Human neural stem cells: a model system for the study of Lesch–Nyhan disease neurological aspects

Abstract

The study of Lesch-Nyhan-diseased (LND) human brain is crucial for understanding how mutant hypoxanthine-phosphoribosyltransferase (HPRT) might lead to neuronal dysfunction. Since LND is a rare, inherited disorder caused by a deficiency of the enzyme HPRT, human neural stem cells (hNSCs) that carry this mutation are a precious source for delineating the consequences of HPRT deficiency and for developing new treatments. In our study we have examined the effect of HPRT deficiency on the differentiation of neurons in hNSCs isolated from human LND fetal brain. We have examined the expression of a number of transcription factors essential for neuronal differentiation and marker genes involved in dopamine (DA) biosynthetic pathway. LND hNSCs demonstrate aberrant expression of several transcription factors and DA markers. HPRT-deficient dopaminergic neurons also demonstrate a striking deficit in neurite outgrowth. These results represent direct experimental evidence for aberrant neurogenesis in LND hNSCs and suggest developmental roles for other housekeeping genes in neurodevelopmental disease. Moreover, exposure of the LND hNSCs to retinoic acid medium elicited the generation of dopaminergic neurons. The lack of precise understanding of the neurological dysfunction in LND has precluded development of useful therapies. These results evidence aberrant neurogenesis in LND hNSCs and suggest a role for HPRT gene in neurodevelopment. These cells combine the peculiarity of a neurodevelopmental model and a human, neural origin to provide an important tool to investigate the pathophysiology of HPRT deficiency and more broadly demonstrate the utility of human neural stem cells for studying the disease and identifying potential therapeutics.

Neurological Disorders of Purine and Pyrimidine Metabolism

“…Transcriptional aberrations in a number of genes have been described in the HPRT knockout mice, which might play a role in the disease phenotype [119]. Such novel hypothesis has recently been confirmed by studies in HPRTdeficient cell models [120,121] and in HPRT-deficient human neural stem cells [122]. Aberrant expression of several vital transcription factors involved in DA neuron development and in pan-neuronal differentiation has been demonstrated in cultured HPRT-deficient human teratocarcinoma NT cells (NT2), providing direct experimental evidence for aberrant neurogenesis in HPRT deficiency.…”

“…Dopaminergic dysfunction in specific regions of the brain (basal ganglia) was ascertained to underlie the neurodevelopmental manifestations and recent findings [120][121][122] support an unexpected interference of HPRT deficiency on unrelated gene expression. Nevertheless, the molecular mechanism by which this occurs is still unveiled and we report all the previous and recent observations since at present no hypothesis can be completely ruled out.…”

“…Indeed, disruption of purine levels is known to have an important influence on neuronal differentiation in other cells [123]. Altered expression of several transcription factors and DA markers was found in human neural stem cells (hNSCs) isolated from human LNS fetal brain, providing direct experimental evidence for aberrant neurogenesis in LNS [122]. Thus a "housekeeping gene" such as HPRT, merely considered to have important metabolic functions, might also play a vital role in some pathways of mammalian neurogenesis.…”

Recent Advances in the Molecular Pathogenesis of Dystonia-Plus Syndromes and Heredodegenerative Dystonias

“…Engrailed proteins act as axon guidance factors, regulating mRNA translation in growth cones [64], and en1 has been detected in dendrites of dopaminergic neurons [65]. Abnormal neurite outgrowth was also observed in a recent study that used human neural stem cells (NSC) carrying LND mutations to generate dopaminergic neurons in vitro [66]. HPRT-deficient NSCs were found to exhibit reduced neurogenesis even after only 3 days of differentiation.…”

Transcriptomic Approach to Lesch-Nyhan Disease

“…[12–15] Transcription factors, such as engrailed, [10] have been shown to be dysregulated in HPRT-deficient neuronal cells, leading to impaired dopaminergic neurotransmission or early neurodevelopmental problems. [10,16,17] …”