An Integrated Strategy to Study Muscle Development and Myofilament Structure in Caenorhabditis elegans

A crucial step in the development of muscle cells in all metazoan animals is the assembly and anchorage of the sarcomere, the essential repeat unit responsible for muscle contraction. In Caenorhabditis elegans, many of the critical proteins involved in this process have been uncovered through mutational screens focusing on uncoordinated movement and embryonic arrest phenotypes. We propose that additional sarcomeric proteins exist for which there is a less severe, or entirely different, mutant phenotype produced in their absence. We have used Serial Analysis of Gene Expression (SAGE) to generate a comprehensive profile of late embryonic muscle gene expression. We generated two replicate long SAGE libraries for sorted embryonic muscle cells, identifying 7,974 protein-coding genes. A refined list of 3,577 genes expressed in muscle cells was compiled from the overlap between our SAGE data and available microarray data. Using the genes in our refined list, we have performed two separate RNA interference (RNAi) screens to identify novel genes that play a role in sarcomere assembly and/or maintenance in either embryonic or adult muscle. To identify muscle defects in embryos, we screened specifically for the Pat embryonic arrest phenotype. To visualize muscle defects in adult animals, we fed dsRNA to worms producing a GFP-tagged myosin protein, thus allowing us to analyze their myofilament organization under gene knockdown conditions using fluorescence microscopy. By eliminating or severely reducing the expression of 3,300 genes using RNAi, we identified 122 genes necessary for proper myofilament organization, 108 of which are genes without a previously characterized role in muscle. Many of the genes affecting sarcomere integrity have human homologs for which little or nothing is known

Integrin α PAT-2/CDC-42 Signaling Is Required for Muscle-Mediated Clearance of Apoptotic Cells in Caenorhabditis elegans

Clearance of apoptotic cells by engulfment plays an important role in the homeostasis and development of multicellular organisms. Despite the fact that the recognition of apoptotic cells by engulfment receptors is critical in inducing the engulfment process, the molecular mechanisms are still poorly understood. Here, we characterize a novel cell corpse engulfment pathway mediated by the integrin α subunit PAT-2 in Caenorhabditis elegans and show that it specifically functions in muscle-mediated engulfment during embryogenesis. Inactivation of pat-2 results in a defect in apoptotic cell internalization. The PAT-2 extracellular region binds to the surface of apoptotic cells in vivo, and the intracellular region may mediate signaling for engulfment. We identify essential roles of small GTPase CDC-42 and its activator UIG-1, a guanine-nucleotide exchange factor, in PAT-2–mediated cell corpse removal. PAT-2 and CDC-42 both function in muscle cells for apoptotic cell removal and are co-localized in growing muscle pseudopods around apoptotic cells. Our data suggest that PAT-2 functions through UIG-1 for CDC-42 activation, which in turn leads to cytoskeletal rearrangement and apoptotic cell internalization by muscle cells. Moreover, in contrast to PAT-2, the other integrin α subunit INA-1 and the engulfment receptor CED-1, which signal through the conserved signaling molecules CED-5 (DOCK180)/CED-12 (ELMO) or CED-6 (GULP) respectively, preferentially act in epithelial cells to mediate cell corpse removal during mid-embryogenesis. Our results show that different engulfing cells utilize distinct repertoires of receptors for engulfment at the whole organism level

Phenomenology in particle physics, 1971

What is phenomenology? Reach not for your dictionary; make no vain efforts to pronounce it; we will come clean and explain all. Science is noted for a competitive and helpful interaction between theorists and experimentalists. Unfortunately in almost all developing sciences, the moving hand of time drives a widening wedge between theory and experiment. Thus theorists are fully occupied in the mathematical and philosophical intricacies of their latest ideas. Again, experimentalists must concentrate on the design of their apparatus to insure they will get the best possible results current technology will allow. Phenomenology seeks to close the gap between those once close friends, theory and experiment, and so restore the interaction which is both vital to and characteristic of science. Although a classical concept, phenomenology is best known in its second-quantized form. The basic tool of the phenomenologist is, first, the construction of simple models that embody important theoretical ideas, and then, the critical comparison of these models with all relevant experimental data. It follows that a phenomenologist must combine a broad understanding of theory with a complete knowledge of current and future feasible experiments in order to allow him to interact meaningfully with both major branches of a science. The impact of phenomenology is felt in both theory and experiment. Thus it can pinpoint unexpected experimental observations and so delineate areas where new theoretical ideas are needed. Further, it can suggest the most useful experiments to be done to test the latest theories. This is especially important in these barren days where funds are limited, experiments take many "physicist-years" to complete, and theories are multitudinous and complicated. Phenomenology is applicable in many sciences but this conference was organized with the hope of emphasizing the wide scope and importance of phenomenology in particle physics. In fact, in the time available, not even all the important applications to particle physics could be covered. Some of these omissions were repaired in a workshop, held at Caltech just after the main conference reported here, and devoted to physics at intermediate energies (~< 5 GeV). This area is particularly suitable for phenomenology as the qualitative features have been well explored and further progress demands difficult experiments with high statistics. Phenomenology can indicate, for instance, which of the some hundred (quasi) two body reactions will be most fruitful to study. In the following we map some of the more active fields of phenomenology indicating where they have been covered in either the present volume, our companion workshop, or elsewhere. The contents of the current volume are summarized in more detail in the abstracts of the invited papers which have been collected together in pages xi to xvi. We are indebted to many people for making this conference possible: Professor R.B. Leighton for his generous sponsorship; Nancy Hopkins and James Black of the Caltech Alumni Office for their efficient and cheerful organization; the session chairmen, M. Gell-Mann, W. Selove, J.D. Bjorken, M.J. Moravcsik, J.D. Jackson, T. Ferbel, R.L. Walker and S.C. Frautschi, for the smooth running of the conference; Susan Berger for her delightful cover; and our secretaries for their careful typing, with an especial thank you to Chris St.Clair who also drew the amusing illustrations. Alvin Tollestrup originally had the good idea of holding a phenomenology conference: We are grateful to him and our colleagues at Caltech for the encouragement which has made the organization and editing of this conference so enjoyable

Structural and Functional Evaluation of C. elegans Filamins FLN-1 and FLN-2

Filamins are long, flexible, multi-domain proteins composed of an N-terminal actin-binding domain (ABD) followed by multiple immunoglobulin-like repeats (IgFLN). They function to organize and maintain the actin cytoskeleton, to provide scaffolds for signaling components, and to act as mechanical force sensors. In this study, we used transcript sequencing and homology modeling to characterize the gene and protein structures of the C. elegans filamin orthologs fln-1 and fln-2. Our results reveal that C. elegans FLN-1 is well conserved at the sequence level to vertebrate filamins, particularly in the ABD and several key IgFLN repeats. Both FLN-1 and the more divergent FLN-2 colocalize with actin in vivo. FLN-2 is poorly conserved, with at least 23 IgFLN repeats interrupted by large regions that appear to be nematode-specific. Our results indicate that many of the key features of vertebrate filamins are preserved in C. elegans FLN-1 and FLN-2, and suggest the nematode may be a very useful model system for further study of filamin function

Proposal to study multiparticle-peripheral hadron physics at NAL

We propose to build a large wire chamber magnetic spectrometer at NAL to measure multi-body forward-going hadronic systems produced by {pi}'s, K's and protons up to 80 GeV/c. Specific reactions will be isolated in order to study the s and t dependencies of the cross sections for peripheral processes, search for new resonant states and attempt to measure {pi}{pi} and K{pi} inelastic scattering. We propose a physics program for the spectrometer which is initially limited to those processes easiest to measure and which nevertheless spans a large range of strong interaction problems. Technically, the proposed spectrometer is a relatively modest extension of presently operating systems in the 10-20 GeV/c region, and does not present a challenge of uncertain magnitude to construct

Impact of Optimized Breastfeeding on the Costs of Necrotizing Enterocolitis in Extremely Low Birthweight Infants

To estimate risk of NEC for ELBW infants as a function of preterm formula and maternal milk (MM) intake and calculate the impact of suboptimal feeding on NEC incidence and costs