ABCA2
ATP-binding cassette sub-family A member 2 (EC 7.6.2.-) (ATP-binding cassette transporter 2) (ATP-binding cassette 2) [ABC2] [KIAA1062]
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We previously reported that ABCA2, of the A subclass of the ATP-binding cassette (ABC) transporter superfamily, is expressed in mature oligodendrocytes and Schwann cells, the cells responsible for myelination in the brain and the peripheral nerve, respectively. However, unidentified cells expressing ABCA2 also were found. Here, we provide evidence for the expression of ABCA2 in the rodent sciatic nerve not only in Schwann cells, which express the Schwann cell marker S100beta and a zinc finger transcription factor Krox20 (a marker for myelin-forming Schwann cells), but also in Krox20-negative cells, which express glial fibrillary acidic protein (GFAP), a cell adhesion molecule L1, and S100beta weekly. We also analyzed developmental changes in ABCA2 expression in Schwann cells. The expression of ABCA2 in Krox20 /S100beta Schwann cells was found initially in rat facial nerve at postnatal day (PD) 8, in half (52.4%) of the cells showing myelinization at PD 14, and in all of the cells in the adult stage. These results demonstrate that ABCA2 is expressed in non-myelin-forming as well as in myelin-forming Schwann cells, and that ABCA2 may be involved in transport of a substance associated with cellular maturation rather than initial myelin formation in both types of Schwann cells.
MeSH Terms
- ATP-Binding Cassette Transporters
- Aging
- Animals
- Animals, Newborn
- Biomarkers
- Cell Differentiation
- Early Growth Response Protein 1
- Facial Nerve
- Glial Fibrillary Acidic Protein
- Mice
- Mice, Inbred C57BL
- Myelin Sheath
- Nerve Fibers, Myelinated
- Nerve Growth Factors
- Neural Cell Adhesion Molecule L1
- Peripheral Nerves
- Rats
- Rats, Sprague-Dawley
- S100 Calcium Binding Protein beta Subunit
- S100 Proteins
- Schwann Cells
- Sciatic Nerve
Using in situ hybridization for the mouse brain, we analyzed developmental changes in gene expression for the ATP-binding cassette (ABC) transporter subfamilies ABCA1-4 and 7, and ABCG1, 2, 4, 5 and 8. In the embryonic brains, ABCA1 and A7 were highly expressed in the ventricular (or germinal) zone, whereas ABCA2, A3 and G4 were enriched in the mantle (or differentiating) zone. At the postnatal stages, ABCA1 was detected in both the gray and white matter and in the choroid plexus. On the other hand, ABCA2, A3 and A7 were distributed in the gray matter. In addition, marked up-regulation of ABCA2 occurred in the white matter at 14 days-of-age when various myelin protein genes are known to be up-regulated. In marked contrast, ABCA4 was selective to the choroid plexus throughout development. ABCG1 was expressed in both the gray and white matters, whereas ABCG4 was confined to the gray matter. ABCG2 was diffusely and weakly detected throughout the brain at all stages examined. Immunohistochemistry of ABCG2 showed its preferential expression on the luminal membrane of brain capillaries. Expression signals for ABCG5 and G8 were barely detected at any stages. The distinct spatio-temporal expressions of individual ABCA and G transporters may reflect their distinct cellular expressions in the developing and adult brains, presumably, to regulate and maintain lipid homeostasis in the brain.
MeSH Terms
- ATP-Binding Cassette Transporters
- Aging
- Animals
- Animals, Newborn
- Brain
- Embryo, Mammalian
- Immunohistochemistry
- In Situ Hybridization
- Mice
- Mice, Inbred C57BL
- Tissue Distribution