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Articles 31 - 45 of 45
Full-Text Articles in Life Sciences
The Cold Shock Domain Protein Lin-28 Controls Developmental Timing In C. Elegans And Is Regulated By The Lin-4 Rna, Eric Moss, Rosalind Lee, Victor Ambros
The Cold Shock Domain Protein Lin-28 Controls Developmental Timing In C. Elegans And Is Regulated By The Lin-4 Rna, Eric Moss, Rosalind Lee, Victor Ambros
Victor R. Ambros
Mutations in the heterochronic gene lin-28 of C. elegans cause precocious development where diverse events specific to the second larval stage are skipped. lin-28 encodes a cytoplasmic protein with a cold shock domain and retroviral-type (CCHC) zinc finger motifs, consistent with a role for LIN-28 in posttranscriptional regulation. The 3'UTR of lin-28 contains a conserved element that is complementary to the 22 nt regulatory RNA product of lin-4 and that resembles seven such elements in the 3'UTR of the heterochronic gene lin-14. Both lin-4 activity and the lin-4-complementary element (LCE) are necessary for stage-specific regulation of lin-28. Deleting the LCE …
Heterochronic Genes, Victor Ambros
Heterochronic Genes, Victor Ambros
Victor R. Ambros
This chapter focuses on our current understanding of the C. elegans heterochronic gene pathway as determined by genetic characterization of the regulatory interactions among the genes (Ambros and Horvitz 1987; Ambros 1989; Liu and Ambros 1989) and recent progress on the cloning, sequencing, and molecular analysis of genes involved in this pathway (Ruvkun et al. 1989; Arasu et al. 1991; Papp et al. 1991; Wightman et al. 1991; Lee et al. 1993; Rougvie and Ambros 1995; E. Moss et al., in prep). Primary emphasis is placed on the developmental decisions controlled by the heterochronic genes, the regulatory interactions among genes …
Reversal Of Cell Fate Determination In Caenorhabditis Elegans Vulval Development, Susan Euling, Victor Ambros
Reversal Of Cell Fate Determination In Caenorhabditis Elegans Vulval Development, Susan Euling, Victor Ambros
Victor R. Ambros
In Caenorhabditis elegans, the fates of the multipotent vulval precursor cells (VPCs) are specified by intercellular signals. The VPCs divide in the third larval stage (L3) of the wild type, producing progeny of determined cell types. In lin-28 mutants, vulva development is similar to wild-type vulva development except that it occurs precociously, in the second larval stage (L2). Consequently, when lin-28 hermaphrodites temporarily arrest development at the end of L2 in the dauer larva stage, they have partially developed vulvae consisting of VPC progeny. During post-dauer development, these otherwise determined VPC progeny become reprogrammed back to the multipotent, signal-sensitive state …
Heterochronic Genes Control Cell Cycle Progress And Developmental Competence Of C. Elegans Vulva Precursor Cells, Susan Euling, Victor Ambros
Heterochronic Genes Control Cell Cycle Progress And Developmental Competence Of C. Elegans Vulva Precursor Cells, Susan Euling, Victor Ambros
Victor R. Ambros
Heterochronic genes control the timing of vulval development in the C. elegans hermaphrodite. lin-14 or lin-28 loss-of-function mutations cause the vulval precursor cells (VPCs) to enter S phase and to divide one larval stage earlier than in the wild type. A precocious vulva is formed by essentially normal cell lineage patterns, governed by the same intercellular signals as in the wild type. Mutations that prevent the normal developmental down-regulation of lin-14, activity delay or block VPC division and prevent vulval differentiation. A genetic pathway that includes lin-4, lin-14, and lin-28 controls when VPCs complete G1 and also controls when VPCs …
The Heterochronic Gene Lin-29 Encodes A Zinc Finger Protein That Controls A Terminal Differentiation Event In Caenorhabditis Elegans, Ann Rougvie, Victor Ambros
The Heterochronic Gene Lin-29 Encodes A Zinc Finger Protein That Controls A Terminal Differentiation Event In Caenorhabditis Elegans, Ann Rougvie, Victor Ambros
Victor R. Ambros
A hierarchy of heterochronic genes, lin-4, lin-14, lin-28 and lin-29, temporally restricts terminal differentiation of Caenorhabditis elegans hypodermal seam cells to the final molt. This terminal differentiation event involves cell cycle exit, cell fusion and the differential regulation of genes expressed in the larval versus adult hypodermis. lin-29 is the most downstream gene in the developmental timing pathway and thus it is the most direct known regulator of these diverse processes. We show that lin-29 encodes a protein with five zinc fingers of the (Cys)2-(His)2 class and thus likely controls these processes by regulating transcription in a stage-specific manner. Consistent …
The Caenorhabditis Elegans Heterochronic Gene Pathway Controls Stage-Specific Transcription Of Collagen Genes, Zhongchi Liu, Susan Kirch, Victor Ambros
The Caenorhabditis Elegans Heterochronic Gene Pathway Controls Stage-Specific Transcription Of Collagen Genes, Zhongchi Liu, Susan Kirch, Victor Ambros
Victor R. Ambros
In Caenorhabditis elegans, the terminal differentiation of the hypodermal cells occurs at the larval-to-adult molt, and is characterized in part by the formation of a morphologically distinct adult cuticle. The timing of this event is controlled by a pathway of heterochronic genes that includes the relatively direct regulatory gene, lin-29, and upstream genes lin-4, lin-14 and lin-28. Using northern analysis to detect endogenous collagen mRNA levels and collagen/lacZ reporter constructs to monitor collagen transcriptional activity, we show that the stage-specific switch from larval cuticle to adult cuticle correlates with the transcriptional activation of adult-specific collagen genes and repression of larval-specific …
Heterochronic Genes And The Temporal Control Of C. Elegans Development, Victor Ambros, Eric Moss
Heterochronic Genes And The Temporal Control Of C. Elegans Development, Victor Ambros, Eric Moss
Victor R. Ambros
The heterochronic genes of Caenorhabditis elegans encode part of a regulatory system that controls the temporal component of cell fates in development. The genes have been characterized genetically and molecularly, and their study has so far revealed a genetic hierarchy that specifies sequences of developmental events, a novel RNA-mediated mechanism of gene regulation and a reprogramming phenomenon associated with arrested development.
The C. Elegans Heterochronic Gene Lin-4 Encodes Small Rnas With Antisense Complementarity To Lin-14, Rosalind Lee, Rhonda Feinbaum, Victor Ambros
The C. Elegans Heterochronic Gene Lin-4 Encodes Small Rnas With Antisense Complementarity To Lin-14, Rosalind Lee, Rhonda Feinbaum, Victor Ambros
Victor R. Ambros
lin-4 is essential for the normal temporal control of diverse postembryonic developmental events in C. elegans. lin-4 acts by negatively regulating the level of LIN-14 protein, creating a temporal decrease in LIN-14 protein starting in the first larval stage (L1). We have cloned the C. elegans lin-4 locus by chromosomal walking and transformation rescue. We used the C. elegans clone to isolate the gene from three other Caenorhabditis species; all four Caenorhabditis clones functionally rescue the lin-4 null allele of C. elegans. Comparison of the lin-4 genomic sequence from these four species and site-directed mutagenesis of potential open reading frames …
Efficient Gene Transfer In C.Elegans: Extrachromosomal Maintenance And Integration Of Transforming Sequences, Craig Mello, James Cramer, Dan Stinchcomb, Victor Ambros
Efficient Gene Transfer In C.Elegans: Extrachromosomal Maintenance And Integration Of Transforming Sequences, Craig Mello, James Cramer, Dan Stinchcomb, Victor Ambros
Victor R. Ambros
We describe a dominant behavioral marker, rol-6(su-1006), and an efficient microinjection procedure which facilitate the recovery of Caenorhabditis elegans transformants. We use these tools to study the mechanism of C.elegans DNA transformation. By injecting mixtures of genetically marked DNA molecules, we show that large extrachromosomal arrays assemble directly from the injected molecules and that homologous recombination drives array assembly. Appropriately placed double-strand breaks stimulated homologous recombination during array formation. Our data indicate that the size of the assembled transgenic structures determines whether or not they will be maintained extrachromosomally or lost. We show that low copy number extrachromosomal transformation can …
Alternative Temporal Control Systems For Hypodermal Cell Differentiation In Caenorhabditis Elegans, Zhongchi Liu, Victor Ambros
Alternative Temporal Control Systems For Hypodermal Cell Differentiation In Caenorhabditis Elegans, Zhongchi Liu, Victor Ambros
Victor R. Ambros
Beginning of article: In certain multicellular organisms, genetic regulatory systems that specify the timing of cell division, differentiation and morpho-genesis must accommodate environmental and physiological contingencies that perturb or arrest development. For example, Caenorhabditis elegans can either develop continuously through four larval stages (L1–L4) or arrest indefinitely as a 'dauer larva' at the second larval (L2) moult, and later resume L3 and L4 development. At the larva-to-adult (L4) moult of both con-tinuous and 'post-dauer' development, hypodermal cells switch (the 'L/A switch') from a proliferating state to the terminally differentiated state. Four temporal regulators, lin-4, lin-14, lin-28 and lin-29, have been …
Molecular Cloning Of Lin-29, A Heterochronic Gene Required For The Differentiation Of Hypodermal Cells And The Cessation Of Molting In C.Elegans, A. Papp, A. Rougvie, Victor Ambros
Molecular Cloning Of Lin-29, A Heterochronic Gene Required For The Differentiation Of Hypodermal Cells And The Cessation Of Molting In C.Elegans, A. Papp, A. Rougvie, Victor Ambros
Victor R. Ambros
The lin-29 gene product of C.elegans activates a temporal developmental switch for hypodermal cells. Loss-of-function lin-29 mutations result in worms that fail to execute a stage-specific pattern of hypodermal differentiation that includes exist from the cell cycle, repression of larval cuticle genes, activation of adult cuticle genes, and the cessation of molting. Combined genetic and physical mapping of restriction fragment length polymorphisms (RFLPs) was used to identify the lin-29 locus. A probe from the insertion site of a Tc1 (maP1), closely linked and to the left of lin-29 on the genetic map, was used to identify a large set of …
A New Kind Of Informational Suppression In The Nematode Caenorhabditis Elegans, Jonathan Hodgekin, Andrew Papp, Rock Pulak, Victor Ambros, Philip Anderson
A New Kind Of Informational Suppression In The Nematode Caenorhabditis Elegans, Jonathan Hodgekin, Andrew Papp, Rock Pulak, Victor Ambros, Philip Anderson
Victor R. Ambros
Independent reversions of mutations affecting three different Caenorhabditis elegans genes have each yielded representatives of the same set of extragenic suppressors. Mutations at any one of six loci act as allele-specific recessive suppressors of certain allels of unc-54 (a myosin heavy chain gene), lin-29 (a heterochronic gene), and tra-2 (a sex determination gene). The same mutations also suppress certain alleles of another sex determination gene, tra-1, and of a morphogenetic gene, dpy-5. In addition to their suppression phenotype, the suppressor mutations cause abnormal morphogenesis of the male bursa and the hermaphrodite vulva. We name these genes smg-1 through smg-6 (suppressor …
A Hierarchy Of Regulatory Genes Controls A Larva-To-Adult Developmental Switch In C. Elegans, Victor Ambros
A Hierarchy Of Regulatory Genes Controls A Larva-To-Adult Developmental Switch In C. Elegans, Victor Ambros
Victor R. Ambros
The heterochronic genes lin-4, lin-14, lin-28, and lin-29 control the timing of specific postembryonic developmental events in C. elegans. The experiments described here examine how these four genes interact to control a particular stage-specific event of the lateral hypodermal cell lineages. This event, termed the "larva-to-adult switch" (L/A switch), involves several coordinate changes in the behavior of hypodermal cells at the fourth molt: cessation of cell division, formation of adult (instead of larval) cuticle, cell fusion, and cessation of the molting cycle. The phenotypes of multiply mutant strains suggest a model wherein the L/A switch is controlled by the stage-specific …
Molecular Genetics Of The Caenorhabditis Elegans Heterochronic Gene Lin-14, Gary Ruvkun, Victor Ambros, Alan Coulson, Robert Waterston, John Sulston, H. Horvitz
Molecular Genetics Of The Caenorhabditis Elegans Heterochronic Gene Lin-14, Gary Ruvkun, Victor Ambros, Alan Coulson, Robert Waterston, John Sulston, H. Horvitz
Victor R. Ambros
We describe a general strategy for the genetic mapping in parallel of multiple restriction fragment length polymorphism (RFLP) loci. This approach allows the systematic identification for cloning of physical genetic loci within about 100 kb of any gene in Caenorhabditis elegans. We have used this strategy of parallel RFLP mapping to clone the heterochronic gene lin-14, which controls the timing and sequence of many C. elegans postembryonic developmental events. We found that of about 400 polymorphic loci in the C. elegans genome associated with the Tc1 family of repetitive elements, six are within 0.3 map unit of lin-14. The three …
Heterochronic Mutants Of The Nematode Caenorhabditis Elegans, Victor Ambros, R. Horvitz
Heterochronic Mutants Of The Nematode Caenorhabditis Elegans, Victor Ambros, R. Horvitz
Victor R. Ambros
Mutations in the Caenorhabditis elegans genes lin-14, lin-28, and lin-29 cause heterochronic developmental defects: the timing of specific developmental events in several tissues is altered relative to the timing of events in other tissues. These defects result from temporal transformations in the fates of specific cells, that is, certain cells express fates normally expressed by cells generated at other developmental stages. The identification and characterization of genes that can be mutated to cause heterochrony support the proposal that heterochrony is a mechanism for phylogenetic change and suggest cellular and genetic bases for heterochronic variation.