Marius Wernig Laboratory

“Only those who attempt the absurd can achieve the impossible.”

--Albert Einstein

Research in the Wernig Lab

Our lab is generally interested in the mechanisms that determine cell fate identity. Our focus is on epigenetic reprogramming i.e. ways to induce cell fate changes by defined factors such as the reprogramming of somatic cells into pluripotent stem (or iPS) cells. More recently, we have demonstrated that mouse fibroblasts can directly be converted to functional neuronal cells that we termed induced neuronal (iN) cells (Vierbuchen et al., 2010, Nature). The iN cells were generated through expression of the three transcription factors Ascl1, Myt1l, and Brn2. This surprising discovery opened the door to a new area of investigation. We are currently working to apply our finding to human cells, explore the molecular mechanism of the action of the three transcription factors, and determine the neuronal subtype of resulting iN cells. A long term goal is to use this method to evaluate whether iN cells can be used to model neurological diseases. In addition, the emerging iPS cell technology provides new fascinating translational applications such as patient-specific stem cell therapy or disease phenocopy through differentiation into the neural lineage. Our lab has developed new methods to generate iPS cells from human fibroblasts with defined mutations and explores various technologies to improve gene targeting in human iPS cells with a long term goal to correct disease-causing mutations. This work is made possible through a very generous CIRM grant. Another interest of the laboratory is to study self-renewal and differentiation in neural stem/progenitor cells and apply these findings to the tumor precursor cells of glioblastoma. This will shed some light into glioma generation and potentially lead to alternative treatment strategies of this devastating brain disease.

Associate Professor of Pathology and, by courtesy, of Chemical and Systems Biology

Publications

  • Direct targeting of the mouse optic nerve for therapeutic delivery. Journal of neuroscience methods Mesentier-Louro, L. A., Dodd, R., Domizi, P., Nobuta, H., Wernig, M., Wernig, G., Liao, Y. J. 2018

    Abstract

    BACKGROUND: Animal models of optic nerve injury are often used to study central nervous system (CNS) degeneration and regeneration, and targeting the optic nerve is a powerful approach for axon-protective or remyelination therapy. However, the experimental delivery of drugs or cells to the optic nerve is rarely performed because injections into this structure are difficult in small animals, especially in mice.NEW METHOD: We investigated and developed methods to deliver drugs or cells to the mouse optic nerve through 3 different routes: a) intraorbital, b) through the optic foramen and c) transcranial.RESULTS: The methods targeted different parts of the mouse optic nerve: intraorbital proximal (intraorbital), intracranial middle (optic-foramen) or intracranial distal (transcranial) portion.COMPARISON WITH EXISTING METHODS: Most existing methods target the optic nerve indirectly. For instance, intravitreally delivered cells often cannot cross the inner limiting membrane to reach retinal neurons and optic nerve axons. Systemic delivery, eye drops and intraventricular injections do not always successfully target the optic nerve. Intraorbital and transcranial injections into the optic nerve or chiasm have been performed but these methods have not been well described. We approached the optic nerve with more selective and precise targeting than existing methods.CONCLUSIONS: We successfully targeted the murine optic nerve intraorbitally, through the optic foramen, and transcranially. Of all methods, the injection through the optic foramen is likely the most innovative and fastest. These methods offer additional approaches for therapeutic intervention to be used by those studying white matter damage and axonal regeneration in the CNS.

    View details for DOI 10.1016/j.jneumeth.2018.10.038

    View details for PubMedID 30389488

  • CRISPR Activation Screens Systematically Identify Factors that Drive Neuronal Fate and Reprogramming. Cell stem cell Liu, Y., Yu, C., Daley, T. P., Wang, F., Cao, W. S., Bhate, S., Lin, X., Still, C. 2., Liu, H., Zhao, D., Wang, H., Xie, X. S., Ding, S., Wong, W. H., Wernig, M., Qi, L. S. 2018

    Abstract

    Comprehensive identification of factors that can specify neuronal fate could provide valuable insights into lineage specification and reprogramming, but systematic interrogation of transcription factors, and their interactions with each other, has proven technically challenging. We developed a CRISPR activation (CRISPRa) approach to systematically identify regulators of neuronal-fate specification. We activated expression of all endogenous transcription factors and other regulators via a pooled CRISPRa screen in embryonic stem cells, revealing genes including epigenetic regulators such as Ezh2 that can induce neuronal fate. Systematic CRISPR-based activation of factor pairs allowed us to generate a genetic interaction map for neuronal differentiation, with confirmation of top individual and combinatorial hits as bona fide inducers of neuronal fate. Several factor pairs could directly reprogram fibroblasts into neurons, which shared similar transcriptional programs with endogenous neurons. This study provides an unbiased discovery approach for systematic identification of genes that drive cell-fate acquisition.

    View details for DOI 10.1016/j.stem.2018.09.003

    View details for PubMedID 30318302

  • The fragile X mutation impairs homeostatic plasticity in human neurons by blocking synaptic retinoic acid signaling. Science translational medicine Zhang, Z., Marro, S. G., Zhang, Y., Arendt, K. L., Patzke, C., Zhou, B., Fair, T., Yang, N., Sudhof, T. C., Wernig, M., Chen, L. 2018; 10 (452)

    Abstract

    Fragile X syndrome (FXS) is an X chromosome-linked disease leading to severe intellectual disabilities. FXS is caused by inactivation of the fragile X mental retardation 1 (FMR1) gene, but how FMR1 inactivation induces FXS remains unclear. Using human neurons generated from control and FXS patient-derived induced pluripotent stem (iPS) cells or from embryonic stem cells carrying conditional FMR1 mutations, we show here that loss of FMR1 function specifically abolished homeostatic synaptic plasticity without affecting basal synaptic transmission. We demonstrated that, in human neurons, homeostatic plasticity induced by synaptic silencing was mediated by retinoic acid, which regulated both excitatory and inhibitory synaptic strength. FMR1 inactivation impaired homeostatic plasticity by blocking retinoic acid-mediated regulation of synaptic strength. Repairing the genetic mutation in the FMR1 gene in an FXS patient cell line restored fragile X mental retardation protein (FMRP) expression and fully rescued synaptic retinoic acid signaling. Thus, our study reveals a robust functional impairment caused by FMR1 mutations that might contribute to neuronal dysfunction in FXS. In addition, our results suggest that FXS patient iPS cell-derived neurons might be useful for studying the mechanisms mediating functional abnormalities in FXS.

    View details for DOI 10.1126/scitranslmed.aar4338

    View details for PubMedID 30068571

  • Stem cell therapy for treatment of ischemic optic neuropathy Mesentier-Louro, L., Yang, N., Shariati, A., Domizi, P., Dodd, R., Wernig, G., Wernig, M., Liao, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2018
  • Transdifferentiation of human adult peripheral blood T cells into neurons. Proceedings of the National Academy of Sciences of the United States of America Tanabe, K., Ang, C. E., Chanda, S., Olmos, V. H., Haag, D., Levinson, D. F., Sudhof, T. C., Wernig, M. 2018

    Abstract

    Human cell models for disease based on induced pluripotent stem (iPS) cells have proven to be powerful new assets for investigating disease mechanisms. New insights have been obtained studying single mutations using isogenic controls generated by gene targeting. Modeling complex, multigenetic traits using patient-derived iPS cells is much more challenging due to line-to-line variability and technical limitations of scaling to dozens or more patients. Induced neuronal (iN) cells reprogrammed directly from dermal fibroblasts or urinary epithelia could be obtained from many donors, but such donor cells are heterogeneous, show interindividual variability, and must be extensively expanded, which can introduce random mutations. Moreover, derivation of dermal fibroblasts requires invasive biopsies. Here we show that human adult peripheral blood mononuclear cells, as well as defined purified T lymphocytes, can be directly converted into fully functional iN cells, demonstrating that terminally differentiated human cells can be efficiently transdifferentiated into a distantly related lineage. T cell-derived iN cells, generated by nonintegrating gene delivery, showed stereotypical neuronal morphologies and expressed multiple pan-neuronal markers, fired action potentials, and were able to form functional synapses. These cells were stable in the absence of exogenous reprogramming factors. Small molecule addition and optimized culture systems have yielded conversion efficiencies of up to 6.2%, resulting in the generation of >50,000 iN cells from 1 mL of peripheral blood in a single step without the need for initial expansion. Thus, our method allows the generation of sufficient neurons for experimental interrogation from a defined, homogeneous, and readily accessible donor cell population.

    View details for DOI 10.1073/pnas.1720273115

    View details for PubMedID 29866841

Marius Wernig Laboratory