Apoptosis of male germ-line stem cells after laser ablation of their niche

Abstract

Male germ-line stem cells (GSCs) and their niche-the apical cells or hub cells-display a unique feature at the apices of insect testicular follicles. In the locust, Locusta migratoria, the niche consists of only one large apical cell surrounded by about 60 GSCs. The apical cell can be readily identified in the intact follicle. Using laser ablation it is feasible to destroy the apical cell exclusively without injuring neighboring GSCs or any other cells. The most immediate effect on GSCs is the loss of their structural polarity. Beginning about 3 h after laser treatment chromatin starts to clump and condense in individual GSCs, and some show the first signs of cellular breakdown. These symptoms intensify during the 96-h observation period after laser ablation of the apical cell. TUNEL staining and electron microscopic observations confirm an apoptotic cell death of the GSCs. Laser ablation of individual GSCs had no effect on neighboring GSCs or the apical cell. Destroyed apical cells were not replaced during the observation period. Mitotic divisions of GSCs ceased after about 24 h after apical cell ablation. It is speculated that it might be a general principle in stem cell-niche relationships that stem cells undergo apoptosis when the niche is dysfunctional. This could be a control mechanism to prevent tumor growth of orphaned GSCs.

Specific roles of Target of rapamycin in the control of stem cells and their progeny in theDrosophilaovary

“…Consistent with the niche promoting GSC survival, GSCs die at higher rates when separated from somatic cells in culture (Niki, 2009). Laser ablation of the single apical niche cell causes death of Locusta migratoria male GSCs (Zahn et al, 2007). This model, however, does not account for a normal number of Tor mutant cystoblasts and 2-cell cysts.…”

Competitiveness for the niche and mutual dependence of the germline and somatic stem cells in the Drosophila testis are regulated by the JAK/STAT signaling

“…Through asymmetric cell division, a stem cell in adult tissues can produce an offspring that will maintain the stem cell populations and a daughter cell that will differentiate into various short-lived cell types to replace damaged or dying cells (Yamashita et al, 2007; Fuller and Spradling, 2007, Morrison and Spradling, 2008). Specialized microenvironments, known as stem cell niches regulate the behavior of stem cells and its differentiating progeny (Xie and Spradling, 2000; Donovan and Gearhart, 2001; Ohlstein et al, 2004; Yamashita et al, 2007; Fuller and Spradling, 2007, Nystul and Spradling, 2007; Zahn et al, 2007; Xie et al, 2008; Jin et al, 2008; Morrison and Spradling, 2008). Two or more types of stem cells and stromal cells frequently co-exist in a particular microenvironment (Yamashita et al, 2007; Li and Xie, 2005; Decotto and Spradling, 2005; Fuller and Spradling, 2007).…”

Human embryonic stem cells: A model for human ageing in vitro

“…Micro-RNAs (mi-RNAs) are endogenous non-coding small RNA molecules which negatively regulate gene expression post-transcriptionally through mRNA cleavage, mRNA decay (Giraldez et al, 2006) or translational repression (see Carrington and Ambrose, 2003;Zahn et al, 2007 for review) and were first discovered by Lee et al (1993). The expression profile of mi-RNAs differs in ESC from other tissue (Murchison et al, 2005).…”