Biglycan is a novel binding partner of fibroblast growth factor receptor 3c (FGFR3c) in the human testis

FGF9 variant in 46,XY DSD patient suggests a role for dimerization in sex determination

46,XY gonadal dysgenesis (GD) is a Disorder/Difference of Sex Development (DSD) that can present with phenotypes ranging from ambiguous genitalia to complete male-to-female sex reversal. Around 50% of 46,XY DSD cases receive a molecular diagnosis. In mice, Fibroblast growth factor 9 (FGF9) is an important component of the male sex-determining pathway. Two FGF9 variants reported to date disrupt testis development in mice, but not in humans. Here, we describe a female patient with 46,XY GD harbouring the rare FGF9 variant (missense mutation), NM_002010.2:c.583G > A;p.(Asp195Asn) (D195N). By biochemical and cell-based approaches, the D195N variant disrupts FGF9 protein homodimerisation and FGF9-heparin-binding, and reduces both Sertoli cell proliferation and Wnt4 repression. XY Fgf9D195N/D195N foetal mice show a transient disruption of testicular cord development, while XY Fgf9D195N/- foetal mice show partial male-to-female gonadal sex reversal. In the general population, the D195N variant occurs at an allele frequency of 2.4 × 10-5 , suggesting an oligogenic basis for the patient's DSD. Exome analysis of the patient reveals several known and novel variants in genes expressed in human foetal Sertoli cells at the time of sex determination. Taken together, our results indicate that disruption of FGF9 homodimerization impairs testis determination in mice and, potentially, also in humans in combination with other variants.

Dysregulated genes in undifferentiated spermatogonia and Sertoli cells are associated with the spermatogenic arrest in cattleyak

Hybrid male sterility (HMS) is a reproductive isolation mechanism limiting the formation of fertile offspring through interspecific fertilization. Cattleyak is the interspecific hybrid presenting significant heterosis in several economic traits, but HMS restricted its wide reproduction in cettleyak breeding. In this study, we detected the specifically expressed genes of a variety of cells (undifferentiated spermatogonia, primary spermatocytes, secondary spermatocytes, haploid spermatids, sperm, Sertoli cells, Leydig cells, and macrophages) in the testis of yak and cattleyak, and found that the spermatogenesis of cattleyak might be blocked at meiosis I, and the expression of niche factors (NR5A1, GATA4, STAR, CYP11A1, CD68, TNF, and CX3CR1) in undifferentiated spermatogonia niche was abnormal. Then we isolated the undifferentiated spermatogonia and Sertoli cells from yak and cattleyak by enzyme digestion, and detected the specific genes in the two bovid testicular cells as well as the proliferation capacity of the undifferentiated spermatogonia. These results indicated that weak proliferation ability and scarce number of undifferentiated spermatogonia and abnormal gene expressions in Sertoli cells may contribute to male sterility of cattleyak.

CellCall: integrating paired ligand-receptor and transcription factor activities for cell-cell communication

With the dramatic development of single-cell RNA sequencing (scRNA-seq) technologies, the systematic decoding of cell-cell communication has received great research interest. To date, several in-silico methods have been developed, but most of them lack the ability to predict the communication pathways connecting the insides and outsides of cells. Here, we developed CellCall, a toolkit to infer inter- and intracellular communication pathways by integrating paired ligand-receptor and transcription factor (TF) activity. Moreover, CellCall uses an embedded pathway activity analysis method to identify the significantly activated pathways involved in intercellular crosstalk between certain cell types. Additionally, CellCall offers a rich suite of visualization options (Circos plot, Sankey plot, bubble plot, ridge plot, etc.) to present the analysis results. Case studies on scRNA-seq datasets of human testicular cells and the tumor immune microenvironment demonstrated the reliable and unique functionality of CellCall in intercellular communication analysis and internal TF activity exploration, which were further validated experimentally. Comparative analysis of CellCall and other tools indicated that CellCall was more accurate and offered more functions. In summary, CellCall provides a sophisticated and practical tool allowing researchers to decipher intercellular communication and related internal regulatory signals based on scRNA-seq data. CellCall is freely available at https://github.com/ShellyCoder/cellcall.

Ovotesticular disorders of sex development in FGF9 mouse models of human synostosis syndromes

In mice, male sex determination depends on FGF9 signalling via FGFR2c in the bipotential gonads to maintain the expression of the key testis gene SOX9. In humans, however, while FGFR2 mutations have been linked to 46,XY disorders of sex development (DSD), the role of FGF9 is unresolved. The only reported pathogenic mutations in human FGF9, FGF9S99N and FGF9R62G, are dominant and result in craniosynostosis (fusion of cranial sutures) or multiple synostoses (fusion of limb joints). Whether these synostosis-causing FGF9 mutations impact upon gonadal development and DSD etiology has not been explored. We therefore examined embryonic gonads in the well-characterized Fgf9 missense mouse mutants, Fgf9S99N and Fgf9N143T, which phenocopy the skeletal defects of FGF9S99N and FGF9R62G variants, respectively. XY Fgf9S99N/S99N and XY Fgf9N143T/N143T fetal mouse gonads showed severely disorganized testis cords and partial XY sex reversal at 12.5 days post coitum (dpc), suggesting loss of FGF9 function. By 15.5 dpc, testis development in both mutants had partly recovered. Mitotic analysis in vivo and in vitro suggested that the testicular phenotypes in these mutants arise in part through reduced proliferation of the gonadal supporting cells. These data raise the possibility that human FGF9 mutations causative for dominant skeletal conditions can also lead to loss of FGF9 function in the developing testis, at least in mice. Our data suggest that, in humans, testis development is largely tolerant of deleterious FGF9 mutations which lead to skeletal defects, thus offering an explanation as to why XY DSDs are rare in patients with pathogenic FGF9 variants.

OPG-Fc treatment partially rescues low bone mass phenotype in mature Bgn/Fmod deficient mice but is deleterious to the young mouse skeleton

Biglycan (Bgn) and Fibromodulin (Fmod) are small leucine rich proteoglycans (SLRPs) which are abundant in the extra-cellular matrix (ECM) of mineralized tissues. We have previously generated a Bgn/Fmod double knock-out (DKO) mouse model and found it has a 3-fold increase in osteoclastogenesis compared with Wild type (WT) controls, resulting in a markedly low bone mass (LBM) phenotype. To try and rescue/repair the LBM phenotype of Bgn/Fmod DKO mice by suppressing osteoclast formation and activity, 3- and 26-week-old Bgn/Fmod DKO mice and age/gender matched WT controls were treated with OPG-Fc for 6 weeks after which bone parameters were evaluated using DEXA, micro-computed tomography (μCT) and serum biomarkers analyses. In the appendicular skeleton, OPG-Fc treatment improved some morphometric and geometric parameters in both the trabecular and cortical compartments in Bgn/Fmod DKO female and male mice, especially in the repair module. For many of the skeletal parameters analyzed, the Bgn/Fmod DKO mice were more responsive to the treatment than their WT controls. In addition, we found that OPG-Fc treatment was not able to prevent or ameliorate the formation of ectopic ossification, which are common lesions seen in aged joints and are one of the phenotypical hallmarks of our Bgn/Fmod DKO model. Analysis of skull bones, specifically the occipital bone, showed the treatment recovered some parameters of LBM phenotype in the craniofacial skeleton, more so in the younger rescue module. Using OPG-Fc as treatment alleviated, yet did not completely restore, the severe osteopenia and mineralized tissue structural abnormalities that Bgn/Fmod DKO mice suffer from.

Sterile inflammation as a factor in human male infertility: Involvement of Toll like receptor 2, biglycan and peritubular cells

Changes in the wall of seminiferous tubules in men with impaired spermatogenesis imply sterile inflammation of the testis. We tested the hypothesis that the cells forming the wall of seminiferous tubules, human testicular peritubular cells (HTPCs), orchestrate inflammatory events and that Toll like receptors (TLRs) and danger signals from the extracellular matrix (ECM) of this wall are involved. In cultured HTPCs we detected TLRs, including TLR2. A TLR-2 ligand (PAM) augmented interleukin 6 (IL-6), monocyte chemo-attractant protein-1 (MCP-1) and pentraxin 3 (PTX3) in HTPCs. The ECM-derived proteoglycan biglycan (BGN) is secreted by HTPCs and may be a TLR2-ligand at HTPCs. In support, recombinant human BGN increased PTX3, MCP-1 and IL-6 in HTPCs. Variable endogenous BGN levels in HTPCs derived from different men and differences in BGN levels in the tubular wall in infertile men were observed. In testes of a systemic mouse model for male infertility, testicular sterile inflammation and elevated estradiol (E2) levels, BGN was also elevated. Hence we studied the role of E2 in HTPCs and observed that E2 elevated the levels of BGN. The anti-estrogen ICI 182,780 blocked this action. We conclude that TLR2 and BGN contribute to sterile inflammation and infertility in man.

The cytoprotective effect of biglycan core protein involves Toll-like receptor 4 signaling in cardiomyocytes

AIMS

Exogenously administered biglycan (core protein with high-molecular weight glycosaminoglycan chains) has been shown to protect neonatal cardiomyocytes against simulated ischemia/reperfusion injury (SI/R), however, the mechanism of action is not clear. In this study we aimed to investigate, which structural component of biglycan is responsible for its cardiocytoprotective effect and to further explore the molecular mechanisms involved in the cytoprotection.

METHODS AND RESULTS

A pilot study was conducted to demonstrate that both native (glycanated) and deglycanated biglycan can attenuate cell death induced by SI/R in a dose-dependent manner in primary neonatal cardiomyocytes isolated from Wistar rats. In separate experiments, we have shown that similarly to glycanated biglycan, recombinant human biglycan core protein (rhBGNc) protects cardiomyocytes against SI/R injury. In contrast, the glycosaminoglycan component dermatan sulfate had no significant effect on cell viability, while chondroitin sulfate further enhanced cell death induced by SI/R. Treatment of cardiomyocytes with rhBGNc reverses the effect of SI/R upon markers of necrosis, apoptosis, mitochondrial membrane potential, and autophagy. We have also shown that pharmacological blockade of Toll-like receptor 4 (TLR4) signaling or its downstream mediators (IRAK1/4, ERK, JNK and p38 MAP kinases) abolished the cytoprotective effect of rhBGNc against SI/R injury. Pretreatment of cardiomyocytes with rhBGNc for 20h resulted in increased Akt phosphorylation and NO production without having significant effect on phosphorylation of ERK1/2, STAT3, and on the production of superoxide. Treatment over 10min and 1h with rhBGNc increased ERK1 phosphorylation, while the SI/R-induced increase in superoxide production was attenuated by rhBGNc. Blockade of NO synthesis also prevented the cardiocytoprotective effect of rhBGNc.

CONCLUSIONS

The core protein of exogenous biglycan protects myocardial cells from SI/R injury via TLR4-mediated mechanisms involving activation of ERK, JNK and p38 MAP kinases and increased NO production. The cytoprotective effect of rhBGNc is due to modulation of SI/R-induced changes in necrosis, apoptosis and autophagy.

Identifying functional cancer-specific miRNA-mRNA interactions in testicular germ cell tumor

Testicular cancer is the most common cancer in men aged between 15 and 35 and more than 90% of testicular neoplasms are originated at germ cells. Recent research has shown the impact of microRNAs (miRNAs) in different types of cancer, including testicular germ cell tumor (TGCT). MicroRNAs are small non-coding RNAs which affect the development and progression of cancer cells by binding to mRNAs and regulating their expressions. The identification of functional miRNA-mRNA interactions in cancers, i.e. those that alter the expression of genes in cancer cells, can help delineate post-regulatory mechanisms and may lead to new treatments to control the progression of cancer. A number of sequence-based methods have been developed to predict miRNA-mRNA interactions based on the complementarity of sequences. While necessary, sequence complementarity is, however, not sufficient for presence of functional interactions. Alternative methods have thus been developed to refine the sequence-based interactions using concurrent expression profiles of miRNAs and mRNAs. This study aims to find functional cancer-specific miRNA-mRNA interactions in TGCT. To this end, the sequence-based predicted interactions are first refined using an ensemble learning method, based on two well-known methods of learning miRNA-mRNA interactions, namely, TaLasso and GenMiR++. Additional functional analyses were then used to identify a subset of interactions to be most likely functional and specific to TGCT. The final list of 13 miRNA-mRNA interactions can be potential targets for identifying TGCT-specific interactions and future laboratory experiments to develop new therapies.

Spermatogonial cells: mouse, monkey and man comparison

In all mammals, spermatogonia are defined as constituting the mitotic compartment of spermatogenesis including stem, undifferentiated and differentiating cell types, possessing distinct morphological and molecular characteristics. Even though the real nature of the spermatogonial stem cell and its regulation is still debated the general consensus holds that in steady-state spermatogenesis the stem cell compartment needs to balance differentiation versus self-renewal. This review highlights current understanding of spermatogonial biology, the kinetics of amplification and the signals directing spermatogonial differentiation in mammals. The focus will be on relevant similarities and differences between rodents and non human and human primates.

PLAP-1/Asporin Positively Regulates FGF-2 Activity

PLAP-1 is an extracellular matrix protein that is predominantly expressed in the periodontal ligament within periodontal tissue. It was previously revealed that PLAP-1 negatively regulates bone morphogenetic protein 2 and transforming growth factor β activity through direct interactions. However, the interaction between PLAP-1 and other growth factors has not been defined. Here, we revealed that PLAP-1 positively regulates the activity of fibroblast growth factor 2 (FGF-2), a critical growth factor in tissue homeostasis and repair. In this study, we isolated mouse embryonic fibroblasts (MEFs) from Plap-1(-/-) mice generated in our laboratory. Interestingly, Plap-1(-/-) MEFs exhibited enhanced responses to bone morphogenetic protein 2 but defective responses to FGF-2, and Plap-1 transfection into Plap-1(-/-) MEFs rescued these defective responses. In addition, binding assays revealed that PLAP-1 promotes FGF-2-FGF receptor 1 (FGFR1) complex formation by direct binding to FGF-2. Immunocytochemistry analyses revealed colocalization of PLAP-1 and FGF-2 in wild-type MEFs and reduced colocalization of FGF-2 and FGFR1 in Plap-1(-/-) MEFs compared with wild-type MEFs. Taken together, PLAP-1 positively regulates FGF-2 activity through a direct interaction. Extracellular matrix-growth factor interactions have considerable effects; thus, this approach may be useful in several regenerative medicine applications.