Brianne J Ray et al. (2004) East Coast Worm Meeting "Histone variant H2A.Z is essential for development in C.elegans"

Adam Raymond, William G Kelly, Brianne J Ray

[East Coast Worm Meeting, 2004]

Brianne J Ray et al. (2003) International Worm Meeting "Investigations into the role of variant histone H2A.Z in C. elegans development."

Bill Kelly, Adam Raymond, Brianne J Ray

[International Worm Meeting, 2003]

The core nucleosome histones H2A, H2B, H3, and H4 are crucial for the maintenance of stable chromatin environments, yet nucleosomes can be very dynamic complexes. A number of histone variants have been identified that can replace the canonical core histones in nucleosomes and thus influence chromatin formation in a potentially more specific manner than the canonical core histones. Drosophila histone H3 variants H3.3 and Cid, for example, are enriched in transcriptionally active and silent centromeric heterochromatin, respectively. Both variants can replace histone H3 in a non-replication-coupled mechanism that is currently unclear. Histone variants are therefore thought to play dynamic and important roles in balancing active and inactive areas of gene expression, thus contributing to defined heterochromatin and euchromatin states.Variants of core histone H2A are also enriched in "interesting" chromatin in a variety of systems. For example, macroH2A1 is enriched on the inactive X in mammals, and phospho-H2A.X accumulates at sites of DNA damage. Yeast variant H2A.Z (Htz1) has been reported to be necessary to prevent spreading of heterochromatin into active genes near telomeres. The tetrahymena H2A.Z homologue is abundant in transcriptionally active macronuclei, but absent from quiescent micronuclei, while KO of H2A.Z causes early embryonic lethality in mice. These results together suggest H2A.Z may play an epigenetic role in maintaining active sites during development.We are interested in the role of H2A.Z in the development of C. elegans. We have identified a single H2A.Z homologue in worms, R08C7.3, which exhibits 78.6 AA identity to human H2A.Z and 51.8% identity with other worm H2As (all of which bear ~100% identity to each other). RNAi targeting this ORF causes high embryonic lethality (67-70%) with all escapers arresting as defective larvae. Weakly affected early brood members from dsRNA-injected animals grow up sterile. We have raised peptide antibodies to unique sequence of this protein and are beginning to look at its distribution by IF. Results from this, as well as further characterizations of the RNAi phenotype, will be presented.

Ray A et al. (2014) J Neurosci "RTCB-1 mediates neuroprotection via XBP-1 mRNA splicing in the unfolded protein response pathway."

Zhang S, Caldwell GA, Rentas C, Ray A, Caldwell KA

[J Neurosci, 2014]

Parkinson's disease (PD), the second most prevalent neurodegenerative disorder, is characterized by the degeneration of dopamine (DA) neurons and age-dependent formation of protein inclusions that contain the -synuclein (-syn) protein. RNA interference (RNAi) screening using Caenorhabditis elegans identified RTCB-1, an uncharacterized gene product, as one of several significant modifiers of -syn protein misfolding. RTCB-1 is the worm ortholog of the human HSPC117 protein, a component of RNA trafficking granules in mammalian neurons. Here we show that RTCB-1 protects C. elegans DA neurons from age-dependent degeneration induced by human -syn. Moreover, neuronal-specific RNAi depletion of rtcb-1 enhanced -syn-induced degeneration. Similar results were obtained when worms were exposed to the DA neurotoxin 6-hydroxydopamine. HSPC117 has been characterized recently as an essential subunit of the human tRNA splicing ligase complex. tRNA ligases have alternative functions in RNA repair and nonconventional mRNA splicing events. For example, in yeast, unconventional splicing of HAC1, a transcription factor that controls the unfolded protein response (UPR), is mediated by a tRNA ligase. In C. elegans, we demonstrate that RTCB-1 is necessary for xbp-1 (worm homolog of HAC1) mRNA splicing. Moreover, using a RNA ligase-dead mutant, we determine that the ligase activity of worm RTCB-1 is required for its neuroprotective role, which, in turn, is mediated through XBP-1 in the UPR pathway. Collectively, these studies highlight the mechanistic intersection of RNA processing and proteostasis in mediating neuroprotection.

Zhang YH et al. (1995) International C. elegans Meeting "A C. elegans Pax-6 HOMOLOG GOVERNS THE IDENTITY OF A PERIPHERAL SENSE ORGAN"

Emmons SW, Zhang YH, Hall DH

[International C. elegans Meeting, 1995]

How do cells find their correct neighbors during the differentiation of precise tissue architecture? This problem arises in the assembly of sense organs in C. elegans. In the male tail, each sensory ray has a distinct morphogenetic identity. Mutations that alter ray identities disrupt the specificity of ray assembly, resulting in fused rays. The mab-18 locus is required for expression of the ray 6 identity. mab-18 consists of the homeodomain portion of a C. elegans Pax-6 gene. cDNAs that rescue the mab-18 mutant phenotype start within a large intron separating Pax-6-like paired and homeodomains. Reporter gene expression shows that a promoter within the intron is activated during ray 6 development and remains active in the adult. It is also transiently activated during ray 8 development. We propose that the mab-18 transcription factor regulates expression of ray 6-specific cell recognition and adhesion molecules. These may be expressed by the ray structural cell. By eliminating the neurons with a laser, we have shown that the morphogenetic properties of rays are determined by the structural cell. In a wild type background the ray 6 structural cell generates a normal ray 6 with thick, tapering morphology. In a mab-18 mutant background it forms a thin, cylindrical ray at the position of ray 4. If ray 4 is present, the ray 6 structural cell fuses with the ray 4 structural cell. When neurons are present, both ray 4 and ray 6 neurons are incorporated into the fused ray.

Ishii N et al. (1990) Int J Radiat Biol "X-ray inactivation of Caenorhabditis elegans embryos or larvae."

Suzuki K, Ishii N

[Int J Radiat Biol, 1990]

The lethal effects of X-irradiation were examined in staged populations of Caenorhabditis elegans embryos or larvae. Radiation resistance decreased slightly throughout the first, proliferative phase of embryogenesis. This might be due to the increase in target size, since most cells in C. elegans are autonomously determined. Animals irradiated in the second half of embryogenesis were about 40-fold more resistant to the lethal effects of X-rays. This is probably due to the absence of cell divisions during this time. The radiation resistance increased still more with advancing larval stages. A radiation hypersensitive mutant, rad-1, irradiated in the first half of embryogenesis, is about 30-fold more sensitive than wild-type, but in the second half it is the same as wild-type.

Fitch DHA et al. (1995) Worm Breeder's Gazette "Changes in Cell Positions and Contacts Underlie the Evolution of Ray Pattern."

Emmons SW, Fitch DHA

[Worm Breeder's Gazette, 1995]

Changes in cell positions and contacts underlie the evolution of ray pattern

Poletti G et al. (2004) Eur Phys J D "Soft X-ray contact microscopy of nematode Caenorhabditis elegans."

Zullini A, Prag A, Krousky E, Desai T, Pfeifer M, Poletti G, Renner O, Kralikova B, Mocek T, Juha L, Bernardinello A, Orsini F, Skala J, Lamia CL, Cotelli F, Kadlec C, Batani D, Ullschmied J

[Eur Phys J D, 2004]

Soft X-ray Contact Microscopy (SXCM) of Caenorhabditis elegans nematodes with typical length similar to 800 mum and diameter similar to 30 mum has been performed using the PALS laser source of wavelength lambda = 1.314 mum and pulse duration tau ( FWHM) = 400 ps. Pulsed soft X-rays were generated using molybdenum and gold targets with laser intensities I greater than or equal to 10(14) W/cm(2). Images have been recorded on PMMA photo resists and analyzed using an atomic force microscope operating in contact mode. Cuticle features and several internal organs have been identified in the SXCM images including lateral field, cuticle annuli, pharynx, and hypodermal and neuronal cell nuclei.

Baird SE et al. (1988) Worm Breeder's Gazette "sixless males."

Baird SE, Emmons SW

[Worm Breeder's Gazette, 1988]

We have isolated an EMS-induced mutation, bx23, that specifically affects the development of sensory ray 6 in C. elegans males. In mutant individuals, the morphologically thickened ray 6 is missing, and in its place there is an ectopic ray that is located adjacent to, and is morphologically similar to ray 4. In most animals, the ectopic ray and ray 4 are fused on both sides. This phenotype is reflected in L4 males where the distinctive ray 6 papilla is missing and an ectopic papilla is present adjacent to the ray 4 papilla. bx23 does not affect male mating efficiency and no mutant phenotypes have been observed in bx23 hermaphrodites. The bx23 mutation has been mapped to approximately position +4.8 of linkage group X. No male specific defects have been described for any genes in this region. Thus, it appears that the bx23 mutation identifies a new gene that is required specifically for the differentiation of ray 6. The V6 cell lineage has not been determined in bx23 males, and therefore two simple explanations are possible to explain the mutant phenotype. First, it is possible that the V6 lineage is not affected by bx23. In this case, bx23 males would be defective in both the posterior migrations of the ray 6 precursor cell (R6) and its descendants, and in the differentiation of the ray 6 B neuron. Alternatively, a lineage defect could result in the failure of the R6 lineage and the recruitment of an ectopic ray from a different branch on the V6 lineage. For example, a ray cell group could be recruited from the anterior sister of the ray 4 precursor cell, V6.pppaa.

Baird SE et al. (2005) BMC Evolutionary Biology "The genetics of ray pattern variation in Caenorhabditis briggsae."

Baird SE, Bohrer JC, Davidson CR

[BMC Evolutionary Biology, 2005]

BACKGROUND:How does intraspecific variation relate to macroevolutionary change in morphology? This question can be addressed in species in which derived characters are present but not fixed. In rhabditid nematodes, the arrangement of the nine bilateral pairs of peripheral sense organs (rays) in tails of males is often the most highly divergent character between species. The development of ray pattern involves inputs from hometic gene expression patterns, TGFbeta signalling, Wnt signalling, and other genetic pathways. In Caenorhabditis briggsae, strain-specific variation in ray pattern has provided an entree into the evolution of ray pattern. Some strains were fixed for a derived pattern. Other strains were more plastic and exhibited derived and ancestral patterns at equal frequencies.RESULTS:Recombinant inbred lines (RILs) constructed from crosses between the variant C. briggsae AF16 and HK104 strains exhibited a wide range of phenotypes including some that were more extreme than either parental strain. Transgressive segregation was significantly associated with allelic variation in the C. briggsae homolog of abdominal B, Cb-egl-5. At least two genes that affected different elements of ray pattern, ray position and ray fusion, were linked to a second gene, mip-1. Consistent with this, the segregation of ray position and ray fusion phenotypes were only partially correlated in the RILs.CONCLUSIONS:The evolution of ray pattern has involved allelic variation at multiple loci. Some of these loci impact the specification of ray identities and simultaneously affect multiple ray pattern elements. Others impact individual characters and are not constrained by covariance with other ray pattern elements. Among the genetic pathways that may be involved in ray pattern evolution is specification of anteroposterior positional information by homeotic genes.

Scott Everet Baird (2001) International C. elegans Meeting "Ray pattern and HOM-C gene variation in Caenorhabditis briggsae."

Scott Everet Baird

[International C. elegans Meeting, 2001]

Ray pattern is one of the most variable morphological characters in rhabditid nematodes. Within Caenorhabditis , a modified ray pattern in which ray 3 is posterior of the anus and frequently fused with ray 4 is diagnostic for C. briggsae . This diagnostic character is based on observations of a limited number of C. briggsae strains. Recently, a C. briggsae strain, PB800, was obtained that exhibited an elegans ray pattern at a high frequency. Prompted by this observation, ray pattern variation has been assessed in four other C. briggsae strains, AF16, HK104, HK105, and VT847. AF16 and VT847 exhibited predominately the canonical briggsae pattern whereas HK104, HK105, and PB800 exhibited briggsae and elegans patterns at approximately equal frequencies. PB800 also exhibited a sixless phenotype, in which ray six is morphological transformed and fused with ray 4, at an approximately 1% frequency. In C. elegans this phenotype results at high frequency from mutations mab-18 and mab 21 and at low frequency from haploinsufficiency of egl-5 . Moreover, altered levels egl-5 and mab-5 expression can mimic the canonical C. briggsae ray pattern. Thus, ray pattern variation in C. briggsae may result from allelic variation in C. briggsae HOM-C genes. To test this hypothesis, PCR product length polymorphisms have been identified in the C. briggsae homolog of egl-5 ( Cb_egl-5 ). These Cb_egl-5 polymorphisms will be tested for linkage to variation in ray pattern. If linkage is detected, additional experiments will be conducted to map the C. briggsae ray pattern variants to a single locus.