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Culture induced changes in Blood-Brain Barrier transcriptome: implications for amino acid transporters in vivo

ABSTRACT: Tight homeostatic control of brain amino acids (AA) depends on transport via solute family carrier proteins expressed by the Blood-Brain Barrier (BBB) microvascular endothelial cells (BMEC). To characterize the mouse BMEC transcriptome and probe culture-induced changes microarray analyses of PECAM-1+ endothelial cells (ppMBMECs) were compared with primary MBMECs (pMBMEC) cultured in the presence or absence of glial cells, and with b.End5 endothelioma cell-line. Selected cell marker and AA transporter mRNA levels were further verified by real-time RT PCR. Regardless of glial co-culture expression of a large subset of genes was strongly altered by a brief culture step. This is consistent with the known dependence of BMECs on in vivo interactions to maintain physiological functions, e.g. tight barrier formation, and their consequent de-differentiation in culture. Seven (4F2hc, Lat1, Taut, Snat3, Snat5, Xpct, Cat1) of nine highly in vivo expressed AA transporter mRNAs were strongly down-regulated for all cultures and two (Snat2, Eaat3) were variably regulated. In contrast, five AA transporter mRNAs with low in vivo expression, including y+Lat2, xCT, and Snat1, were strongly up-regulated by culture. We hypothesized that the AA transporters highly expressed in ppMBMECs and strongly down-regulated in culture play a major in vivo role for BBB transendothelial transport. Keywords: culture vs non-cultured

ORGANISM(S): Mus musculus

PROVIDER: GSE14375 | GEO | 2009/06/01

SECONDARY ACCESSION(S): PRJNA111419

REPOSITORIES: GEO

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Project description:The low permeability and high selectivity of the blood vessels of the brain and central nervous system (CNS) characterize the blood-brain barrier (BBB). Tight junctions, a lack of fenestrations, and low rates of transcytosis in the endothelial cells of the vasculature prevent passive diffusion of most molecules other than water, gases and some lipid soluble molecules (Obermeier, Daneman, & Ransohoff, 2013). Any additional nutrients must be transported across the barrier with the help of transporter proteins. Two protein families account for most transporters. ABC transporters use ATP to power primary-active transport to move molecules across the BBB against an electrochemical gradient, frequently excluding drugs from entering the brain. Some SLC transporters facilitate transport of solutes along an electrochemical gradient, while others permit secondary-active transport by coupling the flow of a solute traveling down the electrochemical gradient to power another solute against its electrochemical gradient. Brain microvessel endothelial cells (BMEC) from human cerebral cortex were enriched through a homogenization and centrifugation procedure. Two BMEC and two tissue were sequenced with paired-end reads on a SOLiD 5500 Wildfire. Raw data was aligned using LifeScope Genomic Analysis, gene expression determined through Cufflinks, and splice junctions identified by aligning to a custom database of known to known and known to novel junctions. We found numerous examples of transporters with enriched expression in the isolated BMECs compared to whole brain tissue. In total, 131 transporter genes or pseudogenes (109 SLC, 22 ABC) are enriched at least 1.25 fold in BMEC enriched samples, and 57 of these are enriched over 2-fold (50 SLC, 7 ABC). Thirteen genes were found to have at least twice as many counts in BMEC enriched samples than in whole tissue for at least one alternative splice junction. Inversely, 23 genes were found to have at least one alternative splice junction with half as many counts in BMEC enriched samples than in whole tissue.

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Culture induced changes in Blood-Brain Barrier transcriptome: implications for amino acid transporters in vivo

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