A systematic RNAi screen identifies a critical role for mitochondria in C. elegans longevity

We report a systematic RNA interference (RNAi) screen of 5,690 Caenorhabditis elegans genes for gene inactivations that increase lifespan. We found that genes important for mitochondrial function stand out as a principal group of genes affecting C. elegans lifespan. A classical genetic screen identified a mutation in the mitochondrial leucyl-tRNA synthetase gene (lrs-2) that impaired mitochondrial function and was associated with longer-lifespan. The long-lived worms with impaired mitochondria had lower ATP content and oxygen consumption, but differential responses to free-radical and other stresses. These data suggest that the longer lifespan of C. elegans with compromised mitochrondria cannot simply be assigned to lower free radical production and suggest a more complex coupling of metabolism and longevity.     

Evolutionary plasticity of genetic interaction networks

Non-additive genetic interactions contribute to many genetic disorders, but they are extremely difficult to predict. Here we show that genetic interactions identified in yeast, unlike gene functions or protein interactions, are not highly conserved in animals. Genetic interactions are therefore unlikely to represent simple redundancy between genes or pathways, and genetic interactions from yeast do not directly predict genetic interactions in higher eukaryotes, including humans.     

Genetic determinants of ulcerative colitis include the ECM1 locus and five loci implicated in Crohn's disease

We report results of a nonsynonymous SNP scan for ulcerative colitis and identify a previously unknown susceptibility locus at ECM1. We also show that several risk loci are common to ulcerative colitis and Crohn's disease (IL23R, IL12B, HLA, NKX2-3 and MST1), whereas autophagy genes ATG16L1 and IRGM, along with NOD2 (also known as CARD15), are specific for Crohn's disease. These data provide the first detailed illustration of the genetic relationship between these common inflammatory bowel diseases.     

Systematic mapping of genetic interactions in Caenorhabditis elegans identifies common modifiers of diverse signaling pathways

Most heritable traits, including disease susceptibility, are affected by interactions between multiple genes. However, we understand little about how genes interact because very few possible genetic interactions have been explored experimentally. We have used RNA interference in Caenorhabditis elegans to systematically test approximately 65,000 pairs of genes for their ability to interact genetically. We identify approximately 350 genetic interactions between genes functioning in signaling pathways that are mutated in human diseases, including components of the EGF/Ras, Notch and Wnt pathways. Most notably, we identify a class of highly connected 'hub' genes: inactivation of these genes can enhance the phenotypic consequences of mutation of many different genes. These hub genes all encode chromatin regulators, and their activity as genetic hubs seems to be conserved across animals. We propose that these genes function as general buffers of genetic variation and that these hub genes may act as modifier genes in multiple, mechanistically unrelated genetic diseases in humans.     

Enterotoxin residues determining T-cell receptor V beta binding specificity.

Superantigens such as the staphylococcal enterotoxins bind to major histocompatibility complex (MHC) class II molecules and activate T cells through a specific interaction between the V beta region of the T-cell antigen receptor (TCR) and the toxin. The TCR beta-chain alone is sufficient to produce the interaction with the enterotoxin-class II complex. Identification of the regions of enterotoxins that interact with TCR has so far proved equivocal because of difficulties in distinguishing between direct effects on T-cell recognition and indirect effects resulting from alteration of binding to class II. For example, amino-terminal truncations of SEB abrogated T-cell stimulation whereas carboxy-terminal truncation of SEA stopped its mitogenic activity. The most comprehensive study to date, accounting for both enterotoxin binding to class II and enterotoxin interactions with the TCR, identified two functionally important regions for SEB binding to TCR. Although the amino-acid sequences of staphylococcal enterotoxins A and E are 82% identical, they activate T cells bearing different V beta elements. We have assayed the binding of cells coated with these enterotoxins to soluble secreted TCR beta-chain protein and find that V beta 3 binds enterotoxin A but not E, whereas V beta 11 binds enterotoxin but not A. To map the amino-acid residues responsible for these different binding specificities, we prepared a series of hybrids between the two staphylococcal enterotoxins. We report that just two amino-acid residues near the carboxy terminus of the enterotoxins are responsible for the discrimination between these molecules by V beta 3 and V beta 11.(ABSTRACT TRUNCATED AT 250 WORDS)     

Herpesvirus vector gene transfer and expression of beta-glucuronidase in the central nervous system of MPS VII mice.

Genetic disorders affecting the central nervous system (CNS) can potentially be treated by gene transfer using vectors which infect and express genes in post-mitotic neurons. Herpesviruses establish latent infections in neurons during which only one viral gene (LAT) is expressed, thus the LAT promoter may express foreign genes in latently infected CNS cells. Expression of a beta-glucuronidase gene driven by the LAT promoter was tested in mice lacking this enzyme, which are a model for a human genetic disease affecting the CNS (mucopolysaccharidosis VII, Sly disease). Cells expressing the missing enzymatic activity were present in the trigeminal ganglia and brainstems of latently infected animals, up to four months post-inoculation, demonstrating the potential of this approach for the long-term expression of foreign genes in the CNS.     

ADAMTS5 is the major aggrecanase in mouse cartilage in vivo and in vitro

Aggrecan is the major proteoglycan in cartilage, endowing this tissue with the unique capacity to bear load and resist compression. In arthritic cartilage, aggrecan is degraded by one or more 'aggrecanases' from the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family of proteinases. ADAMTS1, 8 and 9 have weak aggrecan-degrading activity. However, they are not thought to be the primary aggrecanases because ADAMTS1 null mice are not protected from experimental arthritis, and cleavage by ADAMTS8 and 9 is highly inefficient. Although ADAMTS4 and 5 are expressed in joint tissues, and are known to be efficient aggrecanases in vitro, the exact contribution of these two enzymes to cartilage pathology is unknown. Here we show that ADAMTS5 is the major aggrecanase in mouse cartilage, both in vitro and in a mouse model of inflammatory arthritis. Our data suggest that ADAMTS5 may be a suitable target for the development of new drugs designed to inhibit cartilage destruction in arthritis, although further work will be required to determine whether ADAMTS5 is also the major aggrecanase in human arthritis.     

Genomic sequence of the pathogenic and allergenic filamentous fungus Aspergillus fumigatus

Aspergillus fumigatus is exceptional among microorganisms in being both a primary and opportunistic pathogen as well as a major allergen. Its conidia production is prolific, and so human respiratory tract exposure is almost constant. A. fumigatus is isolated from human habitats and vegetable compost heaps. In immunocompromised individuals, the incidence of invasive infection can be as high as 50% and the mortality rate is often about 50% (ref. 2). The interaction of A. fumigatus and other airborne fungi with the immune system is increasingly linked to severe asthma and sinusitis. Although the burden of invasive disease caused by A. fumigatus is substantial, the basic biology of the organism is mostly obscure. Here we show the complete 29.4-megabase genome sequence of the clinical isolate Af293, which consists of eight chromosomes containing 9,926 predicted genes. Microarray analysis revealed temperature-dependent expression of distinct sets of genes, as well as 700 A. fumigatus genes not present or significantly diverged in the closely related sexual species Neosartorya fischeri, many of which may have roles in the pathogenicity phenotype. The Af293 genome sequence provides an unparalleled resource for the future understanding of this remarkable fungus.