Use of an expression library to clone genes by complemcntation. RE. Palmer and P.W. Sternberg, HHMI and Division of Biology, Caltech, Pasadena, CA 91125
Specification of vulval cell fates by sequential signaling pathways Jeffrey S. Simske and Stuart K. Kim, Dept. of Developmental Biology, Stanford University Medical Center, Stanford CA 94305
Evolution of vulva-formation: Part II: Species with a central vulva Ralf J. Sommer & Paul W. Sternberg, California Institute of Technology, Division of Biology 156-29, Pasadena, CA 91125
Activity of the polyray-1 maintenance gene must be overcome to allow for correct temporal expression of HOM-C genes Julin Maloof and Cynthia Kenyon, Dept of Biochemistry, UCSF, San Francisco, CA 94143 0554
In these studies we have purified and characterized two proteins involved in Ca-regulation in Caenorhabditis st is calmodulin (CaM) which is considered to be an intracellular receptor for calcium because of the large number of cellular processes it activates in a Ca-dependent manner. The second protein which is similar to CaM in many of its physical and chemical properties, we have called the troponin-C like protein (TnCLP) . Because of a report which suggested invertebrate CaMs are dissimilar to those of vertebrates our studies on C. elegans CaM have focused on a comparison of its properties to those of bovine brain CaM. The C. elegans protein shows no major difference in amino acid composition, cyanogen bromide (CNBr) peptide maps, electrophoretic behavior or enzymatic properties in those studies. The C. elegans TnCLP, which copurifies with the CaM until DE-52 ion exchange chromatography, can be distinguished from CaM. It differs in amino acid composition, CNBr peptide maps and molecular weight, and lacks the ability to activate bovine brain cyclic nucleotide phosphodiesterase. Our concern with it has centered about defining its possible physiological roles. TnCLP forms Ca-dependent complexes with rabbit fast skeletal muscle troponin I and troponin T. It copurifies with thin myofilaments. These observations coupled with its inability to activate bovine brain cyclic nucleotide phosphodiesterase suggest that C. elegans TnCLP is not a second generalized Ca-dependent activator like CaM, but functions as a troponin C. We believe that the C. elegans TnCLP and CaM are responsible for the 2 thin and thick myofilament Ca-regulation that has been reported in C. elegans. The TnCLP acting in a troponin-like complex to regulate thin filaments. The CaM acting on thick filaments through a myosin light chain kinase as has been reported for other actomyosin contractile systems. In support of that later contention we have shown that there is an in vitro Ca and CaM dependent phosphorylation of one of the C. elegans myosin light chains. We expect these studies will serve as the basis for elucidating the Ca-dependent events in muscle contraction (as well as in other processes) both in vivo and in vitro through the analysis of genetic variants of C. elegans that may be blocked in different steps or pathways of Ca-regulation.
Evolution of vulva formation: Part IV: Variation in AC position can cause a shift of vulva formation towards p(4- 6).p Ralf J. Sommer & Paul W. Sternberg, HHMI & California Institute of Technology, Division of Biology 156-29, Pasadena, CA
Using Ascaris as a model system, we are studying ionic mechanisms of the spontaneous electrical activity in nematode somatic muscle. The fast spike potentials appear to be Ca+2 mediated; their amplitude depends on the external Ca+2 concentration, they are TTX insensitive, they persist when Na+ is replaced by Tris+, choline+, or Cs+, and they are blocked by Co+2 and La+3. When the normal solution is replaced by one containing 11 mM Ba+2 and 0.15 mM Ca+2 as the only divalent cations, the slow waves underlying the normal spike activity appear to increase dramatically in amplitude and duration; spike activity gradually disappears. The duration and amplitude of the slow waves at steady state under these conditions increase with Ba+2 concentration, reaching values of 1-2 minutes and 50-60 mV, respectively, in 26 mM Ba+2. These results and others lead us to conclude that the slow waves are also Ca+2 mediated. The muscles are depolarized by 0.1 mM ouabain, suggesting some involvement of an electrogenic pump in maintaining the membrane potential. TEA, in concentrations as low as 1 mM, has pronounced effects on the spontaneous myogenic activity, consistent with the effects observed when TEA is injected iontophoretically into C. elegans.
Dpy-27: A Protein Required for Dosage Compensation Is Associated with the X chromosome in XX Animals Pao-Tien Chuangl, Donna Albertson2 and Barbara Meyerl, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720~ and MRC Laboratory of Molecular biology, Hills Road, Cambridge, CB2 2QH UK2