| First Author | Garcia-Perez L B | Year | 2022 |
| Journal | PhD Thesis - Imperial College London | Mgi Jnum | J:343153 |
| Mgi Id | MGI:7564245 | Doi | 10.25560/96446 |
| Citation | Garcia-Perez L B (2022) A quantitative analysis of tissue development: understanding the role of two mutually repressing transcription factors, Irx3 and Olig2, in the developing spinal cord. PhD Thesis - Imperial College London |
| abstractText | The plasticity required to form a multicellular organism is frequently manifested in cells switching between different gene expression programmes during development. One mechanism underpinning this is the genetic toggle switch, which is composed of cross-repressing transcriptional determinants that ensure discrete and robust cell fate transitions. Thus, a detailed molecular understanding of how genetic switches operate is important. To address this, I focused on the transcription factors Irx3 and Olig2, which form a genetic switch controlled by the Shh morphogen that determines the generation of V2 interneuron and motor neuron progenitors in the vertebrate neural tube. The relative molecular abundance of Irx3 and Olig2 was measured, both at the mRNA and protein levels, in the mouse embryonic spinal cord. In addition, their corresponding absolute abundances were determined using an in vitro system of neural differentiation. Olig2 expression proved to be several times higher than Irx3 expression. However, Olig2 protein stability was found to be less than half of Irx3 stability. To explore the influence of molecular stability and abundance, Irx3 protein stability was selectively decreased, which concomitantly reduced Irx3 protein copy number per cell. This perturbation altered the transition path from Irx3 to Olig2 expressing cells and lead to a faster Irx3-to-Olig2 transition. Moreover, it increased the probability, amplitude and variability of Olig2 transcription, and affected another Shh-responsive gene, Gli1. Finally, the transcriptional effects of the reduced Irx3 protein stability and copy number resembled those seen in cells lacking the Irx3 protein. Overall this work provides insight into the intrinsic molecular properties that determine aspects of cell fate transitions, such as their start and end points, rate and variability. Furthermore, the quantitative molecular measurements presented here can be used to constrain mathematical models of gene expression and make predictions about genetic switches in other scenarios. |
