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EGF, Wnt and Hox interactions during patterning of Caenorhabditis elegans equivalence groups

Citation

Seah, Adeline (2009) EGF, Wnt and Hox interactions during patterning of Caenorhabditis elegans equivalence groups. Dissertation (Ph.D.), California Institute of Technology. http://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
Author Email:seah (AT) caltech.edu
Record Number:CaltechETD:etd-05242009-123432
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-05242009-123432
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 Dec 2012 02:46

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