Current Biology
Volume 16, Issue 3, 7 February 2006, Pages 287-295
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Wnt Signaling and CEH-22/tinman/Nkx2.5 Specify a Stem Cell Niche in C. elegans

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Summary

Wnt signaling regulates many aspects of metazoan development, including stem cells 1, 2, 3. In C. elegans, Wnt/MAPK signaling controls asymmetric divisions 4, 5. A recent model proposed that the POP-1/TCF DNA binding protein works together with SYS-1/β-catenin to activate transcription of target genes in response to Wnt/MAPK signaling [6]. The somatic gonadal precursor (SGP) divides asymmetrically to generate distal and proximal daughters of distinct fates: only its distal daughter generates a distal tip cell (DTC), which is required for stem cell maintenance [7]. No DTCs are produced in the absence of POP-1/TCF or SYS-1/β-catenin, and extra DTCs are made upon overexpression of SYS-1/β-catenin 6, 8, 9. Here we report that POP-1/TCF and SYS-1/β-catenin directly activate transcription of ceh-22/nkx2.5 isoforms in SGP distal daughters, a finding that confirms the proposed model of Wnt/MAPK signaling. In addition, we demonstrate that the CEH-22/Nkx2.5 homeodomain transcription factor is a key regulator of DTC specification. We speculate that these conserved molecular regulators of the DTC niche in nematodes may provide insight into specification of stem cell niches more broadly.

SIGNALING
DEVBIO
STEMCELL

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