Abstract TMP101: Epigenetics in Blood Brain Barrier Formation and Maintenance

Abstract

The blood brain barrier (BBB), unique to the central nervous system (CNS) vessels, tightly controls the passage of molecules between the blood and the brain. BBB breakdown is documented in many pathological conditions including, stroke, and contributes to the severity of disease and poor outcome. Currently, there is no efficient treatment strategy to prevent BBB breakdown or restore disrupted BBB . Despite BBB’s importance in the CNS function, t he genetic program and mechanism, that regulates BBB formation and maintenance is poorly characterized. To understand the molecular features underlying BBB gene regulation during development we utilize endothelial cell (EC) cultures derived from brain of both embryonic (E-13.5) and adult mice and investigated differences in BBB gene expression and epigenetic status using real time PCR analysis and ChIP-qPCR. We found that a distinct BBB profile exist in the CNS ECs during BBB formation and maintenance . When compared to embryonic ECs, adult ECs showed a significant down regulation in expression of tight junction (TJ) genes such as CLDN-1 , CLDN -11 , ZO-1 and OCLN . Conversely, another important TJ gene CLDN- 5 shows a significant increase in adult ECs. Further, we found that epigenetic-histone modifications are involved in the repression in the TJ gene in adult ECs. To more fully understand the role of Wnt/β-catenin in BBB formation and maintenance we block the downstream of the Wnt/β-catenin signaling pathway using LF3 (block the interaction of β-catenin and transcription factor TCF4) in developing ECs. This results in a adult BBB phenotype in developing ECs indicating, silencing of Wnt/β-catenin pathway is required for BBB maturation . Further, epigenetic component HDAC2 was increased significantly in developing ECs when Wnt/β-catenin signaling is blocked demonstrating this pathway can modulate the epigenetics of CNS ECs . In summary, we describe that BBB genes have distinguished expression pattern during BBB formation and maintenance, guided by the Wnt/β-catenin pathway through epigenetic modifications. Understanding the fundamental epigenetic and regulatory mechanisms of BBB formation and maintenance is critical for developing therapeutic interventions against BBB breakdown.