A Caltech Library Service

Temporally Changing Roles of Morphogen Dorsal in the Drosophila Early Embryo


Irizarry, Jihyun (2021) Temporally Changing Roles of Morphogen Dorsal in the Drosophila Early Embryo. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/t53b-vc87.


Morphogen gradients provide positional cues during development, with cell fate specification proceeding in a morphogen concentration-dependent manner during patterning. However, morphogens also are dynamic as their concentrations change not only in space but also in time, but how these dynamics are translated into cell fate specification over time is not well understood. To provide a better understanding of morphogens’ temporal roles, we studied how Drosophila dorsal-ventral body patterning is controlled by the dynamic morphogen Dorsal (Dl). Dl is present in a nuclear-cytoplasmic gradient along the dorsal-ventral (DV) axis, but Dl levels also continuously increase between and within nuclear cell divisions associated with the early syncytial embryo. To experimentally manipulate Dl levels in time in order to determine whether these dynamics are important, we developed a light-activated degradation system. The blue light inducible degron domain, BLID, was fused to the C-terminus of Dl by genomic editing using CRISPR-Cas9. To assay effects on temporally manipulated Dl levels, we combined this light-inducible degradation system with the MS2-MCP.GFP nascent transcript imaging system, and used to monitor transcription changes in vivo at the snail (sna) locus, a gene requiring high Dl levels. We found that while high Dl levels are required for sna activation at early nuclear cycle 14, late expression can be supported even if Dl levels are extinguished. Twist, an early Dl target gene, is later auto-activating and can support the later sna expression without Dl. Surprisingly, we found that peak levels of Dl, present at late nuclear cycle 14, are required only to fine tune, in particular to decrease, sna levels. This differential action of Dl, first functioning as an activator and next as a damper of expression, is manifest by the coordinate action of two enhancers acting at the sna locus. Here, we highlight how morphogen roles change in time, and suggest that this may be a general characteristic of dynamic morphogens that allows them to control developmental patterning.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Dorsal Rel transcriptional factor, opotogenetics, cis-regulatory module, Twist, Snail
Degree Grantor:California Institute of Technology
Division:Biology and Biological Engineering
Major Option:Biology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Stathopoulos, Angelike
Thesis Committee:
  • Bronner, Marianne E. (chair)
  • Rothenberg, Ellen V.
  • Guttman, Mitchell
  • Stathopoulos, Angelike
Defense Date:31 July 2020
Non-Caltech Author Email:yamaojp77 (AT)
Funding AgencyGrant Number
Record Number:CaltechTHESIS:09052020-090207113
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 2. adapted for Appendices A. adapted for Appendices B.
Irizarry, Jihyun0000-0003-3967-2288
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13865
Deposited By: Jihyun Irizarry
Deposited On:16 Oct 2020 15:39
Last Modified:26 Oct 2021 20:22

Thesis Files

PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page