Biomedical subjects

G Seydoux

Publications and source records attributed to G Seydoux.

23 records · Page 2Linked to original sources

PubMed1993

Isolation and characterization of mutations causing abnormal eversion of the vulva in Caenorhabditis elegans.

In Caenorhabditis elegans hermaphrodites, morphogenesis of the vulva culminates in a process called vulval eversion, whereby a passageway is made from the uterus through the vulva to the outside of the animal. We have screened for mutations causing abnormal eversion of the vulva (evl mutations) to identify new genes involved in vulval development, and found that evl mutants are relatively common after EMS mutagenesis. We also hoped to identify genes involved in lin-12-mediated cell fate decisions, since lin-12 null mutants have abnormally everted vulvae, but none of the 68 evl mutations recovered in our screen appeared to be good candidates for genes that function with lin-12. Initial genetic and phenotypic analysis of 30 evl mutations revealed that all affect the development of the uterus, but only some affect the vulval precursor cell lineages. We used laser ablation to show that the uterus and anchor cell are important for correct vulval eversion in wild type; the anchor cell is important early in the L3 stage, before the vulval cells have been generated, but not later, when vulval eversion occurs. We conclude that certain evl mutations may influence vulval eversion by primarily affecting the development of the somatic gonad, while others may affect processes required in the development of both structures.

Alleles↗

PubMed1991

Interaction between ran1+ protein kinase and cAMP dependent protein kinase as negative regulators of fission yeast meiosis.

In fission yeast, meiosis is initiated by transcriptional activation of the mei3+ gene under the combined influence of the four mating type genes. The mei3+ gene product acts as a meiotic inducer by binding to and inhibiting the ran1+ protein kinase. Inactivation of ran1+ kinase is both necessary and sufficient to allow meiotic differentiation. We describe a class of mutants which are unable to undergo both normal meiosis and meiosis induced by inactivation of ran1+. In addition to these defects, the cells are sterile and unable to enter stationary phase. We have determined that the mutants define two complementation groups, designated cgs1+ and cgs2+ (continues to grow in stationary). The wild type allele of each gene has been isolated and sequence analysis of cgs1+ shows that it encodes a protein homologous to the regulatory subunit of cyclic AMP dependent protein kinase (cAPK). Biochemical studies demonstrate that in cgs1-1 containing cells, cAPK activity is unregulated by cyclic AMP (cAMP). Sequence analysis of cgs2+ shows that the predicted protein it encodes shares homology with a phosphodiesterase from Dictyostelium discoideum and biochemical studies demonstrate that cells containing a mutant allele of cgs2+ have elevated levels of cAMP. Thus, both genes encode proteins that regulate the activity of cAPK. We have previously shown that cells overproducing ran1+ kinase are meiotically defective. Here, we provide direct evidence that the meiotic defect caused by either unregulated cAPK activity or unregulated ran1+ kinase activity is due to inability to induce transcription of the mei2+ gene, which is required for meiotic initiation. We propose that the switch from vegetative growth to meiosis in fission yeast requires inactivation of ran1+ kinase and is prevented by unregulated levels of cAPK.

Amino Acid Sequence↗

PubMed1990

Analysis of gain-of-function mutations of the lin-12 gene of Caenorhabditis elegans.

Certain cell fate decisions are specified by cell-cell interactions during the development of the nematode Caenorhabditis elegans. For example, in a wild-type hermaphrodite gonad, two cells, Z1.ppp and Z4.aaa, have the potential to become the anchor cell (AC). Intercellular communication establishes their fates and ensures that only one cell becomes the AC, while the other becomes a ventral uterine precursor cell (VU). One component of this intercellular communication seems to be the 'AC-to-VU' signal from the presumptive AC that causes the other cell to become a VU. Genetic and developmental studies indicated that the lin-12 gene specifies the fates of Z1.ppp and Z4.aaa. Molecular studies suggest that lin-12 directly participates in their communications, perhaps acting as the receptor for the 'AC-to-VU' signal. Here, we report the molecular lesions associated with lin-12 gain-of-function mutations, cell isolation experiments, and genetic studies of an unusual lin-12 allele. These data suggest that self-association of the putative lin-12-encoded receptor leads to its activation, and that certain gain-of-function mutations result in ligand-independent activation.

Alleles↗

PubMed1990

Cell-cell interactions prevent a potential inductive interaction between soma and germline in C. elegans.

In each gonadal arm of wild-type C. elegans hermaphrodites, the somatic distal tip cell (DTC) maintains distal germline nuclei in mitosis, while proximal nuclei enter meiosis. We have identified two conditions under which a proximal somatic cell, the anchor cell (AC), inappropriately maintains proximal germline nuclei in mitosis: when defined somatic gonadal cells have been ablated in wild type, and in lin-12 null mutants. Laser ablations and mosaic analysis indicate that somatic gonadal cells neighboring the AC normally require lin-12 activity to prevent the inappropriate AC-germline interaction. The AC-germline interaction, like the DTC-germline interaction, requires glp-1 activity. In one model, we propose that the AC sends an intercellular signal intended to interact with the lin-12 product in somatic gonadal cells; when lin-12 activity is absent, the signal interacts instead with the related glp-1 product in germline. Our data illustrate the importance of mechanisms that prevent inappropriate interactions during development.

Animals↗

PubMed1989

Cell autonomy of lin-12 function in a cell fate decision in C. elegans.

The lin-12 gene of C. elegans encodes a predicted transmembrane protein that controls a decision by two cells, Z1.ppp and Z4.aaa, between the anchor cell (AC) and ventral uterine precursor cell (VU) fates. We performed laser ablation experiments to demonstrate that specification of the VU fate of Z1.ppp or Z4.aaa depends on an "AC-to-VU" signal from the presumptive AC. We generated genetic mosaics in which defined cells lacked lin-12 activity. By correlating the fates of Z1.ppp and Z4.aaa with the lin-12 genotype of nearly every cell in these mosaics, we conclude that lin-12 function is VU cell autonomous. We present a model in which lin-12 functions in the receiving mechanism for the "AC-to-VU" signal leading to the specification of the AC and VU fates of Z1.ppp and Z4.aaa.

Animals↗