Neural induction and neural stem cell development

ChIP-qPCR for Polycomb Group Proteins During Neuronal Differentiation of Human Pluripotent Stem Cells

Neuronal differentiation is an intricate and a complex process which involves crosstalk among various signaling pathways, growth factors, transcription factors, and epigenetic modifiers. During different stages of neuronal development, there are various histone modifiers which drive the expression of lineage-specific genes. Polycomb group proteins are one of the histone modifiers that control transcriptional repression of specific genes in development, differentiation, and functionality of various tissues. Chromatin immunoprecipitation (ChIP) is a widely used technique to investigate the interaction of proteins and DNA; ChIP combined with quantitative real-time PCR (qPCR) gives a quantitative data about the occupancy of specific protein on a particular stretch of DNA, and this can help us investigate how a protein regulates expression of a specific gene. In this chapter, we describe a protocol for ChIP coupled to qPCR during early neuronal differentiation to identify the specific genomic targets regulated by components of Polycomb repressive complex 1.

The role and mechanisms of polycomb repressive complex 2 on the regulation of osteogenic and neurogenic differentiation of stem cells

The stem cells differentiate into osteoblasts or neurocytes is the key process for treatment of bone- or neural tissue-related diseases which is caused by ageing, fracture, injury, inflammation, etc Polycomb group complexes (PcGs), especially the polycomb repressive complex 2 (PRC2), act as pivotal epigenetic regulators by modifying key developmental regulatory genes during stem cells differentiation. In this review, we summarize the core subunits, the variants and the potential functions of PRC2. We also highlight the underlying mechanisms of PRC2 associated with the osteogenic and neurogenic differentiation of stem cells, including its interaction with non-coding RNAs, histone acetyltransferases, histone demethylase, DNA methyltransferase and polycomb repressive complex 1. This review provided a substantial information of epigenetic regulation mediated by PRC2 which leads to the osteogenic and neurogenic differentiation of stem cells.

Polycomb repressive complex 1: Regulators of neurogenesis from embryonic to adult stage

Development of vertebrate nervous system is a complex process which involves differential gene expression and disruptions in this process or in the mature brain, may lead to neurological disorders and diseases. Extensive work that spanned several decades using rodent models and recent work on stem cells have helped uncover the intricate process of neuronal differentiation and maturation. There are various morphological changes, genetic and epigenetic modifications which occur during normal mammalian neural development, one of the chromatin modifications that controls vital gene expression are the posttranslational modifications on histone proteins, that controls accessibility of translational machinery. Among the histone modifiers, polycomb group proteins (PcGs), such as Ezh2, Eed and Suz12 form large protein complexes-polycomb repressive complex 2 (PRC2); while Ring1b and Bmi1 proteins form core of PRC1 along with accessory proteins such as Cbx, Hph, Rybp and Pcgfs catalyse histone modifications such as H3K27me3 and H2AK119ub1. PRC1 proteins are known to play critical role in X chromosome inactivation in females but they also repress the expression of key developmental genes and tightly regulate the mammalian neuronal development. In this review we have discussed the signalling pathways, morphogens and nuclear factors that initiate, regulate and maintain cells of the nervous system. Further, we have extensively reviewed the recent literature on the role of Ring1b and Bmi1 in mammalian neuronal development and differentiation; as well as highlighted questions that are still unanswered.

Post-Translational Modifications of Histones in Vertebrate Neurogenesis

The process of neurogenesis, through which the entire nervous system of an organism is formed, has attracted immense scientific attention for decades. How can a single neural stem cell give rise to astrocytes, oligodendrocytes, and neurons? Furthermore, how is a neuron led to choose between the hundreds of different neuronal subtypes that the vertebrate CNS contains? Traditionally, niche signals and transcription factors have been on the spotlight. Recent research is increasingly demonstrating that the answer may partially lie in epigenetic regulation of gene expression. In this article, we comprehensively review the role of post-translational histone modifications in neurogenesis in both the embryonic and adult CNS.

Differentiation of rhesus adipose stem cells into dopaminergic neurons

LIM homeobox transcription factor 1a (Lmx1a) has the capacity to initiate the development program of neuronal cells and promote the differentiation of embryonic stem cells into dopaminergic neurons. In this study, rhesus adipose stem cells were infected with recombinant adenovirus carrying the Lmx1a gene and co-cultured with embryonic rat neural stem cells. Cell differentiation was induced using sonic hedgehog and fibroblast growth factor-8. Immunofluorescence staining showed that cells were positive for neuron-specific enolase and β-tubulin III. Reverse transcription-PCR results demonstrated that rhesus adipose stem cells were not only positive for neuron-specific enolase and β-tubulin III, but also positive for the dopaminergic neuron marker, tyrosine hydroxylase, neurofilament, glial cell line-derived neurotrophic factor family receptor α2 and nuclear receptor related factor 1. The number of Lmx1a gene-infected cells expressing the dopaminergic neuron marker was substantially greater than the number of cells not infected with Lmx1α gene. These results suggest that Lmx1a-mediated regulation combined with the strategy of co-culture with neural stem cells can robustly promote the differentiation of rhesus adipose stem cells into dopaminergic neurons.

Zfhx1b induces a definitive neural stem cell fate in mouse embryonic stem cells

Inducing a stable and predictable program of neural cell fate in pluripotent cells in vitro is an important goal for utilizing these cells for modeling human disease mechanisms. However, the extent to which in vitro neural specification recapitulates in vivo neural specification remains to be fully established. We previously demonstrated that in the mouse embryo, activation of fibroblast growth factor (FGF) signalling promotes definitive neural stem cell (NSC) development through the upregulation of the transcription factor Zfhx1b. Here, we asked whether Zfhx1b is similarly required during neural lineage development of embryonic stem (ES) cells. Zfhx1b gene expression is rapidly upregulated in mouse ES cells cultured in a permissive neural-inducing environment, compared to ES cells in a standard pluripotency maintenance environment, and is potentiated by FGF signalling. However, overexpression of Zfhx1b in ES cells in maintenance conditions, containing serum and leukemia inhibitory factor (LIF), is sufficient to induce Sox1 expression, a marker found in neural precursors and to promote definitive NSC colony formation. Knockdown of Zfhx1b in ES cells using siRNA did not affect the initial transition of ES cells to a neural cell fate, but did diminish the ability of these neural cells to develop further into definitive NSCs. Thus, our findings using ES cells are congruent with evidence from mouse embryos and support a model, whereby intercellular FGF signaling induces Zfhx1b, which promotes the development of definitive NSCs subsequent to an initial neural specification event that is independent of this pathway.

Stem cells and cell replacement therapy for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder caused by a progressive degeneration of the midbrain dopamine (DA) neurons in the substantia nigra pars compacta (SNc) that predominantly affects the ventral population projecting to the dorsal striatum and leads to a gradual dysfunction of the motor system. There is currently no cure for PD. Pharmacological and surgical (e.g. deep brain stimulation) interventions can alleviate some of the symptoms, but lose their efficacy over time. The distinct loss of DA neurons in the SN offers the opportunity to assay neuronal cell replacement, and the clinical transplantation of fetal midbrain neuroblasts in PD patients has shown that this approach is feasible. However, there are multiple problems associated with the use of fetus-derived material, including limited availability. DA neurons derived from stem cells (SC) represent an alternative and unlimited cell source for cell replacement therapies. Currently, human pluripotent SC, such as embryonic (ES), and most recently, induced pluripotent stem cells (iPS), and multipotent (tissue-specific) adult SC are available, although the methodology for a reliable and efficient production of DA neurons necessary for biomedical applications is still underdeveloped. Here, we discuss some essentials for SC and SC-derived DA neurons to become therapeutic agents.

FGF dependent regulation of Zfhx1b gene expression promotes the formation of definitive neural stem cells in the mouse anterior neurectoderm

Background

Mouse definitive neural stem cells (NSCs) are derived from a population of LIF-responsive primitive neural stem cells (pNSCs) within the neurectoderm, yet details on the early signaling and transcriptional mechanisms that control this lineage transition are lacking. Here we tested whether FGF and Wnt signaling pathways can regulate Zfhx1b expression to control early neural stem cell development.

Results

By microinjecting FGF8b into the pro-amniotic cavity ex vivo at 7.0 days post-coitum (dpc) and culturing whole embryos, we demonstrate that neurectoderm-specific gene expression (for example, Sox2, Nestin, Zfhx1b) is increased, whereas Wnt3a represses neurectoderm gene expression. To determine whether FGF signaling also mediates the lineage transition from a pNSC to a NSC, 7.0-dpc embryos were microinjected with either FGF8b or inhibitors of the FGF receptor-MAP kinase signaling pathway ex vivo, cultured as whole embryos to approximately 8.5 dpc and assayed for clonal NSC colony formation. We show that pre-activation of FGF signaling in the anterior neurectoderm causes an increase in the number of colony forming NSCs derived later from the anterior neural plate, whereas inhibition of FGF signaling significantly reduces the number of NSC colonies. Interestingly, inhibition of FGF signaling causes the persistence of LIF-responsive pNSCs within the anterior neural plate and over-expression of Zfhx1b in these cells is sufficient to rescue the transition from a LIF-responsive pNSC to an FGF-responsive NSC.

Conclusion

Our data suggest that definitive NSC fate specification in the mouse neurectoderm is facilitated by FGF activation of Zfhx1b.

Survival, differentiation, and reversal of heroin neurobehavioral teratogenicity in mice by transplanted neural stem cells derived from embryonic stem cells

Cell therapies in animal models of neurobehavioral defects are normally derived from neural stem cells (NSC) of the developing cortex. However, the clinical feasibility of NSC therapies would be greatly improved by deriving transplanted cells and from a tissue culture source that is self-renewing, containing cells that potentially differentiate into the desired neuronal phenotypes. These cultures can be engineered to contain the appropriate factors to support their therapeutic action and likely evoke lesser immune reactions. In the current study, we employed our model of mice neurobehaviorally impaired via prenatal exposure to heroin, to test the therapeutic efficacy of NSC derived from murine embryonic stem cells culture (ESC). The culture contained elongated bipolar cells, 90% of which are positive for nestin, the intermediate filament protein found in neural precursors. After removal of growth factors, the NSC differentiated into neurons (34.0% +/- 3.8% NF-160 positive), including cholinergic cells (ChAT positive), oligodendrocytes (29.9% +/- 4.2% O(4)), and astrocytes (36.1% +/- 4.7% GFAP positive). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis confirmed the immunocytochemical findings. Mice made deficient in Morris maze behavior by prenatal heroin exposure (10 mg/kg heroin s.c. on gestational days 9-18) were transplanted into the hippocampus region on postnatal day 35 with the ES culture-derived NSC (ES-NSC) labeled with dialkylcarbocyanine (Dil) cell tracker. Dil+ and NF160+ cells were detected in the hippocampal region (50% +/- 8% survival). The transplantation completely restored maze performance to normal; e.g., on day 3, transplantation improved the behavior from the deficient level of 11.9-sec latency to the control of 5.6-sec latency (44.5% improvement).

Legume lectin FRIL preserves neural progenitor cells in suspension culture in vitro

In vitro maintenance of stem cells is crucial for many clinical applications. Stem cell preservation factor FRIL (Flt3 receptor-interacting lectin) is a plant lectin extracted from Dolichos Lablab and has been found preserve hematopoietic stem cells in vitro for a month in our previous studies. To investigate whether FRIL can preserve neural progenitor cells (NPCs), it was supplemented into serum-free suspension culture media. FRIL made NPC grow slowly, induced cell adhesion, and delayed neurospheres formation. However, FRIL did not initiate NPC differentiation according to immunofluorescence and semiquantitive RT-PCR results. In conclusion, FRIL could also preserve neural progenitor cells in vitro by inhibiting both cell proliferation and differentiation.

Directing the differentiation of embryonic stem cells to neural stem cells

Embryonic stem cells (ESCs) are a potential source of neural derivatives that can be used in stem cell-based therapies designed to treat neurological disorders. The derivation of specific neuronal or glial cell types from ESCs invariably includes the production of neural stem cells (NSCs). We describe the basic mechanisms of neural induction during vertebrate embryogenesis and how this information helped formulate several protocols used to generate NSCs from ESCs. We highlight the advantages and disadvantages of each approach and review what has been learned about the intermediate stages in the transition from ESC to NSC. Recent data describing how specific growth factors and signaling molecules regulate production of NSCs are described and a model synthesizing this information is presented.