamatergic neurons, which are involved in the neurotoxic effects of N-GQDs in the nematode C. elegans. This study not only suggests a fast and economic C. elegans model to undertake the risk assessment of nanomaterials in the nervous system, but also provides a valuable deep learning approach to quantitatively track subtle morphological changes of neurons at an unbiased level in a nanotoxicological study using C. elegans.

A fat-promoting plant extract from Artemisia scoparia exerts geroprotective effects on C. elegans health & lifespan

Like other biological processes, aging is not random, but subject to molecular control. Natural products that act on conserved metabolic pathways may provide entry points to extend animal lifespan and promote healthy aging. Here, we show that a botanical extract from Artemisia scoparia (SCO), which promotes fat storage and metabolic resiliency in mice, exerts pro-longevity effects on the nematode Caenorhabditis elegans, even when administered in mid-adulthood. SCO-treated worms exhibit significantly higher levels of fat compared to controls but live up to 40% longer, with signs of improved stress resistance in late age. Molecularly, SCO links elevated fat to enhanced longevity and stress resistance via activation of the transcription factor DAF-16/FOXO and upregulation of DAF-16-targeted Δ9 desaturases, lifespan-extending metabolic enzymes that oversee the biosynthesis of monounsaturated fatty acids. These findings identify SCO as a natural product that can modify fat regulation for longevity benefit and add to growing evidence indicating that elevated fat can be pro-longevity in some circumstances.

Graptopetalum paraguayense Extract Ameliorates Proteotoxicity in Aging and Age-Related Diseases in Model Systems

Declines in physiological functions are the predominant risk factors for age-related diseases, such as cancers and neurodegenerative diseases. Therefore, delaying the aging process is believed to be beneficial in preventing the onset of age-related diseases. Previous studies have demonstrated that Graptopetalum paraguayense (GP) extract inhibits liver cancer cell growth and reduces the pathological phenotypes of Alzheimer’s disease (AD) in patient IPS-derived neurons. Here, we show that GP extract suppresses β-amyloid pathology in SH-SYS5Y-APP695 cells and APP/PS1 mice. Moreover, AMP-activated protein kinase (AMPK) activity is enhanced by GP extract in U87 cells and APP/PS1 mice. Intriguingly, GP extract enhances autophagy in SH-SYS5Y-APP695 cells, U87 cells, and the nematode Caenorhabditis elegans, suggesting a conserved molecular mechanism by which GP extract might regulate autophagy. In agreement with its role as an autophagy activator, GP extract markedly diminishes mobility decline in polyglutamine Q35 mutants and aged wild-type N2 animals in C. elegans. Furthermore, GP extract significantly extends lifespan in C. elegans.

Tubular lysosome induction couples animal starvation to healthy aging

Dietary restriction promotes longevity via autophagy activation. However, changes to lysosomes underlying this effect remain unclear. Using the nematode Caenorhabditis elegans, we show that induction of autophagic tubular lysosomes, which occurs upon dietary restriction or mTOR inhibition, is a critical event linking reduced food intake to lifespan extension. We find that starvation induces tubular lysosomes not only in affected individuals but also in well-fed descendants, and the presence of gut tubular lysosomes in well-fed progeny is predictive of enhanced lifespan. Furthermore, we demonstrate that expression of Drosophila SVIP, a tubular-lysosome activator in flies, artificially induces tubular lysosomes in well-fed worms and improves C. elegans health in old age. These findings identify tubular lysosomes as a new class of lysosomes that couples starvation to healthy aging.

Molecular Mechanisms of Sexually Dimorphic Nervous System Patterning in Flies and Worms

Male and female brains display anatomical and functional differences. Such differences are observed in species across the animal kingdom, including humans, but have been particularly well-studied in two classic animal model systems, the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans. Here we summarize recent advances in understanding how the worm and fly brain acquire sexually dimorphic features during development. We highlight the advantages of each system, illustrating how the precise anatomical delineation of sexual dimorphisms in worms has enabled recent analysis into how these dimorphisms become specified during development, and how focusing on sexually dimorphic neurons in the fly has enabled an increasingly detailed understanding of sex-specific behaviors.