Shapard EJ et al. (2012) Mycopathologia "Batrachochytrium dendrobatidis can infect and cause mortality in the nematode Caenorhabditis elegans."

San Francisco MJ, Shapard EJ, Moss AS

[Mycopathologia, 2012]

Batrachochytrium dendrobatidis (Bd) has been identified as a causative agent in the precipitous decline of amphibians worldwide. Studies on the fungus including its ability to infect and kill the host require use of frogs, a precious resource. Therefore, the development of an alternate host model to study the virulence of the fungus would be useful. Here, we show that Bd can cause mortality in the nematode Caenorhabditis elegans. Incubation of Bd with C. elegans resulted in greater than 70% mortality in the nematodes over a period of 24 h. Fluorescence microscopy using propidium iodide, a fluorescent dye used to determine cell viability, and tactile assays were used to discriminate between live and dead nematodes. These observations suggest that C. elegans may be a useful model organism to study the pathogenicity and virulence mechanisms of Bd.

Enriquez P et al. (2021) J Biol Chem "Binding specificity and function of the SWI/SNF subunit SMARCA4 bromodomain interaction with acetylated histone H3K14."

Rothbart SB, Rose RB, Krajewski K, Enriquez P, Dowen RH, Strahl BD

[J Biol Chem, 2021]

Bromodomains (BD) are conserved reader modules that bind acetylated lysine residues on histones. Although much has been learned regarding the in vitro properties of these domains, less is known about their function within chromatin complexes. SWI/SNF chromatin-remodeling complexes modulate transcription and contribute to DNA damage repair. Mutations in SWI/SNF subunits have been implicated in many cancers. Here we demonstrate that the BD of Caenorhabditis elegans SMARCA4/BRG1, a core SWI/SNF subunit, recognizes acetylated lysine 14 of histone H3 (H3K14ac), similar to its Homo sapiens ortholog. We identify the interactions of SMARCA4 with the acetylated histone peptide from a 1.29 A-resolution crystal structure of the CeSMARCA4 BD-H3K14ac complex. Significantly, most of the SMARCA4 BD residues in contact with the histone peptide are conserved with other proteins containing family VIII bromodomains. Based on the premise that binding specificity is conserved among bromodomain orthologs, we propose that loop residues outside of the binding pocket position contact residues to recognize the H3K14ac sequence. CRISPR-Cas9-mediated mutations in the SMARCA4 BD that abolish H3K14ac binding in vitro had little or no effect on C. elegans viability or physiological function in vivo. However, combining SMARCA4 BD mutations with knockdown of the SWI/SNF accessory subunit PBRM-1 resulted in severe developmental defects in animals. In conclusion, we demonstrated an essential function for the SWI/SNF bromodomain in vivo and detected potential redundancy in epigenetic readers in regulating chromatin remodeling. These findings have implications for the development of small molecule BD inhibitors to treat cancers and other diseases.

Betancourt-Roman CM et al. (2016) Parasitology "Rethinking the role of invertebrate hosts in the life cycle of the amphibian chytridiomycosis pathogen."

Betancourt-Roman CM, James TY, O'Neil CC

[Parasitology, 2016]

The amphibian pathogen Batrachochytrium dendrobatidis (Bd) has recently emerged as a primary factor behind declining global amphibian populations. Much about the basic biology of the pathogen is unknown, however, such as its true ecological niche and life cycle. Here we evaluated invertebrates as infection models by inoculating host species that had previously been suggested to be parasitized in laboratory settings: crayfish (Procambarus alleni) and nematodes (Caenorhabditis elegans). We found neither negative effects on either host nor evidence of persistent infection despite using higher inoculum loads and more pathogen genotypes than tested in previous studies. In contrast, addition of Bd to C. elegans cultures had a slight positive effect on host growth. Bd DNA was detected on the carapace of 2/34 crayfish 7 weeks post-inoculation, suggesting some means of persistence in the mesocosm. These results question the role of invertebrates as alternative hosts of Bd and their ability to modulate disease dynamics.

Macedo F et al. (2020) FASEB J "Lifespan-extending interventions enhance lipid-supported mitochondrial respiration in Caenorhabditis elegans."

Buis A, Aguilaniu H, Kowaltowski AJ, Romanatto T, Gomes de Assis C, Macedo F, Marques da Cunha F

[FASEB J, 2020]

Dietary restriction and reduced reproduction have been linked to long lifespans in the vast majority of species tested. Although decreased mitochondrial mass and/or function are hallmarks of aging, little is known about the mechanisms by which these organelles contribute to physiological aging or to the effects of lifespan-extending interventions, particularly with respect to oxidative phosphorylation and energy production. Here, we employed the nematode Caenorhabditis elegans to examine the effects of inhibition of germline proliferation and dietary restriction, both of which extend the lifespan of C. elegans, on mitochondrial respiratory activity in whole animals and isolated organelles. We found that oxygen consumption rates and mitochondrial mass were reduced in wild-type (WT) C. elegans subjected to bacterial deprivation (BD) compared with animals fed ad libitum (AL). In contrast, BD decreased the rate of oxygen uptake but not mitochondrial mass in germline-less glp-1(e2144ts) mutants. Interestingly, mitochondria isolated from animals subjected to BD and/or inhibition of germline proliferation showed no differences in complex I-mediated respiratory activity compared to control mitochondria, whereas both interventions enhanced the efficiency with which mitochondria utilized lipids as respiratory substrates. Notably, the combination of BD and inhibition of germline proliferation further increased mitochondrial lipid oxidation compared to either intervention alone. We also detected a striking correlation between lifespan extension in response to BD and/or inhibition of germline proliferation and the capacity of C. elegans to generate ATP from lipids. Our results thus suggest that the ability to oxidize lipids may be determinant in enhanced longevity.

Johnson CD et al. (1988) Neuron "The acetylcholinesterase genes of C. elegans: identification of a third gene (ace-3) and mosaic mapping of a synthetic lethal phenotype."

Russell RL, Johnson CD, Herman RK, Stern BD, Rand JB

[Neuron, 1988]

In C. elegans, the newly identified ace-3 is the third gene affecting acetylcholinesterase (AChE) activity. ace-3 II specifically affects class C AChE and is unlinked to ace-1 X or ace-2 I, which affect the other two AChE classes (A and B, respectively). Strains homozygous for an ace-3 mutation have no apparent behavioral or developmental defect; ace-1 ace-3 and ace-2 ace-3 double mutants are also nearly wild type. In contrast, ace-1 ace-2 ace-3 triple mutant animals are paralyzed and developmentally arrested; their embryonic development is relatively unimpaired, but they are unable to grow beyond the hatching stage. Based on the analysis of genetic mosaics, we conclude that in the absence of ace-2 and ace-3 function, the expression of ace-1(+) in muscles cells, but not in neurons, is essential for postembyronic development.

Ishii N et al. (1992) Neuron "UNC-6, a laminin-related protein, guides cell and pioneer axon migrations in C. elegans."

Wadsworth WG, Culotti JG, Hedgecock EM, Ishii N, Stern BD

[Neuron, 1992]

The unc-6 gene is required for the guidance of pioneer axons and migrating cells along the body wall in C. elegans. In mutants, dorsal and ventral migrations are disrupted, but longitudinal movements are largely unaffected. The gene was tagged for molecular cloning by two independent transposon insertions. Based on genomic and cDNA sequencing, the gene encodes a novel laminin-related protein, UNC-6 (591 amino acids). The N-terminus is homologous to the N-termini (i.e., domains V1, V-1, V-2, and V-3) of laminin subunits, while the C-terminus is a unique domain. We propose that UNC-6 is a component of an extracellular matrix cue that guides dorsoventral migrations on the epidermis.

Park S et al. (2020) Int J Mol Sci "A Molecular Basis for Reciprocal Regulation between Pheromones and Hormones in Response to Dietary Cues in C. elegans."

Park S, Park JY, Paik YK

[Int J Mol Sci, 2020]

Under stressful conditions, the early larvae of C. elegans enter dauer diapause, a non-aging period, driven by the seemingly opposite influence of ascaroside pheromones (ASCRs) and steroid hormone dafachronic acids (DAs). However, the molecular basis of how these small molecules engage in competitive crosstalk in coordination with insulin/IGF-1 signaling (IIS) remains elusive. Here we report a novel transcriptional regulatory pathway that seems to operate between the ASCR and DA biosynthesis under ad libitum (AL) feeding conditions or bacterial deprivation (BD). Although expression of the ASCR and DA biosynthetic genes reciprocally inhibit each other, ironically and interestingly, such dietary cue-mediated modulation requires the presence of the competitors. Under BD, induction of ASCR biosynthetic gene expression required DA, while ASCR suppresses the expression of the DA biosynthetic gene daf-36. The negative regulation of DA by ASCR was IIS-dependent, whereas daf-36 regulation appeared to be independent of IIS. These observations suggest that the presence of ASCR determines the IIS-dependency of DA gene expression regardless of dietary conditions. Thus, our work defines a molecular basis for a novel reciprocal gene regulation of pheromones and hormones to cope with stressful conditions during development and aging.

Leung-Hagesteijn CJ et al. (1992) Cell "UNC-5, a transmembrane protein with immunoglobulin and thrombospondin type 1 domains, guides cell and pioneer axon migrations in C. elegans."

Zhou YW, Stern BD, Su M-W, Culotti JG, Spence AM, Leung-Hagesteijn CJ, Hedgecock EM

[Cell, 1992]

The unc-5 gene is required for guiding pioneering axons and migrating cells along the body wall in C. elegans. In mutants, dorsal migrations are disrupted, but ventral and longitudinal movements are largely unaffected. The gene was tagged for molecular cloning by transposon insertions. Based on genomic and cDNA sequencing, the gene encodes UNC-5, a transmembrane protein of 919 aa. The predicted extracellular N-terminus comprises two immunoglobulin and two thrombospondin type 1 domains. Except for an SH3-like motif, the large intracellular C-terminus is novel. Mosaic analysis shows that unc-5 acts in migrating cells and pioneering neurons. We propose that UNC-5 is a transmembrane receptor expressed on the surface of motile cells and growth cones to guide dorsal movements.

Stern MJ et al. (1991) Development "A normally attractive cell interaction is repulsive in two C. elegans mesodermal cell migration mutants."

Stern MJ, Horvitz HR

[Development, 1991]

In wild-type Caenorhabditis elegans hermaphrodites, two bilaterally symmetric sex myoblasts (SMs) migrate anteriorly to flank the precise center of the gonad, where they divide to generate the muscles required for egg laying (J. E. Sulston and H. R. Horvitz (1977) Devl Biol. 56, 110-156). Although this migration is largely independent of the gonad, a signal from the gonad attracts the SMs to their precise final positions (J. H. Thomas, M. J. Stern and H. R. Horvitz (1990) Cell 62, 1041-1052). Here we show that mutations in either of two genes, egl-15 and egl-17, cause the premature termination of the migrations of the SMs. This incomplete migration is caused by the repulsion of the SMs by the same cells in the somatic gonad that are the source of the attractive signal in wild-type animals.

He XY et al. (1998) J Biol Chem "A human brain L-3-hydroxyacyl-coenzyme A dehydrogenase is identical to an amyloid beta-peptide-binding protein involved in Alzheimer's disease."

He XY, Yang SY, Schulz H

[J Biol Chem, 1998]

A novel L-3-hydroxyacyl-CoA dehydrogenase from human brain has been cloned, expressed, purified, and characterized. This enzyme is a homotetramer with a molecular mass of 108 kDa. Its subunit consists of 261 amino acid residues and has structural features characteristic of short chain dehydrogenases. It was found that the amino acid sequence of this human brain enzyme is identical to that of an endoplasmic reticulum amyloid beta-peptide-binding protein (ERAB), which mediates neurotoxicity in Alzheimer's disease (Yan, S. D., Fu, J., Soto, C., Chen, X., Zhu, H., Al-Mohanna, F., Collison, K., Zhu, A., Stern, E., Saido, T., Tohyama, M., Ogawa, S., Roher, A., and Stern, D. (1997) Nature 389, 689-695). The purification of human brain short chain L-3-hydroxyacyl-CoA dehydrogenase made it possible to characterize the structural and catalytic properties of ERAB. This NAD+-dependent dehydrogenase catalyzes the reversible oxidation of L-3-hydroxyacyl-CoAs to form 3-ketoacyl-CoAs, but it does not act on the D-isomers. The catalytic rate constant of the purified enzyme was estimated to be 37 s-1 with apparent Km values of 89 and 20 microM for acetoacetyl-CoA and NADH, respectively. The activity ratio of this enzyme for substrates with chain lengths of C4, C8, and C16 was approximately 1:2:2. The human short chain L-3-hydroxyacyl-CoA dehydrogenase gene is organized into six exons and five introns and maps to chromosome Xp11.2. The amino-terminal NAD-binding region of the dehydrogenase is encoded by the first three exons, whereas the other exons code for the carboxyl-terminal substrate-binding region harboring putative catalytic residues. The results of this study lead to the conclusion that ERAB involved in neuronal dysfunction is encoded by the human short chain L-3-hydroxyacyl-CoA dehydrogenase gene.