Ecdysone signaling opposes epidermal growth factor signaling in regulating cyst differentiation in the male gonad of Drosophila melanogaster

Abstract

The development of stem cell daughters into the differentiated state normally requires a cascade of proliferation and differentiation steps that are typically regulated by external signals. The germline cells of most animals, in specific, are associated with somatic support cells and depend on them for normal development. In the male gonad of Drosophila melanogaster, germline cells are completely enclosed by cytoplasmic extensions of somatic cyst cells, and these cysts form a functional unit. Signaling from the germline to the cyst cells via the Epidermal Growth Factor Receptor (EGFR) is required for germline enclosure and has been proposed to provide a temporal signature promoting early steps of differentiation. A temperature-sensitive allele of the EGFR ligand Spitz (Spi) provides a powerful tool for probing the function of the EGRF pathway in this context and for identifying other pathways regulating cyst differentiation via genetic interaction studies. Using this tool, we show that signaling via the Ecdysone Receptor (EcR), a known regulator of developmental timing during larval and pupal development, opposes EGF signaling in testes. In spi mutant animals, reducing either Ecdysone synthesis or the expression of Ecdysone signal transducers or targets in the cyst cells resulted in a rescue of cyst formation and cyst differentiation. Despite of this striking effect in the spi mutant background and the expression of EcR signaling components within the cyst cells, activity of the EcR pathway appears to be dispensable in a wildtype background. We propose that EcR signaling modulates the effects of EGFR signaling by promoting an undifferentiated state in early stage cyst cells.

Enhancer of polycomb coordinates multiple signaling pathways to promote both cyst and germline stem cell differentiation in the Drosophila adult testis

“…Even though previous studies suggest that somatic gonadal cells control germ cell differentiation and maintain germline identity through multiple signaling pathways [ 8 , 9 , 11 , 16 , 17 , 29 , 49 , 76 , 98 , 118 , 119 , 120 ], it is unclear how these signaling pathways themselves are regulated. Here our ChIP-seq results reveal that E(Pc) is enriched at key components of multiple signaling pathways known to be important in regulating germ cell function.…”

Modulation of Ago2 Loading by Cyclophilin 40 Endows a Unique Repertoire of Functional miRNAs during Sperm Maturation in Drosophila

“…To further explore the molecular basis for Drosophila Cyp40's action in spermatid differentiation, we first considered that, like the mammalian isoform, Cyp40 might regulate the testicular steroid signaling pathways, which is crucial for male fertility. It is well established, however, that these steroid receptors function in somatic lineages, as opposed to the germline, and their misregulation impairs testis development or earlier steps in spermatogenesis (Li et al, 2014;Misra et al, 2017;Qian et al, 2014;Sharma et al, 2017), in ways both spatiotemporally and phenotypically distinct from the defects caused by Cyp40 loss of function in Drosophila.…”

Notch and Delta are required for survival of the germline stem cell lineage in testes of Drosophila melanogaster

“…A temperature-sensitive allele of EGF, spitz 77-20 , has served as an excellent tool for gaining more insight into spermatogenesis. Previous research has established that the spitz 77-20 mutant testis phenotype from animals held at an intermediate temperature of 26.5°C could easily be modified by additional mutations in pathways regulating cyst development [18, 31]. Thus, prior to employing further tools for eliminating Notch signaling from otherwise wt testes we first utilized the spitz 77-20 allele to investigate for a potential genetic interaction.…”