Pharmacological modulation of the Hedgehog pathway differentially affects dorsal/ventral patterning in mouse and human embryonic stem cell models of telencephalic development

Downregulation of tumor-suppressor gene LHX6 in cancer: a systematic review

Introduction. LIM Homeobox 6 (LHX6) encodes a LIM homeodomain transcription factor, contributes to tissue development and morphogenesis, and is mostly expressed in medial ganglionic eminence and odontogenic mesenchyme. However, it has been reported to play a role in cancer progression. This narrative review summarizes literatures that emphasize the molecular regulation of LHX6 in tumorigenesis.

Methods. In our systematic review, the PubMed database was used for the literature search using the combination of words that included “LHX6” and “cancer”. Relevant studies, including in vitro, in vivo experiments, and clinical studies, were analyzed in this review.

Results. We found evidences that LHX6 might be important in the inhibition of tumor cell proliferation, growth, invasion, and metastasis through the suppression of Wnt/β-catenin signaling pathway. Moreover, LHX6 is observed to be downregulated in certain types of cancer due to hypermethylation, thus hindering its tumor suppressing ability. In addition, hypermethylation can also be used to determine the stage of cancer development.

Conclusion. The downregulation of LHX6 expression might be responsible in promoting cancer progression. Future studies are necessary to investigate the potential of LHX6 as a novel cancer biomarker as well as its therapeutic implications towards certain types of cancer.

Transcriptome analysis of comb and testis from Rose-comb Silky chicken (R1/R1) and Beijing Fatty wild type chicken (r/r)

Rose-comb was one of the chicken comb-variants first used by Bateson and Punnet in 1902 to demonstrate Mendelian inheritance in animals. Rose-comb is a monogenic trait that has been widely described in chickens. It is caused by a large structural rearrangement that leads to mis-expression of transcription factor MNR2 on chromosome 7. Rose-comb has pleiotropic effects in homozygous roosters, which is associated with poor sperm mobility. It was postulated that this is caused by the disruption of the CCDC108 gene located at the distal inversion breakpoint. In this study, we did the transcriptional profiling of combs and testes from Rose-comb Silky (RS) (R1/R1) and Beijing Fatty (BF) wild type chickens (r/r) using RNA-seq. We obtained 68,694,797 unique mapped reads and over 80% of the chicken genes were covered for each sample. In combs, we found that differentially expressed genes (DEGs) were significantly enriched in the retinol metabolism (RPE65, CYP26A1, and CYP26C1) and hedgehog-signaling pathway (PTCH1, GLI1, and HHIP), while genes related to cell differentiation and morphogenesis were down-regulated in R1/R1 chickens, suggesting that the transient expression of MNR2 might affect the expression of these genes and influence the development of comb tissue. For testes, DEGs were significantly enriched in the GO terms of binding activates and mitochondrial oxidation-reduction reactions. Our results suggested that the CCDC108 might be functionally related with mitochondrial oxidation-reduction reactions and caused subfertility of roosters. Compared with the genome average, the degree of expression variations within the inversion region did not show significant differences. However, DEGs near the breakpoints showed greater expression variance. Our results demonstrated that the large-scale rearrangements affected the gene expression only around the breakpoint in this case.

MFG-E8 Is Critical for Embryonic Stem Cell-Mediated T Cell Immunomodulation

The molecules and mechanisms pertinent to the low immunogenicity of undifferentiated embryonic stem cells (ESCs) remain poorly understood. Here, we provide evidence that milk fat globule epidermal growth factor 8 (MFG-E8) is a vital mediator in this phenomenon and directly suppresses T cell immune responses. MFG-E8 is enriched in undifferentiated ESCs but diminished in differentiated ESCs. Upregulation of MFG-E8 in ESCs increases the successful engraftment of both undifferentiated and differentiated ESCs across major histocompatibility complex barriers. MFG-E8 suppresses T cell activation/proliferation and inhibits Th1, Th2, and Th17 subpopulations while increasing regulatory T cell subsets. Neutralizing MFG-E8 substantially abrogates these effects, whereas addition of recombinant MFG-E8 to differentiated ESCs restores immunosuppression. Furthermore, we provide the evidence that MFG-E8 suppresses T cell activation and regulates T cell polarization by inhibiting PKCθ phosphorylation through the α3/5βV integrin receptor. Our findings offer an approach to facilitate transplantation acceptance.

•

MFG-E8 is enriched in undifferentiated but diminished in differentiated ESCs

•

MFG-E8 promotes allogeneic engraftment of ESC-derived tissues across the MHC barrier

•

ESC-produced MFG-E8 inhibits Th1/Th2/Th17 while promoting regulatory T cells

•

MFG-E8 modulates T cell polarization via inhibiting PKCθ phosphorylation

Stem cell therapy and cellular engineering for treatment of neuronal dysfunction in Huntington's disease

Huntington's disease (HD) is a fatal inherited neurodegenerative disorder characterized by progressive loss of neurons in the striatum, a sub-cortical region of the forebrain. The sub-cortical region of the forebrain is associated with the control of movement and behavior, thus HD initially presents with coordination difficulty and cognitive decline. Recent reprogramming technologies, including induced pluripotent stem cells (iPSCs) and induced neural stem cells (iNSCs), have created opportunities to understand the pathological cascades that underlie HD and to develop new treatments for this currently incurable neurological disease. The ultimate objectives of stem cell-based therapies for HD are to replace lost neurons and to prevent neuronal dysfunction and death. In this review, we examine the current understanding of the molecular and pathological mechanisms involved in HD. We discuss disease modeling with HD-iPSCs derived from the somatic cells of patients, which could provide an invaluable platform for understanding HD pathogenesis. We speculate about the benefits and drawbacks of using iNSCs as an alternative stem cell source for HD treatment. Finally, we discuss cell culture and engineering systems that promote the directed differentiation of pluripotent stem cell-derived NSCs into a striatal DARPP32(+) GABAergic MSN phenotype for HD. In conclusion, this review summarizes the potentials of cell reprogramming and engineering technologies relevant to the development of cell-based therapies for HD.

Functional differentiation of midbrain neurons from human cord blood-derived induced pluripotent stem cells

Introduction

Human induced pluripotent stem cells (hiPSCs) offer great promise for regenerative therapies or in vitro modelling of neurodegenerative disorders like Parkinson’s disease. Currently, widely used cell sources for the generation of hiPSCs are somatic cells obtained from aged individuals. However, a critical issue concerning the potential clinical use of these iPSCs is mutations that accumulate over lifetime and are transferred onto iPSCs during reprogramming which may influence the functionality of cells differentiated from them. The aim of our study was to establish a differentiation strategy to efficiently generate neurons including dopaminergic cells from human cord blood-derived iPSCs (hCBiPSCs) as a juvenescent cell source and prove their functional maturation in vitro.

Methods

The differentiation of hCBiPSCs was initiated by inhibition of transforming growth factor-β and bone morphogenetic protein signaling using the small molecules dorsomorphin and SB 431542 before final maturation was carried out. hCBiPSCs and differentiated neurons were characterized by immunocytochemistry and quantitative real time-polymerase chain reaction. Since functional investigations of hCBiPSC-derived neurons are indispensable prior to clinical applications, we performed detailed analysis of essential ion channel properties using whole-cell patch-clamp recordings and calcium imaging.

Results

A Sox1 and Pax6 positive neuronal progenitor cell population was efficiently induced from hCBiPSCs using a newly established differentiation protocol. Neuronal progenitor cells could be further maturated into dopaminergic neurons expressing tyrosine hydroxylase, the dopamine transporter and engrailed 1. Differentiated hCBiPSCs exhibited voltage-gated ion currents, were able to fire action potentials and displayed synaptic activity indicating synapse formation. Application of the neurotransmitters GABA, glutamate and acetylcholine induced depolarizing calcium signal changes in neuronal cells providing evidence for the excitatory effects of these ligand-gated ion channels during maturation in vitro.

Conclusions

This study demonstrates for the first time that hCBiPSCs can be used as a juvenescent cell source to generate a large number of functional neurons including dopaminergic cells which may serve for the development of novel regenerative treatment strategies.

Induced pluripotent stem cells from friedreich ataxia patients fail to upregulate frataxin during in vitro differentiation to peripheral sensory neurons

The value of human disease models, which are based on induced pluripotent stem cells (iPSCs), depends on the capacity to generate specifically those cell types affected by pathology. We describe a new iPSC-based model of Friedreich ataxia (FRDA), an autosomal recessive neurodegenerative disorder with an intronic GAA repeat expansion in the frataxin gene. As the peripheral sensory neurons are particularly susceptible to neurodegeneration in FRDA, we applied a development-based differentiation protocol to generate specifically these cells. FRDA and control iPSC lines were efficiently differentiated toward neural crest progenitors and peripheral sensory neurons. The progress of the cell lines through discrete steps of in vitro differentiation was closely monitored by expression levels of key markers for peripheral neural development. Since it had been suggested that FRDA pathology might start early during ontogenesis, we investigated frataxin expression in our development-related model. A pronounced frataxin deficit was found in FRDA iPSCs and neural crest cells compared to controls. Whereas we identified an upregulation of frataxin expression during sensory specification for control cells, this increase was not observed for FRDA peripheral sensory neurons. This early failure, aggravating frataxin deficiency in a specifically vulnerable human cell population, indicates a developmental component in FRDA.

Stepwise, non-adherent differentiation of human pluripotent stem cells to generate basal forebrain cholinergic neurons via hedgehog signaling

Basal forebrain cholinergic neurons (bfCNs) which provide innervation to the hippocampus and cortex, are required for memory and learning, and are primarily affected in Alzheimer's Disease (AD), resulting in related cognitive decline. Therefore generation of a source of bfCNs from human pluripotent stem cells (hPSCs) is crucial for in vitro disease modeling and development of novel AD therapies. In addition, for the advancement of regenerative approaches there is a requirement for an accurate developmental model to study the neurogenesis and survival of this population. Here we demonstrate the efficient production of bfCNs, using a novel embryoid body (EB) based non-adherent differentiation (NAdD) protocol. We establish a specific basal forebrain neural stem cell (NSC) phenotype via expression of the basal forebrain transcription factors NKX2.1 and LHX8, as well as the general forebrain marker FOXG1. We present evidence that this lineage is achieved via recapitulation of embryonic events, with induction of intrinsic hedgehog signaling, through the use of a 3D non-adherent differentiation system. This is the first example of hPSC-derived basal forebrain-like NSCs, which are scalable via self-renewal in prolonged culture. Furthermore upon terminal differentiation these basal forebrain-like NSCs generate high numbers of cholinergic neurons expressing the specific markers ChAT, VACht and ISL1. These hPSC-derived bfCNs possess characteristics that are crucial in a model to study AD related cholinergic neuronal loss in the basal forebrain. Examples are expression of the therapeutic target p75(NTR), the release of acetylcholine, and demonstration of a mature, and functional electrophysiological profile. In conclusion, this work provides a renewable source of human functional bfCNs applicable for studying AD specifically in the cholinergic system, and also provides a model of the key embryonic events in human bfCN development.

Hedgehog signaling pathway and ovarian cancer

Epithelial ovarian carcinoma (EOC) is the most common form of ovarian malignancies and the most lethal gynecologic malignancy in the United States. To date, in spite of treatment to it with the extensive surgical debulking and chemotherapy, the prognosis of EOC remains dismal. Recently, it has become increasingly clear that in many instances, the signaling and molecular players that control development are the same, and when inappropriately regulated, drive tumorigenesis and cancer development. Here, we discuss the possible involvement of Hedgehog (Hh) pathway in the cellular regulation and development of cancer in the ovaries. Using the in vitro and in vivo assays developed has facilitated the dissection of the mechanisms behind Hh-driven ovarian cancers formation and growth. Based on recent studies, we propose that the inhibition of Hh signaling may interfere with spheroid-like structures in ovarian cancers. The components of the Hh signaling may provide novel drug targets, which could be explored as crucial combinatorial strategies for the treatment of ovarian cancers.

Expression of early developmental markers predicts the efficiency of embryonic stem cell differentiation into midbrain dopaminergic neurons

Dopaminergic neurons derived from pluripotent stem cells are among the best investigated products of in vitro stem cell differentiation owing to their potential use for neurorestorative therapy of Parkinson's disease. However, the classical differentiation protocols for both mouse and human pluripotent stem cells generate a limited percentage of dopaminergic neurons and yield a considerable cellular heterogeneity comprising numerous scarcely characterized cell populations. To improve pluripotent stem cell differentiation protocols for midbrain dopaminergic neurons, we established extensive and strictly quantitative gene expression profiles, including markers for pluripotent cells, neural progenitors, non-neural cells, pan-neuronal and glial cells, neurotransmitter phenotypes, midbrain and nonmidbrain populations, floor plate and basal plate populations, as well as for Hedgehog, Fgf, and Wnt signaling pathways. The profiles were applied to discrete stages of in vitro differentiation of mouse embryonic stem cells toward the dopaminergic lineage and after transplantation into the striatum of 6-hydroxy-dopamine-lesioned rats. The comparison of gene expression in vitro with stages in the developing ventral midbrain between embryonic day 11.5 and 13.5 ex vivo revealed dynamic changes in the expression of transcription factors and signaling molecules. Based on these profiles, we propose quantitative gene expression milestones that predict the efficiency of dopaminergic differentiation achieved at the end point of the protocol, already at earlier stages of differentiation.

Identification of differentially expressed non-coding RNAs in embryonic stem cell neural differentiation

Protein-coding genes, guiding differentiation of ES cells into neural cells, have extensively been studied in the past. However, for the class of ncRNAs only the involvement of some specific microRNAs (miRNAs) has been described. Thus, to characterize the entire small non-coding RNA (ncRNA) transcriptome, involved in the differentiation of mouse ES cells into neural cells, we have generated three specialized ribonucleo-protein particle (RNP)-derived cDNA libraries, i.e. from pluripotent ES cells, neural progenitors and differentiated neural cells, respectively. By high-throughput sequencing and transcriptional profiling we identified several novel miRNAs to be involved in ES cell differentiation, as well as seven small nucleolar RNAs. In addition, expression of 7SL, 7SK and vault-2 RNAs was significantly up-regulated during ES cell differentiation. About half of ncRNA sequences from the three cDNA libraries mapped to intergenic or intragenic regions, designated as interRNAs and intraRNAs, respectively. Thereby, novel ncRNA candidates exhibited a predominant size of 18-30 nt, thus resembling miRNA species, but, with few exceptions, lacking canonical miRNA features. Additionally, these novel intraRNAs and interRNAs were not only found to be differentially expressed in stem-cell derivatives, but also in primary cultures of hippocampal neurons and astrocytes, strengthening their potential function in neural ES cell differentiation.