Berger, Daniel et al. (2015) International Worm Meeting "The mind of an L1 worm - how do neuronal circuits function and remodel throughout development?."

Samuel, Aravinthan, Emmons, Scott, Neubauer, Marianna, Lichtman, Jeff, Witvliet, Daniel, Chisholm, Andrew, Laskova, Valeriya, Mitchell, James, Mulcahy, Ben, Cook, Steven, Zhen, Mei, Schalek, Richard, Berger, Daniel, Hall, David, Holmyard, Douglas, Kersen, David, Qu, Angie

[International Worm Meeting, 2015]

When humans and worms are born, they have neuronal circuits in place to integrate sensory cues and effect appropriate behavioural or homeostatic responses. During the course of development, a substantial amount of remodelling occurs in the nervous system. New neurons are born and integrated into existing circuits, and existing neurons and circuits are remodelled. The rules of this remodelling are poorly characterised, because in order to investigate neuronal circuit development one needs a connectome-level analysis of the circuit across multiple time points, in multiple animals. This strategy requires serial-section electron microscopy, which has been very low-throughput and labour-intensive.C. elegans represents an ideal organism to perform these studies on, because of their small size and stereotypical development - some of the reasons they were chosen for the original adult serial-section EM reconstruction that culminated in the acquisition of the adult connectome, dubbed 'The mind of a worm'. Since the publication of this landmark paper, new technologies have been developed that improve the fidelity and throughput of the connectome reconstruction, including better fixation methods, increased computational power and more advanced microscopes.We are reconstructing the entire nervous system of multiple L1 worms using serial-section transmission and scanning electron microscopy. The L1 worm is of special interest because of the major remodelling that occurs at the end of L1, including the birth of new major classes of motor neurons. We are finding both conserved and unreported structure and connectivity from the published adult wiring diagram. This dataset will be used as a framework to functionally interrogate the interplay between developing circuits and sensorimotor behaviours, and the mechanisms that allow this dialogue to take place.

Kosinski, K.E. et al. (2019) International Worm Meeting "Autophagy in Meiotic Fidelity."

Yanowitz, J., Melendez, A., Kosinski, K.E.

[International Worm Meeting, 2019]

Autophagy is a conserved cellular recycling process crucial for homeostasis. In this multistep process, cellular material destined for degradation is enclosed in the autophagosome, a double membrane-bound organelle that fuses with the lysosome for degradation. Beclin1/BECN1 is crucial for the initial nucleation step of autophagosome formation and is a haploinsufficient tumor suppressor in mammals (Liang et al., 1999; Yue et al., 2003; Qu et al., 2003). The role of autophagy in cellular homeostasis is well documented, but its function in the maintenance of genomic stability remains unclear. We recently described roles for BEC-1, the C. elegans ortholog of mammalian BEC-1/BECN1, and several other autophagy genes in germline stem cell homeostasis (Ames et al., 2017). Specifically, we found that BEC-1, as well as ATG-18 (in mammals, WIPI1/2), ATG-16.2 (ATG16L) and ATG-7 (ATG7), are required for the late larval expansion of germline stem cell progenitors during development. A role for BEC-1 in the DNA damage response (DDR) to UV, where it exhibits crosstalk with CEP-1, the C. elegans ortholog of p53 has been reported (Hoffman et al., 2014). CEP-1 is well known for its roles in promoting genomic integrity through the DDR, including cell cycle control, apoptosis, and DNA repair. CEP-1 was recently shown to act in meiosis, suppressing nonhomologous end-joining (NHEJ), to commit repair of double-strand breaks (DSBs) to the error-free homologous recombination (HR) pathway (Mateo et al., 2016). We are now investigating the mechanism(s) by which BEC-1 and autophagy genes promote DNA damage repair. Our preliminary data indicates a role for autophagy in promoting meiotic fidelity. Meiotic crossover events are initiated by induction of DSBs, which are faithfully repaired by homologous recombination to maintain genomic stability. The major hallmarks of meiosis include pairing of homologous chromosomes, synapsis, DSB formation and crossover repair. A defect at any of these steps leads to chromosomal abnormalities and lethality in C. elegans. Our current work seeks to elucidate at which step of meiosis autophagy genes are required. To this end, we are examining the role of different autophagy genes, including bec-1/becn1 and atg-7, in the promotion of faithful pairing, segregation, crossover formation and resolution of chromosomes in the germline during meiosis.