The cerebral angiome: High resolution MicroCT imaging of the whole brain cerebrovasculature in female and male mice.

The cerebrovascular system provides crucial functions that maintain metabolic and homeostatic states of the brain. Despite its integral role of supporting cerebral viability, the topological organization of these networks remains largely uncharacterized. This void in our knowledge surmises entirely from current technological limitations that prevent the capturing of data through the entire depth of the brain. We report high-resolution reconstruction and analysis of the complete vascular network of the entire brain at the capillary level in adult female and male mice using a vascular corrosion cast procedure. Vascular network analysis of the whole brain revealed sex-related differences of vessel hierarchy. In addition, region-specific network analysis demonstrated different patterns of angioarchitecture between brain subregions and sex. Furthermore, our group is the first to provide a three-dimensional analysis of the angioarchitecture and network organization in a single reconstructed tomographic data set that encompasses all hierarchy of vessels in the brain of the adult mouse.

Over-expression of miR-34a induces rapid cognitive impairment and Alzheimer's disease-like pathology.

Autosomal dominant Alzheimer disease (AD) is caused by rare mutations in one of three specific genes. This is in contrast to idiopathic, late-onset AD (LOAD), which has a more polygenetic risk profile and represents more than 95% of cases. Previously, we have demonstrated that increased expression of microRNA (miRNA)-34a (miR-34a) in AD brain targets genes linked to synaptic plasticity, energy metabolism, and resting state network activity. Here we report the generation of a heterozygous, conditional miR-34a overexpression mouse (miR-34a+/-(TetR-TetO-miR-34a) Transgenic Mice). Doxycycline-treated mice of either sex exhibited profound behavioral impairment compared to untreated groups with only 1-2 months of over-expression of miR-34a. Cognitive impairment of individual mice in T- and Y-maze tasks correlated with elevated miR-34a expression in many parts of the brain including the hippocampus and prefrontal cortex, regions which are known to be involved in this task and implicated in LOAD dysfunction. Immunocytochemistry of brain sections from mice show high amyloid ß and phosphorylated tau-specific staining in the hippocampus and cortex. Analysis of protein samples from these mice revealed that miR-34a targets specific genes involved in memory formation, amyloid precursor protein (APP) metabolism and phosphorylation-dephosphorylation of tau. Thus, our results suggest that the polygenetic dysfunction caused by miR-34a may occur in LOAD and disclose miR-34a as a potential therapeutic target. SIGNIFICANCE STATEMENT: Late-onset Alzheimer disease (LOAD) is associated with multiple gene alleles, a polygenetic profile of risk factors that is difficult to model in animals. Our approach to modeling LOAD was to produce a conditional over-expressing, miR-34a mouse using doxycycline-induction to activate expression. We observed that miR-34a over-expression results in a rapid cognitive impairment, associated with accumulation of intracellular Aß and tau hyperphosphorylation in multiple brain regions. Targets for miR-34a, including ADAM10, NMDAR 2B, and SIRT1 RNAs, were profoundly reduced by miR-34a over-expression. Collectively, these results indicate that a rapid, profound cognitive decline and Alzheimer's disease neuropathology can be induced with miR-34a over-expression, suggesting that this animal model may represent a polygenetic risk factor model for LOAD.

Expression of microRNA-34a in Alzheimer's disease brain targets genes linked to synaptic plasticity, energy metabolism, and resting state network activity.

Polygenetic risk factors and reduced expression of many genes in late-onset Alzheimer's disease (AD) impedes identification of a target(s) for disease-modifying therapies. We identified a single microRNA, miR-34a that is over expressed in specific brain regions of AD patients as well as in the 3xTg-AD mouse model. Specifically, increased miR-34a expression in the temporal cortex region compared to age matched healthy control correlates with severity of AD pathology. miR-34a over expression in patient's tissue and forced expression in primary neuronal culture correlates with concurrent repression of its target genes involved in synaptic plasticity, oxidative phosphorylation and glycolysis. The repression of oxidative phosphorylation and glycolysis related proteins correlates with reduced ATP production and glycolytic capacity, respectively. We also found that miR-34a overexpressed neurons secrete miR-34a containing exosomes that are taken up by neighboring neurons. Furthermore, miR-34a targets dozens of genes whose expressions are known to be correlated with synchronous activity in resting state functional networks. Our analysis of human genomic sequences from the tentative promoter of miR-34a gene shows the presence of NFκB, STAT1, c-Fos, CREB and p53 response elements. Together, our results raise the possibilities that pathophysiology-induced activation of specific transcription factor may lead to increased expression of miR-34a gene and miR-34a mediated concurrent repression of its target genes in neural networks may result in dysfunction of synaptic plasticity, energy metabolism, and resting state network activity. Thus, our results provide insights into polygenetic AD mechanisms and disclose miR-34a as a potential therapeutic target for AD.