Novel transcriptional regulators of Drosophila Intestinal Stem Cell Homeostasis and Ageing

Abstract

Adult stem cells are central to tissue maintenance, yet their regenerative capacity declines with age. In the Drosophila midgut, ageing intestinal stem cells (ISC) display increased proliferation, impaired diAerentiation, alongside a progressive loss of tissue integrity. The molecular drivers of these changes remain incompletely understood. This thesis integrates transcriptomics, functional genetics, and chromatin mapping to uncover regulators of ISC behaviour in homeostasis and ageing.

Transcriptomic analysis identified the Odd-skipped family genes sob and drm as previously uncharacterised candidate regulators of ISC. sob is expressed in young ISCs but declines with age, and its ortholog OSR2 exhibits a similar pattern in mouse intestine. At the whole organism level sob regulates lifespan and at the stem cell level it regulates proliferation and the balance of enteroendocrine and enterocyte diAerentiation. Transcriptomic and genetic interaction experiments identified downstream mechanisms, showing Sob acts via Numb, Dawdle, and Exex. In parallel, drm was found to be expressed at the midgut–hindgut boundary, and its expression increases with age. Manipulation of drm expression identified roles regulating both the midgut and hindgut local to the boundary and the organisation of the boundary itself, along with perturbed Wingless signalling. These results establish sob and drm as novel regulators of ISC function and gut homeostasis during ageing. The final chapter focused on method development, successfully optimising a suitable ISC specific AGES driver for Targeted DamID during ageing. This will allow future work to systematically map changes in chromatin and transcriptional regulation in ageing stem cells.

Together, these findings identify and characterise novel transcriptional regulators of homeostasis whose mis regulation contributes to age related decline in function. Future work integrating gene expression with transcriptional networks and chromatin dynamics will build a more comprehensive picture of the mechanisms that erode stem cell homeostasis during ageing and set the stage for strategies to preserve regenerative capacity in old tissues.