Human ES Cell Culture Conditions Fail to Preserve the Mouse Epiblast State

Mouse embryonic stem cells (mESCs) and mouse epiblast stem cells (mEpiSCs) are the pluripotent stem cells (PSCs), derived from the inner cell mass (ICM) of preimplantation embryos at embryonic day 3.5 (E3.5) and postimplantation embryos at E5.5-E7.5, respectively. Depending on their environment, PSCs can exist in the so-called naive (ESCs) or primed (EpiSCs) states. Exposure to EpiSC or human ESC (hESC) culture condition can convert mESCs towards an EpiSC-like state. Here, we show that the undifferentiated epiblast state is however not stabilized in a sustained manner when exposing mESCs to hESC or EpiSC culture condition. Rather, prolonged exposure to EpiSC condition promotes a transition to a primitive streak- (PS-) like state via an unbiased epiblast-like intermediate. We show that the Brachyury-positive PS-like state is likely promoted by endogenous WNT signaling, highlighting a possible species difference between mouse epiblast-like stem cells and human Embryonic Stem Cells

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

Differentielle Modulation der BMP-Signalwege durch Activin/Nodal und FGF- Signalwege in der Lineage-Spezifikation von humanen embryonalen Stammzellen

Human embryonic stem cells (hESC) can be differentiated into both embryonic and extraembryonic lineages via the modulation of signaling pathways. BMP signalling is known to support differentiation of hESCs into multiple lineages, including trophoblast (TE). It has been shown that that TE formation can be induced in hESCs using BMP4 or BMP2 or SB431542 (a TGFßRI specific inhibitor) or via OCT4 knock down. In our current study we show for the first time that inhibition of FGF signaling in hESCs also supports trophoblast differentiation, inducing hCG secretion. Further, we also show that inhibition of FGF signaling (-FGF), either alone or in conjunction with BMP signaling activation and ACTIVIN/NODAL signaling inhibition (+BMP-TGF-FGF) induces hESC differentiation to non-invasive, epithelial, βhCG hormone secreting multinucleated syncytiotrophoblast. The latter treatment (+BMP-TGF-FGF) induced an accelerated differentiation process. Our results also indicate that BMP signaling activation (+BMP) or an additional inhibition of ACTIVIN/NODAL signaling either with or without exogenous FGF signaling activation (+BMP-TGF or +BMP-TGF+FGF) supports differentiation of hESCs to embryonic mesendoderm and extraembryonic trophoblast lineages, but does not support neurectodermal differentiation. Taken together, the insights from this study can be used to understand early lineage segregation events during embryo development. Further, we can also understand syncytiotrophoblast formation, endocrine functions of placenta, drug metabolism or pathological conditions, which could provide direction for the pre-clinical development of rational therapeutics.Humane embryonale Stammzellen (hESC) können durch die Modulation von Signaltransduktionskaskaden sowohl in die embryonale als auch in die extraembryonale Linie differenziert werden. Die BMP- Signaltransduktionskaskaden sind bekannt dafür, eine unterstützende Wirkung auf die Differenzierung der hESCs in multiple Linien auszuüben, einschließlich der Differenzierung in Trophoblast (TE). Es konnte gezeigt werden, dass die TE Bildung aus hESCs durch BMP4, BMP2, SB431542 (einem spezifischen TGFßRI Inhibitor) oder mittels eines OCT4-Knock-Downs induziert werden kann. In der vorliegenden Studie zeigen wir erstmalig, dass die Inhibition der FGF- Signaltransduktion die Trophoblastdifferenzierung mit anschließender hCG Sekretion fördert. Zudem zeigen wir, dass die Inhibition der FGF- Signaltransduktion (-FGF) allein oder in Kombination mit einer Aktivierung der BMP-Signaltransduktion bei gleichzeitiger ACTIVIN/NODAL Inhibition (+BMP-TGF- FGF) die Differenzierung von hESCs in nicht-invasive, ßhCG-Hormon sezernierende, multinukleäre Synzytiotrophoblasten induziert. Die Wirkung der letztgenannten, kombinierten Behandlung (+BMP-TGF-FGF) von hESC ist dabei besonders effizient. Unsere Ergebnisse deuten darauf hin, dass die Aktivierung der BMPSignaltransduktion (+BMP) oder eine zusätzliche Inhibition der ACTIVIN/NODALSignaltransduktion, entweder mit oder ohne gleichzeitiger Aktivierung der FGFSignaltransduktion (+BMP-TGF oder +BMP-TGF+FGF), die Differenzierung der hESCs in Richtung embryonales Mesoderm und extraembryonalem Trophoblast unterstützt, nicht aber die des Neuroectoderms. Zusammengenommen können die Erkenntnisse dieser Studie helfen die Ereignisse der frühen Keimblatt- oder Liniensegregation der Embryogenese zu verstehen. Außerdem können wir die Bildung der Synzytiotrophoblasten, die endokrine Funktion und den Wirkstoffmetabolismus der Plazenta sowie pathologische Umstände verstehen lernen und somit die Entwicklung prä-klinischer Therapien vorantreiben

The origins of human embryonic stem cells : a biological conundrum

Human inner cell mass (ICM) cells isolated from in vitro fertilized blastocysts are the progenitor cells used to establish in vitro stable human embryonic stem cells (hESCs) which are pluripotent and self-renew indefinitely. This long-term perpetuation of hESCs in the undifferentiated state is thought to be an in vitro adaptation of the ICM cells. To investigate at the molecular level how hESCs acquired their unique properties, transcriptional profiles of isolated ICM cells and undifferentiated hESCs were compared. We identified 33 genes enriched in the ICM compared to the trophectoderm and hESCs. These genes are involved in signaling cascades (SEMA7A and MAP3K10), cell proliferation (CUZD1 and MS4A7) and chromatin remodeling (H1FOO and HRMT1L4). Furthermore, primordial germ cell-specific genes (SGCA and TEX11) were detected as expressed in the ICM cells and not hESCs. We propose that the transcriptional differences observed between ICM cells and hESCs might be accounted for by adaptive reprogramming events induced by the in vitro culture conditions which are distinct from that of in vitro fertilized blastocysts. hESCs are a distinct cell type lacking in the human embryo but, nonetheless, resemble the ICM in their ability to differentiate into cells representative of the endodermal, ectodermal and mesodermal cell lineages

Epoxidized Soybean Oil-Based Epoxy Blend Cured with Anhydride-Based Cross-Linker: Thermal and Mechanical Characterization

The present research is based on a comparative study of anhydride cured biobased and petroleum-based epoxy network. The effect of epoxidized soybean oil (ESO) bioresin on petroleum-based epoxy (DGEBA) at varying compositions cured with methyl­hexahydrophthalic anhydride (MHHPA) as curing agent and 2-methyl imidazole (2-MI) as the catalyst has been investigated. The tensile strength of virgin epoxy (42.94 MPa) increased to 48.62 MPa with the addition of 20% of ESO. The fracture toughness parameters; critical stress intensity factor (<i>K</i>_IC) and critical strain energy release rate revealed enhancement of toughness in the biobased blends. Differential scanning calorimetry studies confirmed an enhancement in the peak temperature and a reduction in the heat of curing in virgin epoxy on incorporation of ESO content. The thermomechanical and fracture morphological properties of virgin epoxy, ESO, and its biobased blends were investigated by thermogravimetric analysis, dynamic mechanical analysis, atomic force microscopy, and scanning electron microscopy, respectively