ABSTRACT
Weight homeostasis is exquisitely sensitive to changes in the abundance of melanocortin-4 receptor (MC4-R). To begin to understand the factors that regulate MC4-R gene expression, we determined there are no introns in the gene, there are multiple starts of transcription, and a cluster of 3' ends. A series of MC4-R-luciferase gene reporter chimerics was developed and transfected into cell lines expressing (UMR106; GT1-7; HEK293) and not expressing (Neuro 2A) endogenous MC4-R mRNA. The longest construct, which includes approximately 3.3 kb 5'-flanking, 425 bp 5'-untranslated (UTR) and 1852 bp 3'-flanking, significantly increased luciferase reporter gene expression 24-, 13-, and 3-fold compared to pGL3-basic when expressed in HEK293, UMR106, and GT1-7 cells, respectively. Deletion analysis of mMC4-R 5'-flanking cDNA identified full mMC4-R promoter activity within 178 bp upstream of the major start of transcription. The mMC4-R gene structure and reporter chimerics provide a fundamental framework for the identification of specific factors regulating MC4-R gene expression.
Subject(s)
5' Flanking Region/genetics , Gene Expression Regulation/genetics , Mice/genetics , Receptors, Corticotropin/genetics , 3' Flanking Region/genetics , 5' Flanking Region/physiology , Animals , Base Sequence , Cloning, Molecular , Humans , Molecular Sequence Data , Promoter Regions, Genetic/genetics , RNA, Messenger/metabolism , Rats , Receptor, Melanocortin, Type 4 , Sequence Alignment , Tissue Distribution , Transcription, Genetic/genetics , Tumor Cells, CulturedABSTRACT
The pro-opiomelanocortin-derived peptides and the melanocortin receptors are implicated in various functions within the CNS including the regulation of food intake. In the present study, we used in situ hybridization, with specific 35S-labelled ovine riboprobes to map the expression of melanocortin receptor-3 (MC3-R) and -4 (MC4-R) mRNA in the diencephalon and brainstem of normal female sheep. Furthermore, we examined the effect of long-term alterations in energy balance on the distribution and expression of MC3-R and MC4-R mRNA in food-restricted and ad libitum-fed ovariectomized female sheep. The distribution of melanocortin receptors generally resembled that of the rat. A high number of MC3-R-labelled cells were seen in the ventral division of the lateral septum and the medial preoptic area. In the hypothalamus, a moderate number of MC3-R-labelled cells was observed in the lateral hypothalamic area while other nuclear groups had low to intermediate numbers of MC3-R-labelled cells. The distribution of MC4-R mRNA was generally similar to that of MC3-R mRNA in the septal/preoptic and hypothalamic regions, with a high number of labelled cells present in the intermediate division of the lateral septum. Within the hypothalamus, no MC4-R mRNA expression was observed in the arcuate nucleus. There was more widespread distribution of moderate to low numbers of MC4-R mRNA-expressing cells in the brainstem compared to that of MC3-R mRNA. Unlike findings in the rat, only a low number of cells expressed melanocortin receptor mRNA in the ovine hypothalamic nuclei associated with feeding behavior. The number of melanocortin receptor-labelled cells and the level of expression (silver grains/cell) in the hypothalamic feeding centers was similar in food-restricted and ad libitum-fed animals. These findings suggest that long-term alterations in metabolic status do not change the melanocortin receptor mRNA distribution and/or expression in the sheep hypothalamus.
Subject(s)
Body Weight/physiology , Hypothalamus/metabolism , RNA, Messenger/metabolism , Receptors, Corticotropin/genetics , Receptors, Peptide/genetics , Animals , Female , In Situ Hybridization , Receptor, Melanocortin, Type 3 , Receptor, Melanocortin, Type 4 , Sheep , Time Factors , Tissue DistributionABSTRACT
In the past decade, the scientific community has realized the value of three-dimensional (3D) structural information and '3D searching' has started to become an important new methodology for computer-aided drug design. During this time, molecular modeling information generated from various sources has proliferated due to the growing availability of software and hardware and the increasing use of crystallographic and spectroscopic techniques. This information needs to be organized to allow for its effective storage and retrieval. This paper presents an approach to address this problem with a recently introduced program, MACCS-3D. In particular, this approach utilizes MACCS-3D's capability of handling data specific for atoms and atom pairs. With this software, various biological, computational, and spectroscopic data can be merged, allowing scientists from different disciplines to access and use this information more efficiently.
