Reduced levels of dopamine and altered metabolism in brains of HPRT knock-out rats: a new rodent model of Lesch-Nyhan Disease

Abstract

Lesch-Nyhan disease (LND) is a severe neurological disorder caused by loss-of-function mutations in the gene encoding hypoxanthine phosphoribosyltransferase (HPRT), an enzyme required for efficient recycling of purine nucleotides. Although this biochemical defect reconfigures purine metabolism and leads to elevated levels of the breakdown product urea, it remains unclear exactly how loss of HPRT activity disrupts brain function. As the rat is the preferred rodent experimental model for studying neurobiology and diseases of the brain, we used genetically-modified embryonic stem cells to generate an HPRT knock-out rat. Male HPRT-deficient rats were viable, fertile and displayed normal caged behaviour. However, metabolomic analysis revealed changes in brain biochemistry consistent with disruption of purine recycling and nucleotide metabolism. Broader changes in brain biochemistry were also indicated by increased levels of the core metabolite citrate and reduced levels of lipids and fatty acids. Targeted MS/MS analysis identified reduced levels of dopamine in the brains of HPRT-deficient animals, consistent with deficits noted previously in human LND patients and HPRT knock-out mice. The HPRT-deficient rat therefore provides a new experimental platform for future investigation of how HPRT activity and disruption of purine metabolism affects neural function and behaviour.

From engineering to editing the rat genome

“…Meek and co-workers inactivated the gene encoding hypoxanthine phosphoribosyltransferase (HPRT), a key regulator of the purine salvage pathway, generating a mutation that in humans causes the debilitating neurological disease Lesch–Nyhan Syndrome (Lesch and Nyhan 1964 ). The Hprt mutant rats showed a deficit in dopamine in their brains, consistent with observations in human Lesch–Nyhan patients and mutant mice, and may therefore represent a suitable animal model to investigate the behavioural changes associated with HPRT deficiency (Meek et al 2016 ). In a further demonstration of the utility of the rat model, Uenoyama and colleagues knocked out the gene encoding rat Kisspeptin, a neuropeptide involved in the regulation of puberty and reproduction (Irwig et al 2004 ; Matsui et al 2004 ).…”

Rescuing compounds for Lesch-Nyhan disease identified using stem cell–based phenotypic screening

“…The next step of this work would be to test the efficiency of the hit compounds in animal models of LND. HGPRT-knockout rodent models exhibit metabolic abnormalities consistent with deficient purine salvage (10,20,21). To some extend, reduction of dopamine concentration in the caudate-putamen nuclei was also reported both in mice and rats (20,22).…”

“…HGPRT-knockout rodent models exhibit metabolic abnormalities consistent with deficient purine salvage (10,20,21). To some extend, reduction of dopamine concentration in the caudate-putamen nuclei was also reported both in mice and rats (20,22). Unfortunately, the rodent model failed to recapitulate the neuropsychiatric characteristics of LND, i.e., dystonia and self-injurious behavior (10,20).…”

“…To some extend, reduction of dopamine concentration in the caudate-putamen nuclei was also reported both in mice and rats (20,22). Unfortunately, the rodent model failed to recapitulate the neuropsychiatric characteristics of LND, i.e., dystonia and self-injurious behavior (10,20). This lack of spontaneous neurobehavioral phenotype renders these models unsuitable for testing the efficacy of the compounds at a functional and integrated level.…”

Femtomolar and selective dopamine detection by a gold nanoparticle enhanced surface plasmon resonance aptasensor

“…Dopamine is a neurotransmitter that is a member of the catecholamine family in the brain and a precursor to epinephrine and norepinephrine [3]. Also, it is a major transmitter in the extrapyramidal system of the brain, important in regulating movement, and related to neurodegenerative diseases, such as Parkinson's disease, Alzheimer's disease, and Huntington's disease [4,5]. Sensing strategies that can provide fast, ultrasensitive and selective analysis of dopamine is key in monitoring these neurodegenerative diseases.…”