G-protein signaling is required for increasing germline stem cell division frequency in response to mating in Drosophila males

Abstract

Adult stem cells divide to renew the stem cell pool and replenish specialized cells that are lost due to death or usage. However, little is known about the mechanisms regulating how stem cells adjust to a demand for specialized cells. A failure of the stem cells to respond to this demand can have serious consequences, such as tissue loss, or prolonged recovery post injury. Here, we challenge the male germline stem cells (GScs) of Drosophila melanogaster for the production of specialized cells, sperm cells, using mating experiments. We show that repeated mating reduced the sperm pool and increased the percentage of GScs in M-and S-phase of the cell cycle. the increase in dividing GScs depended on the activity of the highly conserved G-proteins. Germline expression of RNA-Interference (RNAi) constructs against G-proteins, or a dominant negative G-protein eliminated the increase in GSC division frequency in mated males. consistent with a role for the G-proteins in regulating GSc division frequency, RNA-i against seven out of 35 G-protein coupled receptors (GPCRs) within the germline cells also eliminated the capability of males to increase the numbers of dividing GSCs in response to mating. Metazoan tissues undergo homeostasis wherein stem cells divide and their daughter cells proliferate and differentiate to replace lost cells. The human hematopoietic stem cells, for example, renew a remarkable number of about one trillion blood cells per day 1,2. Stem cells have to maintain a baseline mitotic activity for the production of daughter cells that account for the daily turnover of differentiated cells. However, whether stem cells can modulate their mitotic activity in response to demands that challenge the system is not fully explored. In some instances, stem cells respond to physiological cues; for example, murine hematopoietic stem cells divide more frequently during pregnancy due to increased oestrogen levels 3. In Drosophila melanogaster, intestinal stem cells initiate extra cell divisions upon ablation of differentiated gut cells, and GSCs modulate their mitotic activity in response to environmental conditions, such as nutrient availability and temperature 4-7. Drosophila is an excellent model for identifying the molecules and mechanisms that regulate and fine-tune tissue homeostasis. A plethora of genetic tools are available for manipulating and monitoring dividing adult stem cells. The small size of the fly, the short generation cycle, and the fairly low costs covering their maintenance allow for high throughput screens. Here, we subjected several thousand male and several million virgin female flies to mating experiments, a task challenging to perform with vertebrate model organisms. We discovered that repeated mating caused a reproducible and significant increase in GSC division frequency in Drosophila wild-type (wt) males. Our analysis revealed that this response to mating was dependent on the activity of G-proteins. Impairing G-protein activity from the germline cells eliminated the ability of the GSCs to in...

Regulation of Mating-Induced Increase in Female Germline Stem Cells in the Fruit Fly Drosophila melanogaster

“…Of note, a recent study reported that mating stimuli alter the dynamics of male GSCs in D. melanogaster ( Aston and Schulz, 2020 ; Malpe et al, 2020 ). Unlike female GSCs, there is no significant change in the number of male GSCs before and after mating.…”

The trade‐off between investment in weapons and fertility is mediated through spermatogenesis in the leaf‐footed cactus bug Narnia femorata

“…In Drosophila melanogaster, males respond to perceived sperm competition risk by increasing sperm production (Moatt et al, 2014). A recent study has shown that mating increases the division rate of germline stem cells in the testes of D. melanogaster through G protein signaling (Malpe et al, 2020). However, this sort of mechanistic studies depends on established molecular markers to identify the germline stem cells and niche cells, and genetic tools lacking in most species.…”

“…In O. fasciatus, and presumably N. femorata, sperm arise originally from germline stem cells at the tip of each testis tubule (Schmidt et al, 2002). As shown in D. melanogaster (Malpe et al, 2020), variation in sperm production could arise through the rate of production of germ cells through division of the germline stem cells. Alternatively, variation could arise through the modulation of the sperm production process (Extavour, 2013;Kaczmarczyk & Kopp, 2011;Moore, 2014;Ramm & Schärer, 2014).…”

The impact of genetic background and gender on the increase in mitotic index in response to mating ofDrosophila melanogaster

“…Drosophila females have far more stem cells compared to males. In the males, each of the two testicular tubules has an average of 5-12 GSCs (Hardy et al, 1979;Malpe et al, 2020). Each of the two female ovaries contains 15-20 tubes, called ovarioles, in which the eggs develop.…”

“…Instead, we demonstrated that males had to interact with more than three virgin females and for more than 24 hours for an increase in MI GSC to be statistically relevant (Malpe et al, 2020). To compare the effect of mating on the genders, we performed female mating experiments.…”