Cyst stem cell lineage eIF5 non-autonomously prevents testicular germ cell tumor formation via eIF1A/eIF2γ-mediated pre-initiation complex

Abstract

Background Stem cell niche maintains stem cell population identity and is essential for the homeostasis of self-renewal and differentiation in Drosophila testes. However, the mechanisms of CySC lineage signals-mediated soma–germline communications in response to external stimuli are unclear. Methods Pre-initiation complex functions were evaluated by UAS-Gal4-mediated cell effects. RNA sequencing was conducted in NC and eIF5 siRNA-treated cells. Genetic interaction analysis was used to indicate the relationships between eIF5 and eIF1A/eIF2γ in Drosophila testes. Results Here, we demonstrated that in CySCs, translation initiation factor eIF5 mediates cyst cell differentiation and the non-autonomously affected germ cell differentiation process. CySCs lacking eIF5 displayed unbalanced cell proliferation and apoptosis, forming testicular germ cell tumors (TGCTs) during spermatogenesis. eIF5 transcriptional regulation network analysis identified multiple metabolic processes and several key factors that might be involved in germ cell differentiation and TGCT formation. Importantly, knockdown of eIF1A and eIF2γ, key components of pre-initiation complex, mimicked the phenotype of knocking down eIF5 in the stem cell niche of Drosophila testes. Genetic interaction analysis indicated that eIF5 was sufficient to rescue the phenotype of tumorlike structures induced by down-regulating eIF1A or eIF2γ in CySCs. Conclusions These findings demonstrated that CySC lineage eIF5, together with eIF1A or eIF2γ, mediates soma–germline communications for the stem cell niche homeostasis in Drosophila testes, providing new insights for the prevention of TGCTs.

Single-cell RNA sequencing reveals cell landscape following antimony exposure during spermatogenesis in Drosophila testes

“…5A), leading to the differentiation defects of elongated spermatids. Orb was used as a classical marker with highly enriched expression level in elongated spermatids [23,32]. Our results showed that the expression pattern of Orb protein was disturbed at late stage of spermatogenesis in control and Sb-exposed testes (Fig.…”

“…DNA staining highly condensed at the early-stage nuclei of germ cells and the nuclei of clusters of elongated spermatozoa in the Drosophila testis [16,23]. Based on the above observation, we next counted the number of elongated spermatid clusters and found a significant and dose-dependent decrease (Fig.…”

“…Immunofluorescence was carried out as described previously [16,23,56]. Briefly, fly testes were dissected in 1 × phosphate-buffered saline (PBS), fixed for 30 min in 4% paraformaldehyde (PFA), washed three times with 0.3% PBS-Triton X-100 (PBST), and incubated in 5% bovine serum albumin (BSA) for 30 min.…”

“…Hub cells maintain the self-renewal and differentiation of the two other types of stem cells [20,21]. Interestingly, germ cells occupy the majority of testicular components, and their maintenance and differentiation are strictly controlled by functional signals that originate from somatic cells in Drosophila testes [22,23]. CySCs differentiate into cyst cells and provide the environment necessary to trigger germ cell growth and differentiation via non-autonomous effects [24].…”

Structure and molecular basis of spermatid elongation in theDrosophilatestis

“…Drosophila oo18 RNA-binding protein (Orb) and Orb2 are two highly conserved RNA-binding proteins belonging to the cytoplasmic polyadenylation element binding (CPEB) protein family, which plays a critical role in mRNA transport and local translation [55]. Both Orb and Orb2 are highly enriched in elongated spermatids and regulate spermatogenesis [22,56]. Immunofluorescence staining in the Drosophila testis shows that Orb and Orb2 proteins have low levels of expression in mitotic spermatogonia and extremely high levels in elongated spermatids.…”