Striatal Neurodevelopment Is Dysregulated in Purine Metabolism Deficiency and Impacts DARPP-32, BDNF/TrkB Expression and Signaling: New Insights on the Molecular and Cellular Basis of Lesch-Nyhan Syndrome

Abstract

Lesch-Nyhan Syndrome (LNS) is a neurodevelopmental disorder caused by mutations in the gene encoding the purine metabolic enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT). This syndrome is characterized by an array of severe neurological impairments that in part originate from striatal dysfunctions. However, the molecular and cellular mechanisms underlying these dysfunctions remain largely unidentified. In this report, we demonstrate that HPRT-deficiency causes dysregulated expression of key genes essential for striatal patterning, most notably the striatally-enriched transcription factor B-cell leukemia 11b (Bcl11b). The data also reveal that the down-regulated expression of Bcl11b in HPRT-deficient immortalized mouse striatal (STHdh) neural stem cells is accompanied by aberrant expression of some of its transcriptional partners and other striatally-enriched genes, including the gene encoding dopamine- and cAMP-regulated phosphoprotein 32, (DARPP-32). Furthermore, we demonstrate that components of the BDNF/TrkB signaling, a known activator of DARPP-32 striatal expression and effector of Bcl11b transcriptional activation are markedly increased in HPRT-deficient cells and in the striatum of HPRT knockout mouse. Consequently, the HPRT-deficient cells display superior protection against reactive oxygen species (ROS)-mediated cell death upon exposure to hydrogen peroxide. These findings suggest that the purine metabolic defect caused by HPRT-deficiency, while it may provide neuroprotection to striatal neurons, affects key genes and signaling pathways that may underlie the neuropathogenesis of LNS.

MicroRNAs

“…Our studies have demonstrated a significant deficit of cAMP production in HPRT-deficient cells upon activation with the cAMP agonist forskolin . Additionally, our data further revealed that the deficit in cAMP production in HPRT-deficient cells is accompanied by alteration in protein kinase A (PKA)-related phosphorylation of several phosphoproteins, among them synapsin I, TH, DARPP-32, and CREB (Guibinga et al, 2014;Guibinga & Barron, unpublished data).…”

“…We have already reported that Bcl11b expression is markedly downregulated in HPRT-deficient murine neural progenitor striatal cells and in the striatum of adult HPRT-KO mouse as well as in human HPRT-deficient neuron-like cells (Guibinga et al, 2014). Bcl11b is a key transcription factor which drives the expression of a hundreds of striatally enriched genes (Desplats, Lambert, & Thomas, 2008;Tang et al, 2011), among them is PDE10 whose the expression is severely perturbed in HPRT-deficient cells and in the striatum of HPRT-KO mice (Guibinga , Table 1 Cluster of the most significantly upregulated miRNAs in HPRT-deficient human neuron-like cells (differentiated NT2 cells).…”

“…Several signaling pathways converge onto CREB to regulate the expression of a wide number of genes, such as synapsin I, Tyrosine hydroxylase (TH), and DARPP-32 (dopamine and cAMP-regulated neuronal phosphoprotein) (Guibinga, Barron, & Pandori, 2014;Guibinga, Hsu, & Friedmann, 2010;) that possess a cyclic AMP response element (CRE) consensus sequence in their promoters (Browning, Huganir, & Greengard, 1985;Di Benedetto, D'Addario, Candeletti, & Romualdi, 2007;Hemmings, Nairn, & Greengard, 1986). Together with the aforementioned neurodevelopmental transcription factor genes identified by gene ontology (GO) analysis of miR-181a and other analyses (Guibinga et al, 2012;Guibinga et al, 2010), CREB1 was also shown to be among the potential targets of miR-181a .…”

“…The aberrant expression of Bcl11b has also been shown to affect the expression of the gene encoding DARPP-32 (ppp1r1b) (Arlotta, Molyneaux, Jabaudon, Yoshida, & Macklis, 2008); DARPP-32 is a key signaling molecule that integrates the neurotransmission in the striatum (Svenningsson et al, 2004). In the context of HPRT deficiency, we have recently demonstrated that the expression and the signaling of ppp1r1b/darpp-32 is significantly disrupted in HPRTdeficient cells and striatal tissues derived from HPRT-KO mice (Guibinga et al, 2014). …”

“…Its role in HPRT deficiency was recently uncovered (Guibinga et al, 2014) through its association and partnership with the transcription factor Mash1, which was one of the first transcription factors whose expression was found to be significantly dysregulated in HPRT-deficient cells (Guibinga et al, 2010). FoxG1 has multiple functions in the developing brain, among them driving neuronal specification in the forebrain via the repression of other transcription factors in early progenitor cells (Kumamoto et al, 2013).…”