Recessive GCH1 Deficiency Causing DOPA-Responsive Dystonia Diagnosed by Reported Negative Exome.

An exome sequencing result on a child with atypical gait was reported as negative; follow-up biochemical evaluation and reanalysis led to diagnosis of treatable DOPA-responsive dystonia.

GCH1 Deficiency Activates Brain Innate Immune Response and Impairs Tyrosine Hydroxylase Homeostasis.

The Parkinson's disease (PD) risk gene GTP cyclohydrolase 1 (GCH1) catalyzes the rate-limiting step in tetrahydrobiopterin (BH4) synthesis, an essential cofactor in the synthesis of monoaminergic neurotransmitters. To investigate the mechanisms by which GCH1 deficiency may contribute to PD, we generated a loss of function zebrafish gch1 mutant (gch1-/-), using CRISPR/Cas technology. gch1-/- zebrafish develop marked monoaminergic neurotransmitter deficiencies by 5 d postfertilization (dpf), movement deficits by 8 dpf and lethality by 12 dpf. Tyrosine hydroxylase (Th) protein levels were markedly reduced without loss of ascending dopaminergic (DAergic) neurons. L-DOPA treatment of gch1-/- larvae improved survival without ameliorating the motor phenotype. RNAseq of gch1-/- larval brain tissue identified highly upregulated transcripts involved in innate immune response. Subsequent experiments provided morphologic and functional evidence of microglial activation in gch1-/- The results of our study suggest that GCH1 deficiency may unmask early, subclinical parkinsonism and only indirectly contribute to neuronal cell death via immune-mediated mechanisms. Our work highlights the importance of functional validation for genome-wide association studies (GWAS) risk factors and further emphasizes the important role of inflammation in the pathogenesis of PD.SIGNIFICANCE STATEMENT Genome-wide association studies have now identified at least 90 genetic risk factors for sporadic Parkinson's disease (PD). Zebrafish are an ideal tool to determine the mechanistic role of genome-wide association studies (GWAS) risk genes in a vertebrate animal model. The discovery of GTP cyclohydrolase 1 (GCH1) as a genetic risk factor for PD was counterintuitive, GCH1 is the rate-limiting enzyme in the synthesis of dopamine (DA), mutations had previously been described in the non-neurodegenerative movement disorder dopa-responsive dystonia (DRD). Rather than causing DAergic cell death (as previously hypothesized by others), we now demonstrate that GCH1 impairs tyrosine hydroxylase (Th) homeostasis and activates innate immune mechanisms in the brain and provide evidence of microglial activation and phagocytic activity.

Early-onset autosomal dominant GTP-cyclohydrolase I deficiency: Diagnostic delay and residual motor signs.

OBJECTIVE: Autosomal dominant (AD) guanosine triphosphate cyclohydrolase 1 (GCH1) deficiency is the most common cause of dopa-responsive dystonia (DRD). Patients with GCH1 deficiency are likely to experience diagnostic delay, but its consequences have not been described thoroughly in patients with early-onset disease. We describe the diagnostic delay and residual motor signs (RMS) observed in patients with early-onset (before 15 years of age) disease. METHODS: Twelve patients with early-onset AD GCH1 deficiency from a single center were included in the case series analysis. For the meta-analysis, the PubMed database was searched for articles on early-onset AD GCH1 deficiency published from 1995 to 2019. RESULTS: In the case series, the mean duration of diagnostic delay was 5.6 years. Two patients exhibited RMS, and four patients underwent orthopedic surgery. The literature search yielded 137 AD GCH1 deficiency cases for review; gait disturbance was reported in 92.7% of patients, diurnal fluctuation of symptoms in 91.9%, and RMS in 39%. The mean duration of diagnostic delay was 14.6 years overall: 12.0 years in RMS-negative patients and 21.2 years in RMS-positive patients. CONCLUSIONS: Diagnostic delay in early-onset AD GCH1 deficiency is more closely associated with later RMS. Early clinical suspicion, timely diagnosis, and levodopa treatment may reduce the occurrence of RMS in patients with early-onset AD GCH1 deficiency.

GTP-cyclohydrolase deficiency induced peripheral and deep microcirculation dysfunction with age.

The present study assessed the impact of impaired tetrahydrobiopterin (BH4) production on vasoreactivity from conduit and small arteries along the vascular tree as seen during aging. For this purpose, the mutant hyperphenylalaninemic mouse (hph-1) was used. This model is reported to be deficient in GTP cyclohydrolase I, a rate limiting enzyme in BH4 biosynthesis. BH4 is a key regulator of vascular homeostasis by regulating the nitric oxide synthase 3 (NOS3) activity. In GTP-CH deficient mice, the aortic BH4 levels were decreased, by -77% in 12 week-middle-aged mice (young) and by -83% in 35-45 week-middle-aged mice (middle-aged). In young hph-1, the mesenteric artery ability to respond to flow was slightly reduced by 9%. Aging induced huge modification in many vascular functions. In middle-aged hph-1, we observed a decrease in aortic cGMP levels, biomarker of NO availability (-46%), in flow-mediated vasodilation of mesenteric artery (-31%), in coronary hyperemia response measured in isolated heart following transient ischemia (-27%) and in cutaneous microcirculation dilation in response to acetylcholine assessed in vivo by laser-doppler technic (-69%). In parallel, the endothelium-dependent relaxation in response to acetylcholine in conduit blood vessel, measured on isolated aorta rings, was unchanged in hph-1 mice whatever the age. Our findings demonstrate that in middle-aged GTP-CH depleted mice, the reduction of BH4 was characterized by an alteration of microcirculation dilatory properties observed in various parts of the vascular tree. Large conduit blood vessels vasoreactivity, ie aorta, was unaltered even in middle-aged mice emphasizing the main BH4-deletion impact on the microcirculation.

Zinc supplementation protects against diabetic endothelial dysfunction via GTP cyclohydrolase 1 restoration.

This study explored whether zinc supplementation alleviates diabetic endothelial dysfunction and the possible mechanisms underlying. We found that high glucose exposure significantly increased reactive oxygen species (ROS) and decreased guanosine 5'-triphosphate cyclohydrolase 1 (GTPCH1) and tetrahydrobiopterin (BH4) levels in bovine aortic endothelial cells (BAECs) in a time-dependent manner. High glucose increased zinc release from GTPCH1 in a similar trend. Zinc supplementation restored GTPCH1 and BH4 levels and blocked ROS accumulation in both BACEs and wild type GTPCH1 transfected HEK293 cells, but not in the zinc-free C141R mutant of GTPCH1 transfected ones. In vivo experiments showed that exogenous supplementation of zinc to streptozotocin (STZ)-induced diabetic mice partially improved the impaired maximal endothelium-dependent vasorelaxation, reversed the aberrant reduction of GTPCH1 and BH4, and suppressed the elevation of ROS in the aortas. In conclusion, our study demonstrated a novel mechanism that via GTPCH1 restoration zinc supplementation exerts a protective benefit on diabetic endothelial dysfunction.

GTP-Cyclohydrolase I deficiency presenting as malignant hyperphenylalaninemia, recurrent hyperthermia and progressive neurological dysfunction in a South Asian child - a case report.

BACKGROUND: Tetrahydrobiopterin (BH4) deficiencies are disorders affecting phenylalanine homeostasis, and catecholamine and serotonin biosynthesis. GTP-Cyclohydrolase I deficiency (OMIM 600225) is an extremely rare variant of inborn error of BH4 synthesis which exists in recessive and dominant forms. The recessive form presents with complex neurological and autonomic dysfunction whilst the dominant form presents as Dopa-responsive dystonia. CASE PRESENTATION: We describe a South Asian child who initially presented with neurological dysfunction and recurrent vomiting and later developed recurrent hyperthermia for several months. The child did not have screening for hyperphenylalaninemia at birth and was found to have marked hyperphenylalaninemia after clinical presentation at 5 months. Further evaluation revealed BH4 deficiency. GTP-Cyclohydrolase I deficiency (GTPCH) was identified based on normal dihydro pteridine reductase activity and markedly reduced neopterin in dried blood spot test. After institution of treatment and control of high phenylalanine levels, clinical deterioration decelerated yet with noticeable residual neurological dysfunction. CONCLUSION: To authors' knowledge, this is first report of GTPCH deficiency in a South Asian child. The case highlights practical issues regarding diagnosis of GTPCH deficiency, especially in countries without broader universal newborn screening programs for early detection of inherited metabolic disorders. Testing for GTPCH deficiency should be considered for patients with unexplained neurological and autonomic symptoms following initial metabolic screen.

A novel GTPCH deficiency mouse model exhibiting tetrahydrobiopterin-related metabolic disturbance and infancy-onset motor impairments.

BACKGROUND: GTP cyclohydrolase I (GTPCH) deficiency could impair the synthesis of tetrahydrobiopterin and causes metabolic diseases involving phenylalanine catabolism, neurotransmitter synthesis, nitric oxide production and so on. Though improvements could be achieved by tetrahydrobiopterin and neurotransmitter precursor levodopa supplementation, residual motor and mental deficits remain in some patients. An appropriate GTPCH deficiency animal model with clinical symptoms, especially the motor impairments, is still not available for mechanism and therapy studies yet. OBJECTIVES AND METHODS: To investigate whether the heterozygous GTPCH missense mutation p.Leu117Arg identified from a patient with severe infancy-onset dopa-responsive motor impairments is causative and establish a clinical relevant GTPCH deficiency mouse model, we generated a mouse mutant mimicking this missense mutation using the CRISPR/Cas9 technology. Series of characterization experiments on the heterozygous and homozygous mutants were conducted. RESULTS: The expressions of GTPCH were not significantly changed in the mutants, but the enzyme activities were impaired in the homozygous mutants. BH4 reduction and phenylalanine accumulation were observed both in the liver and brain of the homozygous mutants. Severer metabolic disturbance occurred in the brain than in the liver. Significant reduction of neurotransmitter dopamine, norepinephrine and serotonin was observed in the brains of homozygous mutants. Live-born homozygous mutants exhibited infancy-onset motor and vocalization deficits similar to the disease symptoms observed in the patient, while no obvious symptoms were observed in the young heterozygous mutant mice. With benserazide-levodopa treatment, survival of the homozygous mutants was improved but not completely rescued. CONCLUSIONS: The GTPCH p.Leu117Arg missense mutation is deleterious and could cause tetrahydrobiopterin, phenylalanine and neurotransmitter metabolic disturbances and infancy-onset motor dysfunctions recessively. This is the first GTPCH deficiency mouse model which could be live-born and exhibits significant motor impairments. The different extents of BH4 reduction and phenylalanine accumulation observed between liver and brain in response to GTPCH deficiency gives potential new insights into the vulnerability of brain to GTPCH deficiency.

Mast cell tetrahydrobiopterin contributes to itch in mice.

GTP cyclohydrolase (GCH1) governs de novo synthesis of the enzyme cofactor, tetrahydrobiopterin (BH4), which is essential for biogenic amine production, bioactive lipid metabolism and redox coupling of nitric oxide synthases. Overproduction of BH4 via upregulation of GCH1 in sensory neurons is associated with nociceptive hypersensitivity in rodents, and neuron-specific GCH1 deletion normalizes nociception. The translational relevance is revealed by protective polymorphisms of GCH1 in humans, which are associated with a reduced chronic pain. Because myeloid cells constitute a major non-neuronal source of BH4 that may contribute to BH4-dependent phenotypes, we studied here the contribution of myeloid-derived BH4 to pain and itch in lysozyme M Cre-mediated GCH1 knockout (LysM-GCH1-/- ) and overexpressing mice (LysM-GCH1-HA). Unexpectedly, knockout or overexpression in myeloid cells had no effect on nociceptive behaviour, but LysM-driven GCH1 knockout reduced, and its overexpression increased the scratching response in Compound 48/80 and hydroxychloroquine-evoked itch models, which involve histamine and non-histamine dependent signalling pathways. Mechanistically, GCH1 overexpression increased BH4, nitric oxide and hydrogen peroxide, and these changes were associated with increased release of histamine and serotonin and degranulation of mast cells. LysM-driven GCH1 knockout had opposite effects, and pharmacologic inhibition of GCH1 provided even stronger itch suppression. Inversely, intradermal BH4 provoked scratching behaviour in vivo and BH4 evoked an influx of calcium in sensory neurons. Together, these loss- and gain-of-function experiments suggest that itch in mice is contributed by BH4 release plus BH4-driven mediator release from myeloid immune cells, which leads to activation of itch-responsive sensory neurons.

Tetrahydrobiopterin modulates ubiquitin conjugation to UBC13/UBE2N and proteasome activity by S-nitrosation.

Nitric Oxide (NO) is an intracellular signalling mediator, which affects many biological processes via the posttranslational modification of proteins through S-nitrosation. The availability of NO and NOS-derived reactive oxygen species (ROS) from enzymatic uncoupling are determined by the NO synthase cofactor Tetrahydrobiopterin (BH4). Here, using a global proteomics "biotin-switch" approach, we identified components of the ubiquitin-proteasome system to be altered via BH4-dependent NO signalling by protein S-nitrosation. We show S-nitrosation of ubiquitin conjugating E2 enzymes, in particular the catalytic residue C87 of UBC13/UBE2N, leading to impaired polyubiquitylation by interfering with the formation of UBC13~Ub thioester intermediates. In addition, proteasome cleavage activity in cells also seems to be altered by S-nitrosation, correlating with the modification of cysteine residues within the 19S regulatory particle and catalytic subunits of the 20S complex. Our results highlight the widespread impact of BH4 on downstream cellular signalling as evidenced by the effect of a perturbed BH4-dependent NO-Redox balance on critical processes within the ubiquitin-proteasome system (UPS). These studies thereby uncover a novel aspect of NO associated modulation of cellular homeostasis.

Roles for endothelial cell and macrophage Gch1 and tetrahydrobiopterin in atherosclerosis progression.

Aims: GTP cyclohydrolase I catalyses the first and rate-limiting reaction in the synthesis of tetrahydrobiopterin (BH4), an essential cofactor for nitric oxide synthases (NOS). Both eNOS and iNOS have been implicated in the progression of atherosclerosis, with opposing effects in eNOS and iNOS knockout mice. However, the pathophysiologic requirement for BH4 in regulating both eNOS and iNOS function, and the effects of loss of BH4 on the progression of atherosclerosis remains unknown. Methods and results: Hyperlipidemic mice deficient in Gch1 in endothelial cells and leucocytes were generated by crossing Gch1fl/flTie2cre mice with ApoE-/- mice. Deficiency of Gch1 and BH4 in endothelial cells and myeloid cells was associated with mildly increased blood pressure. High fat feeding for 6 weeks in Gch1fl/flTie2CreApoE-/- mice resulted in significantly decreased circulating BH4 levels, increased atherosclerosis burden and increased plaque macrophage content. Gch1fl/flTie2CreApoE-/- mice showed hallmarks of endothelial cell dysfunction, with increased aortic VCAM-1 expression and decreased endothelial cell dependent vasodilation. Furthermore, loss of BH4 from pro-inflammatory macrophages resulted in increased foam cell formation and altered cellular redox signalling, with decreased expression of antioxidant genes and increased reactive oxygen species. Bone marrow chimeras revealed that loss of Gch1 in both endothelial cells and leucocytes is required to accelerate atherosclerosis. Conclusion: Both endothelial cell and macrophage BH4 play important roles in the regulation of NOS function and cellular redox signalling in atherosclerosis.

Tetrahydrobiopterin (BH4 ): Targeting endothelial nitric oxide synthase as a potential therapy for pulmonary hypertension.

PURPOSE: Pulmonary Hypertension (PH) is complex disease which is associated with endothelial and cardiac dysfunction. Tetrahydrobiopterin (BH4 ) regulates endothelial nitric oxide synthase (eNOS) to produce nitric oxide rather than superoxide which maintains normal endothelial and cardiac function. This study explores the therapeutic potential of BH4 in experimental PH. METHODS: Monocrotaline-induced PH in rats and Hph-1 deficiency in mice were used for animal experiments. Hemodynamic measurements using pressure transducers were conducted for pulmonary and cardiac pressures, and Langendorff apparatus was used for isolated heart experiments; preventive as well as rescue treatment protocols were conducted; tissues were collected for histological and biochemical studies. RESULTS: In vivo acute BH4 administration reduced pulmonary artery pressure (PAP) only in the MCT rat. In a Langendorff preparation, BH4 increased right ventricular systolic pressure (RVSP) in right ventricular hypertrophy (RVH) but not in control. In "prevention" therapy, BH4 (10 and 100 mg/kg) attenuated the development of PH in rat MCT model. eNOS protein levels in lung homogenates were maintained and cGMP levels were increased. In "rescue" therapy, BH4 (10 and 100 mg/kg) ameliorated pulmonary vascular muscularization in a dose-dependent manner. RVSP was reduced in RVH and pulmonary vascular muscularization was attenuated. BH4 at 10 mg/kg reduced RV myocyte diameter while BH4 at 100 mg/kg reversed it to control level. BH4 restored normal levels of eNOS protein and in a dose of 100 mg/kg enhanced lung tissue levels of BH4 , cGMP, and NO compared to placebo. CONCLUSION: The current study provides scientific evidence for a therapeutic potential of BH4 in PH and invites further investigation.

Tetrahydrobiopterin in antenatal brain hypoxia-ischemia-induced motor impairments and cerebral palsy.

Antenatal brain hypoxia-ischemia, which occurs in cerebral palsy, is considered a significant cause of motor impairments in children. The mechanisms by which antenatal hypoxia-ischemia causes brain injury and motor deficits still need to be elucidated. Tetrahydrobiopterin is an important enzyme cofactor that is necessary to produce neurotransmitters and to maintain the redox status of the brain. A genetic deficiency of this cofactor from mutations of biosynthetic or recycling enzymes is a well-recognized factor in the development of childhood neurological disorders characterized by motor impairments, developmental delay, and encephalopathy. Experimental hypoxia-ischemia causes a decline in the availability of tetrahydrobiopterin in the immature brain. This decline coincides with the loss of brain function, suggesting this occurrence contributes to neuronal dysfunction and motor impairments. One possible mechanism linking tetrahydrobiopterin deficiency, hypoxia-ischemia, and neuronal injury is oxidative injury. Evidence of the central role of the developmental biology of tetrahydrobiopterin in response to hypoxic ischemic brain injury, especially the development of motor deficits, is discussed.

A key role for tetrahydrobiopterin-dependent endothelial NOS regulation in resistance arteries: studies in endothelial cell tetrahydrobiopterin-deficient mice.

BACKGROUND AND PURPOSE: The cofactor tetrahydrobiopterin (BH4) is a critical regulator of endothelial NOS (eNOS) function, eNOS-derived NO and ROS signalling in vascular physiology. To determine the physiological requirement for de novo endothelial cell BH4 synthesis for the vasomotor function of resistance arteries, we have generated a mouse model with endothelial cell-specific deletion of Gch1, encoding GTP cyclohydrolase 1 (GTPCH), an essential enzyme for BH4 biosynthesis, and evaluated BH4-dependent eNOS regulation, eNOS-derived NO and ROS generation. EXPERIMENTAL APPROACH: The reactivity of mouse second-order mesenteric arteries was assessed by wire myography. High performance liquid chromatography was used to determine BH4, BH2 and biopterin. Western blotting was used for expression analysis. KEY RESULTS: Gch1fl/fl Tie2cre mice demonstrated reduced GTPCH protein and BH4 levels in mesenteric arteries. Deficiency in endothelial cell BH4 leads to eNOS uncoupling, increased ROS production and loss of NO generation in mesenteric arteries of Gch1fl/fl Tie2cre mice. Gch1fl/fl Tie2cre mesenteric arteries had enhanced vasoconstriction to U46619 and phenylephrine, which was abolished by L-NAME. Endothelium-dependent vasodilatations to ACh and SLIGRL were impaired in mesenteric arteries from Gch1fl/fl Tie2cre mice, compared with those from wild-type littermates. Loss of eNOS-derived NO-mediated vasodilatation was associated with increased eNOS-derived H2 O2 and cyclooxygenase-derived vasodilator in Gch1fl/fl Tie2cre mesenteric arteries. CONCLUSIONS AND IMPLICATIONS: Endothelial cell Gch1 and BH4-dependent eNOS regulation play pivotal roles in maintaining vascular homeostasis in resistance arteries. Therefore, targeting vascular Gch1 and BH4 biosynthesis may provide a novel therapeutic target for the prevention and treatment of microvascular dysfunction in patients with cardiovascular disease.

Inhibition of Aberrant MicroRNA-133a Expression in Endothelial Cells by Statin Prevents Endothelial Dysfunction by Targeting GTP Cyclohydrolase 1 in Vivo.

BACKGROUND: GTP cyclohydrolase 1 (GCH1) deficiency is critical for endothelial nitric oxide synthase uncoupling in endothelial dysfunction. MicroRNAs (miRs) are a class of regulatory RNAs that negatively regulate gene expression. We investigated whether statins prevent endothelial dysfunction via miR-dependent GCH1 upregulation. METHODS: Endothelial function was assessed by measuring acetylcholine-induced vasorelaxation in the organ chamber. MiR-133a expression was assessed by quantitative reverse transcription polymerase chain reaction and fluorescence in situ hybridization. RESULTS: We first demonstrated that GCH1 mRNA is a target of miR-133a. In endothelial cells, miR-133a was robustly induced by cytokines/oxidants and inhibited by lovastatin. Furthermore, lovastatin upregulated GCH1 and tetrahydrobiopterin, and recoupled endothelial nitric oxide synthase in stressed endothelial cells. These actions of lovastatin were abolished by enforced miR-133a expression and were mirrored by a miR-133a antagomir. In mice, hyperlipidemia- or hyperglycemia-induced ectopic miR-133a expression in the vascular endothelium, reduced GCH1 protein and tetrahydrobiopterin levels, and impaired endothelial function, which were reversed by lovastatin or miR-133a antagomir. These beneficial effects of lovastatin in mice were abrogated by in vivo miR-133a overexpression or GCH1 knockdown. In rats, multiple cardiovascular risk factors including hyperglycemia, dyslipidemia, and hyperhomocysteinemia resulted in increased miR-133a vascular expression, reduced GCH1 expression, uncoupled endothelial nitric oxide synthase function, and induced endothelial dysfunction, which were prevented by lovastatin. CONCLUSIONS: Statin inhibits aberrant miR-133a expression in the vascular endothelium to prevent endothelial dysfunction by targeting GCH1. Therefore, miR-133a represents an important therapeutic target for preventing cardiovascular diseases.

[Autosomal recessive GTPCH 1 deficiency: the importance of the analysis of neurotransmitters in cerebrospinal fluid]. / Deficit de GTPCH 1 autosomico recesivo: importancia del analisis de los neurotransmisores en el liquido cefalorraquideo.

INTRODUCTION: A deficiency of the enzyme guanosine triphosphate cyclohydrolase I (GTPCH 1) causes a reduction in the synthesis of tetrahydrobiopterin (BH4), a cofactor that is essential in the synthesis of tyrosine, dopamine and serotonin. It is an infrequent disease that produces psychomotor delay or regression and movement disorders, although treatment can improve or even correct the clinical signs and symptoms. CASE REPORT: We report the case of a girl with autosomal recessive GTPCH deficiency, who was diagnosed at 14 months by means of an analysis of the cerebrospinal fluid with pterin, HVA and 5-HIAA deficiency, and positive phenylalanine overload test and genetic study. The clinical features began at the age of 5 months with intermittent upper limb and brain tremors, both at rest and intentional, that disappeared after a month. Psychomotor development was normal, mild axial hypotonia being found in the examination while the complementary tests that were performed were normal. The patient later presented psychomotor regression with loss of head control, diminished active movements, difficulty in bimanual manipulation, hypomimia and severe global hypotonia, which was the reason for the study of a progressive encephalopathy. Following the diagnosis of GTPCH deficiency, replacement therapy was established with levodopa/carbidopa, OH tryptophan and BH4, with excellent progress made in motor and cognitive functioning. Today, the patient is 5 years old, has an adequate psychomotor development for her age, is in the third year of preschool education and has caught up with the level of the rest of her classmates. CONCLUSION: In this case attention must be drawn to the extremely satisfactory motor and cognitive improvement of the patient after starting replacement therapy, as in many cases the cognitive level is usually affected on a permanent basis.

TITLE: Deficit de GTPCH 1 autosomico recesivo: importancia del analisis de los neurotransmisores en el liquido cefalorraquideo.Introduccion. El deficit de la enzima trifosfato de guanosina ciclohidrolasa 1 (GTPCH 1) origina una disminucion de la sintesis de la tetrahidrobiopterina (BH4), cofactor indispensable en la sintesis de la tirosina, la dopamina y la serotonina. Es una enfermedad poco frecuente que produce un retraso o regresion psicomotora y trastornos del movimiento, y en la que el tratamiento puede mejorar o incluso corregir la clinica. Caso clinico. Niña afecta de deficit de GTPCH con herencia autosomica recesiva, diagnosticada a los 14 meses con estudio del liquido cefalorraquideo con deficit de pterinas, HVA y 5-HIAA, test de sobrecarga de fenilalanina y estudio genetico positivos. La clinica comenzo a los 5 meses con temblor cefalico y de las extremidades superiores, en reposo e intencional, intermitente, que desaparecio en un mes. El desarrollo psicomotor era normal, destacaba una hipotonia axial leve en la exploracion y las pruebas complementarias realizadas fueron normales. Posteriormente presento regresion psicomotora con perdida del sosten cefalico, disminucion de los movimientos activos, dificultad para la manipulacion bimanual, hipomimia e hipotonia global grave, lo que motivo el estudio de una encefalopatia progresiva. Tras el diagnostico de deficit de GTPCH, inicio tratamiento sustitutivo con levodopa/carbidopa, OH triptofano y BH4, con muy buena evolucion tanto motora como cognitiva. Actualmente, la paciente tiene 5 años, presenta un desarrollo psicomotor adecuado a su edad, cursa tercer curso de educacion infantil y ha alcanzado el nivel de su clase. Conclusion. Hay que destacar en este caso la mejoria tan satisfactoria, tanto motora como cognitiva, tras iniciar el tratamiento sustitutivo, ya que el nivel cognitivo suele quedar afectado en muchos casos.

Non-motor symptoms in genetically defined dystonia: Homogenous groups require systematic assessment.

INTRODUCTION: Dystonia is a movement disorder involving sustained or intermittent muscle contractions resulting in abnormal movements and postures. Identification of disease causing genes has allowed examination of genetically homogenous groups. Unlike the motor symptoms, non-motor characteristics are less clearly defined, despite their impact on a patient's quality of life. This review aims to examine the evidence for non-motor symptoms, addressing cohort size and methods of assessment in each study. METHODS: A systematic and standardised search strategy was used to identify the published literature relating to psychiatric symptoms, cognition, sleep disorders, sensory abnormalities and pain in each of the genetically determined dystonias. Studies were divided according to cohort size, method of assessment and whether comparison was made to an appropriate control group. RESULTS: Ninety-five articles were identified including reported clinical histories (n = 42), case reports and smaller case series (n = 12), larger case series (n = 23) and case-control cohorts (n = 18). Psychiatric symptoms were the most frequently investigated with anxiety, depression and Obsessive-Compulsive disorder being most common. Cognitive impairment involved either global deficits or isolated difficulties in specific domains. Disturbances to sleep were most common in the dopa-responsive dystonias. Sensory testing in DYT1 cases identified an intermediate subclinical phenotype. CONCLUSION: Non-motor symptoms form an integral component of the dystonia phenotype. However, future studies should involve a complete assessment of all symptom subtypes in order to understand the frequency and gene-specificity of these symptoms. This will enable early symptom identification, appropriate clinical management, and provide additional outcome measures in future clinical trials.

Cell-autonomous role of endothelial GTP cyclohydrolase 1 and tetrahydrobiopterin in blood pressure regulation.

Tetrahydrobiopterin (BH4) is an essential cofactor for endothelial nitric oxide synthase (eNOS) function and NO generation. Augmentation of BH4 levels can prevent eNOS uncoupling and can improve endothelial dysfunction in vascular disease states. However, the physiological requirement for de novo endothelial cell BH4 biosynthesis in eNOS function remains unclear. We generated a novel mouse model with endothelial cell-specific deletion of GCH1, encoding GTP cyclohydrolase 1, an essential enzyme for BH4 biosynthesis, to test the cell-autonomous requirement for endothelial BH4 biosynthesis in vivo. Mice with a floxed GCH1 allele (GCH1(fl/fl)) were crossed with Tie2cre mice to delete GCH1 in endothelial cells. GCH1(fl/fl)Tie2cre mice demonstrated virtually absent endothelial NO bioactivity and significantly greater O2 (•-) production. GCH1(fl/fl)Tie2cre aortas and mesenteric arteries had enhanced vasoconstriction to phenylephrine and impaired endothelium-dependent vasodilatations to acetylcholine and SLIGRL. Endothelium-dependent vasodilatations in GCH1(fl/fl)Tie2cre aortas were, in part, mediated by eNOS-derived hydrogen peroxide (H2O2), which mediated vasodilatation through soluble guanylate cyclase. Ex vivo supplementation of aortic rings with the BH4 analogue sepiapterin restored normal endothelial function and abolished eNOS-derived H2O2 production in GCH1(fl/fl)Tie2cre aortas. GCH1(fl/fl)Tie2cre mice had higher systemic blood pressure than wild-type littermates, which was normalized by NOS inhibitor, NG-nitro-L-arginine methyl ester. Taken together, these studies reveal an endothelial cell-autonomous requirement for GCH1 and BH4 in regulation of vascular tone and blood pressure and identify endothelial cell BH4 as a pivotal regulator of NO versus H2O2 as alternative eNOS-derived endothelial-derived relaxing factors.

Monoamine neurotransmitter deficiencies.

Pediatric neurotransmitter disorders refer to a constellation of inherited neurometabolic syndromes attributable to disturbances of neurotransmitter synthesis, degradation, or transport. Monoamine deficiencies represent defects in synthesis of dopamine, serotonin, norepinephrine, and epinephrine or in availability of tetrahydrobiopterin, an important cofactor for monoamine synthesis. Some disorders do not manifest peripheral hyperphenyalaninemia and require CSF neurotransmitter metabolite assay for diagnosis. These include Segawa dopa-responsive dystonia and enzymatic deficiencies of aromatic amino acid decarboxylase, tyrosine hydroxylase, and sepiapterin reductase. The first, autosomal dominantly inherited GTP cyclohydrolase deficiency, has a satisfying response to therapy at any age with benefits maintained over time. The others have more severe and treatment-refractory phenotypes, typically with manifestations well beyond movement disorders. Disorders detectable by elevated serum phenylalanine are deficiencies of GTP cyclohydrolase (homozygous), pterin-carbinolamine dehydratase, dihydropteridine reductase, and pyruvoyl-tetrahydropterin synthase. The latter is the most prevalent and heterogeneous but typically has infantile onset with extrapyramidal as well as bulbar, hypothalamic, limbic, and epileptic manifestations. There are therapeutic roles for neurotransmitter supplementation, and dopaminergic agonists. Basal ganglia calcifications in dihydropteridine reductase deficiency are reversible with folinic acid. Deficiencies of monoamine degradation lead to cognitive, behavioral, and autonomic disorders.

Impaired behavioural pain responses in hph-1 mice with inherited deficiency in GTP cyclohydrolase 1 in models of inflammatory pain.

BACKGROUND: GTP cyclohydrolase 1 (GTP-CH1), the rate-limiting enzyme in the synthesis of tetrahydrobiopterin (BH4), encoded by the GCH1 gene, has been implicated in the development and maintenance of inflammatory pain in rats. In humans, homozygous carriers of a "pain-protective" (PP) haplotype of the GCH1 gene have been identified exhibiting lower pain sensitivity, but only following pain sensitisation. Ex vivo, the PP GCH1 haplotype is associated with decreased induction of GCH1 after stimulation, whereas the baseline BH4 production is not affected. Contrary, loss of function mutations in the GCH1 gene results in decreased basal GCH1 expression, and is associated with DOPA-responsive dystonia (DRD). So far it is unknown if such mutations affect acute and inflammatory pain. RESULTS: In the current study, we examined the involvement of the GCH1 gene in pain models using the hyperphenylalaninemia 1 (hph-1) mouse, a genetic model for DRD, with only 10% basal GTP-CH1 activity compared to wild type mice. The study included assays for determination of acute nociception as well as models for pain after sensitisation. Pain behavioural analysis of the hph-1 mice showed reduced pain-like responses following intraplantar injection of CFA, formalin and capsaicin; whereas decreased basal level of GTP-CH1 activity had no influence in naïve hph-1 mice on acute mechanical and heat pain thresholds. Moreover, the hph-1 mice showed no signs of motor impairment or dystonia-like symptoms. CONCLUSIONS: In this study, we demonstrate novel evidence that genetic mutations in the GCH1 gene modulate pain-like hypersensitivity. Together, the present data suggest that BH4 is not important for basal heat and mechanical pain, but they support the hypothesis that BH4 plays a role in inflammation-induced hypersensitivity. Our studies suggest that the BH4 pathway could be a therapeutic target for the treatment of inflammatory pain conditions. Moreover, the hph-1 mice provide a valid model to study the consequence of congenital deficiency of GCH1 in painful conditions.