SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Embryonic stem cell

151

Most cases of colorectal cancer (CRC) are initiated by inactivation mutations in the APC gene, which is a negative regulator of the Wnt-β-catenin pathway. Patients with familial adenomatous polyposis (FAP) inherit a germline mutation in one APC allele, and loss of the second allele leads to the development of polyps that will turn malignant if not removed. It is not fully understood which molecular mechanisms are activated by APC loss and when the loss of the second APC allele occurs.

Concepts: Evolution, Genetics, Stem cell, DNA, Cancer, Familial adenomatous polyposis, Embryonic stem cell, Colorectal cancer

147

Generating human podocytes in vitro could offer a unique opportunity to study human diseases. Here, we describe a simple and efficient protocol for obtaining functional podocytes in vitro from human induced pluripotent stem cells. Cells were exposed to a three-step protocol, which induced their differentiation into intermediate mesoderm, then into nephron progenitors and, finally, into mature podocytes. After differentiation, cells expressed the main podocyte markers, such as synaptopodin, WT1, α-Actinin-4, P-cadherin and nephrin at the protein and mRNA level, and showed the low proliferation rate typical of mature podocytes. Exposure to Angiotensin II significantly decreased the expression of podocyte genes and cells underwent cytoskeleton rearrangement. Cells were able to internalize albumin and self-assembled into chimeric 3D structures in combination with dissociated embryonic mouse kidney cells. Overall, these findings demonstrate the establishment of a robust protocol that, mimicking developmental stages, makes it possible to derive functional podocytes in vitro.

Concepts: Embryonic stem cell, Podocyte, Protein, DNA, Gene expression, Induced pluripotent stem cell, Stem cell, Developmental biology

146

Human lymphoblast cells from a female and male patient diagnosed with Alzheimer’s disease (AD) with different genotypes of a functional copy number variation (CNV) in the AD risk gene CR1 were used to generate integration-free induced pluripotent stem cells (iPSCs) employing episomal plasmids expressing OCT4, SOX2, NANOG, LIN28, c-MYC and L-MYC. The iPSCs retained the CR1 CNV, and comparative transcriptome analyses with the human embryonic stem cell line H1 revealed a Pearson correlation of 0.956 for AD1-CR10 and 0.908 for AD1-CR14.

Concepts: Copy number variation, DNA, Cell, Stem cells, Gene, Induced pluripotent stem cell, Embryonic stem cell, Stem cell

146

Epithelial-mesenchymal transition (EMT) and the mesenchymal-epithelial transition (MET) are processes required for embryo organogenesis. Liver develops from the epithelial foregut endoderm from which the liver progenitors, hepatoblasts, are specified. The migrating hepatoblasts acquire a mesenchymal phenotype to form the liver bud. In mid-gestation, hepatoblasts mature into epithelial structures: the hepatocyte cords and biliary ducts. While EMT has been associated with liver bud formation, nothing is known about its contribution to hepatic specification. We previously established an efficient protocol from human embryonic stem cells (hESC) to generate hepatic cells (Hep cells) resembling the hepatoblasts expressing alpha-fetoprotein (AFP) and albumin (ALB). Here we show that Hep cells express both epithelial (EpCAM and E-cadherin) and mesenchymal (vimentin and SNAI-1) markers. Similar epithelial and mesenchymal hepatoblasts were identified in human and mouse fetal livers, suggesting a conserved interspecies phenotype. Knock-down experiments demonstrated the importance of SNAI-1 in Hep cell hepatic specification. Moreover, ChIP assays revealed direct binding of SNAI-1 in the promoters of AFP and ALB genes consistent with its transcriptional activator function in hepatic specification. Altogether, our hESC-derived Hep cell cultures reveal the dual mesenchymal and epithelial phenotype of hepatoblast-like cells and support the unexpected transcriptional activator role of SNAI-1 in hepatic specification.

Concepts: Transcription factor, Transcription, Gallbladder, Gene expression, Gene, Embryonic stem cell, Stem cell, Liver

144

Primary fibroblasts from a high grade steatosis patient were reprogrammed by transduction of retroviruses OCT4, SOX2, c-MYC and KLF4. IPSCs were characterized by immunocytochemistry, embryoid body-formation, DNA-fingerprint, karyotype analysis and comparative transcriptome analyses with the human embryonic stem cell line H1 revealed a Pearsons correlation coefficient of 0.9287. Resource table.

Concepts: Cellular differentiation, Vector space, Stem cells, Transcription factors, Cell biology, Cell, Embryonic stem cell, Stem cell

144

Human lymphoblast cells from a female patient diagnosed with Alzheimer’s disease (AD) possessing the missense mutation TREM2 p.R47H were used to generate integration-free induced pluripotent stem cells (iPSCs) employing episomal plasmids expressing OCT4, SOX2, NANOG, LIN28, c-MYC and L-MYC. The iPSCs retained the TREM2 mutation, and were defined as pluripotent based on (i) expression of pluripotent-associated markers, (ii) embryoid body-based differentiation into cell types representative of the three germ layers and (iii) the similarity between the transcriptomes of the iPSC line and the human embryonic stem cell line H1 with a Pearson correlation of 0.961.

Concepts: Cell biology, Cell, Cellular differentiation, Developmental biology, Stem cells, Induced pluripotent stem cell, Embryonic stem cell, Stem cell

144

During development, endothelial cells (EC) display tissue-specific attributes that are unique to each vascular bed, as well as generic signaling mechanisms that are broadly applied to create a patent circulatory system. We have previously utilized human embryonic stem cells (hESC) to generate tissue-specific EC sub-types (Rafii et al., 2013) and identify pathways that govern growth and trans-differentiation potential of hESC-derived ECs (James et al., 2010). Here, we elucidate a novel Notch-dependent mechanism that induces endothelial to mesenchymal transition (EndMT) in confluent monolayer cultures of hESC-derived ECs. We demonstrate density-dependent induction of EndMT that can be rescued by the Notch signaling inhibitor DAPT and identify a positive feedback signaling mechanism in hESC-ECs whereby trans-activation of Notch by DLL4 ligand induces elevated expression and surface presentation of DLL4. Increased Notch activation in confluent hESC-EC monolayer cultures induces areas of EndMT containing transitional cells that are marked by increased Jagged1 expression and reduced Notch signal integration. Jagged1 loss of function in monolayer hESC-ECs induces accelerated feedback stimulation of Notch signaling, increased expression of cell-autonomous, cis-inhibitory DLL4, and EndMT. These data elucidate a novel interplay of Notch ligands in modulating pathway activation during both expansion and EndMT of hESC-derived ECs.

Concepts: Endothelium, Ibn al-Nafis, Cardiovascular system, Epithelium, Blood vessel, Heart, Stem cell, Embryonic stem cell

144

This study elucidated the stage-specific roles of FGF2 signaling during neural development using in-vitro human embryonic stem cell-based developmental modeling. We found that the dysregulation of FGF2 signaling prior to the onset of neural induction resulted in the malformation of neural rosettes (a neural tube-like structure), despite cells having undergone neural induction. The aberrant neural rosette formation may be attributed to the misplacement of ZO-1, which is a polarized tight junction protein and shown co-localized with FGF2/FGFR1 in the apical region of neural rosettes, subsequently led to abnormal neurogenesis. Moreover, the FGF2 signaling inhibition at the stage of neural rosettes caused a reduction in cell proliferation, an increase in numbers of cells with cell-cycle exit, and premature neurogenesis. These effects may be mediated by NUMB, to which expression was observed enriched in the apical region of neural rosettes after FGF2 signaling inhibition coinciding with the disappearance of PAX6(+)/Ki67(+) neural stem cells and the emergence of MAP2(+) neurons. Moreover, our results suggested that the hESC-based developmental system reserved a similar neural stem cell niche in vivo.

Concepts: Stem cells, Cell, Embryonic stem cell, Cell division, Neuron, Neurogenesis, Developmental biology, Stem cell

144

Transgene-mediated programming is a preeminent strategy to direct cellular identity. To facilitate cell fate switching, lineage regulating genes must be efficiently and uniformly induced. However, gene expression is often heterogeneous in transgenic systems. Consistent with this notion, a non-uniform reporter gene expression was detected in our doxycycline (DOX)-regulated, murine embryonic stem (ES) cell clones. Interestingly, a significant fraction of cells within each clone failed to produce any reporter signals upon DOX treatment. We found that the majority of these non-responsive cells neither carry reporter transgene nor geneticin/G418 resistance. This observation suggested that our ES cell clones contained non-recombined cells that survived the G418 selection which was carried out during the establishment of these clones. We successfully eliminated most of these corrupted cells with repeated chemical (G418) selection, however, even after prolonged G418 treatments, a few cells remained non-responsive due to epigenetic silencing. We found that cell sorting has been the most efficient approach to select those cells which can uniformly and stably induce the integrated transgene in this ES cell based platform. Together, our data revealed that post-cloning chemical re-selection or cell sorting strongly facilitate the production of ES cell lines with a uniform transgene induction capacity.

Concepts: Embryonic stem cell, Cell, Cellular differentiation, Stem cell, DNA, Gene expression, Gene, Genetics

90

Recent success in functional recovery by photoreceptor precursor transplantation in dysfunctional retina has led to an increased interest in using embryonic stem cell (ESC) or induced pluripotent stem cell (iPSC)-derived retinal progenitors to treat retinal degeneration. However, cell-based therapies for end-stage degenerative retinas that have lost the outer nuclear layer (ONL) are still a big challenge. In the present study, by transplanting mouse iPSC-derived retinal tissue (miPSC retina) in the end-stage retinal-degeneration model (rd1), we visualized the direct contact between host bipolar cell terminals and the presynaptic terminal of graft photoreceptors by gene labeling, showed light-responsive behaviors in transplanted rd1 mice, and recorded responses from the host retina with transplants by ex vivo micro-electroretinography and ganglion cell recordings using a multiple-electrode array system. Our data provides a proof of concept for transplanting ESC/iPSC retinas to restore vision in end-stage retinal degeneration.

Concepts: Eye, Stem cells, Photoreceptor cell, Induced pluripotent stem cell, Embryonic stem cell, Retina, Neuron, Stem cell