A fat-specific enhancer is the primary determinant of gene expression for adipocyte P2 in vivo.

Abstract

The murine gene for adipocyte P2 encodes an adipocyte-specific member of the family of intracellular lipid binding proteins. The region upstream from the start of transcription of this gene has been found to contain binding sites for the transcription factors c-jun/c-fos and C/EBP (CCAAT/enhancer binding protein) and several short sequence elements found in other adipocyte gene promoters, termed fat-specific elements. To identify DNA sequences that were responsible for the high level of transcription of the gene for adipocyte P2 in vivo, we made a series of transgenic mice containing 168 base pairs (bp), 247 bp, 1.7 kilobases (kb), and 5.4 kb of 5' flanking sequence linked to the bacterial gene chloramphenicol acetyltransferase. Although plasmids containing only 168 bp of 5' sequence including the C/EBP and AP-1 (activation protein 1) binding sites were expressed well in cultured adipocytes, high levels of chloramphenicol acetyltransferase activity in the adipose tissue oftransgenic mice were not observed until the 5' flanking region was extended to kb -5.4. An enhancer mapping between kb -4.9 and kb -5.4 upstream from the start of transcription was identified by transfection of further deletions into cultured adipocytes. This enhancer, when linked to a bp -63 promoter fragment from the gene for adipocyte P2, directed very high level chloramphenicol acetyltransferase expression specifically to adipose tissue in transgenic mice. These results identify a functional adipose-specific enhancer and indicate that it is the major determinant of tissue specificity of the gene for adipocyte P2. These results also demonstrate that the proximal-promoter binding sites for AP-1 and C/EBP are not sufficient or necessary to give adipose-tissue-specific expression in vivo, though they may play an important role in the response of this promoter to glucocorticoids.The major role of the adipocyte in higher eukaryotes is the storage of nutritional energy in the form of triglycerides. Disordered gene expression in the adipocyte may result in pathological conditions such as lipodystrophy and obesity, the latter of which contributes heavily to morbidity and mortality through associated cardiovascular disorders and diabetes. In addition, the ability to genetically alter the expression of adipocyte genes and thus control the fatness of feed animals remains an important goal of agricultural research. Thus, the regulation of adipocyte gene expression is of interest for biological, medical, and agricultural reasons.

DNA demethylation modulates mouse leptin promoter activity during the differentiation of 3T3-L1 cells

“…The region, however, could not bear all the important cis-acting regions for leptin induction during adipocytes differentiation as an example of the aP2 promoter [25].…”

Chronically increased glucose uptake by adipose tissue leads to lactate production and improved insulin sensitivity rather than obesity in the mouse

“…Generation of transgenic mice A 3.1 kb XmaI-NotI fragment containing the rat hepatic Gck cDNA and the polyadenylation signal of the SV40 virus was introduced downstream of the Ap2 (also known as Fabp4) promoter at the XmaI-NotI site in the pAp2 plasmid [24,25]. The entire Ap2-Gck chimeric gene (8.5 kb) was microinjected into fertilised eggs as described by our group elsewhere [4].…”

Ectopic recombination in the central and peripheral nervous system by aP2/FABP4‐Cre mice: Implications for metabolism research

“…In some instances conditional cell type selective knockouts had to be generated to circumvent embryonic lethality of global mouse knockouts [1][2][3]. Adipocyte selective inactivation of genes was possible through the identification of promoter sequences of the aP2 (fatty acid binding protein 4, FABP4) gene [4] and the introduction of Cre/loxP technology [5]. In recent years, these adipocyte restricted knockouts were also used with the particular purpose to define the function of a protein in these lipid storing cells, independent of its role in other tissues [6][7][8], or to uncover the function of the protein in mature adipocytes as opposed to its role during adipogenesis [9].…”