Fang-Yen C et al. (2012) Methods Cell Biol "Laser microsurgery in Caenorhabditis elegans."

Avery L, Fang-Yen C, Gabel CV, Samuel AD, Bargmann CI

[Methods Cell Biol, 2012]

Laser killing of cell nuclei has long been a powerful means of examining the roles of individual cells in C. elegans. Advances in genetics, laser technology, and imaging have further expanded the capabilities and usefulness of laser surgery. Here, we review the implementation and application of currently used methods for target edoptical disruption in C. elegans.

Yen, C. et al. (2017) International Worm Meeting "Mitochondrial ALH-6 is essential for sperm quality and regulates male reproductive senescence."

Curran, S.P., Lynn, D.A., Yen, C.

[International Worm Meeting, 2017]

Reproduction is essential to perpetuate life. Mitochondria integrity and functionality has been linked to proper sperm function across multiple species. Most studies have examined the negative impact of the environment or acute stress plays on sperm function and reproductive output. However, the mechanistic impact that normal cellular metabolism plays in the regulation of sperm quality and activity remains unclear. Here, we show that C. elegans with mutations in alh-6, a conserved proline metabolism gene, display early reproductive senescence. Loss of proline catabolism results in specific deficits in sperm number, size, and activation. These defects in sperm quality are linked to changes in mitochondria morphology, metabolic output, and reactive oxygen species (ROS) generation. Intriguingly, the reproductive defects in alh-6 mutants are not simply due to reduced flux through the proline catabolism pathway. Instead the premature reproductive senescence in alh-6 mutants is caused by aberrant ROS homeostasis and loss of energy storing metabolites; however the relative impact that altered levels of ROS and metabolic intermediates plays in the sperm number, size, and activation phenotypes is remarkably different. Finally, the expression of the mammalian ortholog of alh-6, Aldh4a1, is significantly reduced with age in mouse testes suggesting a potential conserved role of alh-6 in male reproductive fitness. Taken together, we have uncovered a novel role for a conserved and central amino acid catabolism pathway on normal sperm function and our work uncovers a new variable to measure which can predict and alter the rate of aging of the male reproductive system.

Fang-Yen C et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "Optogenetic dissection of the C. elegans locomotory circuit"

Wen Q, Fang-Yen C, Samuel A, Leifer A

[Neuronal Development, Synaptic Function and Behavior, Madison, WI, 2010]

C. elegans moves forward by propagating sinusoidal dorso-ventral bending waves from head to tail. While the basic elements of the locomotory circuit were identified by laser ablation experiments (Chalfie et al), relatively little is known about how the circuit generates and propagates undulatory waves. We have used quantitative behavioral assays of worms in structured environments and during ChR2/Halo-mediated perturbations to explore basic principles of locomotory circuit function. To test the hypothesis that the propagation of the bending wave is mediated by bending itself (sometimes called the stretch receptor hypothesis) we analyzed the behavior of worms before and after transient Halorhodopsin-mediated paralysis of body wall muscles. We found that (1) after cessation of paralysis the undulatory wave recovers nearly uniformly over the entire length of the animal, and (2) the phase shift between pre-paralysis and post-paralysis undulations increases linearly with the duration of optical paralysis, with slope approximately equal to the undulatory frequency. These results suggest that the generation and propagation of locomotory undulations do not strictly require bending feedback. We also describe results using an optical system capable of arbitrary spatiotemporal perturbation of neural circuits in freely behaving worms.

Yen, C. et al. (2019) International Worm Meeting "Incomplete proline catabolism depletes FAD pools and abolishes male sperm competitive advantages."

Curran, S., Mih, N., Ruter, D., Pang, S., Yen, C.

[International Worm Meeting, 2019]

Exposure to environmental stress has a clinically established influence on male reproductive health, but the impact of normal cellular metabolism on sperm quality and function is less well-defined. Here we show that homeostatic changes in mitochondrial dynamics driven by defective mitochondrial proline catabolism result in pleiotropic consequences on sperm quality and competitive fitness. Disruption of alh-6, which converts 1-pyrroline-5-carboxylate (P5C) to glutamate, results in P5C accumulation that drives oxidative stress, activation of SKN-1, and a reduction of energy-storing flavin adenine dinucleotide (FAD) levels. These molecular changes lead to premature male reproductive senescence by reducing sperm quality. These sperm-specific defects are suppressed by abating P5C metabolism, by treatment with antioxidants to combat reactive oxygen species (ROS), or by feeding diets that restore FAD levels. Our results define a role for mitochondrial proline catabolism and FAD homeostasis on sperm function and specify strategies to pharmacologically reverse unintended outcomes from SKN-1/Nrf transcriptional activation.

Fang-Yen C et al. (2015) Philos Trans R Soc Lond B Biol Sci "Illuminating neural circuits and behaviour in Caenorhabditis elegans with optogenetics."

Samuel AD, Alkema MJ, Fang-Yen C

[Philos Trans R Soc Lond B Biol Sci, 2015]

The development of optogenetics, a family of methods for using light to control neural activity via light-sensitive proteins, has provided a powerful new set of tools for neurobiology. These techniques have been particularly fruitful for dissecting neural circuits and behaviour in the compact and transparent roundworm Caenorhabditis elegans. Researchers have used optogenetic reagents to manipulate numerous excitable cell types in the worm, from sensory neurons, to interneurons, to motor neurons and muscles. Here, we show how optogenetics applied to this transparent roundworm has contributed to our understanding of neural circuits.

Fang-Yen C et al. (2010) Proc Natl Acad Sci U S A "Biomechanical analysis of gait adaptation in the nematode Caenorhabditis elegans."

Xie J, Wen Q, Kodger T, Fang-Yen C, Samuel AD, Chen S, Kawai R, Wyart M

[Proc Natl Acad Sci U S A, 2010]

To navigate different environments, an animal must be able to adapt its locomotory gait to its physical surroundings. The nematode Caenorhabditis elegans, between swimming in water and crawling on surfaces, adapts its locomotory gait to surroundings that impose approximately 10,000-fold differences in mechanical resistance. Here we investigate this feat by studying the undulatory movements of C. elegans in Newtonian fluids spanning nearly five orders of magnitude in viscosity. In these fluids, the worm undulatory gait varies continuously with changes in external load: As load increases, both wavelength and frequency of undulation decrease. We also quantify the internal viscoelastic properties of the worm's body and their role in locomotory dynamics. We incorporate muscle activity, internal load, and external load into a biomechanical model of locomotion and show that (i) muscle power is nearly constant across changes in locomotory gait, and (ii) the onset of gait adaptation occurs as external load becomes comparable to internal load. During the swimming gait, which is evoked by small external loads, muscle power is primarily devoted to bending the worm's elastic body. During the crawling gait, evoked by large external loads, comparable muscle power is used to drive the external load and the elastic body. Our results suggest that C. elegans locomotory gait continuously adapts to external mechanical load in order to maintain propulsive thrust.

Fang-Yen C et al. (2009) Proc Natl Acad Sci U S A "Two size-selective mechanisms specifically trap bacteria-sized food particles in Caenorhabditis elegans."

Samuel AD, Fang-Yen C, Avery L

[Proc Natl Acad Sci U S A, 2009]

Caenorhabditis elegans is a filter feeder: it draws bacteria suspended in liquid into its pharynx, traps the bacteria, and ejects the liquid. How pharyngeal pumping simultaneously transports and filters food particles has been poorly understood. Here, we use high-speed video microscopy to define the detailed workings of pharyngeal mechanics. The buccal cavity and metastomal flaps regulate the flow of dense bacterial suspensions and exclude excessively large particles from entering the pharynx. A complex sequence of contractions and relaxations transports food particles in two successive trap stages before passage into the terminal bulb and intestine. Filtering occurs at each trap as bacteria are concentrated in the central lumen while fluids are expelled radially through three apical channels. Experiments with microspheres show that the C. elegans pharynx, in combination with the buccal cavity, is tuned to specifically catch and transport particles of a size range corresponding to most soil bacteria.

WC Yen et al. (1999) International C. elegans Meeting "Reproductive Isolation in Caenorhabditis"

WC Yen, SE Baird

[International C. elegans Meeting, 1999]

Reproductive isolation refers to all genetic mechanisms that prevent or limit gene flow between species. The combination of C. elegans (males)/CB5161 (females) is cross-fertile but hybrid animals arrest during embryogenesis. Arrested embryos displayed four distinct terminal phenotypes. 70% failed to gastrulate. Of these 42% arrested at the 28-30 cell stage and 28% continued to divide until approximately 100 cells were present. 30% of the hybrid embryos did gastrulate. Of these, 18% arrested at the onset of morphogenesis and 12% arrested at the two-fold stage. Embryonic lineages were consistent with this arrest profile. In eleven hybrid embryos, no lineage defects were observed prior to the division of the E founder cell. In seven hybrids, either E did not divide (1), or E.a and E.p did not divide (3), or E.a and E.p divided aberrantly along an A-P axis. These embyros failed to gastrulate and arrested either at the 28 cell stage or at the 100 cell stage. In four hybrids, E.a and E.p divided normally. These hybrids gastrulated and arrested either at the onset of morphogenesis (3) or at the two-fold stage (1). In C. elegans , gastrulation defects result from inhibition of zygotic transcription, from defects in endoderm specification, and from mutations in genes with direct effects on gastrulation. Two zygotic genes that exhibit gastrulation-defective phenotypes due to defects in endoderm specification are end-1 and rrs-1 . We are testing these genes for dysgenic interactions in C. elegans /CB5161 hybrids. We also are scoring hybrid embryos for the presence of rhabditin granules as a marker for gut differentiation. Finally, we are using a pes-10::gfp reporter to assess zygotic transcription in hybrid embryos.

Churgin MA et al. (2022) Methods Mol Biol "An Imaging System for Monitoring C. elegans Behavior and Aging."

Churgin MA, Fang-Yen C

[Methods Mol Biol, 2022]

Many experiments in C. elegans neurobiology rely on imaging its behavior. Here we describe procedures for building a flexible and inexpensive imaging system using standard optical and mechanical components.

Churgin MA et al. (2015) Methods Mol Biol "An Imaging System for C. elegans Behavior."

Churgin MA, Fang-Yen C

[Methods Mol Biol, 2015]

Many experiments in C. elegans neurobiology and development benefit from automated imaging of worm behavior. Here we describe procedures for building a flexible and inexpensive imaging system using standard optical and mechanical components.