Marius Marc-Daniel Mader, Alexa Scavetti, Yongjin Yoo, Aaron Tianyue Chai, Takeshi Uenaka, Marius Wernig

Migration of transplanted allogeneic myeloid cells into the brain following systemic haematopoietic stem and progenitor cell transplantation (HCT) holds great promise as a therapeutic modality to correct genetic deficiencies in the brain such as lysosomal storage diseases1-3. However, the toxic myeloablation required for allogeneic HCT can cause serious, life-threatening side effects, limiting its applicability. Moreover, transplanted allogeneic myeloid cells are highly vulnerable to rejection even in an immune-privileged organ like the brain. Here we report a brain-restricted, high-efficiency microglia replacement approach without myeloablative preconditioning. Contrary to previous assumptions, we found that haematopoietic stem cells are not required to repopulate the myeloid compartment of the brain environment, and Sca1- committed progenitor cells were highly efficient in replacing microglia following intracerebral injection. This finding enabled the development of brain-restricted preconditioning and avoided long-term peripheral engraftment, thus eliminating complications such as graft-versus-host disease. Evaluating its therapeutic potential, we found that our allogeneic microglia replacement method rescued the mouse model of Sandhoff disease, a lysosomal storage disease caused by hexosaminidase B deficiency. In support of the translational relevance of this approach, we discovered that human embryonic stem cell-derived myeloid progenitor cells display a similar engraftment potential following brain-restricted conditioning. Our results overcome current limitations of conventional HCT and may pave the way for the development of allogeneic microglial cell therapies for the brain.

Yi Miao, Haoqing Wang, Kevin M Jude, Jie Wang, Jinzhao Wang, Marius Wernig, Thomas C Südhof

The adhesion-GPCR Brain-specific Angiogenesis Inhibitor-3 (BAI3) plays a crucial role in organizing synapses in the brain. However, how BAI3 engages one of its ligands, the C1q-like proteins (C1qls), remains largely unexplored. Here, we present the single-particle cryo-electron microscopy (cryo-EM) structure of the C1ql3-BAI3 complex at 2.8 Å resolution. The structure reveals a hexameric configuration, where C1ql3 forms a central homotrimer that effectively captures three BAI3 molecules. These BAI3 molecules fit snugly into the grooves between the trimeric C1q domains of the C1qls, employing calcium ion (Ca2+)-mediated interactions that differ from previously characterized structures of C1q-like domain-mediated complexes. Furthermore, we conducted mutant analysis and cell surface staining, which confirmed the essential contact residues involved in this interaction. This unique binding mechanism not only enhances our understanding of the C1ql-BAI3-mediated synaptic organization but also sheds light on the functional dynamics of BAI3 in the brain.

Ching-Chieh Chou, Ryan Vest, Miguel A Prado, Joshua Wilson-Grady, Joao A Paulo, Yohei Shibuya, Patricia Moran-Losada, Ting-Ting Lee, Jian Luo, Steven P Gygi, Jeffery W Kelly, Daniel Finley, Marius Wernig, Tony Wyss-Coray, Judith Frydman

Ageing is the most prominent risk factor for Alzheimer's disease (AD). However, the cellular mechanisms linking neuronal proteostasis decline to the characteristic aberrant protein deposits in the brains of patients with AD remain elusive. Here we develop transdifferentiated neurons (tNeurons) from human dermal fibroblasts as a neuronal model that retains ageing hallmarks and exhibits AD-linked vulnerabilities. Remarkably, AD tNeurons accumulate proteotoxic deposits, including phospho-tau and amyloid β, resembling those in APP mouse brains and the brains of patients with AD. Quantitative tNeuron proteomics identify ageing- and AD-linked deficits in proteostasis and organelle homeostasis, most notably in endosome-lysosomal components. Lysosomal deficits in aged tNeurons, including constitutive lysosomal damage and ESCRT-mediated lysosomal repair defects, are exacerbated in AD tNeurons and linked to inflammatory cytokine secretion and cell death. Providing support for the centrality of lysosomal deficits in AD, compounds ameliorating lysosomal function reduce amyloid β deposits and cytokine secretion. Thus, the tNeuron model system reveals impaired lysosomal homeostasis as an early event of ageing and AD.

Jinzhao Wang, Thomas Sudhof, Marius Wernig

Neuroligins are postsynaptic cell-adhesion molecules that regulate synaptic function with a remarkable isoform specificity. Although Nlgn1 and Nlgn2 are highly homologous and biochemically interact with the same extra- and intracellular proteins, Nlgn1 selectively functions in excitatory synapses whereas Nlgn2 functions in inhibitory synapses. How this excitatory/inhibitory (E/I) specificity arises is unknown. Using a comprehensive structure-function analysis, we here expressed wild-type and mutant neuroligins in functional rescue experiments in cultured hippocampal neurons lacking all endogenous neuroligins. Electrophysiology confirmed that Nlgn1 and Nlgn2 selectively restored excitatory and inhibitory synaptic transmission, respectively, in neuroligin-deficient neurons, aligned with their synaptic localizations. Chimeric Nlgn1-Nlgn2 constructs reveal that the extracellular neuroligin domains confer synapse specificity, whereas their intracellular sequences are exchangeable. However, the cytoplasmic sequences of Nlgn2, including its Gephyrin-binding motif that is identically present in the Nlgn1, is essential for its synaptic function whereas they are dispensable for Nlgn1. These results demonstrate that although the excitatory vs. inhibitory synapse specificity of Nlgn1 and Nlgn2 are both determined by their extracellular sequences, these neuroligins enable normal synaptic connections via distinct intracellular mechanisms.

Takeshi Uenaka, Sascha Jung, Ishan Kumar, Kit Vodehnal, Mohit Rastogi, Yongjin Yoo, Mark Koontz, Christian Thome, Wanhua Li, Tamara Chan, Erin M Green, Kirill Chesnov, Zijun Sun, Shuyuan Zhang, Jinzhao Wang, Anthony Venida, Anne-Laure Mahul Mellier, Micaiah Atkins, Meredith Jackrel, Jan M Skotheim, Tony Wyss-Coray, Monther Abu-Remaileh, Hilal A Lashuel, Michael C Bassik, Thomas C Südhof, Antonio Del Sol, Erik Ullian, Marius Wernig

Microglia are the immune cells of the central nervous system and are thought to be key players in both physiological and disease conditions. Several microglial features are poorly conserved between mice and human, such as the function of the neurodegeneration-associated immune receptor Trem2. Induced pluripotent stem cell (iPSC)-derived microglia offer a powerful opportunity to generate and study human microglia. However, human iPSC-derived microglia often exhibit activated phenotypes in vitro, and assessing their impact on other brain cell types remains challenging due to limitations in current co-culture systems. Here, we developed fully defined brain microtissues, composed of human iPSC-derived neurons, astrocytes, and microglia, co-cultured in 2D or 3D formats. Our microtissues are stable and self-sufficient over time, requiring no exogenous cytokines or growth factors. All three cell types exhibit morphologies characteristic of their in vivo environment and show functional properties. Co-cultured microglia develop more homeostatic phenotypes compared to microglia exposed to exogenous cytokines. Hence, these tri-cultures provide a unique approach to investigate cell-cell interactions between brain cell types. We found that astrocytes and not neurons are sufficient for microglial survival and maturation, and that astrocyte-derived M-CSF is essential for microglial survival. Single-cell and single-nucleus RNA sequencing analyses nominated a network of reciprocal communication between cell types. Brain microtissues faithfully recapitulated pathogenic α-synuclein seeding and aggregation, suggesting their usefulness as human cell models to study not only normal but also pathological cell biological processes.

Markus Wöhr, Wendy M Fong, Justyna A Janas, Moritz Mall, Christian Thome, Madhuri Vangipuram, Lingjun Meng, Thomas C Südhof, Marius Wernig

No abstract

Kelsie Eichel, Takeshi Uenaka, Vivek Belapurkar, Rui Lu, Shouqiang Cheng, Joseph S Pak, Caitlin A Taylor, Thomas C Südhof, Robert Malenka, Marius Wernig, Engin Özkan, David Perrais, Kang Shen

No abstract

Tamara C Chan, Mohit Rastogi, Micah X Williams, Samuel Zhang, Sophia M Shi, Steven R Shuken, Teresa Bartling, Katleen Wild, Micaiah Atkins, Oliver Hahn, Joao A Paulo, Saša Jereb, S Andrew Shuster, Yongjin Yoo, Alan Napole, Victoria G Hernandez, Liqun Luo, Marion S Buckwalter, Beth Stevens, Benjamin E Deverman, Deborah Kronenberg-Versteeg, Steven P Gygi, Tony Wyss-Coray, Marius Wernig

Microglial tiling-the phenomenon of consistent cell-to-cell distances and non-overlapping processes-is regarded as a qualitative indicator of homeostasis, but mechanisms of microglial tiling are unknown. We used cell-surface proximity labeling and mass spectrometry to profile the microglial cell-surface proteome in an in vitro model of homeostatic glial physiology and used single-cell RNA sequencing and public databases to identify candidate cell-surface proteins that might modulate tiling. We designed an image-based functional assay which measures six morphological/spatial readouts to screen these proteins for modulation of tiling. CD72, a coreceptor to the B cell receptor that is expressed by microglia, disrupted tiling; we validated its effects in vitro and in situ in organotypic hippocampal brain slices. Phosphoproteomic studies revealed that CD72 modulates pathways associated with cell adhesion, repulsive receptors, microglial activation, and cytoskeletal organization. These results lay the groundwork for further investigation of the functional roles of tiling in homeostasis and disease.

Gernot Neumayer, Jessica L Torkelson, Shengdi Li, Kelly McCarthy, Hanson H Zhen, Madhuri Vangipuram, Marius M Mader, Gulilat Gebeyehu, Taysir M Jaouni, Joanna Jacków-Malinowska, Avina Rami, Corey Hansen, Zongyou Guo, Sadhana Gaddam, Keri M Tate, Alberto Pappalardo, Lingjie Li, Grace M Chow, Kevin R Roy, Thuylinh Michelle Nguyen, Koji Tanabe, Patrick S McGrath, Amber Cramer, Anna Bruckner, Ganna Bilousova, Dennis Roop, Jean Y Tang, Angela Christiano, Lars M Steinmetz, Marius Wernig, Anthony E Oro

We present Dystrophic Epidermolysis Bullosa Cell Therapy (DEBCT), a scalable platform producing autologous organotypic iPS cell-derived induced skin composite (iSC) grafts for definitive treatment. Clinical-grade manufacturing integrates CRISPR-mediated genetic correction with reprogramming into one step, accelerating derivation of COL7A1-edited iPS cells from patients. Differentiation into epidermal, dermal and melanocyte progenitors is followed by CD49f-enrichment, minimizing maturation heterogeneity. Mouse xenografting of iSCs from four patients with different mutations demonstrates disease modifying activity at 1 month. Next-generation sequencing, biodistribution and tumorigenicity assays establish a favorable safety profile at 1-9 months. Single cell transcriptomics reveals that iSCs are composed of the major skin cell lineages and include prominent holoclone stem cell-like signatures of keratinocytes, and the recently described Gibbin-dependent signature of fibroblasts. The latter correlates with enhanced graftability of iSCs. In conclusion, DEBCT overcomes manufacturing and safety roadblocks and establishes a reproducible, safe, and cGMP-compatible therapeutic approach to heal lesions of DEB patients.

Paras S Minhas, Jeffrey R Jones, Amira Latif-Hernandez, Yuki Sugiura, Aarooran S Durairaj, Qian Wang, Siddhita D Mhatre, Takeshi Uenaka, Joshua Crapser, Travis Conley, Hannah Ennerfelt, Yoo Jin Jung, Ling Liu, Praveena Prasad, Brenita C Jenkins, Yeonglong Albert Ay, Matthew Matrongolo, Ryan Goodman, Traci Newmeyer, Kelly Heard, Austin Kang, Edward N Wilson, Tao Yang, Erik M Ullian, Geidy E Serrano, Thomas G Beach, Marius Wernig, Joshua D Rabinowitz, Makoto Suematsu, Frank M Longo, Melanie R McReynolds, Fred H Gage, Katrin I Andreasson

Impaired cerebral glucose metabolism is a pathologic feature of Alzheimer's disease (AD), with recent proteomic studies highlighting disrupted glial metabolism in AD. We report that inhibition of indoleamine-2,3-dioxygenase 1 (IDO1), which metabolizes tryptophan to kynurenine (KYN), rescues hippocampal memory function in mouse preclinical models of AD by restoring astrocyte metabolism. Activation of astrocytic IDO1 by amyloid β and tau oligomers increases KYN and suppresses glycolysis in an aryl hydrocarbon receptor-dependent manner. In amyloid and tau models, IDO1 inhibition improves hippocampal glucose metabolism and rescues hippocampal long-term potentiation in a monocarboxylate transporter-dependent manner. In astrocytic and neuronal cocultures from AD subjects, IDO1 inhibition improved astrocytic production of lactate and uptake by neurons. Thus, IDO1 inhibitors presently developed for cancer might be repurposed for treatment of AD.

Teodorus Theo Susanto, Victoria Hung, Andrew G Levine, Yuxiang Chen, Craig H Kerr, Yongjin Yoo, Juan A Oses-Prieto, Lisa Fromm, Zijian Zhang, Travis C Lantz, Kotaro Fujii, Marius Wernig, Alma L Burlingame, Davide Ruggero, Maria Barna

Ribosomes are emerging as direct regulators of gene expression, with ribosome-associated proteins (RAPs) allowing ribosomes to modulate translation. Nevertheless, a lack of technologies to enrich RAPs across sample types has prevented systematic analysis of RAP identities, dynamics, and functions. We have developed a label-free methodology called RAPIDASH to enrich ribosomes and RAPs from any sample. We applied RAPIDASH to mouse embryonic tissues and identified hundreds of potential RAPs, including Dhx30 and Llph, two forebrain RAPs important for neurodevelopment. We identified a critical role of LLPH in neural development linked to the translation of genes with long coding sequences. In addition, we showed that RAPIDASH can identify ribosome changes in cancer cells. Finally, we characterized ribosome composition remodeling during immune cell activation and observed extensive changes post-stimulation. RAPIDASH has therefore enabled the discovery of RAPs in multiple cell types, tissues, and stimuli and is adaptable to characterize ribosome remodeling in several contexts.

Ching-Chieh Chou, Ryan Vest, Miguel A Prado, Joshua Wilson-Grady, Joao A Paulo, Yohei Shibuya, Patricia Moran-Losada, Ting-Ting Lee, Jian Luo, Steven P Gygi, Jeffery W Kelly, Daniel Finley, Marius Wernig, Tony Wyss-Coray, Judith Frydman

Aging is a prominent risk factor for Alzheimer's disease (AD), but the cellular mechanisms underlying neuronal phenotypes remain elusive. Both accumulation of amyloid plaques and neurofibrillary tangles in the brain1 and age-linked organelle deficits2-7 are proposed as causes of AD phenotypes but the relationship between these events is unclear. Here, we address this question using a transdifferentiated neuron (tNeuron) model directly from human dermal fibroblasts. Patient-derived tNeurons retain aging hallmarks and exhibit AD-linked deficits. Quantitative tNeuron proteomic analyses identify aging and AD-linked deficits in proteostasis and organelle homeostasis, particularly affecting endosome-lysosomal components. The proteostasis and lysosomal homeostasis deficits in aged tNeurons are exacerbated in sporadic and familial AD tNeurons, promoting constitutive lysosomal damage and defects in ESCRT-mediated repair. We find deficits in neuronal lysosomal homeostasis lead to inflammatory cytokine secretion, cell death and spontaneous development of Aß and phospho-Tau deposits. These proteotoxic inclusions co-localize with lysosomes and damage markers and resemble inclusions in brain tissue from AD patients and APP-transgenic mice. Supporting the centrality of lysosomal deficits driving AD phenotypes, lysosome-function enhancing compounds reduce AD-associated cytokine secretion and Aβ deposits. We conclude that proteostasis and organelle deficits are upstream initiating factors leading to neuronal aging and AD phenotypes.

Yukun A Hao, Sungmoo Lee, Richard H Roth, Silvia Natale, Laura Gomez, Jiannis Taxidis, Philipp S O'Neill, Vincent Villette, Jonathan Bradley, Zeguan Wang, Dongyun Jiang, Guofeng Zhang, Mengjun Sheng, Di Lu, Edward Boyden, Igor Delvendahl, Peyman Golshani, Marius Wernig, Daniel E Feldman, Na Ji, Jun Ding, Thomas C Südhof, Thomas R Clandinin, Michael Z Lin

A remaining challenge for genetically encoded voltage indicators (GEVIs) is the reliable detection of excitatory postsynaptic potentials (EPSPs). Here, we developed ASAP5 as a GEVI with enhanced activation kinetics and responsivity near resting membrane potentials for improved detection of both spiking and subthreshold activity. ASAP5 reported action potentials (APs) in vivo with higher signal-to-noise ratios than previous GEVIs and successfully detected graded and subthreshold responses to sensory stimuli in single two-photon trials. In cultured rat or human neurons, somatic ASAP5 reported synaptic events propagating centripetally and could detect ∼1-mV EPSPs. By imaging spontaneous EPSPs throughout dendrites, we found that EPSP amplitudes decay exponentially during propagation and that amplitude at the initiation site generally increases with distance from the soma. These results extend the applications of voltage imaging to the quantal response domain, including in human neurons, opening up the possibility of high-throughput, high-content characterization of neuronal dysfunction in disease.

Marius Marc-Daniel Mader, Alan Napole, Danwei Wu, Micaiah Atkins, Alexa Scavetti, Yohei Shibuya, Aulden Foltz, Oliver Hahn, Yongjin Yoo, Ron Danziger, Christina Tan, Tony Wyss-Coray, Lawrence Steinman, Marius Wernig

Multiple sclerosis (MS) is an autoimmune disease characterized by demyelination of the central nervous system (CNS). Autologous hematopoietic cell transplantation (HCT) shows promising benefits for relapsing-remitting MS in open-label clinical studies, but the cellular mechanisms underlying its therapeutic effects remain unclear. Using single-nucleus RNA sequencing, we identify a reactive myeloid cell state in chronic experimental autoimmune encephalitis (EAE) associated with neuroprotection and immune suppression. HCT in EAE mice results in an increase of the neuroprotective myeloid state, improvement of neurological deficits, reduced number of demyelinated lesions, decreased number of effector T cells and amelioration of reactive astrogliosis. Enhancing myeloid cell incorporation after a modified HCT further improved these neuroprotective effects. These data suggest that myeloid cell manipulation or replacement may be an effective therapeutic strategy for chronic inflammatory conditions of the CNS.

Cheen Euong Ang, Victor Hipolito Olmos, Kayla Vodehnal, Bo Zhou, Qian Yi Lee, Rahul Sinha, Aadit Narayanaswamy, Moritz Mall, Kirill Chesnov, Caia S Dominicus, Thomas Südhof, Marius Wernig

Generation of defined neuronal subtypes from human pluripotent stem cells remains a challenge. The proneural factor NGN2 has been shown to overcome experimental variability observed by morphogen-guided differentiation and directly converts pluripotent stem cells into neurons, but their cellular heterogeneity has not been investigated yet. Here, we found that NGN2 reproducibly produces three different kinds of excitatory neurons characterized by partial coactivation of other neurotransmitter programs. We explored two principle approaches to achieve more precise specification: prepatterning the chromatin landscape that NGN2 is exposed to and combining NGN2 with region-specific transcription factors. Unexpectedly, the chromatin context of regionalized neural progenitors only mildly altered genomic NGN2 binding and its transcriptional response and did not affect neurotransmitter specification. In contrast, coexpression of region-specific homeobox factors such as EMX1 resulted in drastic redistribution of NGN2 including recruitment to homeobox targets and resulted in glutamatergic neurons with silenced nonglutamatergic programs. These results provide the molecular basis for a blueprint for improved strategies for generating a plethora of defined neuronal subpopulations from pluripotent stem cells for therapeutic or disease-modeling purposes.

Yang Song, Jennifer Soto, Sze Yue Wong, Yifan Wu, Tyler Hoffman, Navied Akhtar, Sam Norris, Julia Chu, Hyungju Park, Douglas O Kelkhoff, Cheen Euong Ang, Marius Wernig, Andrea Kasko, Timothy L Downing, Mu-Ming Poo, Song Li

We investigate how matrix stiffness regulates chromatin reorganization and cell reprogramming and find that matrix stiffness acts as a biphasic regulator of epigenetic state and fibroblast-to-neuron conversion efficiency, maximized at an intermediate stiffness of 20 kPa. ATAC sequencing analysis shows the same trend of chromatin accessibility to neuronal genes at these stiffness levels. Concurrently, we observe peak levels of histone acetylation and histone acetyltransferase (HAT) activity in the nucleus on 20 kPa matrices, and inhibiting HAT activity abolishes matrix stiffness effects. G-actin and cofilin, the cotransporters shuttling HAT into the nucleus, rises with decreasing matrix stiffness; however, reduced importin-9 on soft matrices limits nuclear transport. These two factors result in a biphasic regulation of HAT transport into nucleus, which is directly demonstrated on matrices with dynamically tunable stiffness. Our findings unravel a mechanism of the mechano-epigenetic regulation that is valuable for cell engineering in disease modeling and regenerative medicine applications.

Diane L Haakonsen, Michael Heider, Andrew J Ingersoll, Kayla Vodehnal, Samuel R Witus, Takeshi Uenaka, Marius Wernig, Michael Rapé

Stress response pathways detect and alleviate adverse conditions to safeguard cell and tissue homeostasis, yet their prolonged activation induces apoptosis and disrupts organismal health1-3 . How stress responses are turned off at the right time and place remains poorly understood. Here we report a ubiquitin-dependent mechanism that silences the cellular response to mitochondrial protein import stress. Crucial to this process is the silencing factor of the integrated stress response (SIFI), a large E3 ligase complex mutated in ataxia and in early-onset dementia that degrades both unimported mitochondrial precursors and stress response components. By recognizing bifunctional substrate motifs that equally encode protein localization and stability, the SIFI complex turns off a general stress response after a specific stress event has been resolved. Pharmacological stress response silencing sustains cell survival even if stress resolution failed, which underscores the importance of signal termination and provides a roadmap for treating neurodegenerative diseases caused by mitochondrial import defects.

Teodorus Theo Susanto, Victoria Hung, Andrew G Levine, Craig H Kerr, Yongjin Yoo, Yuxiang Chen, Juan A Oses-Prieto, Lisa Fromm, Kotaro Fujii, Marius Wernig, Alma Burlingame, Davide Ruggero, Maria Barna

Ribosomes are emerging as direct regulators of gene expression, with ribosome-associated proteins (RAPs) allowing ribosomes to modulate translational control. However, a lack of technologies to enrich RAPs across many sample types has prevented systematic analysis of RAP number, dynamics, and functions. Here, we have developed a label-free methodology called RAPIDASH to enrich ribosomes and RAPs from any sample. We applied RAPIDASH to mouse embryonic tissues and identified hundreds of potential RAPs, including DHX30 and LLPH, two forebrain RAPs important for neurodevelopment. We identified a critical role of LLPH in neural development that is linked to the translation of genes with long coding sequences. Finally, we characterized ribosome composition remodeling during immune activation and observed extensive changes post-stimulation. RAPIDASH has therefore enabled the discovery of RAPs ranging from those with neuroregulatory functions to those activated by immune stimuli, thereby providing critical insights into how ribosomes are remodeled.

Katie Schaukowitch, Justyna A Janas, Marius Wernig

Direct neuronal reprogramming converts somatic cells of a defined lineage into induced neuronal cells without going through a pluripotent intermediate. This approach not only provides access to the otherwise largely inaccessible cells of the brain for neuronal disease modeling, but also holds great promise for ultimately enabling neuronal cell replacement without the use of transplantation. To improve efficiency and specificity of direct neuronal reprogramming, much of the current efforts aim to understand the mechanisms that safeguard cell identities and how the reprogramming cells overcome the barriers resisting fate changes. Here, we review recent discoveries into the mechanisms by which the donor cell program is silenced, and new cell identities are established. We also discuss advancements that have been made toward fine-tuning the output of these reprogramming systems to generate specific types of neuronal cells. Finally, we highlight the benefit of using direct neuronal reprogramming to study age-related disorders and the potential of in vivo direct reprogramming in regenerative medicine.

Margaret G Guo, David L Reynolds, Cheen E Ang, Yingfei Liu, Yang Zhao, Laura K H Donohue, Zurab Siprashvili, Xue Yang, Yongjin Yoo, Smarajit Mondal, Audrey Hong, Jessica Kain, Lindsey Meservey, Tania Fabo, Ibtihal Elfaki, Laura N Kellman, Nathan S Abell, Yash Pershad, Vafa Bayat, Payam Etminani, Mark Holodniy, Daniel H Geschwind, Stephen B Montgomery, Laramie E Duncan, Alexander E Urban, Russ B Altman, Marius Wernig, Paul A Khavari

Noncoding variants of presumed regulatory function contribute to the heritability of neuropsychiatric disease. A total of 2,221 noncoding variants connected to risk for ten neuropsychiatric disorders, including autism spectrum disorder, attention deficit hyperactivity disorder, bipolar disorder, borderline personality disorder, major depression, generalized anxiety disorder, panic disorder, post-traumatic stress disorder, obsessive-compulsive disorder and schizophrenia, were studied in developing human neural cells. Integrating epigenomic and transcriptomic data with massively parallel reporter assays identified differentially-active single-nucleotide variants (daSNVs) in specific neural cell types. Expression-gene mapping, network analyses and chromatin looping nominated candidate disease-relevant target genes modulated by these daSNVs. Follow-up integration of daSNV gene editing with clinical cohort analyses suggested that magnesium transport dysfunction may increase neuropsychiatric disease risk and indicated that common genetic pathomechanisms may mediate specific symptoms that are shared across multiple neuropsychiatric diseases.

Yongjin Yoo, Gernot Neumayer, Yohei Shibuya, Marius Marc-Daniel Mader, Marius Wernig

Gintautas Vainorius, Maria Novatchkova, Georg Michlits, Juliane Christina Baar, Cecilia Raupach, Joonsun Lee, Ramesh Yelagandula, Marius Wernig, Ulrich Elling

Ascl1 and Ngn2, closely related proneural transcription factors, are able to convert mouse embryonic stem cells into induced neurons. Despite their similarities, these factors elicit only partially overlapping transcriptional programs, and it remains unknown whether cells are converted via distinct mechanisms. Here we show that Ascl1 and Ngn2 induce mutually exclusive side populations by binding and activating distinct lineage drivers. Furthermore, Ascl1 rapidly dismantles the pluripotency network and installs neuronal and trophoblast cell fates, while Ngn2 generates a neural stem cell-like intermediate supported by incomplete shutdown of the pluripotency network. Using CRISPR-Cas9 knockout screening, we find that Ascl1 relies more on factors regulating pluripotency and the cell cycle, such as Tcf7l1. In the absence of Tcf7l1, Ascl1 still represses core pluripotency genes but fails to exit the cell cycle. However, overexpression of Cdkn1c induces cell cycle exit and restores the generation of neurons. These findings highlight that cell type conversion can occur through two distinct mechanistic paths, even when induced by closely related transcription factors.

Yingfei Liu, Jinzhao Wang, Thomas C Südhof, Marius Wernig

The production of induced neuronal (iN) cells from human embryonic stem cells (ESCs) and induced pluripotent stem cells by the forced expression of proneural transcription factors is rapid, efficient and reproducible. The ability to generate large numbers of human neurons in such a robust manner enables large-scale studies of human neural differentiation and neuropsychiatric diseases. Surprisingly, similar transcription factor-based approaches for converting mouse ESCs into iN cells have been challenging, primarily because of low cell survival. Here, we provide a detailed approach for the efficient and reproducible generation of functional iN cells from mouse ESC cultures by the genetically induced expression of neurogenin-2. The resulting iN cells display mature pre- and postsynaptic specializations and form synaptic networks. Our method provides the basis for studying neuronal development and enables the direct comparison of cellular phenotypes in mouse and human neurons generated in an equivalent way. The procedure requires 14 d and can be carried out by users with expertise in stem cell culture.

Yongjin Yoo, Gernot Neumayer, Yohei Shibuya, Marius Marc-Daniel Mader, Marius Wernig

Alzheimer's disease (AD) remains one of the grand challenges facing human society. Much controversy exists around the complex and multifaceted pathogenesis of this prevalent disease. Given strong human genetic evidence, there is little doubt, however, that microglia play an important role in preventing degeneration of neurons. For example, loss of function of the microglial gene Trem2 renders microglia dysfunctional and causes an early-onset neurodegenerative syndrome, and Trem2 variants are among the strongest genetic risk factors for AD. Thus, restoring microglial function represents a rational therapeutic approach. Here, we show that systemic hematopoietic cell transplantation followed by enhancement of microglia replacement restores microglial function in a Trem2 mutant mouse model of AD.

Ching-Chieh Chou, Ryan Vest, Miguel A Prado, Joshua Wilson-Grady, Joao A Paulo, Yohei Shibuya, Patricia Moran-Losada, Ting-Ting Lee, Jian Luo, Steven P Gygi, Jeffery W Kelly, Daniel Finley, Marius Wernig, Tony Wyss-Coray, Judith Frydman

The role of proteostasis and organelle homeostasis dysfunction in human aging and Alzheimer's disease (AD) remains unclear. Analyzing proteome-wide changes in human donor fibroblasts and their corresponding transdifferentiated neurons (tNeurons), we find aging and AD synergistically impair multiple proteostasis pathways, most notably lysosomal quality control (LQC). In particular, we show that ESCRT-mediated lysosomal repair defects are associated with both sporadic and PSEN1 familial AD. Aging- and AD-linked defects are detected in fibroblasts but highly exacerbated in tNeurons, leading to enhanced neuronal vulnerability, unrepaired lysosomal damage, inflammatory factor secretion and cytotoxicity. Surprisingly, tNeurons from aged and AD donors spontaneously develop amyloid-β inclusions co-localizing with LQC markers, LAMP1/2-positive lysosomes and proteostasis factors; we observe similar inclusions in brain tissue from AD patients and APP-transgenic mice. Importantly, compounds enhancing lysosomal function broadly ameliorate these AD-associated pathologies. Our findings establish cell-autonomous LQC dysfunction in neurons as a central vulnerability in aging and AD pathogenesis.