A piggyBac-based platform for genome editing and clonal rhesus macaque iPSC line derivation.

Non-human primates (NHPs) are, due to their close phylogenetic relationship to humans, excellent animal models to study clinically relevant mutations. However, the toolbox for the genetic modification of NHPs is less developed than those for other species like mice. Therefore, it is necessary to further develop and refine genome editing approaches in NHPs. NHP pluripotent stem cells (PSCs) share key molecular signatures with the early embryo, which is an important target for genomic modification. Therefore, PSCs are a valuable test system for the validation of embryonic genome editing approaches. In the present study, we made use of the versatility of the piggyBac transposon system for different purposes in the context of NHP stem cell technology and genome editing. These include (1) Robust reprogramming of rhesus macaque fibroblasts to induced pluripotent stem cells (iPSCs); (2) Culture of the iPSCs under feeder-free conditions even after removal of the transgene resulting in transgene-free iPSCs; (3) Development of a CRISPR/Cas-based work-flow to edit the genome of rhesus macaque PSCs with high efficiency; (4) Establishment of a novel protocol for the derivation of gene-edited monoclonal NHP-iPSC lines. These findings facilitate efficient testing of genome editing approaches in NHP-PSC before their in vivo application.

Prenatal and postnatal experiences associated with epigenetic changes in the adult mouse brain.

To analyze the influences of early-life history on the brain epigenome, the offspring of mouse dams kept in an enriched or standard environment were exposed postnatally to enriched, standard, or adverse conditions. The methylation patterns of 7 candidate genes (9 loci) involved in developmental programming of stress vulnerability/resilience and psychiatric disease were analyzed in 6 brain regions of adult male and female mice. Exposure to an enriched prenatal environment was associated with widespread epigenetic changes (all of small effect size), affecting 29 of 324 (9%) gene/region-specific methylation patterns. The effects of either adverse or enriched postnatal conditions were tested separately in the two prenatal cohorts. Significant changes were observed in 2 of 324 (0.6%) loci in offspring of dams in a standard environment and 6 of 324 (1.9%) loci in animals that were exposed prenatally to an enriched environment. Prenatal life experiences appear to have a bigger effect on the adult brain epigenome than postnatal experiences. Positive prenatal life experiences may increase epigenetic plasticity of the brain later in life. All observed between-group differences were sex-specific, consistent with largely different developmental trajectories of the male and female brain. Multiple changes of small effect size are consistent with a multifactorial model of developmental programming of adult behavior and disease susceptibility.

DNA methylation and mRNA expression of developmentally important genes in bovine oocytes collected from donors of different age categories.

Epigenetic changes are critical for the acquisition of developmental potential by oocytes and embryos, yet these changes may be sensitive to maternal ageing. Here, we investigated the impact of maternal ageing on DNA methylation and mRNA expression in a panel of eight genes that are critically involved in oocyte and embryo development. Bovine oocytes were collected from donors of three different age categories-prepubertal (9-12 months old), mature (3-7 years old), and aged (8-11 years old)-and were analyzed for gene-specific DNA methylation (bTERF2, bREC8, bBCL-XL, bPISD, bBUB1, bDNMT3Lo, bH19, and bSNRPN) and mRNA expression (bTERF2, bBCL-XL, bPISD, and bBUB1). A total of 1,044 alleles with 88,740 CpGs were amplified and sequenced from 362 bovine oocytes. Most of the detected molecules were either fully methylated or completely unmethylated. Only 9 out of 1,044 alleles (<1%) were abnormally methylated (>50% of CpGs with an aberrant methylation status), and seven of the nine abnormally methylated alleles were within only two candidate genes (bDNMT3Lo and bH19). No significant differences were detected with regard to mRNA expression between oocytes from the three groups of donors. These results suggest that genes predominantly important for early embryo development (bH19 and bDNMT3Lo) are less resistant to abnormal methylation than genes critically involved in oocyte development (bTERF2, bBCL-XL, bPISD, bBUB1, and bSNRPN). Establishment of DNA methylation in bovine oocytes seems to be largely resistant to changes caused by maternal ageing, irrespective of whether the genes are critical to achieve developmental competence in oocytes or early embryos. Mol. Reprod. Dev. 83: 802-814, 2016 © 2016 Wiley Periodicals, Inc.

Development of a New Antileishmanial Aziridine-2,3-Dicarboxylate-Based Inhibitor with High Selectivity for Parasite Cysteine Proteases.

Leishmaniasis is one of the major neglected tropical diseases of the world. Druggable targets are the parasite cysteine proteases (CPs) of clan CA, family C1 (CAC1). In previous studies, we identified two peptidomimetic compounds, the aziridine-2,3-dicarboxylate compounds 13b and 13e, in a series of inhibitors of the cathepsin L (CL) subfamily of the papain clan CAC1. Both displayed antileishmanial activity in vitro while not showing cytotoxicity against host cells. In further investigations, the mode of action was characterized in Leishmania major. It was demonstrated that aziridines 13b and 13e mainly inhibited the parasitic cathepsin B (CB)-like CPC enzyme and, additionally, mammalian CL. Although these compounds induced cell death of Leishmania promastigotes and amastigotes in vitro, the induction of a proleishmanial T helper type 2 (Th2) response caused by host CL inhibition was observed in vivo. Therefore, we describe here the synthesis of a new library of more selective peptidomimetic aziridine-2,3-dicarboxylates discriminating between host and parasite CPs. The new compounds are based on 13b and 13e as lead structures. One of the most promising compounds of this series is compound s9, showing selective inhibition of the parasite CPs LmaCatB (a CB-like enzyme of L. major; also named L. major CPC) and LmCPB2.8 (a CL-like enzyme of Leishmania mexicana) while not affecting mammalian CL and CB. It displayed excellent leishmanicidal activities against L. major promastigotes (50% inhibitory concentration [IC50] = 37.4 µM) and amastigotes (IC50 = 2.3 µM). In summary, we demonstrate a new selective aziridine-2,3-dicarboxylate, compound s9, which might be a good candidate for future in vivo studies.

Extended in vitro maturation affects gene expression and DNA methylation in bovine oocytes.

To mimic post-ovulatory ageing, we have extended the in vitro maturation (IVM) phase to 48 h and examined effects on (i) developmental potential, (ii) expression of a panel of developmentally important genes and (iii) gene-specific epigenetic marks. Results were compared with the 24 h IVM protocol (control) usually employed for bovine oocytes. Cleavage rates and blastocyst yields were significantly reduced in oocytes after extended IVM. No significant differences were observed in the methylation of entire alleles in oocytes for the genes bH19, bSNRPN, bZAR1, bOct4 and bDNMT3A. However, we found differentially methylated CpG sites in the bDNMT3Ls locus in oocytes after extended IVM and in embryos derived from them compared with controls. Moreover, embryos derived from the 48 h matured oocyte group were significantly less methylated at CpG5 and CpG7 compared with the 24 h group. CpG7 was significantly hypermethylated in embryos produced from the control oocytes, but not in oocytes matured for 48 h. Furthermore, methylation for CpG5-CpG8 of bDNMT3Ls was significantly lower in oocytes of the 24 h group compared with embryos derived therefrom, whereas no such difference was found for oocytes and embryos of the in vitro aged group. Expression of most of the selected genes was not affected by duration of IVM. However, transcript abundance for the imprinted gene bIGF2R was significantly reduced in oocytes analyzed after extended IVM compared with control oocytes. Transcript levels for bPRDX1, bDNMT3A and bBCLXL were significantly reduced in 4- to 8-cell embryos derived from in vitro aged oocytes. These results indicate that extended IVM leads to ageing-like alterations and demonstrate that epigenetic mechanisms are critically involved in ageing of bovine oocytes, which warrants further studies into epigenetic mechanisms involved in ageing of female germ cells, including humans.