Direct conversion of fibroblasts to neurons by a new mechanism – p53 regulation
Ontology highlight
ABSTRACT: Direct conversion from fibroblast to neuron has recently been successfully induced bypassing the pluripotent state. However, the conversion takes a few months with low percentages of success. Here we found that depletion of p53, which can converted fibroblasts into three major neural lineages: neurons, astrocytes and oligodendrocytes. Furthermore, our method provided a high efficiency of conversion in aging fibroblasts, where published methods failed. This finding may help developing a prototype for neuron replacement therapy, including foraging people vulnerable to neurological disorders. p53 has been shown to inhibit reprogramming of fibroblasts to iPS cells, by depletion of p53 in human fibroblasts, we study the function of p53 in induced neuron process. By induction of p53 knockdown fibroblasts with special neuron medium, we can get mature neurons directly. In the induction process, many neurogenic transcription factors were up-regulated, and we prove that p21 is not involved in this process.
Project description:Direct conversion from fibroblasts to neurons is a potential cell replacement therapy for neurological disorders, and a variety of combinations of transcription factors have been tried. We notice that the efficiency of conversion from aging fibroblasts was much lower than in early stage cells, which is consistent with the notion that cellular senescence impairs conversion of fibroblasts to neurons. Here, we found that the transient knockdown of the p16Ink4a/p19Arf locus was sufficient to convert human fibroblasts to neurons. Futhermore, expression of hTERT alone, another mechanism behind immortalization, also induced neuron conversion. Our results show that the acquisition of immortality is a crucial step for the conversion of human fibroblasts into induced neurons. Transient knockdown of p16/p19 or p53 expression or exogenous overexpression of hTERT can induce primary fibroblasts to immortality. In the following, treated cells were cultured in neuron-induction medium. We can observe the morphology change and detect the neuronal markers. Also, some of the induced neurons could generate action potentials and neurotransmitter-induced currents in optimal conditions.
Project description:Neural stem/progenitor cell (NSPC) proliferation and self-renewal, as well as insult-induced differentiation, decrease markedly with age, but the molecular mechanisms responsible for these declines remain unclear. Here we show that levels of NAD+ and nicotinamide phosphoribosyltransferase (Nampt), the rate-limiting enzyme in mammalian NAD+ biosynthesis, decrease with age in the hippocampus. Ablation of Nampt in adult NSPCs reduced their pool and proliferation in vivo. The decrease in the NSPC pool during aging can be rescued by enhancing hippocampal NAD+ levels. Nampt is the main source of NSPC NAD+ levels and required for G1/S progression of the NSPC cell cycle. Nampt is also critical for oligodendrocytic lineage fate decisions through a mechanism mediated redundantly by Sirt1 and Sirt2. Ablation of Nampt in the adult NSPCs in vivo reduced NSPC-mediated oligodendrogenesis upon injury. These phenotypes recapitulate defects in NSPCs during aging, implicating Nampt-mediated NAD+ biosynthesis as a mediator of these age-associated functional declines. Total RNA obtained from neurospheres derived from postnatal hippocampi subjected to 48 hours in vitro of incubation with Nampt-specific inhibitor FK866 (10 nM, 4 samples) or vehicle (DMSO, 1:1000, 4 samples).
Project description:Direct conversion from fibroblast to neuron has recently been successfully induced bypassing the pluripotent state. However, the conversion takes a few months with low percentages of success. Here we found that depletion of p53, which can converted fibroblasts into three major neural lineages: neurons, astrocytes and oligodendrocytes. Furthermore, our method provided a high efficiency of conversion in aging fibroblasts, where published methods failed. This finding may help developing a prototype for neuron replacement therapy, including foraging people vulnerable to neurological disorders.
Project description:The direct conversion of human skin fibroblasts to neurons has a low efficiency and unclear mechanism. Here, we show that the knockdown of PTBP2 (nPTB) significantly enhanced the transdifferentiation induced by ASCL1, MiR124-9/9* and p53 shRNA to generate mostly GABAergic neurons. Longitudinal RNAseq analyses identified the continuous induction of many RNA Splicing Regulators (RSRs). Among these, the knockdown of RBFOX3, which encodes the mature neuronal marker NeuN, significantly abrogated the transdifferentiation. Overexpression of RBFOX3 significantly enhanced the conversion induced by AMp; the enhancement was occluded by PTBP2 knockdown. We found that PTBP2 attenuation significantly favored neuron-specific alternative splicing (AS) of many genes involved in synaptic transmission, signal transduction, and axon formation. RBFOX3 knockdown significantly reversed the effect, while RBFOX3 overexpression enhanced it. The study reveals the critical role of neuron-specific AS in the direct conversion of human skin fibroblasts to neurons by showing that PTBP2 attenuation enhances this mechanism in concert with RBFOX3.
Project description:Gonadectomy (GDX) induces sex steroid-producing adrenocortical tumors in certain mouse strains and in the domestic ferret. Complementary approaches, including DNA methylation mapping and microarray expression profiling, were used to identify novel genetic and epigenetic markers of GDX-induced adrenocortical neoplasia in female DBA/2J mice. Markers were validated by quantitative RT-PCR, laser capture microdissection, in situ hybridization, and immunohistochemistry. Two genes with hypomethylated promoters, Igfbp6 and Foxs1, were upregulated in post-GDX adrenocortical neoplasms. The neoplastic cells also exhibited hypomethylation of the fetal adrenal enhancer of Sf1, an epigenetic signature that typifies descendants of fetal adrenal rather than gonadal cells. Expression profiling demonstrated upregulation of gonadal-like genes, including Spinlw1, Insl3, and Foxl2, in GDX-induced adrenocortical tumors of the mouse. One of these markers, FOXL2, was detected in adrenocortical tumor specimens from gonadectomized ferrets. These new markers may prove useful for studies of steroidogenic cell development and for diagnostic testing. Total RNA extracted from whole adrenal glands of gonadectomized and non-gonadectomized mice.
Project description:Gene expression analysis of 2-month-old Ctrl and Tfam-SCKO mice. At this age mitochondrial function is disrupted in the Schwann cells of Tfam-SCKO mice ,but their nerves display only very limited pathology. Mitochondrial dysfunction is a common cause of peripheral neuropathy. Much effort has been devoted to examining the role played by neuronal/axonal mitochondria, but how mitochondrial deficits in peripheral nerve glia (Schwann cells, SCs) contribute to peripheral nerve diseases remains unclear. Here, we investigate a mouse model of peripheral neuropathy secondary to SC mitochondrial dysfunction (Tfam-SCKOs). We show that disruption of SC mitochondria activates a maladaptive integrated stress response through actions of heme-regulated inhibitor kinase (HRI), and causes a shift in lipid metabolism away from fatty acid synthesis toward oxidation. These alterations in SC lipid metabolism result in depletion of important myelin lipid components as well as in accumulation of acylcarnitines, an intermediate of fatty acid b-oxidation. Importantly, we show that acylcarnitines are released from SCs and induce axonal degeneration. A maladaptive integrated stress response as well as altered SC lipid metabolism are thus underlying pathological mechanisms in mitochondria-related peripheral neuropathies. Total RNA samples were prepared by isolating and pooling RNA from three different 2-month-old MPZ-Tfam KO and Ctrl mice. 2 replicates per genotype were used in this experiment and they were prepared entirely independently.
Project description:Direct conversion from fibroblasts to neurons is a potential cell replacement therapy for neurological disorders, and a variety of combinations of transcription factors have been tried. We notice that the efficiency of conversion from aging fibroblasts was much lower than in early stage cells, which is consistent with the notion that cellular senescence impairs conversion of fibroblasts to neurons. Here, we found that the transient knockdown of the p16Ink4a/p19Arf locus was sufficient to convert human fibroblasts to neurons. Futhermore, expression of hTERT alone, another mechanism behind immortalization, also induced neuron conversion. Our results show that the acquisition of immortality is a crucial step for the conversion of human fibroblasts into induced neurons.
Project description:Bulk RNA was extracted via trizol at Fibroblasts stage, 5 days, 10 days, 15 days, and 20 days of fibroblast to neuron conversion using traditional NC media, or NC media supplemented with ZM336372, pyrintegrin, AZ960, and KC7F2
Project description:End stage liver disease due to Hepatitis C Virus (HCV) infection is a major health concern worldwide. Liver fibrosis following chronic HCV infection plays a pivotal role in loss of liver function and end stage liver disease. However the dynamics and molecular events that lead to fibrosis in HCV infection are poorly defined. Therefore, we determined the influence of HCV infection in altering the miRNA expression levels which can modulate immune responses to HCV leading to fibrosis. Analysis of the miRNA expression profiles of HCV infected liver biopsies revealed that 45 miRNAs were differentially expressed in the HCV infected liver when compared to normal livers. In silico target prediction of these differentially expressed miRNAs indicated that their targets include chemokine/cytokine signaling, cell cycle genes and extracellular matrix protein gene expression. Gene expression profiling using whole genome microarray demonstrated that 1320 genes were differentially expressed in chronic HCV liver when compared to normal. These genes could be functionally grouped into those involved in cell cycle regulation, cytokines and chemokines expression, cell adhesion, intracellular signaling and enzymes. Further pathway analysis using GeneGo software identified cell adhesion, cytoskeleton remodeling, cytokine signaling and metabolic pathways as the major pathways activated in chronic HCV. Combinatorial target prediction analysis of miRNA expression along with gene expression analysis indicated that differentially expressed microRNAs in HCV significantly impact transforming growth factor beta (TGF-?) signaling pathway, cell adhesion (integrin expression), chemokine signaling, Notch signaling and cell-cycle( Cyclin D,K) regulation. Overall these results demonstrate that chronic HCV infection induces specific miRNA signatures that will modulate genes involved in the cytoskeletal remodeling and cytokine signaling that can promote the development of fibrosis following HCV infection. Liver biopsies from chronic HCV patients and control liver biopsies from normal subjects (donor liver prior to transplantation) were used to analyze the miRNA and gene expression profile. Patients with HBV and/or HIV were excluded from the study. This Series represents the mRNA gene expression profiling data only.
Project description:We were able to achieve an initial stable intermediate phase by the transduction of Oct4, Klf4, and c-Myc. Furthermore, over-expression of Sox2 in these intermediate stage cells leads to final iPS cell phase. After examining the gene expression profiles from the initial to final iPS cell phases, we have identified Sox2 downstream genes important for iPS cell induction. 4 groups of cells are analyzed. Each group contains cells from 4 indepent dishes. The four groups are: ES cells, iPS cells, intermediate stage cells (OKM cells) and MEFs