The specification and differentiation of dentate gyrus granule neurons in the hippocampus require temporally and spatially coordinated actions of both intrinsic and extrinsic molecules. The basic helix-loop-helix transcription factor Neurogenin2 (Ngn2) and NeuroD1 are key regulators in these processes. Based on existing classification, we analyzed the molecular events occurring during hippocampal neurogenesis, primarily focusing on juvenile animals. We found that Ngn2 is transiently expressed by late type-2a amplifying progenitors. The Ngn2 progenies mature into hippocampal granule neurons. Interestingly, the loss of Ngn2 at early stages of development leads to a robust reduction in neurogenesis, but does not disturb granule neuron maturation per se. We found that the role of Ngn2 is to maintain progenitors in an undifferentiated state, allowing them to amplify prior to their maturation into granule neurons upon NeuroD1 induction. When we overexpressed Ngn2 and NeuroD1 in vivo, we found NeuroD1 to exhibit a more pronounced neuron-inductive effect, leading to granule neuron commitment, than that displayed by Ngn2. Finally, we observed that all markers expressed during the transcriptional control of hippocampal neurogenesis in rodents are also present in the human hippocampus. Taken together, we demonstrate a critical role of for Ngn2 and NeuroD1 in controlling neuronal commitment and hippocampal granule neuroblast formation, both during embryonic development and in post-natal hippocampal granule neurogenesis.

In this study, we sought evidence for alpha-synuclein (ASYN) expression in oligodendrocytes, as a possible endogenous source of ASYN to explain its presence in glial inclusions found in multiple system atrophy (MSA) and Parkinson's disease (PD). We identified ASYN in oligodendrocyte lineage progenitors isolated from the rodent brain, in oligodendrocytes generated from embryonic stem cells, and in induced pluripotent stem cells produced from fibroblasts of a healthy individual and patients diagnosed with MSA or PD, in cultures in vitro. Notably, we observed a significant decrease in ΑSYN during oligodendrocyte maturation. Additionally, we show the presence of transcripts in PDGFRΑ/CD140a(+) cells and SOX10(+) oligodendrocyte lineage nuclei isolated by FACS from rodent and human healthy and diseased brains, respectively. Our work identifies ASYN in oligodendrocyte lineage cells, and it offers additional in vitro cellular models that should provide significant insights of the functional implication of ASYN during oligodendrocyte development and disease.

The hippocampus is important for memory formation and is severely affected in the brain with Alzheimer disease (AD). Our understanding of early pathogenic processes occurring in hippocampi in AD is limited due to tissue unavailability. Here, we report a chemical approach to rapidly generate free-floating hippocampal spheroids (HSs), from human induced pluripotent stem cells. When used to model AD, both APP and atypical PS1 variant HSs displayed increased Aβ42/Aβ40 peptide ratios and decreased synaptic protein levels, which are common features of AD. However, the two variants differed in tau hyperphosphorylation, protein aggregation, and protein network alterations. NeuroD1-mediated gene therapy in HSs-derived progenitors resulted in modulation of expression of numerous genes, including those involved in synaptic transmission. Thus, HSs can be harnessed to unravel the mechanisms underlying early pathogenic changes in the hippocampi of AD patients, and provide a robust platform for the development of therapeutic strategies targeting early stage AD.

Induced pluripotent stem cells (iPSCs) are becoming an important source of pre-clinical models for research focusing on neurodegeneration. They offer the possibility for better understanding of common and divergent pathogenic mechanisms of brain diseases. Moreover, iPSCs provide a unique opportunity to develop personalized therapeutic strategies, as well as explore early pathogenic mechanisms, since they rely on the use of patients’ own cells that are otherwise accessible only post-mortem, when neuronal death-related cellular pathways and processes are advanced and adaptive. Neurodegenerative diseases are in majority of unknown cause, but mutations in specific genes can lead to familial forms of these diseases. For example, mutations in the superoxide dismutase 1 gene lead to the motor neuron disease amyotrophic lateral sclerosis (ALS), while mutations in the SNCA gene encoding for alpha-synuclein protein lead to familial Parkinson’s disease (PD). The generations of libraries of familial human ALS iPSC lines have been described, and the iPSCs rapidly became useful models for studying cell autonomous and non-cell autonomous mechanisms of the disease. Here we report the generation of a comprehensive library of iPSC lines of familial PD and an associated synucleinopathy, multiple system atrophy (MSA). In addition, we provide examples of relevant neural cell types these iPSC can be differentiated into, and which could be used to further explore early disease mechanisms. These human cellular models will be a valuable resource for identifying common and divergent mechanisms leading to neurodegeneration in PD and MSA.

Neurons derived from neural stem cells could potentially be used for cell therapy in neurodegenerative disorders, such as Parkinson's disease. To achieve controlled differentiation of neural stem cells, we expressed transcription factors involved in the development of midbrain dopaminergic neurons in rat and human neural progenitors. Using retroviral-mediated transgene delivery, we overexpressed Lmx1a (LIM homeobox transcription factor 1, alpha), Msx1 (msh homeobox homolog 1), Ngn2 (neurogenin 2), or Pitx3 (paired-like homeodomain transcription factor 3) in neurospheres derived from embryonic day 14.5 rat ventral mesencephalic progenitors. We also expressed either Lmx1a or Msx1 in the human embryonic midbrain-derived progenitor cell line NGC-407. Rat cells transduced with Ngn2 exited the cell cycle and expressed the neuronal marker microtubule-associated protein 2 and catecholamine-neuron protein vesicular monoamine transporter 2. Interestingly, Pitx3 downregulated the expression of SOX2 (SRY-box containing gene 2) and Nestin, altered cell morphology, but never induced neuronal or glial differentiation. Ngn2 exhibited a strong neuron-inducing effect. In contrast, few Lmx1a-transduced cells matured into neurons, and Msx1 overexpression promoted oligodendrogenesis rather than neuronal differentiation. Importantly, none of these four genes, alone or in combination, enhanced differentiation of rat neural stem cells into dopaminergic neurons. Notably, the overexpression of Lmx1a, but not Msx1, in human neural progenitors increased the yield of tyrosine hydroxylase-immunoreactive cells by threefold. Together, we demonstrate that induced overexpression of transcription factor genes has profound and specific effects on the differentiation of rat and human midbrain progenitors, although few dopamine neurons are generated.