Wnt6 regulates the homeostasis of the stem cell niche via Rac1-and Cdc42-mediated noncanonical Wnt signalling pathways in Drosophila testis

Signaling pathways in Drosophila testis niche: Local signals that regulate stem cell fate

Stem cells are located in a well-structured and specialized microenvironment called the niche. The niche provides signaling molecules to control the survival, self-renewal, and differentiation of stem cells. As tissues generally contain different types of stem cells, it is important to understand how these stem cells are coordinately regulated by various signaling pathways. The Drosophila testis niche serves as an excellent model for studying such processes, because it harbors 2 types of stem cells, germline stem cells and somatic cyst stem cells. In this review, we summarize the roles of key signaling pathways in stem cell maintenance and differentiation in the Drosophila testis.

Whole-genome de novo sequencing reveals genomic variants associated with differences of sex development in SRY negative pigs

BACKGROUND

Differences of sex development (DSD) are congenital conditions in which chromosomal, gonadal, or phenotypic sex is atypical. In more than 50% of human DSD cases, a molecular diagnosis is not available. In intensively farmed pig populations, the incidence of XX DSD pigs is relatively high, leading to economic losses for pig breeders. Interestingly, in the majority of 38, XX DSD pigs, gonads still develop into testis-like structures or ovotestes despite the absence of the testis-determining gene (SRY). However, the current understanding of the molecular background of XX DSD pigs remains limited.

METHODS

Anatomical and histological characteristics of XX DSD pigs were analysed using necropsy and HE staining. We employed whole-genome sequencing (WGS) with 10× Genomics technology and used de novo assembly methodology to study normal female and XX DSD pigs. Finally, the identified variants were validated in 32 XX DSD pigs, and the expression levels of the candidate variants in the gonads of XX DSD pigs were further examined.

RESULTS

XX DSD pigs are characterised by the intersex reproductive organs and the absence of germ cells in the seminiferous tubules of the gonads. We identified 4,950 single-nucleotide polymorphisms (SNPs) from non-synonymous mutations in XX DSD pigs. Cohort validation results highlighted two specific SNPs, "c.218T > C" in the "Interferon-induced transmembrane protein 1 gene (IFITM1)" and "c.1043C > G" in the "Newborn ovary homeobox gene (NOBOX)", which were found exclusively in XX DSD pigs. Moreover, we verified 14 candidate structural variants (SVs) from 1,474 SVs, identifying a 70 bp deletion fragment in intron 5 of the WW domain-containing oxidoreductase gene (WWOX) in 62.5% of XX DSD pigs. The expression levels of these three candidate genes in the gonads of XX DSD pigs were significantly different from those of normal female pigs.

CONCLUSION

The nucleotide changes of IFITM1 (c.218T > C), NOBOX (c.1043 C > G), and a 70 bp deletion fragment of the WWOX were the most dominant variants among XX DSD pigs. This study provides a theoretical basis for better understanding the molecular background of XX DSD pigs. DSD are conditions affecting development of the gonads or genitalia. These disorders can happen in many different types of animals, including pigs, goats, dogs, and people. In people, DSD happens in about 0.02-0.13% of births, and in pigs, the rate is between 0.08% and 0.75%. Pigs have a common type of DSD where the animal has female chromosomes (38, XX) but no SRY gene, which is usually found on the Y chromosome in males. XX DSD pigs may look like both males and females on the outside and have testis-like or ovotestis (a mix of ovary and testis) gonads inside. XX DSD pigs often lead to not being able to have piglets, slower growth, lower chance of survival, and poorer meat quality. Here, we used a method called whole-genome de novo sequencing to look for variants in the DNA of XX DSD pigs. We then checked these differences in a larger group of pigs. Our results reveal the nucleotide changes in IFITM1 (c.218T > C), NOBOX (c.1043 C > G), and a 70 bp deletion fragment in intron 5 of the WWOX, all linked to XX DSD pigs. The expression levels of these three genes were also different in the gonads of XX DSD pigs compared to normal female pigs. These variants are expected to serve as valuable molecular markers for XX DSD pigs. Because pigs are a lot like humans in their genes, physiology, and body structure, this research could help us learn more about what causes DSD in people.

New insights into ginsenoside Rg1 regulating the niche to inhibit age-induced germline stem cells depletion through targeting ECR/BMP signaling pathway in Drosophila

PURPOSE

The age-induced imbalance in ecological niches leads to the loss of GSCs, which is the main reason for ovarian germline senescence. Ginsenoside Rg1 can delay ovarian senescence. Here, we shed light on new insights of ginsenoside Rg1 in regulating the niche to maintain GSCs self-renewal and discussing related molecular mechanisms.

METHODS

The differences among GSC number, reproductive capacity of naturally aging female Drosophila after ginsenoside Rg1 feeding were analyzed by immunofluorescence and behavior monitoring. The expressions of the active factors in the niche and the BMP signaling were analyzed through Western blot and RT-qPCR. The target effect was verified in the ECR mutant and combined with the molecular docking.

RESULTS

Ginsenoside Rg1 inhibited the age-induced reduction of the GSCs number and restored offspring production and development. Ginsenoside Rg1 promoted the expression of anchor proteins E-cadherin, stemness maintenance factor Nos and differentiation promoting factor Bam, thereby GSCs niche homeostasis was regulated. In addition, ginsenoside Rg1 was bound to the LBD region of the hormone receptor ECR. Ginsenoside Rg1 promotes the regeneration of GSCs by targeting the ECR to increase pSmad1/5/8 expression and thereby activating the BMP signaling pathway. In addition, ginsenoside Rg1 maintenance of niche homeostasis to promote GSCs regeneration is dependent on ECR as demonstrated in ECR mutants.

CONCLUSIONS

Ginsenoside Rg1 regulated the ecological niche homeostasis of GSCs and promoted the regeneration of GSCs by targeting the ECR/BMP signaling pathway in hormone-deficient states in aging ovaries. It is of great significance for prolonging fertility potential and delaying ovarian senescence.

Single-cell RNA sequencing analysis to evaluate antimony exposure effects on cell-lineage communications within the Drosophila testicular niche

The increasing production and prevalence of antimony (Sb)-related products raise concerns regarding its potential hazards to reproductive health. Upon environmental exposure, Sb reportedly induces testicular toxicity during spermatogenesis; moreover, it is known to affect various testicular cell populations, particularly germline stem cell populations. However, the cell-cell communication resulting from Sb exposure within the testicular niche remains poorly understood. To address this gap, herein we analyzed testicular single-cell RNA sequencing data from Sb-exposed Drosophila. Our findings revealed that the epidermal growth factor receptor (EGFR) and WNT signaling pathways were associated with the stem cell niche in Drosophila testes, which may disrupt the homeostasis of the testicular niche in Drosophila. Furthermore, we identified several ligand-receptor pairs, facilitating the elucidation of intercellular crosstalk involved in Sb-mediated reproductive toxicology. We employed scRNA-seq analysis and conducted functional verification to investigate the expression patterns of core downstream factors associated with EGFR and WNT signatures in the testes under the influence of Sb exposure. Altogether, our results shed light on the potential mechanisms of Sb exposure-mediated testicular cell-lineage communications.

Signaling Pathways in Drosophila gonadal Stem Cells

The stem cells' ability to divide asymmetrically to produce differentiating and self-renewing daughter cells is crucial to maintain tissue homeostasis and development. Stem cell maintenance and differentiation rely on their regulatory microenvironment termed 'niches'. The mechanisms of the signal transduction pathways initiated from the niche, regulation of stem cell maintenance and differentiation were quite challenging to study. The knowledge gained from the study of Drosophila melanogaster testis and ovary helped develop our understanding of stem cell/niche interactions and signal pathways related to the regulatory mechanisms in maintaining homeostasis of adult tissue. In this review, we discuss the role of signaling pathways in Drosophila gonadal stem cell regeneration, competition, differentiation, dedifferentiation, proliferation, and fate determination. Furthermore, we present the current knowledge on how these signaling pathways are implicated in cancer, and how they contribute as potential candidates for effective cancer treatment.