Iyer, Jyoti et al. (2021) International Worm Meeting "The Chromatin Remodeling Protein CHD-1 and the EFL-1/DPL-1 Transcription Factor Cooperatively Down Regulate CDK-2 to Control SAS-6 Levels and Centriole Number"

Smith, Amy, Sankaralingam, Prabhu, Kropp, Peter, O'Connell, Kevin, Bowerman, Bruce, Guargliardo, Sarah, Bergwell, Mary, Gentry, Lindsey, Liu, Yan, Iyer, Jyoti

[International Worm Meeting, 2021]

Centrioles are submicron-scale, barrel-shaped organelles typically found in pairs, and play important roles in ciliogenesis and bipolar spindle assembly. In general, successful execution of centriole-dependent processes is highly reliant on the ability of the cell to stringently control centriole number. This in turn is mainly achieved through the precise duplication of centrioles during each S phase. Aberrations in centriole duplication disrupt spindle assembly and cilia based signaling and have been linked to cancer, primary microcephaly and a variety of growth disorders. Studies aimed at understanding how centriole duplication is controlled have mainly focused on the post-translation regulation of two key components of this pathway: the master regulatory kinase ZYG-1/Plk4 and the scaffold component SAS-6. In contrast, how transcriptional control mechanisms might contribute to this process have not been well explored. Here we show that the chromatin remodeling protein CHD-1 contributes to the regulation of centriole duplication in the C. elegans embryo. Specifically, we find that loss of CHD-1 or inactivation of its ATPase activity can restore embryonic viability and centriole duplication to a strain expressing insufficient ZYG-1 activity. Interestingly, loss of CHD-1 is associated with increases in the levels of two ZYG-1-binding partners: SPD-2, the centriole receptor for ZYG-1 and SAS-6. Finally, we explore transcriptional regulatory networks governing centriole duplication and find that CHD-1 and a second transcription factor, EFL-1/DPL-1 cooperate to down regulate expression of CDK-2, which in term promotes SAS-6 protein levels. Disruption of this transcriptional regulatory network results in the production of extra centrioles.

Jessica Amrozowicz Kerins et al. (2005) International Worm Meeting "The C. elegans Ortholog of Yeast CDC40/PRP17 Functions in the Proliferation versus Meiotic Development Decision"

Laura Berry, Daimon Simmons, Jessica Amrozowicz Kerins, Dave Hansen, Tim Schedl

[International Worm Meeting, 2005]

GLP-1 is a member of the Notch family of receptors and promotes germ cell proliferation in C. elegans. Activation of the germline GLP-1 receptor is spatially regulated by the distal tip cell transmembrane ligand, LAG-2. Binding of LAG-2 to GLP-1 induces receptor cleavage generating GLP-1(INTRA), which is then presumed to translocate to the nucleus, bind LAG-1, and alter the pattern of transcription. Disruption of this pathway causes all proliferating germ cells to prematurely enter meiosis. Conversely, constitutive activation by the glp-1(oz112gf) mutation results in the formation of a germline tumor where proliferative cells are found throughout the gonad. Two pathways, one containing GLD-1, the other containing GLD-2, function redundantly downstream of GLP-1 to inhibit proliferation and/or promote meiotic development. GLP-1 signaling, in effect, inhibits both pathways to promote germ cell proliferation. We have taken a forward genetic approach to identify genes that function downstream of GLP-1 to promote entry into meiosis, or that function to negatively regulate GLP-1. This approach uses sensitized genetic backgrounds to screen for tumorous mutants. One screen utilized the weak glp-1(oz264gf) mutant and identified the allele oz273 as a strong tumorous enhancer. oz273 also displays a Mog (masculinization of the germline) phenotype in the glp-1(+) background, similar to teg-1, another mutant that enhances a weak glp-1(gf) background (see Hansen et al, this meeting). Also similar to teg-1, the gld-2oz273 mutant is tumorous, suggesting that teg-1 and oz273 could be functioning in the same pathway to regulate entry into meiosis. The gene disrupted by the oz273 lesion is F49D11.1, which codes a 567 amino acid protein that is orthologous to yeast CDC40/PRP17 and human PRP17. These proteins are required for the second step of pre-mRNA splicing (Jones et al, 1995; Umen et al, 1995). The oz273 mutation is an 873 bp deletion that removes the first 173 amino acids encoded by exon 2, including four of six WD-40 repeats. Also within the deleted region is a motif that is critical for splicing in yeast (Lindsey-Boltz et al, 2000), suggesting that the oz273 deletion is a strong loss-of-function or null allele. Experiments are currently underway to further characterize the gene and determine if other splicing factors regulate entry into meiosis (also see Hanazawa et al, this meeting).