Micro-CT imaging reveals<i> Mekk3 </i>heterozygosity prevents cerebral cavernous malformations in <i>Ccm2</i>-deficient mice

Mutations in CCM1 (aka KRIT1), CCM2, or CCM3 (aka PDCD10) gene cause cerebral cavernous malformation in humans. Mouse models of CCM disease have been established by deleting Ccm genes in postnatal animals. These mouse models provide invaluable tools to investigate molecular mechanism and therapeutic approaches for CCM disease. However, the full value of these animal models is limited by the lack of an accurate and quantitative method to assess lesion burden and progression. In the present study we have established a refined and detailed contrast enhanced X-ray micro-CT method to measure CCM lesion burden in mouse brains. As this study utilized a voxel dimension of 9.5μm (leading to a minimum feature size of approximately 25μm), it is therefore sufficient to measure CCM lesion volume and number globally and accurately, and provide high-resolution 3-D mapping of CCM lesions in mouse brains. Using this method, we found loss of Ccm1 or Ccm2 in neonatal endothelium confers CCM lesions in the mouse hindbrain with similar total volume and number. This quantitative approach also demonstrated a rescue of CCM lesions with simultaneous deletion of one allele of Mekk3. This method would enhance the value of the established mouse models to study the molecular basis and potential therapies for CCM and other cerebrovascular diseases

Transcriptome of iPSC-derived neuronal cells reveals a module of co-expressed genes consistently associated with autism spectrum disorder

Evaluation of expression profile in autism spectrum disorder (ASD) patients is an important approach to understand possible similar functional consequences that may underlie disease pathophysiology regardless of its genetic heterogeneity. Induced pluripotent stem cell (iPSC)-derived neuronal models have been useful to explore this question, but larger cohorts and different ASD endophenotypes still need to be investigated. Moreover, whether changes seen in this in vitro model reflect previous findings in ASD postmortem brains and how consistent they are across the studies remain underexplored questions. We examined the transcriptome of iPSC-derived neuronal cells from a normocephalic ASD cohort composed mostly of high-functioning individuals and from non-ASD individuals. ASD patients presented expression dysregulation of a module of co-expressed genes involved in protein synthesis in neuronal progenitor cells (NPC), and a module of genes related to synapse/neurotransmission and a module related to translation in neurons. Proteomic analysis in NPC revealed potential molecular links between the modules dysregulated in NPC and in neurons. Remarkably, the comparison of our results to a series of transcriptome studies revealed that the module related to synapse has been consistently found as upregulated in iPSC-derived neurons-which has an expression profile more closely related to fetal brain-while downregulated in postmortem brain tissue, indicating a reliable association of this network to the disease and suggesting that its dysregulation might occur in different directions across development in ASD individuals. Therefore, the expression pattern of this network might be used as biomarker for ASD and should be experimentally explored as a therapeutic target

Topoisomerase I inhibition leads to length-dependent gene expression changes in human primary astrocytes

Topoisomerase I is required for the proper expression of long genes (> 100 kb) in mouse and human cortical neurons, including many candidate genes for autism spectrum disorder (ASD) [1]. Given the important role of astrocytes in brain development [2], we investigated whether long genes, including autism susceptibility genes, also require topoisomerase I expression in human primary astrocytes. We carried genome-wide expression profiling of cultured human primary astrocytes following treatment with the topoisomerase I inhibitor Topotecan, using Illumina microarrays. We identified several thousands of differentially expressed genes and confirmed that topoisomerase I inhibition affects gene expression in human primary astrocytes in a length-dependent manner. We also identified over 20 ASD-associated genes that show topoisomerase-dependent gene expression in human primary astrocytes but have not been previously reported as topoisomerase-I-dependent in neurons. The microarray data have been deposited in NCBI GEO (https://www.ncbi.nlm.nih.gov/geo/) under accession number GSE90052

Transcriptional response to mitochondrial protease IMMP2L knockdown in human primary astrocytes

IMMP2L encodes the inner membrane peptidase subunit 2, a mitochondrial protease involved in cleaving the space-sorting signals of mitochondrial membrane proteins. IMMP2L has been implicated in Tourette syndrome, but how its dysfunction contributes to the neurodevelopmental phenotype remains unclear. Here we show that IMMP2L transcription requires Topoisomerase I in human primary astrocytes, and characterize the downstream effects of IMMP2L knockdown on gene expression. We demonstrate that IMMP2L knockdown leads to dysregulation of genes involved in central nervous system development. We also find that the transcriptional response to IMMP2L knockdown partially overlaps the one induced by mitochondrial complex III inhibition. Overall, these data bring further insight into the molecular consequences of IMMP2L dysfunction in the brain