Establishment of regeneration and transformation protocols to create hypoalleregenic peanut (Arachis hypogaea) and mustard (Brassica juncea) through genome editing

A stable and reproducible in vitro regeneration system is necessary for genetic engineering, however, explant responses vary widely between and within species and are highly dependent on the culture conditions. Despite decades of research, plant regeneration is still challenging especially with some plant species referred to as recalcitrant. In this study, we investigated the regeneration and genetic transformation capacities of different lines of peanut (Arachis hypogaea) that is considered recalcitrant and Brown mustard (Brassica juncea) in order to enable editing of the allergens Ara h 1 and Bra J I in peanut and mustard, respectively, via CRISPR/Cas9. Moreover, we demonstrated that, several of the first edited mustard lines displayed reduced or total absence of the Bra J I protein. Firstly, the factors affecting the adventitious shoot regeneration of both plant species were investigated using four peanut lines and six mustard lines from two geographical regions (Europe and India). In both species, shoot regeneration was significantly influenced by the explant type and the genetic make-up of the different lines tested. In mustard, the 5 days old cotyledon explants of all lines showed better responses than hypocotyls regarding adventitious shoot regeneration whereas in peanut the leaflet explants of 5-day-old seedlings exhibited superiority. The combinations of different types of cytokinins and auxins were tested on the explants of both plant species. In all peanut lines, the leaflet explants responded best on medium with 22.19 µM 6-benzylaminopurine (BAP) (+ 2.3 µM kinetin), which was reduced to 7.40 µM BAP after eight weeks, with regeneration rates of 10-89.1% and a mean shoot number per regenerating explant of 1-3.1 shoots. For mustard, the medium containing 8.88 µM BAP, 5.37 µM 1-naphthaleneacetic acid (NAA), and 9.95 µM Silver nitrate (AgNO3) resulted in the highest shoot regeneration rates (58-72% and 65-90% for the European and Indian lines, respectively) as well as the highest shoot numbers per regenerating explant (2.2-2.7 and 2.3-3.0). Furthermore, the effect of different light qualities on shoot regeneration from leaflet explants of the peanut lines was investigated in order to promote shoot induction and elongation. A strong effect of the culture temperature on the regeneration efficiency was observed as different light treatments were connected with different culture temperatures. However, red and blue LEDs could substitute tubular fluorescent lamps without affecting shoot regeneration. In the second step, Agrobacterium-mediated transformation of both plant species was investigated. Transgenic plants carrying large deletions of 566 up to 790 bp as well as indels in the targeted regions especially, indels in all four Bra j I alleles were obtained with the mustard lines tested. Seed viability was investigated in several transgenic mustard lines through in vitro and ex vitro germination. A decrease in seed viability and seed formation was observed in some edited lines, which indicated that the mutation of the major allergen Bra J I in mustard affected seed development. Part of the seeds exhibited aberrant phenotypes that resulted in the rupture of the testa already in the siliques. In contrast, the regenerated shoots from the different transformation experiments with various peanut lines exhibited a lack of transgenicity

StemCellNet: an interactive platform for network-oriented investigations in stem cell biology.

Stem cells are characterized by their potential for self-renewal and their capacity to differentiate into mature cells. These two key features emerge through the interplay of various factors within complex molecular networks. To provide researchers with a dedicated tool to investigate these networks, we have developed StemCellNet, a versatile web server for interactive network analysis and visualization. It rapidly generates focused networks based on a large collection of physical and regulatory interactions identified in human and murine stem cells. The StemCellNet web-interface has various easy-to-use tools for selection and prioritization of network components, as well as for integration of expression data provided by the user. As a unique feature, the networks generated can be screened against a compendium of stemness-associated genes. StemCellNet can also indicate novel candidate genes by evaluating their connectivity patterns. Finally, an optional dataset of generic interactions, which provides large coverage of the human and mouse proteome, extends the versatility of StemCellNet to other biomedical research areas in which stem cells play important roles, such as in degenerative diseases or cancer. The StemCellNet web server is freely accessible at http://stemcellnet.sysbiolab.eu

Large intergenic non-coding RNA-RoR modulates reprogramming of human induced pluripotent stem cells

February 17, 2011The conversion of lineage-committed cells to induced pluripotent stem cells (iPSCs) by reprogramming is accompanied by a global remodeling of the epigenome[superscript 1, 2, 3, 4, 5], resulting in altered patterns of gene expression[superscript 2, 6, 7, 8, 9]. Here we characterize the transcriptional reorganization of large intergenic non-coding RNAs (lincRNAs)[superscript 10, 11] that occurs upon derivation of human iPSCs and identify numerous lincRNAs whose expression is linked to pluripotency. Among these, we defined ten lincRNAs whose expression was elevated in iPSCs compared with embryonic stem cells, suggesting that their activation may promote the emergence of iPSCs. Supporting this, our results indicate that these lincRNAs are direct targets of key pluripotency transcription factors. Using loss-of-function and gain-of-function approaches, we found that one such lincRNA (lincRNA-RoR) modulates reprogramming, thus providing a first demonstration for critical functions of lincRNAs in the derivation of pluripotent stem cells

An embryonic stem cell–like gene expression signature in poorly differentiated aggressive human tumors

Cancer cells possess traits reminiscent of those ascribed to normal stem cells. It is unclear, however, whether these phenotypic similarities reflect the activity of common molecular pathways. Here, we analyze the enrichment patterns of gene sets associated with embryonic stem (ES) cell identity in the expression profiles of various human tumor types. We find that histologically poorly differentiated tumors show preferential overexpression of genes normally enriched in ES cells, combined with preferential repression of Polycomb-regulated genes. Moreover, activation targets of Nanog, Oct4, Sox2 and c-Myc are more frequently overexpressed in poorly differentiated tumors than in well-differentiated tumors. In breast cancers, this ES-like signature is associated with high-grade estrogen receptor (ER)-negative tumors, often of the basal-like subtype, and with poor clinical outcome. The ES signature is also present in poorly differentiated glioblastomas and bladder carcinomas. We identify a subset of ES cell-associated transcription regulators that are highly expressed in poorly differentiated tumors. Our results reveal a previously unknown link between genes associated with ES cell identity and the histopathological traits of tumors and support the possibility that these genes contribute to stem cell–like phenotypes shown by many tumors

Suppression of Lung Adenocarcinoma Progression by Nkx2-1

Despite the high prevalence and poor outcome of patients with metastatic lung cancer the mechanisms of tumour progression and metastasis remain largely uncharacterized. Here we modelled human lung adenocarcinoma, which frequently harbours activating point mutations in KRAS and inactivation of the p53 pathway, using conditional alleles in mice. Lentiviral-mediated somatic activation of oncogenic Kras and deletion of p53 in the lung epithelial cells of Kras[superscript LSL-G12D/+];p53[superscript flox/flox] mice initiates lung adenocarcinoma development4. Although tumours are initiated synchronously by defined genetic alterations, only a subset becomes malignant, indicating that disease progression requires additional alterations. Identification of the lentiviral integration sites allowed us to distinguish metastatic from non-metastatic tumours and determine the gene expression alterations that distinguish these tumour types. Cross-species analysis identified the NK2-related homeobox transcription factor Nkx2-1 (also called Ttf-1 or Titf1) as a candidate suppressor of malignant progression. In this mouse model, Nkx2-1 negativity is pathognomonic of high-grade poorly differentiated tumours. Gain- and loss-of-function experiments in cells derived from metastatic and non-metastatic tumours demonstrated that Nkx2-1 controls tumour differentiation and limitsmetastatic potential in vivo. Interrogation of Nkx2-1-regulated genes, analysis of tumours at defined developmental stages, and functional complementation experiments indicate that Nkx2-1 constrains tumours in part by repressing the embryonically restricted chromatin regulator Hmga2. Whereas focal amplification of NKX2-1 in a fraction of human lung adenocarcinomas has focused attention on its oncogenic function, our data specifically link Nkx2-1 downregulation to loss of differentiation, enhanced tumour seeding ability and increased metastatic proclivity. Thus, the oncogenic and suppressive functions ofNkx2-1 in the sametumourNational Institutes of Health (U.S.) (grant U01-CA84306 )National Institutes of Health (U.S.) (grant K99-CA151968)Howard Hughes Medical InstituteLudwig Center for Molecular OncologyNational Cancer Institute (U.S.) (Cancer Center Support (core) grant P30-CA14051

Heterochromatin Protein 1β (HP1β) has distinct functions and distinct nuclear distribution in pluripotent versus differentiated cells

Background: Pluripotent embryonic stem cells (ESCs) have the unique ability to differentiate into every cell type and to self-renew. These characteristics correlate with a distinct nuclear architecture, epigenetic signatures enriched for active chromatin marks and hyperdynamic binding of structural chromatin proteins. Recently, several chromatin-related proteins have been shown to regulate ESC pluripotency and/or differentiation, yet the role of the major heterochromatin proteins in pluripotency is unknown. Results: Here we identify Heterochromatin Protein 1β (HP1β) as an essential protein for proper differentiation, and, unexpectedly, for the maintenance of pluripotency in ESCs. In pluripotent and differentiated cells HP1β is differentially localized and differentially associated with chromatin. Deletion of HP1β, but not HP1aα, in ESCs provokes a loss of the morphological and proliferative characteristics of embryonic pluripotent cells, reduces expression of pluripotency factors and causes aberrant differentiation. However, in differentiated cells, loss of HP1β has the opposite effect, perturbing maintenance of the differentiation state and facilitating reprogramming to an induced pluripotent state. Microscopy, biochemical fractionation and chromatin immunoprecipitation reveal a diffuse nucleoplasmic distribution, weak association with chromatin and high expression levels for HP1β in ESCs. The minor fraction of HP1β that is chromatin-bound in ESCs is enriched within exons, unlike the situation in differentiated cells, where it binds heterochromatic satellite repeats and chromocenters. Conclusions: We demonstrate an unexpected duality in the role of HP1β: it is essential in ESCs for maintaining pluripotency, while it is required for proper differentiation in differentiated cells. Thus, HP1β function both depends on, and regulates, the pluripotent state

Transcriptome Analysis during Human Trophectoderm Specification Suggests New Roles of Metabolic and Epigenetic Genes

In humans, successful pregnancy depends on a cascade of dynamic events during early embryonic development. Unfortunately, molecular data on these critical events is scarce. To improve our understanding of the molecular mechanisms that govern the specification/development of the trophoblast cell lineage, the transcriptome of human trophectoderm (TE) cells from day 5 blastocysts was compared to that of single day 3 embryos from our in vitro fertilization program by using Human Genome U133 Plus 2.0 microarrays. Some of the microarray data were validated by quantitative RT-PCR. The TE molecular signature included 2,196 transcripts, among which were genes already known to be TE-specific (GATA2, GATA3 and GCM1) but also genes involved in trophoblast invasion (MUC15), chromatin remodeling (specifically the DNA methyltransferase DNMT3L) and steroid metabolism (HSD3B1, HSD17B1 and FDX1). In day 3 human embryos 1,714 transcripts were specifically up-regulated. Besides stemness genes such as NANOG and DPPA2, this signature included genes belonging to the NLR family (NALP4, 5, 9, 11 and 13), Ret finger protein-like family (RFPL1, 2 and 3), Melanoma Antigen family (MAGEA1, 2, 3, 5, 6 and 12) and previously unreported transcripts, such as MBD3L2 and ZSCAN4. This study provides a comprehensive outlook of the genes that are expressed during the initial embryo-trophectoderm transition in humans. Further understanding of the biological functions of the key genes involved in steroidogenesis and epigenetic regulation of transcription that are up-regulated in TE cells may clarify their contribution to TE specification and might also provide new biomarkers for the selection of viable and competent blastocysts

Dissecting the First Transcriptional Divergence During Human Embryonic Development

The trophoblast cell lineage is specified early at the blastocyst stage, leading to the emergence of the trophectoderm and the pluripotent cells of the inner cell mass. Using a double mRNA amplification technique and a comparison with transcriptome data on pluripotent stem cells, placenta, germinal and adult tissues, we report here some essential molecular features of the human mural trophectoderm. In addition to genes known for their role in placenta (CGA, PGF, ALPPL2 and ABCG2), human trophectoderm also strongly expressed Laminins, such as LAMA1, and the GAGE Cancer/Testis genes. The very high level of ABCG2 expression in trophectoderm, 7.9-fold higher than in placenta, suggests a major role of this gene in shielding the very early embryo from xenobiotics. Several genes, including CCKBR and DNMT3L, were specifically up-regulated only in trophectoderm, indicating that the trophoblast cell lineage shares with the germinal lineage a transient burst of DNMT3L expression. A trophectoderm core transcriptional regulatory circuitry formed by 13 tightly interconnected transcription factors (CEBPA, GATA2, GATA3, GCM1, KLF5, MAFK, MSX2, MXD1, PPARD, PPARG, PPP1R13L, TFAP2C and TP63), was found to be induced in trophectoderm and maintained in placenta. The induction of this network could be recapitulated in an in vitro trophoblast differentiation model

Complex variation in Afrotropical mammal communities with human impact

The diversity and composition of mammal communities are strongly influenced by human activities, though these relationships may vary across broad scales. Understanding this variation is key to conservation, as it provides a baseline for planning and evaluating management interventions. We assessed variation in the structure and composition of Afrotropical medium and large mammal communities within and outside protected areas, and under varying human impact. We collected data at 512 locations from 22 study sites in 12 Afrotropical countries over 7 years and 3 months (2011–2018) with 164,474 camera trap days in total. Half of these sites are located inside protected areas and half in unprotected areas. The sites are comparable in that they all harbor at least one great ape species, indicating a minimum level of habitat similarity, though they experience varying degrees of human impact. We applied Bayesian Regression models to relate site protection status and the degree of human impact to mammal communities. Protected area status was positively associated with the proportion of all threatened species, independent of the degree of human impact. Similarly, species richness was associated with area protection but was more sensitive to human impact. For all other attributes of the mammal communities, the pattern was more complex. The influence of human impact partially overrides the positive effects of protected area status, resulting in comparable mammal communities being observed both within protected areas and in similarly remote locations outside these areas. We observed a common pattern for large carnivores, whose probability of occurrence declined significantly with increasing human impact, independent of site protection status. Mammal communities benefit from sustainability measures of socio-economic context that minimize human impact. Our results support the notion that conservation of mammalian species can be achieved by reducing human impact through targeted conservation measures, adopting landscape-level management strategies, fostering community engagement, and safeguarding remote habitats with high mammal diversity

Transcriptome Profiling of Human Pre-Implantation Development

BACKGROUND: Preimplantation development is a crucial step in early human development. However, the molecular basis of human preimplantation development is not well known. METHODOLOGY: By applying microarray on 397 human oocytes and embryos at six developmental stages, we studied the transcription dynamics during human preimplantation development. PRINCIPAL FINDINGS: We found that the preimplantation development consisted of two main transitions: from metaphase-II oocyte to 4-cell embryo where mainly the maternal genes were expressed, and from 8-cell embryo to blastocyst with down-regulation of the maternal genes and up-regulation of embryonic genes. Human preimplantation development proved relatively autonomous. Genes predominantly expressed in oocytes and embryos are well conserved during evolution. SIGNIFICANCE: Our database and findings provide fundamental resources for understandin