Project description:The loss of Tmem106b results in an age-dependent loss of cerebellar Purkinje cells accompanied with motor function deficits. Tmem106b deficiency also results in lysosomal enlargement in both Purkinje cells and microglia, and increased neuroinflammation including complement system activation. These data suggest that, in addition to myelination, Tmem106b also plays important role in maintaining the health and survival of cerebellar Purkinje cells during aging.
Project description:TMEM106B has been recently implicated in multiple neurodegenerative diseases. Here, Rademakers et al. report a late-onset cerebellar Purkinje cell loss and progressive decline in motor function and gait deficits in a conventional Tmem106b-/- mouse model. By using high-power microscopy and bulk RNA sequencing, the authors further identify lysosomal and immune dysfunction as potential underlying mechanisms of the Purkinje cell loss.
Project description:Contactin-associated protein-like 2 (Caspr2) is a neurexin-like protein that has been associated with numerous neurological conditions. However, the mechanisms underlying Caspr2 function in the central nervous system remain incompletely understood. Here, we report on a functional role for Caspr2 in the developing cerebellum. Loss of Caspr2 impairs Purkinje cell dendritic development, alters cell signaling and results in motor coordination deficits. Caspr2 is highly enriched at synaptic specializations in the cerebellum. Using a proteomic approach, we identify type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) as a specific synaptic interaction partner of the Caspr2 extracellular domain (ECD) in the molecular layer (ML) of the developing cerebellum. The interaction of Caspr2 ECD with IP3R1 inhibits IP3R1-mediated changes in cellular morphology. Together, our work defines a mechanism by which Caspr2 controls the development and function of the cerebellum, and advances our understanding of how Caspr2 dysfunction might lead to specific brain disorders.
Project description:Genetic variants that define two distinct haplotypes at the TMEM106B locus have been implicated in multiple neurodegenerative diseases and in healthy brain aging. In frontotemporal dementia (FTD), the high expressing TMEM106B risk haplotype was shown to increase susceptibility for FTD with TDP-43 inclusions (FTD-TDP) and to modify disease penetrance in progranulin mutation carriers (FTD-GRN). To further elucidate the biological function of TMEM106B and determine whether lowering TMEM106B may be a viable therapeutic strategy, we performed brain transcriptomic analyses in 8-month-old animals from our recently developed Tmem106b-/- mouse model. We included 10 Tmem106b+/+ (WT), 10 Tmem106b+/- and 10 Tmem106-/- mice. The most differentially expressed genes (153 down-regulated and 60 upregulated) were identified between Tmem106b-/- and WT animals, with an enrichment for genes implicated in myelination-related cellular processes including axon ensheathment and oligodendrocyte differentiation. Co-expression analysis also revealed that the most downregulated group of correlated genes was enriched for myelination-related processes. We further detected a significant loss of Olig2-positive cells in the corpus callosum of Tmem106b-/- mice, which was present already in young animals (21 days) and persisted until old age (23 months), without worsening. qPCR revealed a reduction of differentiated but not undifferentiated oligodendrocytes cellular markers. While no obvious changes in myelin were observed at the ultrastructure levels in unchallenged animals, treatment with cuprizone revealed that Tmem106b-/- mice are more susceptible to cuprizone-induced de-myelination and have a reduced capacity to re-myelinate, a finding which we were able to replicate in a newly generated Tmem106b CRISPR/cas9 knock-out mouse model. Finally, using a TMEM106B HeLa knock-out cell line, we determined that loss of TMEM106B leads to abnormalities in the distribution of lysosomes and PLP1 trafficking but not to differences in MOG trafficking which is lysosome-independent. Together these findings reveal an important function for TMEM106B in myelination with possible consequences for therapeutic strategies aimed at lowering TMEM106B levels.
Project description:RNA-seq evaluation of enriched Purkinje cells from the post-mortem human cerebellum. Purkinje cells were removed via laser capture microdissection and pooled for RNA-extraction and sequencing. 24 ET patients and 16 controls healthy age matched were compared.
Project description:Specific medications to combat cerebellar ataxias, a group of debilitating movement disorders characterized by difficulty with walking, balance and coordination. Notably, cerebellar microglial activation appears to be a common feature in different types of ataxic patients and rodent models. However, the causal link between the activation of microglia in the cerebellum and ataxias remains inconclusive. In the present study, using a classic mouse model of cerebellar ataxia induced by 3-acetylpyridine (3-AP), we find a early-onset and long-lasting microglial activation accompanied by neuronal loss and dysfunction in the cerebellum. Transcriptome and behavior analyses indicate that microglial depletion in 3-AP ataxic mice decreases neuroinflammatory response in the cerebellum and rescues the ataxic motor symptoms including motor incoordination, gait abnormality, and locomotor dysfunction. Moreover, specific chemogenetic activation of cerebellar microglia in the vermis by M3D(Gq), a designer receptor exclusively activated by designer drugs (DREADDs), directly induces an expression of pro-inflammatory cytokines and aggravates ataxic motor deficits of 3-AP mice. On the contrary, inhibition of cerebellar microglial activation by M4D(Gi) or minocycline reduces the production of pro-inflammatory cytokines including TNF-α and alleviates motor deficits. Furthermore, blockage of TNF-α signaling attenuates the microglial-triggered hyperactivity of Purkinje cells (PCs). These results suggest that cerebellar microglial activation aggravates neuroinflammatory response, and subsequently induces dysfunction of PCs, which in turn triggers ataxic motor deficits. Our findings thus reveal a causal relationship between pro-inflammatory activation of cerebellar microglia and the ataxic motor symptoms, which may offer novel evidence for therapeutic intervention for cerebellar ataxias by targeting microglia and microglia-derived inflammatory mediators.
Project description:Thiele2013 - Cerebellum Purkinje cells
The model of cerebellum Purkinje cells metabolism is derived from the community-driven global reconstruction of human metabolism (version 2.02, MODEL1109130000
).
This model is described in the article:
A community-driven global reconstruction of human metabolism.
Thiele I, et al
.
Nature Biotechnology
Abstract:
Multiple models of human metabolism have been reconstructed, but each represents only a subset of our knowledge. Here we describe Recon 2, a community-driven,
consensus 'metabolic reconstruction', which is the most comprehensive representation of human metabolism that is applicable to computational modeling. Compared
with its predecessors, the reconstruction has improved topological and functional features, including ~2x more reactions and ~1.7x more unique metabolites. Using
Recon 2 we predicted changes in metabolite biomarkers for 49 inborn errors of metabolism with 77% accuracy when compared to experimental data. Mapping metabolomic
data and drug information onto Recon 2 demonstrates its potential for integrating and analyzing diverse data types. Using protein expression data, we automatically
generated a compendium of 65 cell type-specific models, providing a basis for manual curation or investigation of cell-specific metabolic properties. Recon 2 will
facilitate many future biomedical studies and is freely available at http://humanmetabolism.org/.
This model is hosted on BioModels Database
and identified by: MODEL1310110050
.
To cite BioModels Database, please use: BioModels Database: An enhanced,
curated and annotated resource for published quantitative kinetic models
.
To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer
to CC0 Public Domain Dedication
for more information.
Project description:We performed gene-expression analysis of mouse Purkinje cells as a model M-bM-^@M-^\single-type neuronM-bM-^@M-^]. DNA microarray analysis detected at least 7,055 genes in Purkinje cells, most of which are classified into functional molecule categories. Our comparative analysis between Purkinje cells and the granule cell layer showed that the characteristic expression pattern in Purkinje cells was particularly represented by M-bM-^@M-^\the neural communication systemM-bM-^@M-^] components. Pukinje cells and granule cell layer of the mouse cerebellum were collected by laser microdissection for RNA extraction and hybridization on Affymetrix microarrays.
Project description:Polygenic risk factors influence onset and progression of neurodegenerative diseases, but are difficult to be functionally explored in isolation. Single nucleotide polymorphisms (SNPs) in TMEM106B increase the risk for frontotemporal lobar degeneration (FTLD) of GRN mutation carriers. Currently, it is not clear if progranulin (PGRN) and TMEM106B are synergistically linked and if a gain or a loss-of-function of TMEM106B is responsible for the increased disease risk of patients with PGRN haploinsufficiency. We therefore compared behavioral abnormalities, gene expression patterns, lysosomal activity and TDP-43 pathology in single and double knockout animals. Grn–/–/Tmem106b–/– mice showed a strongly reduced life span and massive motor deficits. Gene expression analysis revealed an upregulation of molecular signatures characteristic for disease associated microglia and autophagy. Dysregulation of maturation of lysosomal proteins as well as a pronounced accumulation of ubiquitinated proteins and wide spread p62 deposition suggest that proteostasis is impaired. Moreover, while single Grn–/– knockouts only occasionally showed TDP-43 pathology, the double knockout mice exhibit robust deposition of phosphorylated TDP-43. Thus, a loss-of-function of TMEM106B may enhance the risk for GRN-associated FTD by reduced protein turnover in the lysosomal/autophagic system.