Isolation and molecular identification of nematode surface mutants with resistance to bacterial pathogens

Numerous mutants of the nematode Caenorhabditis elegans with surface abnormalities have been isolated by utilizing their resistance to a variety of bacterial pathogens (Microbacterium nematophilum, Yersinia pseudotuberculosis, and 2 Leucobacter strains), all of which are able to cause disease or death when worms are grown on bacterial lawns containing these pathogens. Previous work led to the identification of 9 srf or bus genes; here, we report molecular identification and characterization of a further 10 surface-affecting genes. Three of these were found to encode factors implicated in glycosylation (srf-2, bus-5, and bus-22), like several of those previously reported; srf-2 belongs to the GT92 family of putative galactosyltransferases, and bus-5 is homologous to human dTDP-D-glucose 4,6-dehydratase, which is implicated in Catel-Manzke syndrome. Other genes encoded proteins with sequence similarity to phosphatidylinositol phosphatases (bus-6), Patched-related receptors (ptr-15/bus-13), steroid dehydrogenases (dhs-5/bus-21), or glypiation factors (bus-24). Three genes appeared to be nematode-specific (srf-5, bus-10, and bus-28). Many mutants exhibited cuticle fragility as revealed by bleach and detergent sensitivity; this fragility was correlated with increased drug sensitivity, as well as with abnormal skiddy locomotion. Most of the genes examined were found to be expressed in epidermal seam cells, which appear to be important for synthesizing nematode surface coat. The results reveal the genetic and biochemical complexity of this critical surface layer, and provide new tools for its analysis.

Urethral metastasis from renal cell carcinoma: an unusual cause of visible painless haematuria

Urethral metastasis from renal cell carcinoma (RCC) is rare, with only six previously described cases.1–6 The authors report a case which presented eight months post laparoscopic radical nephrectomy with painless, visible haematuria. The epidemiology, potential pathophysiological mechanisms and treatment options are explored.

Genomic clusters, putative pathogen recognition molecules, and antimicrobial genes are induced by infection of C. elegans with M. nematophilum

The interaction between the nematode Caenorhabditis elegans and a Gram-positive bacterial pathogen, Microbacterium nematophilum, provides a model for an innate immune response in nematodes. This pathogen adheres to the rectal and post-anal cuticle of the worm, causing slowed growth, constipation, and a defensive swelling response of rectal hypodermal cells. To explore the genomic responses that the worm activates after pathogenic attack we used microarray analysis of transcriptional changes induced after 6-h infection, comparing virulent with avirulent infection. We defined 89 genes with statistically significant expression changes of at least twofold, of which 68 were up-regulated and 21 were down-regulated. Among the former, those encoding C-type lectin domains were the most abundant class. Many of the 89 genes exhibit genomic clustering, and we identified one large cluster of 62 genes, of which most were induced in response to infection. We tested 41 of the induced genes for involvement in immunity using mutants or RNAi, finding that six of these are required for the swelling response and five are required more generally for defense. Our results indicate that C-type lectins and other putative pathogen-recognition molecules are important for innate immune defense in C. elegans. We also found significant induction of genes encoding lysozymes, proteases, and defense-related proteins, as well as various domains of unknown function. The genes induced during infection by M. nematophilum appear largely distinct from genes induced by other pathogens, suggesting that C. elegans mounts pathogen-specific responses to infection.