Human leucocyte antigen G (HLA-G) and its murine homologue Qa-2 protect from pregnancy loss

During pregnancy, the maternal immune system has to balance tightly between protection against pathogens and tolerance towards a semi-allogeneic organism. Dysfunction of this immune adaptation can lead to severe complications such as pregnancy loss, preeclampsia or fetal growth restriction. The MHC-Ib molecule HLA-G is well known to mediate immunological tolerance. However, no in-vivo studies have yet demonstrated a beneficial role of HLA-G for pregnancy success. Myeloid derived suppressor cells (MDSC) are suppressively acting immune cells accumulating during pregnancy and mediating maternal-fetal tolerance. Here, we analyzed the impact of Qa-2, the murine homologue to HLA-G, on pregnancy outcome in vivo. We demonstrate that lack of Qa-2 led to intrauterine growth restriction and increased abortion rates especially in late pregnancy accompanied by changes in uterine gene expression, altered spiral artery remodeling and protein aggregation in trophoblast cells indicating a preeclampsia-like phenotype. Furthermore, lack of Qa-2 caused decreased accumulation of MDSC and impaired MDSC function. Lastly, we show that application of sHLA-G reduced abortion rates in Qa-2 deficient mice by inducing MDSC. Our results highlight the importance of an interaction between HLA-G and MDSC for pregnancy success and the therapeutic potential of HLA-G for the treatment of immunological pregnancy complications.

An RBPJ-Drosophila Model Reveals Dependence of RBPJ Protein Stability on the Formation of Transcription–Regulator Complexes

Notch signaling activity governs widespread cellular differentiation in higher animals, including humans, and is involved in several congenital diseases and different forms of cancer. Notch signals are mediated by the transcriptional regulator RBPJ in a complex with activated Notch (NICD). Analysis of Notch pathway regulation in humans is hampered by a partial redundancy of the four Notch receptor copies, yet RBPJ is solitary, allowing its study in model systems. In Drosophila melanogaster, the RBPJ orthologue is encoded by Suppressor of Hairless [Su(H)]. Using genome engineering, we replaced Su(H) by murine RBPJ in order to study its function in the fly. In fact, RBPJ largely substitutes for Su(H)’s function, yet subtle phenotypes reflect increased Notch signaling activity. Accordingly, the binding of RBPJ to Hairless (H) protein, the general Notch antagonist in Drosophila, was considerably reduced compared to that of Su(H). An H-binding defective RBPJLLL mutant matched the respective Su(H)LLL allele: homozygotes were lethal due to extensive Notch hyperactivity. Moreover, RBPJLLL protein accumulated at lower levels than wild type RBPJ, except in the presence of NICD. Apparently, RBPJ protein stability depends on protein complex formation with either H or NICD, similar to Su(H), demonstrating that the murine homologue underlies the same regulatory mechanisms as Su(H) in Drosophila. These results underscore the importance of regulating the availability of RBPJ protein to correctly mediate Notch signaling activity in the fly.

miR-424/322 is downregulated in the semen of patients with severe DNA damage and may regulate sperm DNA damage

Sperm DNA integrity is an essential factor for accurate transmission of genetic information. Human sperm DNA damage is a common cause of male infertility but the exact mechanism remains poorly understood. Considering the vital role of microRNA (miRNA) in multiple pathophysiological processes, we hypothesised that testicular miRNA is involved in sperm DNA damage during spermatogenesis. Infertile patients with high sperm DNA fragment index (DFI; n = 94) were selected from 1090 infertile men and a total of 18 testis-specific seminal miRNAs previously identified from human seminal plasma were chosen and tested. miR-29c and miR-424 were downregulated in men with high DFI. The inhibition of these two miRNAs in mice confirmed the role of miR-424 (murine homologue miR-322) in sperm DNA damage during spermatogenesis; by contrast, miR-29c exhibited a negative result. Thus, miR-424/322 is involved in sperm DNA damage. Furthermore, the dysregulation of this miRNA can induce DNA double-strand breaks during spermatogenesis.

Mesenchymal stem/progenitor cells promote the reconstitution of exogenous hematopoietic stem cells in Fancg−/− mice in vivo

Fanconi anemia (FA) is a heterogeneous genetic disorder characterized by bone marrow failure and complex congenital anomalies. Although mutations in FA genes result in a characteristic phenotype in the hematopoietic stem/progenitor cells (HSPCs), little is known about the consequences of a nonfunctional FA pathway in other stem/progenitor cell compartments. Given the intense functional interactions between HSPCs and the mesenchymalmicroenvironment, we investigated the FA pathway on the cellular functions of murine mesenchymal stem/progenitor cells (MSPCs) and their interactions with HSPCs in vitro and in vivo. Here, we show that loss of the murine homologue of FANCG (Fancg) results in a defect in MSPC proliferation and in their ability to support the adhesion and engraftment of murine syngeneic HSPCs in vitro or in vivo. Transplantation of wild-type (WT) but not Fancg−/− MSPCs into the tibiae of Fancg−/− recipient mice enhances the HSPC engraftment kinetics, the BM cellularity, and the number of progenitors per tibia of WT HSPCs injected into lethally irradiated Fancg−/− recipients. Collectively, these data show that FA proteins are required in the BM microenvironment to maintain normal hematopoiesis and provide genetic and quantitative evidence that adoptive transfer of WT MSPCs enhances hematopoietic stem cell engraftment.