Biomedical subjects

John Yochem

Publications and source records attributed to John Yochem.

5 recordsLinked to original sources

PubMed2006

The molecular identities of the Caenorhabditis elegans intraflagellar transport genes dyf-6, daf-10 and osm-1.

The Caenorhabditis elegans genes dyf-6, daf-10, and osm-1 are among the set of genes that affect chemotaxis and the ability of certain sensory neurons to take up fluorescent dyes from the environment. Some genes in this category are known to be required for intraflagellar transport (IFT), which is the bidirectional movement of raft-like particles along the axonemes of cilia and flagella. The cloning of dyf-6, daf-10, and osm-1 are described here. The daf-10 and osm-1 gene products resemble each other and contain WD and WAA repeats. DYF-6, the product of a complex locus, lacks known motifs, but orthologs are present in flies and mammals. Phenotypic analysis of dyf-6 mutants expressing an OSM-6::GFP reporter indicates that the cilia of the amphid and phasmid dendritic endings are foreshortened. Consistent with genetic mosaic analysis, which indicates that dyf-6 functions in neurons of the amphid sensilla, DYF-6::GFP is expressed in amphid and phasmid neurons. Movement of DYF-6::GFP within the ciliated endings of the neurons indicates that DYF-6 is involved in IFT. In addition, IFT can be observed in dauer larvae.

Amino Acid Sequence↗

PubMed2005

Isopentenyl-diphosphate isomerase is essential for viability of Caenorhabditis elegans.

Homozygosity for a mutation in the idi-1 gene of Caenorhabditis elegans results in paralysis during the first larval stage, followed by an arrest of growth and development late in the first larval stage. Apoptotic corpses, which are apparently the result of normal programmed cell death, persist in the arrested larvae. In genetic mosaics, an additional defect becomes evident upon examination with Nomarski optics: cells that are genotypically mutant enlarge, and their cytoplasm becomes dimpled. Electron microscopy indicates that the dimpling reflects an accumulation of many enlarged lysosomes and autophagosomes. The mosaics demonstrate that the lethal mutation acts cell autonomously with respect to this vesicular abnormality and that there is a maternal effect with respect to the time of developmental arrest of mutant progeny. Cloning of the gene reveals that it is the only gene in C. elegans for isopentenyl-diphosphate isomerase, an enzyme that is important for the synthesis of lipophilic molecules, including farnesyl and geranyl diphosphates.

Amino Acid Sequence↗

PubMed2004

Tetraspanin protein (TSP-15) is required for epidermal integrity in Caenorhabditis elegans.

Epidermal integrity is essential for animal development and survival. Here, we demonstrate that TSP-15, a member of the tetraspanin protein family, is required for epithelial membrane integrity in Caenorhabditis elegans. Reduction of tsp-15 function by mutation or by RNA interference elicits abnormalities of the hypodermis, including dissociation of the cuticle and degeneration of the hypodermis. Lethality during molting often results. Examination of GFP transgenic animals, genetic mosaic analysis and rescue assays revealed that TSP-15 functions in hyp7, a large syncytium that composes most of the hypodermis. Assays with a membrane-impermeable dye or leakage analysis of a hypodermal-specific marker indicate that the barrier function of the hypodermal membrane is impaired owing to the loss or reduction of TSP-15. These results indicate that TSP-15 functions in the maintenance of epithelial cell integrity.

Amino Acid Sequence↗

PubMed2004

The identities of sym-2, sym-3 and sym-4, three genes that are synthetically lethal with mec-8 in Caenorhabditis elegans.

On the basis of synthetic lethality, five genes in Caenorhabditis elegans are known to be redundant with the mec-8 gene, which encodes a protein that contains two copies of an RNA recognition motif (RRM) and affects alternative RNA splicing. The molecular identities of two of the redundant genes, sym-1 and sym-5, were previously reported. The remaining three genes have now been cloned, and their synthetically lethal phenotypes with mec-8 are described in more detail. Animals homozygous for mec-8 and sym-2 loss-of-function mutations die during late embryogenesis. The SYM-2 predicted protein contains three RRMs; we propose that SYM-2 and MEC-8 can substitute for each other in promoting the maturation of the transcripts of a vital gene. Animals homozygous for mutations in mec-8 and in either sym-3 or sym-4 have the same striking defect: they arrest development just prior to or just after hatching with a pharynx that appears fully formed but is not properly attached to the body cuticle. sym-3 encodes a protein of unknown function with orthologs in Drosophila and mammals. sym-4 encodes a WD-repeat protein and may also have orthologs in Drosophila and mammals. We propose that SYM-3 and SYM-4 contribute to a common developmental pathway that is redundant with a MEC-8-dependent pathway.

Amino Acid Sequence↗

PubMed2003

Investigating C. elegans development through mosaic analysis.

The analysis of genetically mosaic worms, in which some cells carry a wild-type gene and others are homozygous mutant, can reveal where in the animal a gene acts to prevent the appearance of a mutant phenotype. In this primer article, we describe how Caenorhabditis elegans genetic mosaics are generated, identified and analyzed, and we discuss examples in which the analysis of mosaic worms has provided important information about the development of this organism.

Animals↗