ISSN:0192-253X    

DOI:10.1002/dvg.1020140502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA partial cDNA encoding a novel putative p2, ras guanine nucleotide release‐inducing factor (GRF), GRF2, was amplified from murine embryonic stem cells. The presumptive catalytic region of GRF2 is related to the yeast Ras GRF encoded byCDC25.GRF2 is 80% identical to murineCDC25Mm/ras‐GRF, but is more similar to yeastCDC25than to otherrasGRFs related to theDrosophila son of sevenlessgene product. A 9‐kb GRF2 messenger RNA was highly expressed in brain, but GRF2‐specific antibodies recognized apparent GRF2 proteins in various mouse tissues in addition to brain. Thus GRF2 represents a novel widely‐expressed protein that is highly related toCDC25Mm/ras‐GRF, at least in its catalytic domain. Both GRF2 andCDC25Mm/ras‐GRF are expressed in murine embryonic stem cells, suggesting that different Ras activators may regulateras‐dependent proliferation and differentiation in early mouse development. © 199

ISSN:0192-253X    

DOI:10.1002/dvg.1020140503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractTherap1gene ofDictyostelium discoideumis a member of theras‐gene superfamily of low molecular weight GTPase proteins. Theraplgene is expressed both during growth and development inD. discoideum.To examine the action of the Rapl protein inD. discoideum, therap1cDNA was expressed under the control of the induciblediscoidinpromoter. Treatment with conditioned media, which induces thediscoidinpromoter, increased Rap1 protein levels in vegetative cells approximately six fold. Overexpression of the Rapl protein correlated with the appearance of morphologically aberrant vegetative amoebae: cells were extensively spread and flattened. The distribution of F‐actin was altered in these cells, with an increase in actin staining around the cell periphery. Induction of thediscoidinpromoter by starvation in therapltransformants also resulted in spread flat cells. When starvedD. discoideumamoebae are refed with HL5 media, the cells rapidly respond by rounding up. By contrast, therapltransformant cells showed a pronounced delay in rounding up. Rapid tyrosine phosphorylation of a p45 protein occurred in both control cells and therapltransformant upon refeeding, implying that the signal transduction pathway leading to tyrosine phosphorylation remained functional in therapltransformant. We propose that the Rapl protein functions in the regulation of cell morphology inD. discoideum. © 1993Wiley‐Lis

ISSN:0192-253X    

DOI:10.1002/dvg.1020140504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractMyosin heavy chain (MHC) is encoded by a multigene family containing members which are expressed in developmental and fiber type‐specific patterns. In developing rats, primary (1°) and secondary (2°) myotjbes can be disfinguished by differences in MHC expression: 1° myotubes coexpress embryonic and slow MHC, while 2° myotubes initially express only embryonic MHC. We have used monoclonal antibodies which recognize the embryonic, slow, neonatal, and adult fast IIB/IIX MHCs to examine MHC accumulation in myoblasts obtained from hindlimbs of embryonic day (ED) 14 and ED 20 Sprague‐Dawley rats during differentiation in vitro. Embryonic myoblasts (ED 14), which develop into 1° myotubes in vivo, differentiate as myocytes or small myotubes (i.e., 1–4 nuclei) which express both embryonic and slow MHC. They do not accumulate detectable levels of neonatal or adult fast IIB/IIX MHC. Fetal myoblasts, which develop into secondary myotubes in vivo, fuse to form large myotubes (i.e., 10–50 nuclei) and express predominantly embryonic MHC at 3 days in culture. These myotubes accumulate neonatal and adult fast IIB/IIX isoforms of MHC and eventually contract spontaneously. In contrast to embryonic myotubes, they do not accumulate slow MHC. Our results demonstrate that embryonic and fetal rat myoblasts express different phenotypes in vitro and suggest that they represent distinct myoblast lineages similar to those previously described in chickens and mice. These two lineages may be responsible for the generation of distinct populations of 1° and 2° myotubes in vivo. © 1993

ISSN:0192-253X    

DOI:10.1002/dvg.1020140505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe ecdysoneless locus inDrosophila melanogasterhas been defined previously by a single conditional mutation, I(3)ecd1, that causes an ecdysteroid deficit and larval death at the restrictive temperature, 29°C, although the primary role of the mutation in developmental processes has been unclear. Gene dosage and complementation studies reported here forecd1and five nonconditional lethal alleles indicate that theecdlocus plays prezygotic and postzygotic roles essential for normal embryonic development, the successful completion of each larval molt, adult eclosion, and female fertility. Theecdlocus is also required for normal macrochaete differentiation. For each observed phenotype, the severity of mutational effects was correlated withecdmutant genotypes. In all cases,ecd1homozygotes were least affected. Mutants heteroallelic forecd1and any one of four nonconditional recessive mutations were more severely affected thanecd1homozy‐gotes, revealing these as hypomorphic alleles. For all phenotypic effects, mutants heteroallelic forecd1and a dominant mutation(ecd3D)were most severely affected. These individuals died during embryogenesis at 29°C and developed no macrochaetes on the dorsal thorax when transferred to 29°C during the white prepupal stage. Theecd3Dmutation also caused female semisterility in heterozygotes. Ecdysteroid regulation has been implicated previously in all the developmental processes disrupted by theseecdmutations except for macrochaete differentiation. © 1993 Wiley‐Li

ISSN:0192-253X    

DOI:10.1002/dvg.1020140506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe subtelomeric regions of macronuclear gene‐sized DNA molecules fromStylonychia lemnaewere analyzed. The results obtained indicate that these regions show a highly ordered and common sequence organization: Immediately adjacent to the telomeric sequence a short inverted repeat sequence is found, followed by another 7–9 bp inverted repeat sequence at approximately position 40. A 10 bp consensus sequence found in the subtelomeric regions of all gene‐sized DNA molecules is found at approximately position 60 and in addition at about the same position palindromic sequences showing no homology to each other are localized. The biological significance of this sequence organization is discussed. © 1993Wiley‐L

ISSN:0192-253X    

DOI:10.1002/dvg.1020140507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractEmbryos of the axolotl affected with thecardiac‐lethalmutation form hearts that never begin to beat. A number of other traits characteristic of the mutant phenotype, including edema, underdeveloped gills, shorter stature, and aphagia (the inability to feed), were believed to be secondary effects of the absence of circulation. We have recently demonstrated that the pre‐cardiac mesoderm is directly affected by thecgene, making it unresponsive to normal inductive signals. In this study, we replaced part or all of the mutant pre‐cardiac mesoderm with wild‐type tissue, to produce embryos with normally beating hearts and circulation. As expected, most of the other mutant characteristics were also corrected. However, otherwise normal individuals remained aphagic. All embryos with beating hearts containing mutant tissue also suffered from an unexpected circulatory arrest some time after the onset of circulation. This apparently indicates that there are at least two tissues other than the myocardium which appear to be directly affected by thecgene. These previously unsuspected pleiotropic effects of the mutation may involve poorly‐characterized mesodermal‐neural crest inductive interactions and may also lead to a greater understanding of the link between congenital heart defects and feeding difficulties in humans. © 1993Wil

ISSN:0192-253X    

DOI:10.1002/dvg.1020140508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIt had not previously been known whether synthesis of nuclear‐encoded mitochondrial subunits occurs in pre‐implantation embryos. We have used cytoplasmic injections of antisense RNA transcribed in vitro to study this question. Capped, in vitro transcribed RNA antisense to either cytochrome coxidase subunit IV or VIIc injected into each cell at the two‐cell stage markedly inhibited synthesis of adenine nucleotides by the 8‐ to 16‐cell stage, whereas injection of the cognate sense RNAs gave levels similar to those previously published for normal embryos. These results strongly suggest that translation of nuclear‐encoded mRNAs for mitochondrial subunits is required during pre‐implantation development. It was of additional interest that, not only was ATP decreased, but ADP and AMP as well, with the effect that the charge ratio remained constant. The results also suggest, therefore, that the mechanism by which cells normally regulate their charge ratio, thought to be with adenylate deaminase, is already in place. © 1993W

ISSN:0192-253X    

DOI:10.1002/dvg.1020140509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractPrevious studies of newly synthesized proteins during early development in sea urchins have revealed several different patterns of synthesis that can be used to predict the existence of mRNA classes with distinct regulatory controls. We have identified clones for abundant maternal mRNAs that are actively translated during early development by screening a cDNA library prepared from polysomal poly(A) + RNA isolated from 2‐cell stage (2‐hour)Strongylocentrotus purpuratusembryos. Probes prepared from these cDNA clones and several previously characterized maternal mRNA cDNAs were used to compare relative levels of individual mRNAs in eggs and embryos and their translational status at various developmental stages. These abundant mRNAs can be classified into two major groups which we have termed cleavage stage‐specific (CSS) and post cleavage stage (PCS) mRNAs. The relative levels of the CSS mRNAs are highest during the rapid cleavage stage and decrease dramatically at the blastula stage (12‐hours). In contrast, PCS mRNAs are present at relatively low levels during the rapid cleavage stage and then increase at the blastula stage. Polysome partition profiles reveal that CSS mRNAs are translated more efficiently than PCS mRNAs in the unfertilized egg, at fertilization, and during the cleavage stages. Following the blastula stage, some CSS transcripts move out of polysomes and accumulate as untranslated RNAs, while newly transcribed PCS mRNAS are recruited into polysomes. These data suggest that the rapid cell cycles following fertilization require high levels of specific cleavage stage proteins, and the synthesis of these proteins occurs preferentially over PCS mRNAs. © 1993Wiley

ISSN:0192-253X    

DOI:10.1002/dvg.1020140510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020140501

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY