The Drosophila Accessory Gland as a Model for Postmitotic Regeneration

Abstract

Polyploidy is a state in which a cell contains more DNA than a standard diploid cell (>2C). While polyploidy has been long discussed in plant biology, it has become apparent that polyploidy is more widely present than was previously considered in the animal kingdom. Polyploidy can arise in multiple ways: one being cellular fusion and another being a remodeling of the canonical cell cycle. Importantly, polyploidy has emerged as an important topic in cellular and organ growth during development and during recovery from damage.

The adult Drosophila male accessory gland is functionally analogous to the mammalian prostate and is a developmentally programmed polyploid tissue which undergoes variant cell cycles during gland development. In the second chapter of this thesis, I add two additional cell cycle variants to the current understanding of accessory gland development and present evidence that this tissue undergoes a step-wise cell cycle remodeling throughout tissue development and maturation. Importantly, this work establishes that juvenile hormone signaling may play a part in regulating an adult specific endocycle that occurs shortly post-eclosion and assists with gland maturation by contributing to increased cellular ploidy and male fertility.

The third chapter of this thesis examines the cell cycle status of the accessory gland main cells throughout the lifespan of the fruit fly. While some studies have shown that polyploidy creates a refractory environment for cell cycle re-entry in terminally differentiated cells, this work shows that the adult accessory gland exhibits rare endocycles throughout the fly lifespan and provides evidence that the terminally differentiated main cells remain poised to re-enter the cell cycle when given proper cues. My work establishes that the adult accessory gland can recover from large scale tissue damage and recovered tissues present with cellular hypertrophy and exhibit additional endocycling which occurs alongside a restoration of fertility. Altogether this body of work establishes that the adult Drosophila male accessory gland undergoes a series of cell cycle variants during tissue development and presents a novel damage and recovery paradigm which can be used to elucidate mechanisms of postmitotic, polyploid organ regeneration.