Identification of Wnt Pathway Target Genes Regulating the Division and Differentiation of Larval Seam Cells and Vulval Precursor Cells inCaenorhabditis elegans

Abstract

The evolutionarily conserved Wnt/β-catenin signaling pathway plays a fundamental role during metazoan development, regulating numerous processes including cell fate specification, cell migration, and stem cell renewal. Wnt ligand binding leads to stabilization of the transcriptional effector β-catenin and upregulation of target gene expression to mediate a cellular response. During larval development of the nematode Caenorhabditis elegans, Wnt/β-catenin pathways act in fate specification of two hypodermal cell types, the ventral vulval precursor cells (VPCs) and the lateral seam cells. Because little is known about targets of the Wnt signaling pathways acting during larval VPC and seam cell differentiation, we sought to identify genes regulated by Wnt signaling in these two hypodermal cell types. We conditionally activated Wnt signaling in larval animals and performed cell type–specific "mRNA tagging" to enrich for VPC and seam cell–specific mRNAs, and then used microarray analysis to examine gene expression compared to control animals. Two hundred thirty-nine genes activated in response to Wnt signaling were identified, and we characterized 50 genes further. The majority of these genes are expressed in seam and/or vulval lineages during normal development, and reduction of function for nine genes caused defects in the proper division, fate specification, fate execution, or differentiation of seam cells and vulval cells. Therefore, the combination of these techniques was successful at identifying potential cell type–specific Wnt pathway target genes from a small number of cells and at increasing our knowledge of the specification and behavior of these C. elegans larval hypodermal cells.

Regulation of C. elegans L4 cuticle collagen genes by the heterochronic protein LIN‐29

“…First, we showed that the L4 col genes col-38, col-49, and col-71 are regulated by the Wnt pathway transcription factor BAR-1 (beta-catenin) (Gorrepati et al, 2015;Jackson et al, 2014;Van Der Bent et al, 2015), which binds to its target genes via interaction with the TCF transcription factor POP-1 (Jackson & Eisenmann, 2012). First, we showed that the L4 col genes col-38, col-49, and col-71 are regulated by the Wnt pathway transcription factor BAR-1 (beta-catenin) (Gorrepati et al, 2015;Jackson et al, 2014;Van Der Bent et al, 2015), which binds to its target genes via interaction with the TCF transcription factor POP-1 (Jackson & Eisenmann, 2012).…”

“…Previous work has identified four transcription factors regulating col gene expression. First, we showed that the L4 col genes col-38, col-49, and col-71 are regulated by the Wnt pathway transcription factor BAR-1 (beta-catenin) (Gorrepati et al, 2015;Jackson et al, 2014;Van Der Bent et al, 2015), which binds to its target genes via interaction with the TCF transcription factor POP-1 (Jackson & Eisenmann, 2012).…”

Asymmetric Wnt Pathway Signaling Facilitates Stem Cell-Like Divisions via the Nonreceptor Tyrosine Kinase FRK-1 inCaenorhabditis elegans

“…Previous models consist of variations on cytoplasmic localization of the b-catenin homologs along with the APC homolog, APR-1 (Mizumoto and Sawa 2007b;Baldwin and Phillips 2014;Gorrepati et al 2015), and that it is the shuttling of these proteins, in the presence of a polarizing Wnt signal, that facilitates POP-1 (TCF) export from the nucleus in the posterior daughter cell (Sugioka et al 2011). However, a continuing question in this area remained: Is there a nuclear mechanism that sensitizes WRM-1 to export from the nucleus in the anterior daughter?…”

Mechanisms of Wnt signaling and control

“…Many Wnt target genes are induced in a tissue and context-specific manner, although like other signaling cascades, Wnt signaling induces expression of negative regulators, such as SP5, Nkd1, and Axin2 (Huggins et al, 2017;Jho et al, 2002;Larraguibel et al, 2015;Yan et al, 2001). Wnt stimulation of cell lines, followed by mRNA analyses have uncovered several transcripts induced by Wnt (Gorrepati et al, 2015;Huggins et al, 2017;Jackson, Abete-Luzi, Krause, & Eisenmann, 2014;Maubant et al, 2015;Willert, Epping, Pollack, Brown, & Nusse, 2002). How these are regulated, however, remains elusive; a recent study found that only a subset of β-catenin-bound genomic loci are transcriptionally regulated by Wnt signaling, implying a further requirement for inputs to activate transcription (Nakamura, de Paiva Alves, Veenstra, & Hoppler, 2016).…”