The presence of both negative and positive elements in the 5′-flanking sequence of the rat Na, K-ATPase α3 subunit gene are required for brain expression in transgenic mice

Open Access
Publisher Website
Google Scholar
Abstract
The Na, K-ATPase is an integral plasma membrane protein consisting of α and β subunits, each of which has discrete isoforms expressed in a tissue-specific manner. Of the three functional α isoform genes, the one encoding the α3 isoform is the most tissuerestricted in its expression, being found primarily in the brain. To identify regions of the α3 isoform gene that are involved in directing expression in the brain, a 1.6 kb 5′-flanking sequence was attached to a reporter gene, chloramphenicol acetyltransferase (CAT). The α3 – CAT chimeric gene construct was microinjected into fertilized mouse eggs, and transgenic mice were produced. Analysis of adult transgenic mice from different lines revealed that the transgene is expressed primarily in the brain. To further delineate regions that are needed for conferring expression in this tissue, systematic deletions of the 5′-f lanking sequence of the α3–CAT fusion constructs were made and analyzed, again using transgenic mice. The results from these analyses indicate that DNA sequences required for mediating brain-specific expression of the α3 isoform gene are present within 210 bp upstream of the transcription initiation site. α3-CAT promoter constructs containing scanning mutations in this region were also assayed in transgenic mice. These studies have identified both a functional neural-restrictive silencer element as well as a positively acting cis element.