Role of PRY-1/Axin in heterochronic miRNA-mediated seam cell development

Abstract

Background Caenorhabditis elegans seam cells serve as a good model to understand how genes and signaling pathways interact to control asymmetric cell fates. The stage-specific pattern of seam cell division is coordinated by a genetic network that includes WNT asymmetry pathway components WRM-1, LIT-1, and POP-1, as well as heterochronic microRNAs (miRNAs) and their downstream targets. Mutations in pry-1 , a negative regulator of WNT signaling that belongs to the Axin family, were shown to cause seam cell defects; however, the mechanism of PRY-1 action and its interactions with miRNAs remain unclear. Results We found that pry-1 mutants in C. elegans exhibit seam cell, cuticle, and alae defects. To examine this further, a miRNA transcriptome analysis was carried out, which showed that let-7 ( miR-48, miR-84, miR-241 ) and lin-4 ( lin-4, miR-237 ) family members were upregulated in the absence of pry-1 function. Similar phenotypes and patterns of miRNA overexpression were also observed in C. briggsae pry-1 mutants, a species that is closely related to C. elegans . RNA interference-mediated silencing of wrm-1 and lit-1 in the C. elegans pry-1 mutants rescued the seam cell defect, whereas pop-1 silencing enhanced the phenotype, suggesting that all three proteins are likely important for PRY-1 function in seam cells. We also found that these miRNAs were overexpressed in pop-1 hypomorphic animals, suggesting that PRY-1 may be required for POP-1-mediated miRNA suppression. Analysis of the let-7 and lin-4 -family heterochronic targets, lin-28 and hbl-1 , showed that both genes were significantly downregulated in pry-1 mutants, and furthermore, lin-28 silencing reduced the number of seam cells in mutant animals. Conclusions Our results show that PRY-1 plays a conserved role to maintain normal expression of heterochronic miRNAs in nematodes. Furthermore, we demonstrated that PRY-1 acts upstream of the WNT asymmetry pathway components WRM-1, LIT-1, and POP-1, and miRNA target genes in seam cell development. Electronic supplementary material The online version of this article (10.1186/s12861-019-0197-5) contains supplementary material, which is available to authorized users.

Axin-mediated regulation of lifespan and muscle health inC. elegansinvolves AMPK-FOXO signaling

“…The examination of animals carrying a nonsense mutation in pry-1, mu38, revealed an 80% reduction in the mean lifespan ( Figure 1C; Table S2). A similar phenotype is also observed in a CRISPR allele, gk3682, that deletes roughly 750 bp region including the 5' UTR and first exon (Mallick et al, 2019b) ( Figure 1C; Table S2). As pry-1 is also involved in developmental processes (Mallick et al, 2019a), we took an RNAi approach to knock down the gene function specifically during adulthood.…”

“…Earlier, we reported both mRNA and microRNA (miRNA) transcriptome profiles of pry-1 mutant that revealed 2,665 differentially expressed (DE) proteincoding genes and six miRNAs (Mallick et al, 2019b;Ranawade et al, 2018). The characterization of DE genes revealed pry-1's role in miRNA-mediated seam cell development (Mallick et al, 2019b) and its novel function in lipid metabolism (Ranawade et al, 2018). In this study, we have specifically focused on the genes linked to aging.…”

Axin Family of Scaffolding Proteins in Development: Lessons from C. elegans

“…In support of its role in the asymmetric division of seam cells, pry-1 mutation disrupts the nuclear localization of WRM-1, SYS-1, and POP-1 [66,134,149], thereby leading to increased seam cell proliferation [65,66]. Work from our lab has shown that in the absence of PRY-1 function, POP-1 localization is disrupted in seam cell daughters [66]. As expected, RNAi knockdown of wrm-1 and lit-1 suppressed the seam cell phenotype in pry-1 mutants whereas pop-1 RNAi exacerbated the defect.…”

“…In addition to the above conserved WNT-mediated signaling events, studies in C. elegans have shown the presence of a divergent asymmetry pathway that regulates nuclear factor POP-1 in a WRM-1 (worm armadillo 1)/β-catenin-LIT-1 (loss of intestine 1)/NLK (Nemo-like kinase)-dependent manner (see [65] and references therein, [66]). In these cases, PRY-1 affects asymmetric POP-1 localization to control EMS (endomesodermal) precursor division in the embryo and seam cell divisions in larvae (discussed below).…”

“…The vertebrate homologs of C. elegans genes are listed on the bottom. Panels B and C adopted with permission from [66] and panel D from [148].…”