The C. elegans E2F- and DP-Related Proteins Are Required for Embryonic Asymmetry and Negatively Regulate Ras/MAPK Signaling

Abstract

Early C. elegans embryos exhibit protein asymmetries that allow rapid diversification of cells. Establishing these asymmetries requires the novel protein MEX-5. We show that mutations in the efl-1 and dpl-1 genes cause defects in protein localization resembling defects caused by mutations in mex-5. efl-1 and dpl-1 encode homologs of vertebrate E2F and DP proteins that regulate transcription as a heterodimer. efl-1 and dpl-1 mutants have elevated levels of activated Map kinase in oocytes. Their mutant phenotype and that of mex-5 mutants can be suppressed by reducing Ras/Map kinase signaling. We propose this signaling pathway has a role in embryonic asymmetry and that EFL-1/DPL-1 control the level of Map kinase activation.

Multiple Functions and Dynamic Activation of MPK-1 Extracellular Signal-Regulated Kinase Signaling inCaenorhabditis elegansGermline Development

“…Comparing -1 oocyte stage with dpMPK-1 level, we found that 100% of early -1 oocytes (dispersed diakinesis bivalents, low chromosomal AIR-2 staining) have high dpMPK-1 while .85% of late -1 oocytes (congressed bivalents, high chromosomal AIR-2 staining) have very low dpMPK-1 (Figure 4, B and C; supplemental Table 2). This is consistent with observations of Page et al (2001) who reported that, by completion of MI, dpMPK-1 is not detectable. Thus, as the -1 oocyte undergoes maturation, there is a rapid and dramatic fall in dpMPK-1 level.…”

“…To distinguish between these possibilities, we employed the monoclonal antibody MAPKYT (Sigma; Miller et al 2001;Page et al 2001;Ohmachi et al 2002) to detect the diphosphorylated activated form of MPK-1 (dpMPK-1), while to detect total MPK-1 we used a fraction of the SC94 antibody (Santa Cruz) that was affinity purified to show low cytological cross-reactivity in mpk-1(ga117) null germlines (see materials and methods and supplemental data at http://www.genetics.org/supplemental/ for further antibody characterization). In wild-type hermaphrodites 24 hr post mid-L4, total MPK-1 is found throughout the germline, with slightly lower levels in the distal-most end and slightly higher levels in the proximal region ( Figure 1A; supplemental Figure 2A).…”

“…Molecular markers that allow stages of germline development to be more fully defined and the sex of immature germ cells to be determined have also been identified. An initial description of the pattern of MPK-1 activation (the MEK-2 MEK diphosphorylated form of MPK-1, dpMPK-1) in the hermaphrodite germline has been presented, but not analyzed in the context of core pathway mutant backgrounds (Miller et al 2001;Page et al 2001). MPK-1 activation was found to correlate with oocyte meiotic maturation, consistent with ERK playing a role in the process as it does in other organisms, but experiments have not addressed the importance of mpk-1 function in the maturation process.…”

“…To determine whether the generation of new oocytes influences dpMPK-1 accumulation, we compared younger and older adult females. In adult females, .20 hr post mid-L4, which contain .15 late-stage oocytes arrested in diakinesis and generate new oocytes at a very low rate, dpMPK-1 staining in oocytes is very low, lower than in diplotene oocytes in wild-type hermaphrodites ( Figure 2D; McCarter et al 1999;Miller et al 2001;Page et al 2001). In younger females, however, on average a single diakinesis oocyte reproducibly shows dpMPK-1 staining ( Figure 2C; supplemental Figure 9 at http://www.genetics.org/supplemental/) at an intensity similar to diplotene or early diakinesis in wild-type hermaphrodites.…”

mir-35 is involved in intestine cell G1/S transition and germ cell proliferation in C. elegans

“…[41], dpl-1 (DP-Like) and efl-1 (E2F-Like) [42]. lin-35, lin-36 and efl-1 negatively regulate S phase entry [43,44], while dpl-1 acts as both a positive and negative regulator [44,45]. We found that lin-35(n745), lin-36(n766) and efl-1(se1) could fully suppress intestinal nuclei phenotype of gk262, at both 20 °C and 25 °C (Tables 1 and 3, P > 0.05, Student t-test), indicating that mir-35 regulates G1/ S transition in an Rb/E2F-dependent manner.…”