Blood transcriptomic biomarker as a surrogate of ischemic brain gene expression.

OBJECTIVES: Blood biomarkers for cerebral tissue ischemia are lacking. The goal was to identify a blood transcriptomic signature jointly identified in the ischemic brain. METHODS: A nonhuman primate model with middle cerebral artery (MCA) territory infarction was used to study gene expression by microarray during acute ischemic cerebral stroke in the brain and the blood. Brain samples were collected in the infarcted and contralateral non-infarcted cortex as well as blood samples before and after occlusion. Gene expression was compared between the two brain locations to find differentially expressed genes. The expressions of these genes were then compared in the blood pre- and post-occlusion. RESULTS: Hierarchical clustering of brain expression data revealed strong independent clustering of ischemic and nonischemic brain samples. The top five enriched, up-regulated gene sets in the brain were TNF α signaling, apoptosis, P53 pathway, hypoxia, and UV response up. A comparison of differentially expressed genes in the brain and blood revealed a significant overlap of gene expression patterns. Stringent analysis of blood expression data from pre- and post-occlusion samples in each monkey identified nine genes highly differentially expressed in both the brain and the blood. Many of these up-regulated genes belong to pathways involved in cell death and DNA damage repair. INTERPRETATION: Common gene expression profile can be identified in the brain and blood and clearly differentiates ischemic from nonischemic conditions. Therefore, specific blood transcriptomic signature may represent a surrogate for brain ischemic gene expression.

Sustained (S)-roscovitine delivery promotes neuroprotection associated with functional recovery and decrease in brain edema in a randomized blind focal cerebral ischemia study.

Stroke is a devastating disorder that significantly contributes to death, disability and healthcare costs. In ischemic stroke, the only current acute therapy is recanalization, but the narrow therapeutic window less than 6 h limits its application. The current challenge is to prevent late cell death, with concomitant therapy targeting the ischemic cascade to widen the therapeutic window. Among potential neuroprotective drugs, cyclin-dependent kinase inhibitors such as (S)-roscovitine are of particular relevance. We previously showed that (S)-roscovitine crossed the blood-brain barrier and was neuroprotective in a dose-dependent manner in two models of middle cerebral artery occlusion (MCAo). According to the Stroke Therapy Academic Industry Roundtable guidelines, the pharmacokinetics of (S)-roscovitine and the optimal mode of delivery and therapeutic dose in rats were investigated. Combination of intravenous (IV) and continuous sub-cutaneous (SC) infusion led to early and sustained delivery of (S)-roscovitine. Furthermore, in a randomized blind study on a transient MCAo rat model, we showed that this mode of delivery reduced both infarct and edema volume and was beneficial to neurological outcome. Within the framework of preclinical studies for stroke therapy development, we here provide data to improve translation of pre-clinical studies into successful clinical human trials.

High-throughput analysis of promoter occupancy reveals new targets for Arx, a gene mutated in mental retardation and interneuronopathies.

Genetic investigations of X-linked intellectual disabilities have implicated the ARX (Aristaless-related homeobox) gene in a wide spectrum of disorders extending from phenotypes characterised by severe neuronal migration defects such as lissencephaly, to mild or moderate forms of mental retardation without apparent brain abnormalities but with associated features of dystonia and epilepsy. Analysis of Arx spatio-temporal localisation profile in mouse revealed expression in telencephalic structures, mainly restricted to populations of GABAergic neurons at all stages of development. Furthermore, studies of the effects of ARX loss of function in humans and animal models revealed varying defects, suggesting multiple roles of this gene during brain development. However, to date, little is known about how ARX functions as a transcription factor and the nature of its targets. To better understand its role, we combined chromatin immunoprecipitation and mRNA expression with microarray analysis and identified a total of 1006 gene promoters bound by Arx in transfected neuroblastoma (N2a) cells and in mouse embryonic brain. Approximately 24% of Arx-bound genes were found to show expression changes following Arx overexpression or knock-down. Several of the Arx target genes we identified are known to be important for a variety of functions in brain development and some of them suggest new functions for Arx. Overall, these results identified multiple new candidate targets for Arx and should help to better understand the pathophysiological mechanisms of intellectual disability and epilepsy associated with ARX mutations.

Role of cytoskeletal abnormalities in the neuropathology and pathophysiology of type I lissencephaly.

Type I lissencephaly or agyria-pachygyria is a rare developmental disorder which results from a defect of neuronal migration. It is characterized by the absence of gyri and a thickening of the cerebral cortex and can be associated with other brain and visceral anomalies. Since the discovery of the first genetic cause (deletion of chromosome 17p13.3), six additional genes have been found to be responsible for agyria-pachygyria. In this review, we summarize the current knowledge concerning these genetic disorders including clinical, neuropathological and molecular results. Genetic alterations of LIS1, DCX, ARX, TUBA1A, VLDLR, RELN and more recently WDR62 genes cause migrational abnormalities along with more complex and subtle anomalies affecting cell proliferation and differentiation, i.e., neurite outgrowth, axonal pathfinding, axonal transport, connectivity and even myelination. The number and heterogeneity of clinical, neuropathological and radiological defects suggest that type I lissencephaly now includes several forms of cerebral malformations. In vitro experiments and mutant animal studies, along with neuropathological abnormalities in humans are of invaluable interest for the understanding of pathophysiological mechanisms, highlighting the central role of cytoskeletal dynamics required for a proper achievement of cell proliferation, neuronal migration and differentiation.