Transcriptional Regulation and Its Misregulation in Disease

Rapid Single-Step Induction of Functional Neurons from Human Pluripotent Stem Cells

Transplantation of dopaminergic neurons can potentially improve the clinical outcome of Parkinson's disease, a neurological disorder resulting from degeneration of mesencephalic dopaminergic neurons. In particular, transplantation of embryonic-stem-cell-derived dopaminergic neurons has been shown to be efficient in restoring motor symptoms in conditions of dopamine deficiency. However, the use of pluripotent-derived cells might lead to the development of tumours if not properly controlled. Here we identified a minimal set of three transcription factors--Mash1 (also known as Ascl1), Nurr1 (also known as Nr4a2) and Lmx1a--that are able to generate directly functional dopaminergic neurons from mouse and human fibroblasts without reverting to a progenitor cell stage. Induced dopaminergic (iDA) cells release dopamine and show spontaneous electrical activity organized in regular spikes consistent with the pacemaker activity featured by brain dopaminergic neurons. The three factors were able to elicit dopaminergic neuronal conversion in prenatal and adult fibroblasts from healthy donors and Parkinson's disease patients. Direct generation of iDA cells from somatic cells might have significant implications for understanding critical processes for neuronal development, in vitro disease modelling and cell replacement therapies.

Direct generation of functional dopaminergic neurons from mouse and human fibroblasts

https://sites.bu.edu/phenogeno/files/2014/06/Reconstructing-and-Reprogramming.pdf

Reconstructing and Reprogramming the Tumor-Propagating Potential of Glioblastoma Stem-like Cells

In vivo direct reprogramming of reactive glial cells into functional neurons after brain injury and in an Alzheimer's disease model.

Three papers in this issue demonstrate the production of functional induced neuronal (iN) cells from human fibroblasts, a procedure that holds great promise for regenerative medicine. Pang et al. show that a combination of the three transcription factors Ascl1 (also known as Mash1), Brn2 (or Pou3f2) and Myt1l greatly enhances the neuronal differentiation of human embryonic stem cells. When combined with the basic helix–loop–helix transcription factor NeuroD1, these factors can also convert fetal and postnatal human fibroblasts into iN cells. Caiazzo et al. use a cocktail of three transcription factors to convert prenatal and adult mouse and human fibroblasts into functional dopaminergic neurons. The three are Mash1, Nurr1 (or Nr4a2) and Lmx1a. Conversion is direct with no reversion to a progenitor cell stage, and it occurs in cells from Parkinson's disease patients as well as from healthy donors. Yoo et al. use an alternative approach. They show that microRNAs can have an instructive role in neural fate determination. Expression of miR-9/9* and miR-124 in human fibroblasts induces their conversion into functional neurons, and the process is facilitated by the addition of some neurogenic transcription factors. Somatic cell nuclear transfer, cell fusion, or expression of lineage-specific factors have been shown to induce cell-fate changes in diverse somatic cell types1,2,3,4,5,6,7,8,9,10,11,12. We recently observed that forced expression of a combination of three transcription factors, Brn2 (also known as Pou3f2), Ascl1 and Myt1l, can efficiently convert mouse fibroblasts into functional induced neuronal (iN) cells13. Here we show that the same three factors can generate functional neurons from human pluripotent stem cells as early as 6 days after transgene activation. When combined with the basic helix–loop–helix transcription factor NeuroD1, these factors could also convert fetal and postnatal human fibroblasts into iN cells showing typical neuronal morphologies and expressing multiple neuronal markers, even after downregulation of the exogenous transcription factors. Importantly, the vast majority of human iN cells were able to generate action potentials and many matured to receive synaptic contacts when co-cultured with primary mouse cortical neurons. Our data demonstrate that non-neural human somatic cells, as well as pluripotent stem cells, can be converted directly into neurons by lineage-determining transcription factors. These methods may facilitate robust generation of patient-specific human neurons for in vitro disease modelling or future applications in regenerative medicine.

/pdf/induction-of-human-neuronal-cells-by-defined-transcription-537effsu7t.pdf

Troy Q. Yang

Papers

Induction of human neuronal cells by defined transcription factors