Abstract
At the apical tip of the Drosophila testis, germline and somatic stem cells surround a cluster of somatic cells called the hub. Hub cells produce a self-renewal factor, Unpaired (Upd), that activates the JAK-STAT pathway in adjacent stem cells to regulate stem cell behavior. Therefore, apical hub cells are a critical component of the stem cell niche in the testis. In the course of a screen to identify factors involved in regulating hub maintenance, we identified headcase (hdc). Hub cells depleted for hdc undergo programmed cell death, suggesting that anti-apoptotic pathways play an important role in maintenance of the niche. Using hdc as paradigm, we describe here the first comprehensive analysis on the effects of a progressive niche reduction on the testis stem cell pool. Surprisingly, single hub cells remain capable of supporting numerous stem cells, indicating that although the size and number of niche support cells influence stem cell maintenance, the testis stem cell niche appears to be remarkably robust in the its ability to support stem cells after severe damage.
Highlights
Adult stem cells are found in highly organized and specialized microenvironments, known as niches, within the tissues they sustain [1]
To identify factors involved in regulating hub size and maintenance, we sought to reduce the expression of candidate genes in hub cells
Conclusions a considerable amount is known regarding the initial formation of the apical hub the testis, much less is known about how its function is regulated throughout life
Summary
Adult stem cells are found in highly organized and specialized microenvironments, known as niches, within the tissues they sustain [1]. Stem cell niches are composed of a diversity of cellular and acellular components, all of them important regulators of stem cell maintenance, survival, self-renewal and the initiation of differentiation [2] [3]. Germline stem cells (GSCs) and somatic, cyst stem cells (CySCs) surround and are in direct contact with hub cells, a cluster of approximately 10 somatic cells at the tip of the testis [7] (Fig. 1A). CySCs self-renew and produce cyst cells that surround and ensure differentiation of the developing spermatogonial cyst (Fig. 1A). The architecture and function of the testis stem cell niche are influenced by spatially restricted production and secretion of the JAK-STAT ligand Unpaired (Upd), exclusively by hub cells [8] [9] [10]. In addition to the JAKSTAT pathway, Hh [11] [12] [13] and BMP [14] [15] [16] [17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
