Wnt signaling pathway

Wnt glycoproteins are signaling molecules that control a wide range of developmental processes and is a conserved feature of metazoan development. In C. elegans Wnt signaling has been shown to play a role in cell fate specification and determination of cell polarity, cell migration, and axis determination during axon outgrowth. A 'canonical' Wnt signaling pathway has been elucidated in vertebrate and invertebrate model systems where Wnt binding leads to the stabilization of the transcription factor beta-catenin, which then enters the nucleus to regulate Wnt pathway target genes. Like other species, the C. elegans genome encodes multiple genes for Wnt ligands, EGL-20, LIN-44, MOM-2, CWN-1, CWN-2) and Wnt receptors (LIN-17, MOM-5, MIG-1, CFZ-2, LIN-18). Canonical Wnt signaling in C. elegans, utilizes the beta-catenin BAR-1 to convert POP-1 into an activator and controls the expression of several homeobox genes. However, unlike vertebrates or Drosophila, the C. elegans genome encodes multiple beta-catenin genes (HMP-2, BAR-1, SYS-1, WRM-1), which give rise to noncanonical Wnt signalling pathways: for example, the endoderm induction pathway requires the beta-catenin WRM-1 and parallel input from a mitogen-activated kinase (MAPK) pathway to downregulate POP-1.

Hedgehog signaling

A conserved regulatory cascade that is important in vertebrates and Drosophila for patterning and cell proliferation during development. The main components in this pathway are Hedgehog (Hh), mammalian Sonic hedgehog (Shh), skinny hedgehog (Ski), dispatched (Disp), patched (Ptch), and Smoothened (Smo). C. elegans lacks true Hh and Smo orthologs; however, it does have orthologs of Ski, Disp, and Ptch along with multiple hegdgehog-related (Hh-r), Patched (PTC) and patched-related (PTR) genes.