Project description:Astrocyte-to-neuron conversion has developed into a promising avenue for neuronal replacement therapy. Neurons depend critically on mitochondria function and often die by ferroptosis during the conversion process. Here we examined the extent of adequate mitochondrial reprogramming by morphology and proteome analysis. While mitochondria profoundly changed their morphology during Neurogenin2 (Neurog2) – or Achaete-scute homolog 1 (Ascl1)-mediated astrocyte-to-neuron reprogramming, we found neuron-specific mitochondrial proteins, here identified in a comprehensive proteome analysis of isolated mitochondria from primary neurons and astrocytes, to be only partially and at late stages regulated during the process. To improve this, we used dCas9 technology to induce neuron-specific mitochondrial proteins early during reprogramming. This resulted not only in increased conversion efficiency, but also in faster neuronal generation. Taken together, reprogramming mitochondria in a cell type-specific manner has powerful effects on astrocyte-to-neuron conversion, suggesting mitochondria to be a driving force in this process.
Project description:The acetylation levels of histones and other proteins change during aging and have been linked to neurodegeneration. Here we show that deletion of the histone acetyltransferase (HAT) co-factor Trrap specifically impairs the function of the transcription factor Sp1, reduces its stability and causes a decrease in histone acetylation at Sp1 target genes. Modulation of Sp1 function by Trrap acts as a hub regulating multiple processes involved in neuron and neural stem cells function and maintenance including microtubule dynamics and the Wnt signaling pathway. Consistently, Trrap conditional mutants exhibit all hallmarks of neurodegeneration including dendrite retraction and axonal swellings, neuron death, astrogliosis, microglia activation, demyelination and decreased adult neurogenesis. Our results uncovered a novel functional network, essential to prevent neurodegeneration, and involving the specific regulation of Sp1 transcription factor and its downstream targets by Trrap-HAT.
Project description:Purpose: To test the neuronal conversion and other effects induced by neural transcription factor Neurog2 or Ascl1 in human glioblastoma cells Methods: Retroviral expression of Ascl1, Neurog2 or control GFP in cultured human U251 cells at 6 DPI
Project description:The acetylation levels of histones and other proteins change during aging and have been linked to neurodegeneration. Here we show that deletion of the histone acetyltransferase (HAT) co-factor Trrap specifically impairs the function of the transcription factor Sp1, reduces its stability and causes a decrease in histone acetylation at Sp1 target genes. Modulation of Sp1 function by Trrap acts as a hub regulating multiple processes involved in neuron and neural stem cells function and maintenance including microtubule dynamics and the Wnt signaling pathway. Consistently, Trrap conditional mutants exhibit all hallmarks of neurodegeneration including dendrite retraction and axonal swellings, neuron death, astrogliosis, microglia activation, demyelination and decreased adult neurogenesis. Our results uncovered a novel functional network, essential to prevent neurodegeneration, and involving the specific regulation of Sp1 transcription factor and its downstream targets by Trrap-HAT.
Project description:Here we reveal a hierarchical mechanism in the direct conversion of fibroblasts into induced neuronal (iN) cells mediated by the transcription factors Ascl1, Brn2, and Myt1l. Examination of global transcriptional changes and mapping genome-wide transcription factors occupancy at distinct time points during the transdifferentiation process
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:Specific neuronal types derived from embryonic stem cells (ESCs) can facilitate mechanistic studies and potentially aid in regenerative medicine. Existing induction methods, however, mostly rely on the effects of growth factors, which generally tend to result in mixed populations of neurons. Here we report that over-expression of specific transcription factors (TFs) in ESCs can rather guide the differentiation of ESCs towards specific neuron types. Analysis of published data on gene expression changes early (two days) after induction of each of 185 induced TFs implicated candidate TFs for further ESC differentiation studies. After induction for 6 days four of them (Ascl1, Smad7, Nr2f1, and Ascl2) generated a high proportion (>35%) of cells with neural progenitor marker PSA-NCAM and clear neural morphology on day 14. The capacity of these TFs to induce neural differentiation is inferred to be most likely linked to early activation of the Notch signaling pathway. Among the neuron-like cells, GABA-positive cells were most abundant (32-97% for 4 top TFs), whereas Isl1-positive cells and TH-positive cells were less abundant (<12% and <5%, respectively). Enrichment of cells obtained with the induction of Ascl1, Smad7, and Nr2f1 using beads with anti-PSA-NCAM antibody resulted in essentially pure population of neuron-like cells with expression profiles similar to neural tissues and highly expressed markers of GABAergic neurons. A time-course experiment with induction of Ascl1 showed early upregulation of most neural-specific and GABAergic-specific mRNA and miRNAs. We identified mRNA and miRNAs, whose expression depended on the induction of Ascl1, and showed that they were enriched in Ascl1 target genes. In summary, this study indicates that induction of transcription factors is a promising approach to generate candidate specific neural cell types from ESCs. Transcription factor Ascl1 was induced in mouse ESCs to facilitate neural differentiation. Expression of transgenic Ascl1 was repressed by doxycycline (Dox); thus, it were induced in Dox- conditions, whereas Dox+ conditions represent control cells with no expression of Ascl1 transgene. For neural differentiation, cells were cultured 3 days in alpha-MEM medium and then - in NeuroCult neural differentiation medium for 2-11 days (total up to 14 days). RNA was extracted with mirVana kit (Thermo Fisher Scientific).
Project description:Translational research is commonly performed in the C57B6/J mouse strain, chosen for its genetic homogeneity and phenotypic uniformity. Here, we evaluate the suitability of the white-footed deer mouse (Peromyscus leucopus) as a model organism for aging research, offering a comparative analysis against C57B6/J and diversity outbred (DO) Mus musculus strains. Our study includes comparisons of body composition, skeletal muscle function, and cardiovascular parameters, shedding light on potential applications and limitations of P. leucopus in aging studies. Notably, P. leucopus exhibits distinct body composition characteristics, emphasizing reduced muscle force exertion and a unique metabolism, particularly in fat mass. Cardiovascular assessments showed changes in arterial stiffness, challenging conventional assumptions and highlighting the need for a nuanced interpretation of aging-related phenotypes. Our study also highlights inherent challenges associated with maintaining and phenotyping P. leucopus cohorts. Behavioral considerations, including anxiety-induced responses during handling and phenotyping assessment, pose obstacles in acquiring meaningful data. Moreover, the unique anatomy of P. leucopus necessitates careful adaptation of protocols designed for Mus musculus. While showcasing potential benefits, further extensive analyses across broader age ranges and larger cohorts are necessary to establish the reliability of P. leucopus as a robust and translatable model for aging studies.
Project description:Direct reprogramming from fibroblasts to neurons induces widespread cellular and transcriptional reconfigurations. In this study, we characterized global epigenomic changes during direct reprogramming using whole-genome base-resolution DNA methylome (mC) sequencing. We found that the pioneer transcription factor Ascl1 alone is sufficient for inducing robust non-CG methylation (mCH) accumulation in reprogrammed cells, but co-expression of Brn2 and Mytl1 was required to establish a global mCH pattern reminiscent of mature cortical neurons. Ascl1 alone induced strong promoter CG methylation (mCG) of fibroblast specific genes, while BAM overexpression additionally targets a competing myogenic program and directs a more faithful conversion to neuronal cells. Ascl1 induces local demethylation at its binding sites. Surprisingly, co-expression with Brn2 and Mytl1 inhibited the ability of Ascl1 to induce demethylation, suggesting a contextual regulation of transcription factor - epigenome interaction. Finally, we found that de novo methylation by DNMT3A is required for efficient neuronal reprogramming.