Ernest Arenas Lab

Arenas E

Ásgrímsdóttir ES, and Arenas E

Bryois, J et al.

Toledo EM et al.

Liver X receptors (LXRs) and their ligands are potent regulators of midbrain dopaminergic (mDA) neurogenesis and differentiation. However, the molecular mechanisms by which LXRs control these functions remain to be elucidated. Here, we perform a combined transcriptome and chromatin immunoprecipitation sequencing (ChIP-seq) analysis of midbrain cells after LXR activation, followed by bioinformatic analysis to elucidate the transcriptional networks controlling mDA neurogenesis. Our results identify the basic helix-loop-helix transcription factor sterol regulatory element binding protein 1 (SREBP1) as part of a cluster of proneural transcription factors in radial glia and as a regulator of transcription factors controlling mDA neurogenesis, such as Foxa2. Moreover, loss- and gain-of-function experiments in vitro and in vivo demonstrate that Srebf1 is both required and sufficient for mDA neurogenesis. Our data, thus, identify Srebf1 as a central player in mDA neurogenesis.

Summary of the project: By mapping the dopaminergic cells, which are attacked and lost in the brain of patient with Parkinson's disease, at a molecular level using single-cell RNA sequencing, amongst other tools, our research group hopes to have sufficient information to create new ones, either by using stem cells that are then transplanted into the patient, or by reprogramming existing brain cells in vivo. The project can lead to more exact methods involving designing the right cell types for therapeutic intervention from the start.

More information

KI press release

The Arenas lab is looking for Postdoctoral researchers in the following areas:

Summary of the project: Neurodegenerative diseases and brain injuries affect large patient groups and carry large unmet clinical needs. NSC-Reconstruct will respond to these needs by developing innovative therapies based on cell replacement, cell reprogramming and circuit reconstruction that have the potential to transform how we treat a wide range of neurological diseases and disorders. In this area of clinical science European research has generated groundbreaking knowledge that has resulted in a pioneering human embryonic stem cell-derived product that is now entering clinical trials for Parkinson’s Disease (PD). In NSC-Reconstruct we will move beyond the replacement of a single neuronal type towards future cell therapies with enhanced authenticity, functions and compositions. NSC-Reconstruct will address PD as an example of disorder for which single neuron replacement has been developed. Our focus in PD will be on incorporating improved cell types and on local network reconstruction. We will also work on repairing long distance networks such as those affected in Huntington’s disease and finally in restoring the complex networks and projections of the cerebral cortex to achieve effective repair in conditions known to affect this structure, such as trauma or stroke.

More information: Horizon 2020

KI press release

Ahmed M et al.

Kaiser K et al.

WNTs are lipid-modified proteins that control multiple functions in development and disease via short- and long-range signaling. However, it is unclear how these hydrophobic molecules spread over long distances in the mammalian brain. Here we show that WNT5A is produced by the choroid plexus (ChP) of the developing hindbrain, but not the telencephalon, in both mouse and human. Since the ChP produces and secretes the cerebrospinal fluid (CSF), we examine the presence of WNT5A in the CSF and find that it is associated with lipoprotein particles rather than exosomes. Moreover, since the CSF flows along the apical surface of hindbrain progenitors not expressing Wnt5a, we examined whether deletion of Wnt5a in the ChP controls their function and find that cerebellar morphogenesis is impaired. Our study thus identifies the CSF as a route and lipoprotein particles as a vehicle for long-range transport of biologically active WNT in the central nervous system.

Short description about the project: Parkinson’s disease is a very common neurodegenerative disorder. However, current therapies neither cure, nor slow down disease. Clinical trials have shown that it is possible to transplant and replace brain cells lost by the disease with cells from a fetus – but this approach poses several technical and ethical challenges. Ernest Arenas and his colleagues aim to identify the combination of genes controlling development of dopamine-producing neurons in the substantia nigra (SN), the cell type mainly affected by Parkinson’s disease. For this purpose they will use new methodologies such as single-cell RNA-sequencing and CRISPR/cas9 genome editing. They will apply the new knowledge to develop two methods to genetically control the formation of SN neurons.

More information: Knut and Alice Wallenberg Foundation

KI press release

Rebellato P, Kaczynska D et al.

Theofilopoulos S et al.

The liver X receptors Lxrα/NR1H3 and Lxrβ/NR1H2 are ligand-dependent nuclear receptors critical for midbrain dopaminergic (mDA) neuron development. We previously found that 24(S),25-epoxycholesterol (24,25-EC), the most potent and abundant Lxr ligand in the developing mouse midbrain, promotes mDA neurogenesis in vitro. In this study, we demonstrate that 24,25-EC promotes mDA neurogenesis in an Lxr-dependent manner, in the developing mouse midbrain in vivo and also prevents toxicity induced by the Lxr inhibitor geranylgeranyl pyrophosphate. Furthermore, using MS we show that overexpression of human cholesterol 24S-hydroxylase (CYP46A1) increases the levels of both 24(S)-hydroxycholesterol (24-HC) and 24,25-EC in the developing midbrain, resulting in a specific increase in mDA neurogenesis in vitro and in vivo, but has no effect on occulomotor or red nucleus neurogenesis. 24-HC, unlike 24,25-EC, did not affect in vitro neurogenesis, indicating that the neurogenic effect of 24,25-EC on mDA neurons is specific. Combined, our results indicate that increased levels of 24,25-EC in vivo, by intracerebroventricular delivery in wild-type mice or by overexpression of its biosynthetic enzyme CYP46A1, specifically promote mDA neurogenesis. We propose that increasing the levels of 24,25-EC in vivo may be a useful strategy to combat the loss of mDA neurons in Parkinson’s disease.

The group of Ernest Arenas has been awarded a grant from CZI to systematically analyze and provide an unbiased understanding of the cell types and molecular mechanisms involved in Parkinson's disease. The project will be performed in collaboration with Per Svenningsson (KI), Sten Linnarsson (KI), and Mats Nilsson (SU).

More information: CZI Neurodegeneration Challenge Network

SciLife Lab press release

Griffiths WJ et al.

Tanaka N, Katayama S, Reddy A et al.

Gyllborg D et al.

The development of midbrain dopaminergic (mDA) neurons is controlled by multiple morphogens and transcription factors. However, little is known about the role of extracellular matrix proteins in this process. Here we examined the function of roof plate-specific spondins (RSPO1-4) and the floor plate-specific, spondin 1 (SPON1). Only RSPO2 and SPON1 were expressed at high levels during mDA neurogenesis, and the receptor LGR5 was expressed by midbrain floor plate progenitors. Surprisingly, RSPO2, but not SPON1, specifically promoted the differentiation of mDA neuroblasts into mDA neurons in mouse primary cultures and embryonic stem cells (ESCs). In addition, RSPO2 was found to promote not only mDA differentiation, but also mDA neurogenesis in human ESCs. Our results thus uncover an unexpected function of the matricellular protein RSPO2 and suggest an application to improve mDA neurogenesis and differentiation in human stem cell preparations destined to cell replacement therapy or drug discovery for Parkinson disease.

Zeisel A et al.

Mousebrain.org, wiki page for visualization of data

Okawa S & Saltó C et al.

Yang S et al.

Zeb2 is a homeodomain transcription factor that plays pleiotropic functions during embryogenesis, but its role for midbrain dopaminergic (mDA) neuron development is unknown. Here we report that Zeb2 is highly expressed in progenitor cells in the ventricular zone of the midbrain floor plate and downregulated in postmitotic neuroblasts. Functional experiments show that Zeb2 expression in the embryonic ventral midbrain is dynamically regulated by a negative feedback loop that involves miR-200c. We also find that Zeb2 overexpression reduces the levels of CXCR4, NR4A2, and PITX3 in the developing ventral midbrain in vivo, resulting in migration and mDA differentiation defects. This phenotype was recapitulated by miR-200c knockdown, suggesting that the Zeb2-miR-200c loop prevents the premature differentiation of mDA progenitors into postmitotic cells and their migration. Together, our study establishes Zeb2 and miR-200c as critical regulators that maintain the balance between mDA progenitor proliferation and neurogenesis.

MolNeuro moving in at #Biomedicum! @slinnarsson @mandy_meijer @dgyllborg @LarsBorm @GioeleLaManno @dvd_bruggen @UlrikaKatarina @HjerlingLeffler @D_eck_ard https://t.co/CsHoVCZDw2 pic.twitter.com/ZAeqpmqgV3

— GonçaloCasteloBranco (@GoCasteloBranco) April 25, 2018

Zeisel A et al.

Mousebrain.org, wiki page for visualization of data

A postdoctoral fellow position is available in our lab. The position is in Computational Biology of Single Cell and CRISPR Genomics in Dopamine Neurons.

More information and announcement of position.

Apply here!

Karolinska Institutet is building an ultramodern, purpose-built facility for experimental medical research, Biomedicum. The new laboratory gives Karolinska Institutet more research space and new opportunities to make more effective use of shared infrastructure.

The department of MBB will be relocated to Biomedicum in April 2018.

More information: Biomedicum - Laboratory of the future

Zhang D, et al.

Parkinson’s disease (PD) is a neurodegenerative disorder marked by progressive loss of dopaminergic neurons and motor control. Various factors promote or inhibit neuronal survival. Zhang et al. found that a prosurvival signal was mediated by the transcription cofactor YAP. YAP was activated in midbrain dopaminergic neurons in culture and in mice through an interaction between an integrin and the extracellular matrix protein laminin-511. YAP then transcriptionally activated dopaminergic neuron differentiation factors and a microRNA that decreased the synthesis of the apoptotic protein PTEN. The findings uncover a new role for YAP in neurons and a pathway that might be explored for the purpose of promoting dopaminergic neuron survival in PD patients.

Salašová A, et al.

Autosomal-dominant mutations in the Park8 gene encoding Leucine-rich repeat kinase 2 (LRRK2) have been identified to cause up to 40% of the genetic forms of Parkinson’s disease. However, the function and molecular pathways regulated by LRRK2 are largely unknown. It has been shown that LRRK2 serves as a scaffold during activation of WNT/β-catenin signaling via its interaction with the β-catenin destruction complex, DVL1-3 and LRP6. In this study, we examine whether LRRK2 also interacts with signaling components of the WNT/Planar Cell Polarity (WNT/PCP) pathway, which controls the maturation of substantia nigra dopaminergic neurons, the main cell type lost in Parkinson’s disease patients.

Strakova K et al.

Toledo EM, et al.

Midbrain dopaminergic (mDA) neurons degenerate in Parkinson's disease and are one of the main targets for cell replacement therapies. However, a comprehensive view of the signals and cell types contributing to mDA neurogenesis is not yet available. By analyzing the transcriptome of the mouse ventral midbrain at a tissue and single-cell level during mDA neurogenesis we found that three recently identified radial glia types 1-3 (Rgl1-3) contribute to different key aspects of mDA neurogenesis. While Rgl3 expressed most extracellular matrix components and multiple ligands for various pathways controlling mDA neuron development, such as Wnt and Shh, Rgl1-2 expressed most receptors. Moreover, we found that specific transcription factor networks explain the transcriptome and suggest a function for each individual radial glia. A network controlling neurogenesis was found in Rgl1, progenitor maintenance in Rgl2 and the secretion of factors forming the mDA niche by Rgl3. Our results thus uncover a broad repertoire of developmental signals expressed by each midbrain cell type during mDA neurogenesis. Cells identified for their emerging importance are Rgl3, a niche cell type, and Rgl1, a neurogenic progenitor that expresses ARNTL, a transcription factor that we find is required for mDA neurogenesis.

Toledo EM, Gyllborg D, and Arenas E

Dunnett SB and Rosser AE

Hörtenhuber M. et al.

Kaucka M. et al.

Rivetti di Val Cervo P, et al.

Cell replacement therapies for neurodegenerative disease have focused on transplantation of the cell types affected by the pathological process. Here we describe an alternative strategy for Parkinson's disease in which dopamine neurons are generated by direct conversion of astrocytes. Using three transcription factors, NEUROD1, ASCL1 and LMX1A, and the microRNA miR218, collectively designated NeAL218, we reprogram human astrocytes in vitro, and mouse astrocytes in vivo, into induced dopamine neurons (iDANs). Reprogramming efficiency in vitro is improved by small molecules that promote chromatin remodeling and activate the TGFβ, Shh and Wnt signaling pathways. The reprogramming efficiency of human astrocytes reaches up to 16%, resulting in iDANs with appropriate midbrain markers and excitability. In a mouse model of Parkinson's disease, NeAL218 alone reprograms adult striatal astrocytes into iDANs that are excitable and correct some aspects of motor behavior in vivo, including gait impairments. With further optimization, this approach may enable clinical therapies for Parkinson's disease by delivery of genes rather than cells.

News article at Karolinska Institutet

Press article in TheScientist

Press article in Scientific American

La Manno G, Gyllborg D, et al.

Understanding human embryonic ventral midbrain is of major interest for Parkinson’s disease. However, the cell types, their gene expression dynamics, and their relationship to commonly used rodent models remain to be defined. We performed single-cell RNA sequencing to examine ventral midbrain development in human and mouse. We found 25 molecularly defined human cell types, including five subtypes of radial glia-like cells and four progenitors. In the mouse, two mature fetal dopaminergic neuron subtypes diversified into five adult classes during postnatal development. Cell types and gene expression were generally conserved across species, but with clear differences in cell proliferation, developmental timing, and dopaminergic neuron development. Additionally, we developed a method to quantitatively assess the fidelity of dopaminergic neurons derived from human pluripotent stem cells, at a single-cell level. Thus, our study provides insight into the molecular programs controlling human midbrain development and provides a foundation for the development of cell replacement therapies.

News article at Karolinska Institutet

Supporing Information and Visualization

Villaescusa JC, et al.

Pre‐B‐cell leukemia homeobox (PBX) transcription factors are known to regulate organogenesis, but their molecular targets and function in midbrain dopaminergic neurons (mDAn) as well as their role in neurodegenerative diseases are unknown. Here, we show that PBX1 controls a novel transcriptional network required for mDAn specification and survival, which is sufficient to generate mDAn from human stem cells. Mechanistically, PBX1 plays a dual role in transcription by directly repressing or activating genes, such as Onecut2 to inhibit lateral fates during embryogenesis, Pitx3 to promote mDAn development, and Nfe2l1 to protect from oxidative stress. Notably, PBX1 and NFE2L1 levels are severely reduced in dopaminergic neurons of the substantia nigra of Parkinson's disease (PD) patients and decreased NFE2L1 levels increases damage by oxidative stress in human midbrain cells. Thus, our results reveal novel roles for PBX1 and its transcriptional network in mDAn development and PD, opening the door for new therapeutic interventions.