Human Molecular Genetics Advance Access originally published online on April 2, 2009
Human Molecular Genetics 2009 18(13):2317-2327; doi:10.1093/hmg/ddp164
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Hypoxanthine-guanine phosphoribosyl transferase regulates early developmental programming of dopamine neurons: implications for Lesch-Nyhan disease pathogenesis
1 School of Medicine, Paris Descartes University, 75006 Paris, France 2 Department of Metabolic Biochemistry, Necker-Enfants Malades Hospital, APHP, 75015 Paris, France 3 Neurobiology and Cellular Diversity, CNRS UMR 7637, Ecole Supérieure de Physique et de Chimie Industrielles, 75005 Paris, France 4 Department of Neurology, School of Medicine, Emory University, Atlanta, GA 30302, USA 5 Development and Neuropharmacology, CNRS UMR 8542, Ecole Normale Supérieure, 75005 Paris, France
* To whom correspondence should be addressed at: Department of Metabolic Biochemistry, Necker-Enfants Malades Hospital, 149 rue de Sèvres, 75015 Paris, France. Tel: +33 144495429; Fax: +33 144495130; Email: irene.ceballos{at}nck.aphp.fr
Received February 20, 2009; Accepted March 30, 2009
Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency results in Lesch-Nyhan disease (LND), where affected individuals exhibit a characteristic neurobehavioral disorder that has been linked with dysfunction of dopaminergic pathways of the basal ganglia. Since the functions of HPRT, a housekeeping enzyme responsible for recycling purines, have no direct relationships with the dopaminergic pathways, the mechanisms whereby HPRT deficiency affect them remain unknown. The current studies demonstrate that HPRT deficiency influences early developmental processes controlling the dopaminergic phenotype, using several different cell models for HPRT deficiency. Microarray methods and quantitative PCR were applied to 10 different HPRT-deficient (HPRT–) sublines derived from the MN9D cell line. Despite the variation inherent in such mutant sublines, several consistent abnormalities were evident. Most notable were increases in the mRNAs for engrailed 1 and 2, transcription factors known to play a key role in the specification and survival of dopamine neurons. The increases in mRNAs were accompanied by increases in engrailed proteins, and restoration of HPRT reverted engrailed expression towards normal levels, demonstrating a functional relationship between HPRT and engrailed. The functional relevance of the abnormal developmental molecular signature of the HPRT– MN9D cells was evident in impoverished neurite outgrowth when the cells were forced to differentiate chemically. To verify that these abnormalities were not idiosyncratic to the MN9D line, HPRT– sublines from the SK-N-BE(2) M17 human neuroblastoma line were evaluated and an increased expression of engrailed mRNAs was also seen. Over-expression of engrailed occurred even in primary fibroblasts from patients with LND in a manner that suggested a correlation with disease severity. These results provide novel evidence that HPRT deficiency may affect dopaminergic neurons by influencing early developmental mechanisms.