Learning about cell lineage, cellular diversity and evolution of the human brain through stem cell models

peer reviewe

Peroxisome Proliferator-Activated Receptor gamma enhances the activity of a insulin degrading enzyme-like metalloprotease for amyloid-beta clearance.

Peroxisome proliferator-activated receptor gamma (PPARgamma) activation results in an increased rate of amyloid-beta (Abeta) clearance from the media of diverse cells in culture, including primary neurons and glial cells. Here, we further investigate the mechanism for Abeta clearance and found that PPARgamma activation modulates a cell surface metalloprotease that can be inhibited by metalloprotease inhibitors, like EDTA and phenanthroline, and also by the peptide hormones insulin and glucagon. The metalloprotease profile of the Abeta-degrading mechanism is surprisingly similar to insulin-degrading enzyme (IDE). This mechanism is maintained in hippocampal and glia primary cultures from IDE loss-of-function mice. We conclude that PPARgamma activates an IDE-like Abeta degrading activity. Our work suggests a drugable pathway that can clear Abeta peptide from the brain

The coding and long noncoding single-cell atlas of the developing human fetal striatum.

Deciphering how the human striatum develops is necessary for understanding the diseases that affect this region. To decode the transcriptional modules that regulate this structure during development, we compiled a catalog of 1116 long intergenic noncoding RNAs (lincRNAs) identified de novo and then profiled 96,789 single cells from the early human fetal striatum. We found that D1 and D2 medium spiny neurons (D1- and D2-MSNs) arise from a common progenitor and that lineage commitment is established during the postmitotic transition, across a pre-MSN phase that exhibits a continuous spectrum of fate determinants. We then uncovered cell type-specific gene regulatory networks that we validated through in silico perturbation. Finally, we identified human-specific lincRNAs that contribute to the phylogenetic divergence of this structure in humans. This work delineates the cellular hierarchies governing MSN lineage commitment

The coding and non-coding RNA single-cell atlas of the human fetal striatum

peer reviewedDeciphering how the human striatum develops is paramount to understand diseases affecting this region. To decode the transcriptional modules that regulate this structure during development we first catalogued 1116, de novo identified, lincRNAs and then profiled 96,789 single-cells from the early human fetal striatum. We found that D1 and D2 medium spiny neurons (MSNs) arise from a common progenitor and that lineage commitment is established during the post-mitotic transition, across a pre-MSN phase that exhibits a continuous spectrum of fate determinants. We then uncovered cell type-specific gene regulatory networks that we validated through in silico perturbation. Finally, we identified human-specific lincRNAs that contribute to the phylogenetic divergence of this structure in humans. In conclusion, our study has delineated the cellular hierarchies governing MSN lineage commitment

Pyramidal neurons derived from human pluripotent stem cells integrate efficiently into mouse brain circuits in vivo

The cerebral cortex is the most complex structure of our brain. During evolution, the relative size of the cortex has increased considerably among higher mammals and new cortical areas involved in higher evolved functions have emerged. Here, we describe an intrinsic pathway of corticogenesis from human embryonic (ESC) and induced pluripotent (iPSC) stem cells leading to the sequential generation of first forebrain progenitors and later pyramidal neurons of all six layers identities in a time- dependent fashion, highly reminiscent of the in vivo situation. Moreover, the hESC- derived neurons followed a neuronal maturation program where late born neurons of about two months in vitro expressed a variety of genes involved in cortical neuronal function and where the majority of the neuronal population was characterized by the presence of synapses in vitro. Following transplantation into mouse neonatal brain, human ESC-derived cortical neurons integrated robustly into the host brain and established specific axonal projections and dendritic patterns corresponding to native cortical neurons. The differentiation and connectivity of the transplanted human cortical neurons complexified progressively over several months in vivo, culminating in the establishment of functional synapses with the host circuitry. Importantly, our data not only demonstrate in vitro, as well as in vivo, the cortical identity of the neurons differentiated from human ESC, but also provide a faithful model of human cortical development, from early neurogenesis to neuronal maturation and generation of neuronal circuits, with implications for the modelling and treatment of neuropsychiatric and neurological diseases and brain repair

hPSC-derived corticogenesis generates pyramidal neurons that integrate into brain networks in vivo

Background and novelty The cerebral cortex is the most complex structure of our brain. During evolution, the relative size of the cortex has increased considerably among higher mammals and new cortical areas involved in higher evolved functions have emerged. The study of human cortical development has major implications for brain evolution and cortical related diseases, but has remained elusive due to paucity of experimental models. Here, we describe an intrinsic pathway of corticogenesis from human embryonic (ESC) and induced pluripotent (iPSC) stem cells leading to the sequential generation of first forebrain progenitors and later pyramidal neurons of all six layers identities in a time-dependent fashion, highly reminiscent of the in vivo situation. Experimental approach We describe an in vitro model for the directed differentiation of human pluripotent stem cells in a monolayer fashion and devoided of morphogens, but supplemented with noggin, and inhibitor of the BMP pathway, that has been shown to be required for neuroectoderm specification. Specified progenitors and neurons are later transplanted into mouse newborn brain and analysed after several months in vivo by immunofluorescence analysis and by patch-clamp recordings. Results and discussion Following the in vitro differentiation, human pluripotent stem cells efficiently differentiated into forebrain and telencephalic progenitors based on the expression of various genes tested by immunofluorescence, quantitative PCR and microarray analysis. At later stages, these cells exited cell cycle and became cortical pyramidal neurons, as attested by their pyramidal morphology, but also by the expression of various markers of cortical neurons and cortical layer specific genes. The cortical neurons present markers of connectivity and a mature electrophisiological profile at later stages. Moreover, following grafting into the mouse newborn cortex, the human ESC- derived neurons extended axons to endogenous cortical targets, present numerous synapses and functionally integrated into the host

Pyramidal neurons derived from human pluripotent stem cells mature to form functional synapses in vitro and integrate e ciently into mouse brain circuits in vivo

The generation of in vitro and in vivo models to study human cortical development is essential to address the molecular and cellular mechanisms involved in brain evolution as well as to elucidate major pathways affected in developmental and degenerative cortical diseases. Here we found that human embryonic (ESC) and induced pluripotent (iPSC) stem cells, cultured without added morphogens, recapitulate corticogenesis in vitro leading to the sequential generation of functional pyramidal neurons of all six layers identities. Following transplantation into the mouse neonatal brain, human ESC-derived cortical neurons integrated robustly and established specific axonal projections corresponding to native cortical neurons of diverse cortical layers and areas. Neuronal differentiation and connectivity complexified progressively over several months in vivo, culminating with the development of elaborate dendritic patterns, the presence of dendritic spines, and the establishment of reciprocal synapses with the host in a time dependent fashion highly reminiscent of the human species. Our data demonstrate that human cortical neurons generated in vitro from ESC/iPSC can develop complex hodological properties characteristic of the cerebral cortex in vivo, thereby offering unprecedented opportunities for the modelling of human cortex diseases, and brain repair. Please, state why this workshop is useful for you: My present research is focused on the modeling of human cortical development and the mechanisms altered in some of the diseases affecting the development or the aging cerebral cortex. My future career and work progress could profit from the study of different systems in vitro aiming to reproduce cortical organogenesis, as well as the study of the epigenetic programs determining fate determination in the embryo

An in vivo humanized model for Alzheimer’s disease from pluripotent stem cells

The generation of in vitro and in vivo models to study human corticogenesis is essential to address the molecular and cellular mechanisms involved in developmental and degenerative cortical diseases. We previously found that human pluripotent stem cells (PSC) can recapitulate major milestones of human corticogenesis in vitro. In addition, following the transplantation of human PSC-derived cortical cells into the mouse neonatal brain we observed a functional integration and establishment of specific axonal projections from the human neurons. Several neurological diseases strike the integrity of the cerebral cortex including stroke, epilepsy and neurodegenerative diseases such as Alzheimer’s disease (AD). When some of these diseases have been extensively studied, mostly they have been tackled using murine transgenic models that cannot completely recapitulate the etiology of the disease. Here, we present a novel “in vivo humanized AD model” from human pluripotent stem cells. We transplanted PSC-derived human cortical neurons into the brain of transgenic AD mouse models to characterize early and late effects of amyloid pathology on human neurons. We found that human neurons exposed to the toxic amyloid-beta species in the transgenic mouse brain show very early signs of neurodegeneration, including aberrant accumulation of pre-synaptic neurotransmitter vesicles, and early neuronal loss. Signs of neuronal and axonal degeneration were also observed by EM analysis specifically in the human neurons. Interestingly, the human neurons located at amyloid-beta plaque sites were positive for pathological Tau tangle-like staining, a major hallmark of AD. A preliminary comparative RNA expression analysis at early stages between human neurons transplanted into wild-type and transgenic animals revealed some differentially expressed candidate genes that could shed new light on the biology of early stages of the disease. In conclusion, the humanized model for AD can recapitulate major milestones of the AD human pathology in an in vivo context and could be instrumental for the study of early and late stages of the pathology, opening new venues for future research in the field. Overall, these data demonstrate that cortical neurons derived from human pluripotent stem cells represent an invaluable tool for the modeling of human cortical diseases, in particular adult onset, human specific neurological disorders, such as Alzheimer’s disease