Chandler, Luke et al. (2021) International Worm Meeting "The role of furrow-associated collagen DPY-7 in regulating stress responses varies during larval development"

Choe, Keith, Chandler, Luke

[International Worm Meeting, 2021]

Mutation or loss of six collagen genes (dpy-2, 3, 7, 8, 9, and 10) disrupts annular furrows in adult cuticles and causes a short and wide 'Dumpy' body morphology. Loss of these collagens also activates osmotic, detoxification, and antimicrobial defense genes, but not other stress responses. High environmental osmolarity reduces internal turgor pressure, physically distorts the epidermis, and activates the same stress responses, but non-furrow dpy mutations and other disruptions of the epidermis (e.g., Lon, Rol, Mlt, and Sqt) do not. These results are consistent with a damage sensor associated with furrows in the adult cuticle that regulates responses to environmental stress. Several cuticle characteristics change between molts, but all stages have annular furrows and express furrow-associated collagen genes raising the possibility that this signaling mechanism functions throughout development. We find high variation in stress gene responses to dpy-7 mutation with the largest induction in adults and little or no induction in early larvae. Alternatively, stress responses are induced by osmotic stress at all stages demonstrating that environmental response mechanisms are functional in early larvae. These results suggest that furrows can develop despite dpy-7 mutation or that furrows are not essential for stress response regulation in early larvae. dpy-7 mutants are not Dpy until the L3 stage suggesting that cuticles of early larvae may be able to compensate. We are currently using fluorescent collagen reporters to visualize annular furrows at all stages in dpy-7 mutants and investigating deletion of a furrow collagen reported to cause Dpy at all stages. This work was supported by NSF grant IOS-1452948 to KPC.

Johnson, Lindsay M. et al. (2017) International Worm Meeting "Network architecture and the cumulative effects of spontaneous mutations on the C. elegans metabolome."

Johnson, Lindsay M., Baer, Charles F., Chandler, Luke

[International Worm Meeting, 2017]

A functional metabolic network is key for an organism's survival, and thus for its fitness. Spontaneous mutations reduce fitness, so it stands to reason they affect metabolism in some way. However, not all metabolites are equally important in maintaining organismal function, and the relationship between mutation and an organism's metabolic network has rarely been investigated. By investigating a set of mutation accumulation(MA) lines of Caenorhabditis elegans, we aim to better understand the effect mutations have on the metabolic network. Using a set of 43 MA lines and their ancestor, a pool of 29 metabolites was measured for changes in mean metabolite concentration (?M) and mutational variance (VM). We constructed a metabolic network map of these metabolites for C. elegans from the KEGG database, with the aim of characterizing the relationship between VM, ?M, and heritability found for these 29 metabolites and features of the metabolic network. Initial analysis shows a positive association between the largest k-core grouping of a metabolite and ?M and VM.

Marciniak SJ et al. (2008) Trends Cell Biol "Intracellular serpins, firewalls and tissue necrosis."

Marciniak SJ, Lomas DA

[Trends Cell Biol, 2008]

Luke and colleagues have recently attributed a new role to a member of the serpin superfamily of serine proteinase inhibitors. They have used Caenorhabditis elegans to show that an intracellular serpin is crucial for maintaining lysosomal integrity. We examine the role of this firewall in preventing necrosis and attempt to integrate this with current theories of stress-induced protein degradation. We discuss how mutant serpins cause disease either through polymerization or now, perhaps, by unleashing necrosis.

Rodriguez Mendoza, Victoria et al. (2022) MicroPubl Biol

Harvey, Justin, Al-Rajhi, Amal, Choi, Thine, Chandler, Luke, Buddendorff, Lauren, Liu, Zhexin, Mihalik, Alva, Moravec, Sophie, Gibb, Gabrielle, Raju, Vikram, Rodriguez Mendoza, Victoria, Pilcher, Wendy, Choe, Keith Patrick

[MicroPubl Biol, 2022]

Nematode cuticles are extracellular matrices (ECMs) that function as structural support and permeability barriers. Genetic disruption of specific cuticle collagen structures or secreted epidermal proteins in C. elegans activates stress response genes in epithelial cells suggesting the presence of an extracellular damage signaling mechanism. Cuticles are replaced during development via molting but investigations of extracellular signaling to stress responses have focused on adults. In our current study, we measured cuticle phenotypes and stress response gene expression in all post-embryonic stages of mutant strains for a collagen and two secreted epidermal proteins to gain insights into developmental patterns.

Sotto A et al. (2008) Diabetes Care "Virulence potential of Staphylococcus aureus strains isolated from diabetic foot ulcers: a new paradigm."

Richard JL, Lina G, Jourdan N, Combescure C, Etienne J, Sotto A, Lavigne JP, Bourg G, Vidal L

[Diabetes Care, 2008]

Objective: To assess the virulence potential of Staphylococcus aureus isolated from diabetic foot ulcers and to discriminate non-infected from infected ulcers. Research design and methods: Diabetic patients hospitalized in a diabetic foot department f with a foot ulcer were prospectively enrolled if they had been free of antibiotics treatment over the previous 6-months . At admission, ulcers were classified as infected or non-infected based on clinical examination, according to the IWGDF system. Only patients carrying S. aureus as the sole pathogen were included. In individuals with a grade 1 ulcer, a second bacterial specimen was obtained one month later. Using virulence genotyping markers, clonality tools and an in vivo Caenorhabditis elegans model, we correlated the virulence of 132 S. aureus strains with grade, time of collection and ulcer outcome. Results: Among virulence genes, the most relevant combination derived from the logistic regression was the association of cap8, sea, sei, lukE and hlgv (AUC 0.958). These markers were useful to distinguish non-infected (grade 1)/infected (grades 2-4) ulcers and to predict wound status at the follow-up. Using the nematode model, S. aureus strains isolated from grade 1 ulcers were found to be significantly less virulent than strains from grade >/=2 ulcers (P<0.001). Conclusions: This study highlighted the coexistence of two S. aureus populations on diabetic foot ulcers. A combination of 5 genes was discovered that may help distinguish colonized grade 1 from infected grade >/=2 wounds, predict ulcer outcome and contribute to a more appropriate use of antibiotics.

Stephen C Pak et al. (2005) International Worm Meeting "Protein aggregate formation and disruption of post-embryonic development in worms expressing SRP-2::GFP"

Clifford J Luke, Gary A Silverman, Stephen C Pak

[International Worm Meeting, 2005]

Serpins are high molecular weight serine proteinase inhibitors that irreversibly inactivate target proteinases using a suicide substrate-like mechanism. Although in vitro biochemical characterizations have provided some clues as to the identity of the target proteinases, the pathways in which serpins play a role are currently unknown. To determine whether serpins plays a role in C. elegans development, growth and longevity, we generated mutants that lack or over-express serpin genes. In general, with the exception of srp-6 (see poster by Luke et al.,), null mutants displayed no overt phenotypes. In contrast, transgenic animals over-expressing serpins displayed a variety of developmental and growth defects. In particular, over-expression of SRP-2::GFP resulted in distruption of post-embryonic development characterized by early larval arrest, slow growth and molting defects. Over-expression of SRP-2 mutants harboring amino-acid substitutions that diminish the serpins ability to inhibit proteinases failed to suppress the phenotype. This result suggests that the phenotype is independent of the proteinase-inhibitory function of SRP-2. Preliminary structure/function mapping results suggest that a short, N-terminal portion of SRP-2 is sufficient for the phenotype. Interestingly, we observed large, insoluble SRP-2::GFP aggregates in the cytosol of anterior hypodermal cells. The relationship between aggregate formation and the developmental defects is currently unclear. We are currently conducting a genetic screen to identify modifiers of the SRP-2 developmental and aggregation phenotypes. We hope to present the results of the genetic screen at the conference.