Zengel JM et al. (1980) "Muscle development in C. elegans: A molecular genetic approach."

Epstein HF, Zengel JM

[1980]

Muscle contraction is one of the fundamental processes of animal life. Although biochemical, biophysical, and electron microscopic studies have yielded much valuable information about the structure and function of muscle and its component proteins, there are still many unanswered questions. For example, little is known about the molecular basis for gene expression during the development of muscle, the regulation of synthesis and function of muscle proteins, and the in vivo assembly of the myofilament lattice. Progress in answering these types of questions has been hindered in the past by the lack of a system in which one could use biochemical, biophysical, and cytological techniques in analyzing an animal also suitable for genetic and developmental studies of muscle. However, recent work has demonstrated rather convincingly that the nematode, Caenorhabditis elegans, will be very useful for attacking these problems.

Zengel JM et al. (1980) Cell Motil "Identification of genetic elements associated with muscle structure in the nematode Caenorhabditis elegans."

Epstein HF, Zengel JM

[Cell Motil, 1980]

A search for new mutants with altered body-wall muscle cell structure has been undertaken in the nematode C elegans. One-hundred seventeen mutants were isolated after mutagenesis with ethyl methanesulfonate or ultraviolet light, enrichment by a motility-requiring test, and screening by polarized light microscopy; 102 of these mutants were in ten previously established genes, whereas 15 mutants permitted the identification of seven new complementation groups in C elegans. Two of the new genes map on linkage group I (unc-94 and unc-95) and four genes are sex linked (unc-96, unc-97, unc-98, and unc-99). One complementation group (unc-100) could not be mapped because of the special characteristics of its cohort mutants. Representative mutants of the mapped genes were examined by polarized light and electron microscopy. All of the mutants exhibit disruptions of the normal A and I band organization of thick and thin filaments. Several of the mutants produce collections of thin filament-like structures. In one of these cases, HE177 demonstrated collections of somewhat wider, intermediate-sized filaments as well, and the HE195 mutant produces paracrystalline aggregates of thin filaments amidst looser arrangements of similar structures. The mutants in newly identified genes, as well as the new mutants in previously established genetic loci, have promise as tools in the study of myofibrillar assembly and function. Among the 22 complementation groups associated with body- wall structure in C elegans, it is likely that some genes code for regulatory and morphogenetic functions in addition to the well- studied structural, contractile, and calcium-associated proteins in muscle.

Zengel JM et al. (1979) International C. elegans Meeting "a genetic analysis of 118 new body-wall muscle-defective mutants of Caenorhabditis elegans."

Houts S, Epstein HF, Rein DC, Zengel JM

[International C. elegans Meeting, 1979]

Zengel JM et al. (1980) Proc Natl Acad Sci U S A "Mutants altering coordinate synthesis of specific myosins during nematode muscle development."

Zengel JM, Epstein HF

[Proc Natl Acad Sci U S A, 1980]

Mutations in the unc-52 gene on linkage group II retard the construction of body-wall muscle sarcomeres during larval development in the nematode Caenorhabditis elegans. Unc-52 mutants show decreased accumulation of myosin heavy chains relative to other polypeptides during larval development, correlating with the structural retardation. Pulse radiolabeling experiments show that decreased synthesis of specific body-wall myosin heavy chains that are encoded by the unc-54 gene on linkage group I is responsible for the defective myosin accumulation. In the wild type, a constant ratio of the synthesis of the unc-54-coded myosin B to myosin A, about 2:1, is maintained during the larval stages in which the synthesis of both myosins increases exponentially and rapid sarcomere growth and addition ensues. During the first 26 hr of larval development, before any structural or behavioral effects of unc-52 mutations are apparent, the synthesis of myosin heavy chains is also normal. By 38 hr, decreased synthesis of myosin B is detected in the unc-52 mutant SU200, when sarcomere growth slows considerably. The effects of mutations in the unc-52 locus are trans acting upon the synthesis of unc-54-coded myosin in a specific set of muscle cells during a defined period of larval development.

da Silva AF et al. (2022) Neurotoxicology "JM-20 affects GABA neurotransmission in Caenorhabditis elegans."

Arantes LP, Soares MV, Nunez-Figueredo Y, Cordeiro LM, da Silveira TL, Soares FAA, Baptista FBO, Machado ML, Zamberlan DC, da Silva AF, Rodriguez EO

[Neurotoxicology, 2022]

Along with the discovery of new candidate molecules for pharmaceuticals, several studies have emerged showing different mechanisms of action and toxicological aspects. 3-ethoxycarbonyl-2-methyl-4- (2-nitrophenyl)4,11-dihydro-1H-pyrido [2,3-b] [1,5] benzodiazepine (JM-20) is a hybrid molecule. It is derived from 1,5-benzodiazepines and structurally differentiated by the addition of 1,4-dihydropyridine bonded to the benzodiazepine ring. This gives this molecule potential neuroprotective, antioxidant, and anxiolytic activity. As this is a promising multi-target molecule, further studies are necessary to improve the knowledge about its mechanism of action. In our study, we used Caenorhabditis elegans (C. elegans) to investigate the effects of chronic treatment with JM-20. Nematodes from the wild-type strain (N2) were treated chronically at different concentrations of JM-20. Our results show that JM-20 does not cause mortality, but higher concentrations can delay the development of worms after 48h exposure. We assessed basic behaviors in the worm, and our data demonstrate decreased defecation cycle. Our results suggest that JM-20 acts on the C. elegans GABAergic system because GABA neurotransmission is associated with the worm intestine. We also observed increased locomotor activity and decreased egg-laying after JM-20 treatment. When both behaviors were evaluated in mutants with have reduced levels of GABA (unc-25), this effect is no observed, suggesting the GABAergic modulation. Still, the JM-20 exert similar effect of Diazepam in basic behaviors observed. To reinforce neuromodulatory action, computational analysis was performed, and results showed a JM-20 binding on allosteric sites of nematodes GABA receptors. Overall, this work provided a better understanding of the effects of JM-20 in C. elegans as well as showed the effects of this new molecule on the GABAergic system in this animal model.

Mackenzie JM et al. (1978) Cell "Muscle development in Caenorhabditis elegans: mutants exhibiting retarded sarcomere construction."

Garcea RL, Zengel JM, Epstein HF, Mackenzie JM

[Cell, 1978]

We have studied the structural changes within the body-wall muscle cells of Caenorhabditis elegans during postmitotic development. In wildtype, the number of sarcomeres progressively increases, and each sarcomere appears to grow in length and depth continuously during this period. In mature wild-type cells, the anterior-most body-wall muscle cells have 6--7 sarcomeres; the rest have 9--10 sarcomeres per cell. Twelve mutants in the unc-52 II gene exhibit markedly retarded sarcomere construction and progressive paralysis. Several unc-52 mutants, such as the severely paralyzed SU200, produced only 2--3 sarcomeres per body-wall muscle cell, while the other mildly paralyzed unc-52 mutants, such as SU250, build 3--4 sarcomeres per muscle cell. Other structures such as the pharynx and even the noncontractile organelles of the body-wall muscle cells do not appear to be structurally or functionally altered. The unc-52 body-wall sarcomeres become moderately disorganized as they are outstripped by cell growth; sufficient order is preserved, however, so that the majority of thick and thin filaments still interdigitate. The myosin heavy chains of SU200 body-wall muscle fail to accumulate normally, while the pharyngeal myosin heavy chains do not appear to be specifically affected. This biochemical result correlates well with the specificity of morphological changes in the mutant. A model is discussed in which the biochemical and morphological deficits are explained by a simple regulatory mechanism.

Mackenzie JM et al. (1978) Worm Breeder's Gazette

Zengel JM, Mackenzie JM, Epstein HF, Garcea RL

[Worm Breeder's Gazette, 1978]

We have studied the structural changes within the body-wall muscle cells of Caenorhabditis ostmitotic development. In wild-type, the number of sarcomeres progressively increases, and each sarcomere appears to continuously grow in length and depth during this period. At maturity, in wild-type, the anteriormost body-wall muscle cells have 6-7 sarcomeres and the rest have 9-10 sarcomeres per cell. Twelve mutants in the unc-52 II gene exhibit markedly retarded sarcomere construction and progressive paralysis. Several unc-52 mutants such as the severely paralyzed SU200 produce only 2-3 sarcomeres per body-wall muscle cell while the other less paralyzed unc-52 mutants such as SU250 build 3-4 larger sarcomeres per muscle cell. Other structures such as the pharynx and even the non-contractile organelles of the body-wall muscle cells do not appear to be structurally or functionally altered. The unc-52 body-wall sarcomeres become moderately disorganized as they are outstripped by cell growth, however, sufficient order is preserved so that the majority of thick and thin filaments still interdigitate. The myosin heavy chains of SU200 body-wall muscle fail to accumulate normally while the pharyngeal myosin heavy chains do not appear specifically affected. This biochemical result correlates well with the specificity of morphological changes in the mutant. We are conducting experiments to test whether the unc-52 mutants affect only body-wall myosin heavy chains versus other contractile proteins, and if so, unc-54 or non-unc-54 heavy chains or both. Further experiments are planned to test whether the unc-52 effects are due to a synthetic block or increased turnover of the proteins.

Killeen M et al. (2002) Dev Biol "UNC-5 function requires phosphorylation of cytoplasmic tyrosine 482, but its UNC-40-independent functions also require a region between the ZU-5 and death domains."

Culotti J, Pawson T, Tong J, Steven R, Killeen M, Krizus A, Scott I

[Dev Biol, 2002]

Members of the UNC-5 protein family are transmembrane receptors for UNC-6/netrin guidance cues. To analyze the functional roles of different UNC-5 domains, we sequenced mutations in seven severe and three weak alleles of unc-5 in Caenorhabditis elegans. Four severe alleles contain nonsense mutations. Two weak alleles are truncations of the cytodomain, but one is a missense mutation in an extracellular immunoglobulin domain. To survey the function of different regions of UNC-5, wild-type and mutant unc-5::HA transgenes were tested for their ability to rescue the unc-5(e53) null mutant. Our data reveal partial functional requirements for the extracellular domains and identify a portion of the cytoplasmic juxtamembrane (JM) region as essential for rescue of migrations. When nine cytodomain tyrosines, including seven in the JM region, are mutated to phenylalanine, UNC-5 function and tyrosine phosphorylation are largely compromised. When F482 in the JM region of the mutant protein is reverted to tyrosine, UNC-5 tyrosine phosphorylation and in vivo function are largely recovered, suggesting that Y482 phosphorylation is critical to UNC-5 function in vivo. Our data also show that part of the ZU-5 motif is required for UNC-40-independent signaling of UNC-5.

Garcea RL et al. (1978) Worm Breeder's Gazette "muscle development in C elegans: mutants exhibiting retarded sarcomere construction."

Mackenzie JM, Epstein HF, Zengel JM, Schachat FH, Garcea RL

[Worm Breeder's Gazette, 1978]

Hartman PS et al. (1995) International C. elegans Meeting "UV RADIATION INHIBITS CELL DIVISION IN THE P1 LINEAGE MORE THAN IN THE AB LINEAGE"

Buckles D, Hartman PS

[International C. elegans Meeting, 1995]

Two-cell embryos were irradiated with germicidal (254nm) radiation and subsequent cell divisions were determined using Nomarski DIC microscopy. A dose of 30 Jm-2 (which gave ca. 10% survival) delayed P1 and P2 divisions by 27%, versus only 8% for the equivalent AB divisions. Similarly, although exposure to 150 Jm-2 abolished cytokinesis in some AB descendants (resulting in occasional binucleated cells), the next two cell cycles were only 22% longer than in unirradiated controls. Conversely, the P1 and P2 cell cycles averaged 95% longer. The delays in the EMSt, E, and MSt cell cycles were similar to those in the AB lineage, suggesting the longer delays were limited to the P4 progenitors. "Cell-cycle checkpoints" have been documented in other organisms. These afford additional time for restitution of DNA damage. Such checkpoints are apparently largely inoperative in the AB lineage (which generates soma exclusively) but at least partially functional in the cells which give rise to the germ line.