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EGF, WNT & HOX Interactions during Patterning of Caenorhabditis elegans Equivalence Groups

Citation

Seah, Adeline (2009) EGF, WNT & HOX Interactions during Patterning of Caenorhabditis elegans Equivalence Groups. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/N559-AE78. https://resolver.caltech.edu/CaltechETD:etd-05242009-123432

Abstract

During development, as a single-cell zygote divides multiple times to generate a complete organism, previously undifferentiated cells somehow acquire the correct fates. A group of cells that shares the same developmental potential is called an equivalence group. In Caenorhabditis elegans, the most well-characterized equivalence group is the hermaphroditic Vulval Precursor Cell (VPC) group. Epidermal Growth Factor (EGF) signaling specifies VPC fate partly by upregulation of lin-39/SexcombsReduced/Hox5, while Wnt signaling plays a minor role in vulval induction. EGF and Wnt signaling also act together to pattern the P11/12 equivalence group, present in both C. elegans hermaphrodites and males, by upregulating a different Hox gene, egl-5/Antennapedia/Ultrabithorax/Hox6/8, to specify P12 fate. Previous observations suggest that EGF or Wnt signaling may act through Hox genes to specify fate in two other C. elegans equivalence groups: the Hook Competence Group (HCG) and γ/δ pair. I characterized the roles of EGF and Wnt signaling in the HCG and γ/δ pair and found that upregulation of Hox genes is controlled by either pathway in each group.

I showed that the major hook inductive pathway involves the Wnt ligands and LIN-17/Fz, which specify the 1° and 2° HCG fates. Also, I identified a role for EGF signaling in specifying the 1° fate, although its role is only revealed when Wnt activity is compromised. I provided a link between mab-5/Hox6/8 and Wnt signaling during normal hook development by determining that LIN-17 is required for mab-5/Hox6/8 expression in P11.p.

In the γ/δ pair, I demonstrated that EGF signaling (through the LIN-31/Forkhead and LIN-1/ETS transcription factors) controls ceh-13/Hox1 expression in γ. I did not find any evidence that Wnt signaling specifies the γ fate. Instead, I observed that lin-44/Wnt, mom-2/Wnt and lin-17/Fz are required to orient the γ mitotic spindle. In addition, TGF-β signaling (by dbl-1/Dpp) was previously reported to control γ expression of ceh-13/Hox1. I showed that dbl-1 acts either downstream or in parallel to EGF signaling to specify the γ fate. I also found that dbl-1/Dpp does not appear to specify fates in the VPC and P11/12 equivalence groups, in which EGF signaling plays an important role, suggesting that TGF-β signaling contributes to the specificity of the γ fate.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:EGF; Equivalence groups; Wnt
Degree Grantor:California Institute of Technology
Division:Biology
Major Option:Biology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Sternberg, Paul W.
Thesis Committee:
  • Deshaies, Raymond Joseph (chair)
  • Hay, Bruce A.
  • Anderson, David J.
  • Sternberg, Paul W.
Defense Date:22 January 2009
Record Number:CaltechETD:etd-05242009-123432
Persistent URL:https://resolver.caltech.edu/CaltechETD:etd-05242009-123432
DOI:10.7907/N559-AE78
ORCID:
AuthorORCID
Seah, Adeline0000-0003-0935-8044
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2036
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:29 May 2009
Last Modified:26 Nov 2019 19:45

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