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Leptin protein was thought to be unique to leptin receptor (LepR), but the phenotypes of mice with mutation in LepR [db/db (diabetes)] and leptin [ob/ob (obese)] are not identical, and the cause remains unclear. Here, we show that db/db, but not ob/ob, mice had defect in tenotomy-induced heterotopic ossification (HO), implicating alternative ligand(s) for LepR might be involved. Ligand screening revealed that ANGPTL4 (angiopoietin-like protein 4), a stress and fasting-induced factor, was elicited from brown adipose tissue after tenotomy, bound to LepR on PRRX1+ mesenchymal cells at the HO site, thus promotes chondrogenesis and HO development. Disruption of LepR in PRRX1+ cells, or lineage ablation of LepR+ cells, or deletion of ANGPTL4 impeded chondrogenesis and HO in mice. Together, these findings identify ANGPTL4 as a ligand for LepR to regulate the formation of acquired HO. [ABSTRACT FROM AUTHOR]

PAS is one of the most alarming obstetric diseases with high mortality rates. The regulating mechanism underlying PAS remains to be investigated, and reliable blood biomarkers for PAS have not emerged. Circular RNAs (circRNAs) have become important regulators and biomarkers for disparate human diseases. However, the circRNA profiles of PAS were not reported, and the regulatory role and predictive value of circRNAs in PAS were unknown. Here, we comprehensively profiled the circRNAs in the placenta of PAS by transcriptome sequencing and analysis and uncovered 217 abnormally expressed circRNAs. Through competing endogenous RNA network analysis, we found that the target genes of upregulated circRNAs in PAS were enriched in placenta development-related pathways and further uncovered two circRNAs, circPHACTR4 and circZMYM4, that could regulate trophoblast cells invasion and migration in vitro. Finally, we verified that circPHACTR4 and circZMYM4 were also upregulated in the maternal peripheral blood of PAS women before delivery using transcriptome sequencing and RT-qPCR and evaluated their predictive value by ROC curves. We found that circPHACTR4 and circZMYM4 could serve as effective predicting biomarkers for PAS (area under the curve (AUC): 0.86 and 0.85) and propose an improved model for PAS prenatal prediction by combining the conventional ultrasound diagnosis with the new circRNA predictive factors (AUC: 0.91, specificity: 0.89, sensitivity: 0.82).Altogether, this work provides new resources for deciphering the biological roles of circRNAs in PAS, identified two circRNAs that could regulate trophoblast cells invasion during placentation, and revealed two noninvasive diagnostic markers for PAS. [ABSTRACT FROM AUTHOR]

Processing of pre-mRNA into mRNA is an important regulatory mechanism in eukaryotes that is mediated by the spliceosome, a huge and dynamic ribonucleoprotein complex. Splicing defects are implicated in a spectrum of human disease, but the underlying mechanistic links remain largely unresolved. Using a genome-wide association approach, we have recently identified single nucleotide polymorphisms in humans that associate with nonobstructive azoospermia (NOA), a common cause of male infertility. Here, using genetic manipulation of corresponding candidate loci in Drosophila, we show that the spliceosome component SNRPA1/U2A is essential for male fertility. Loss of U2A in germ cells of the Drosophila testis does not affect germline stem cells, but does result in the accumulation of mitotic spermatogonia that fail to differentiate into spermatocytes and mature sperm. Lack of U2A causes insufficient splicing of mRNAs required for the transition of germ cells from proliferation to differentiation. We show that germ cell-specific disruption of other components of the major spliceosome manifests with the same phenotype, demonstrating that mRNA processing is required for the differentiation of spermatogonia. This requirement is conserved, and expression of human SNRPA1 fully restores spermatogenesis in U2A mutant flies. We further report that several missense mutations in human SNRPA1 that inhibit the assembly of the major spliceosome dominantly disrupt spermatogonial differentiation in Drosophila. Collectively, our findings uncover a conserved and specific requirement for the major spliceosome during the transition from spermatogonial proliferation to differentiation in the male testis, suggesting that spliceosome defects affecting the differentiation of human spermatogonia contribute to NOA. [ABSTRACT FROM AUTHOR]

Fragile X syndrome, a common form of inherited mental retardation, is caused by the loss of fragile X mental retardation protein (FMRP). We have previously demonstrated that dFmr1, the Drosophila ortholog of the fragile X mental retardation 1 gene, plays a role in the proper maintenance of germline stem cells in Drosophila ovary; however, the molecular mechanism behind this remains elusive. In this study, we used an immunoprecipitation assay to reveal that specific microRNAs (miRNAs), particularly the bantam miRNA (bantam), are physically associated with dFmrp in ovary. We show that, like dFmr1, bantam is not only required for repressing primordial germ cell differentiation, it also functions as an extrinsic factor for germline stem cell maintenance. Furthermore, we find that bantam genetically interacts with dFmr1 to regulate the fate of germline stem cells. Collectively, our results support the notion that the FMRP-mediated translation pathway functions through specific miRNAs to control stem cell regulation. [ABSTRACT FROM AUTHOR]

Increasing evidence supports the idea that the regulation of stem cells requires both extrinsic and intrinsic mechanisms. However, much less is known about how intrinsic signals regulate the fate of stem cells. Studies on germline stem cells (GSCs) in the Drosophila ovary have provided novel insights into the regulatory mechanisms of stem cell maintenance. In this study, we demonstrate that a ubiquitin-dependent pathway mediated by the Drosophila eff gene, which encodes the E2 ubiquitin-conjugating enzyme Effete (Eff), plays an essential role in GSC maintenance. We show that Eff both physically and genetically interacts with dAPC2, a key component of the anaphase-promoting complex (APC), which acts as a multisubunit E3 ligase and plays an essential role in targeting mitotic regulators for degradation during exit from mitosis. This interaction indicates that Eff regulates the APC/C-mediated proteolysis pathway in GSCs. Moreover, we show that expression of a stable form of Cyclin A, but not full-length Cyclin A, results in GSC loss. Finally we show that, in common with APC2, Eff is required for the ubiquitylation of Cyclin A, and overexpression of full-length Cyclin A accelerates the loss of GSCs in the eff mutant background. Collectively, our data support the idea that Effete/APC-mediated degradation of Cyclin A is essential for the maintenance of germline stem cells in Drosophila. Given that the regulation of mitotic Cyclins is evolutionarily conserved between flies and mammals, our study also implies that a similar mechanism may be conserved in mammals. [ABSTRACT FROM AUTHOR]

The Argonaute-family proteins play crucial roles in small-RNA-mediated gene regulation. In Drosophila, previous studies have demonstrated that Piwi, one member of the PIWI subfamily of Argonaute proteins, plays an essential role in regulating the fate of germline stem cells (GSCs). However, whether other Argonaute proteins also play similar roles remains elusive. Here, we show that overexpression of Argonaute 1 (AGO1) protein, another subfamily (AGO) of the Argonaute proteins, leads to GSC overproliferation, whereas loss of Ago1 results in the loss of GSCs. Combined with germline clonal analyses of Ago1, these findings strongly support the argument that Ago1 plays an essential and intrinsic role in the maintenance of GSCs. In contrast to previous observations of Piwi function in the maintenance of GSCs, we show that AGO1 is not required for bag of marbles (bam) silencing and probably acts downstream or parallel of bam in the regulation of GSC fate. Given that AGO1 serves as a key component of the miRNA pathway, we propose that an AGO1-dependent miRNA pathway probably plays an instructive role in repressing GSC/cystoblast differentiation. [ABSTRACT FROM AUTHOR]