The orphan nuclear receptor, liver receptor homology-1 (LRH-1), is highly expressed in liver and exocrine pancreas. Although LRH-1 has been shown to be involved in developmental and homeostatic processes, its integrated function remains at present ill-defined. This is in part due to the lack of adequate in vivo mouse models to characterize LRH-1. We propose to elucidate the role of LRH-1 specifically in the liver, by integrating state-of-the-art approaches in mouse genetics, physiology and functional genomic s. The strong genetic, developmental, physiological, and biochemical similarities between mouse and man justifies this approach. As homozygous LRH-1 deficient mice are embryonic lethal, we propose to "flox" the LRH-1 allele, enabling the generation of temp orally and spatially controlled, hepatocyte-specific, LRH-1 mutant mice.
This approach is particularly relevant in metabolic diseases where the pathology affects multiple organs. Using transcriptional profiling, we will obtain a comprehensive molecular fin gerprint to be correlated with the detailed clinical phenotype, in order to identify the signalling pathways controlled by LRH-1.
To complement this mouse model the regulation of LRH-1 activity will also be investigated. LRH-1 is constitutively active and ligands are indispensable for it's basal activity. Consequently, LRH-1 activity may be regulated through phosphorylation. The primary sequence of LRH-1 contains several potential consensus PKA, PKC and MARK phosphorylation sites, and their impact on LRH-1 a ctivity has not been fully elucidated.
Through the use of specific kinase inhibitors, site-directed mutagenesis, EMSA and cofactor recruitment assays the regulation of LRH-1 activity by kinases will be established. Thus this proposal will generate a mouse model, which will reveal the function of hepatic LRH-1 to physiology and pathophysiology, findings that will validate LRH-1 as a therapeutic target to combat disorders linked to its dysfunction in the liver.
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