Lesch-Nyhan Research Articles

Characterization of the dopamine defect in primary cultures of dopaminergic neurons from hypoxanthine phosphoribosyltransferase knockout mice.

Lesch-Nyhan disease (LND) is an X-linked metabolic disorder caused by lack of activity of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT) and characterized by hyperuricemia and debilitating neurological manifestations. The mechanisms underlying the neuropathology are not well understood and the principal neurochemical lesion characterized to date is a deficiency of the dopamine system in the basal ganglia. To facilitate the study of mechanism(s) by which HPRT deficiency causes the dopamine defect, we have compared the survival and dopamine phenotype of primary cultures of dopamine neurons derived from HPRT-deficient mice with the dopaminergic neurons from wild-type mice. The survival of dopaminergic neurons from both sources was promoted to an equal extent by glial cell line-derived neurotrophic factor (GDNF), a potent survival factor for dopamine neurons in vitro. Although the survival of the HPRT-deficient neurons was indistinguishable from that of cells derived from wild-type counterparts, the HPRT-deficient cells demonstrated a persistent deficiency of dopamine content and dopamine uptake with increasing neuritic differentiation, indicating that GDNF does not restore the normal phenotype in HPRT-deficient dopamine neurons despite its well-known protective and regenerative properties in several neurodegeneration models. Nevertheless, the demonstration that GDNF trophic support promotes the survival of these dopaminergic neurons will facilitate gaining a better understanding of the neuropathological mechanisms of LND by allowing a more extensive analysis of the cells central to the Lesch-Nyhan phenotype, the dopaminergic neurons of the basal ganglia.

Adrenergic and noradrenergic plasma levels in Lesch-Nyhan disease.

Noradrenergic dysfunction and abnormality in monoamine oxidase (MAO) enzyme activity have been reported previously in Lesch-Nyhan (LN) disease. This study examines peripheral indices of adrenergic, noradrenergic, and MAO function in children and young adults with LN disease (n = 11), and healthy subjects (n = 9). Blood samples, collected in identical conditions prior to a positron emission tomography (PET) study, were assayed for concentrations of epinephrine (EPI), norepinephrine (NE), and 3-methoxy-4-hydroxyphenylglycol (DHPG) (which results from the degradation of NE by monoamine oxidase type A [MAO-A]). The LN subjects had significantly higher EPI levels by 245% (p < .00) and lower DHPG levels by 42% (p < .00) compared to the control group. No group differences were noted in NE plasma levels. Cognitive function (IQ tested by Stanford Binet Intelligence Scale) was associated with EPI in the LN group (r = 0.77, p = .009), but not in the control group. The abnormally high EPI plasma concentrations may indicate another biochemical dysfunction secondary to the absence of the HPRT enzyme in LN patients. Such a biochemical deficit is likely to originate from the adrenal medulla, which is the primary site of EPI synthesis. The adrenal medulla may be directly affected by the absence of hypoxanthine guanine phosphoribosyl transferase (HPRT) enzyme, or may receive inappropriately high descending activation input from the brain. The abnormally low DHPG levels, in the context of normal NE levels, indicates low MAO activity, either as a primary deficit, or as secondary adaptive changes to spare NE levels that would otherwise be too low for adequate noradrenergic function.

An Unexpected Affected Female Patient in a Classical Lesch–Nyhan Family

Lesch–Nyhan disease is a genetic disorder of purine metabolism caused by defective activity of the enzyme hypoxanthine-guanine phosphoribosyl transferase (HPRT), resulting from mutation in the corresponding gene on the long arm of the X chromosome (Xq26). The classical phenotype, which includes spasticity, involuntary movements, developmental disability, and self-injurious behavior, occurs exclusively in males, while heterozygous, carrier females are clinically normal. We analyzed an Argentine family in which there were male and female siblings with clinically identical classic features of Lesch–Nyhan disease. The mother and an older daughter were carriers and had normal phenotypes. We identified the HPRT mutation in the family. It is a C → T transition at position 508 of the cDNA (c.508 C → T) that changes the CGA codon for Arg(169) to the TGA stop codon (R169X). The female patient was karyotypically normal and heterozygous for the mutation. She inherited the HPRT mutation from her mother, but she also had unexpected nonrandom inactivation of the paternal X chromosome carrying the normal HPRT gene. This additional genetic alteration is the cause of the clinical expression of disease in this female patient.

IMMUNODEFICIENCY CAUSED BY PURINE NUCLEOSIDE PHOSPHORYLASE DEFICIENCY

Purine nucleoside phosphorylase (PNP) is a key enzyme in the purine salvage pathway with adenosine deaminase (ADA). Inherited deficiency of either one of two purine salvage enzymes results in severe combined immunodeficiency (SCID) in humans. 32,33,50 One of the striking features of ADA and PNP deficiencies is the selective effect on the immune system, although the activities of these enzymes are missing in every cell in the body. 50 The biochemical mechanism(s) explaining the pathology of PNP deficiency attempts to address the specificity of this disease toward the immune system. 50,68 Enzyme deficiencies can cause deleterious phenotypes as a result of lack of product of the enzymatic reaction or as a consequence of the cytotoxicity of the accumulating substrates. The lack of products in PNP deficiency is unlikely to contribute to the immune deficiency because deficiency of the next enzyme in the purine salvage pathway hypoxanthine-guanine phosphoribosyl transferase (HGPRT) causes Lesch-Nyhan syndrome with normal immune function. 62 Of the four purine nucleoside substrates of the PNP reaction, inosine, deoxyinosine, guanosine, and deoxyguanosine, only deoxyguanosine has an alternative metabolic fate (i.e., phosphorylation by deoxyguanosine kinase) (Fig. 1). 28,90 Deoxyguanosine is the only logical candidate to mediate the lymphoid abnormalities observed in PNP deficiency. The challenge remains to explain the metabolic, biochemical, and cellular mechanisms that lead to the unique lymphoid specificity of PNP deficiency despite its ubiquitous expression.

Kelley-Seegmiller syndrome due to a unique variant of hypoxanthine-guanine phosphoribosyltransferase: reduced affinity for 5-phosphoribosyl-1-pyrophosphate manifested only at low, physiological substrate concentrations

A male child, who presented at the age of 3.5 years with acute renal failure, was diagnosed as having partial deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT; EC 2.4.2.8). The underlying HPRT mutation was unique in that the specific activity of HPRT in erythrocyte and in fibroblast lysates was normal, but the rate of uptake of hypoxanthine into nucleotides of intact cultured fibroblasts was markedly reduced (23% of normal). The low functioning of HPRT in the intact fibroblasts was associated with decreased utilization of endogenously generated hypoxanthine and with decreased utilization of the cosubstrate 5-phosphoribosyl-1-pyrophosphate (PRPP). The non-utilized hypoxanthine was excreted into the incubation medium. The accumulation of PRPP was indicated by the 2.3-fold increase in the rate of uptake of adenine into intact cell nucleotides and by the 7.5-fold enhancement of the rate of de novo purine synthesis. Kinetic studies of HPRT activity in fibroblast lysates revealed reduced affinity of the enzyme for PRPP (apparent K m 500 μM in comparison to 25 μM in control lysates), manifested in low activity at low (physiological), but not at high PRPP concentrations. The apparent K m for hypoxanthine was normal (23 μM in comparison to 14.2 μM in control lysates). With allopurinol treatment, our patient has had no problems since presentation, and is developing normally at 5 years of age.

Deletion in the hypoxanthine phosphoribosyltransferase gene caused by Alu-Alu recombination in two Japanese patients with Lesch-Nyhan syndrome.

Lesch-Nyhan (LN) syndrome is caused by a severe genetic deficiency of hypoxanthine phosphoribosyltransferase (HPRT), which is characterized by neuropsychological disorders (including self-mutilation) and hyperuricemia. The human HPRT gene is located on the X chromosome and its length is 57 kb1. The coding sequence of 654 bp is divided into 9 exons. Although there is great heterogeneity in the known hprt mutations associated with LN syndrome, approximately 85% of LN mutations are located within the cording region or the splicing sequences of the HPRT gene, which can be easily predicted by examination of HPRT cDNA. However, the remaining 15% are large genomic alterations such as total or partial gene deletions and duplications, which often does not produce HPRT mRNA, and it is difficult to determine mutational breakpoints due to large size of introns. According to our strategy for analysis of LN mutations (Fig. l), we have identified three independent base substitutions in three Japanese LN patients and one identical large genomic deletion in two unrelated Japanese

Adenoviruses encoding HPRT correct the biochemical abnormalities fully only in HPRT-deficient human cell lines: importance of species differences.

The Lesch-Nyhan syndrome (LNS) is an X-linked disorder caused by a virtually complete absence of the key purine recycling enzyme, hypoxanthine-guanine phosphoribosyltransferase (HPRT) It is characterised by uric acid overproduction and severe neurological dysfunction. Despite the early discovery of the link between the neurological symptoms and a deficit in purine salvage the cellular and molecular mechanisms leading to LNS remain unexplained1. Various HPRT deficient ‘knock-out’ mouse models have shown the gross purine overproduction of LNS patients, but not the neurological abnormalities2. An interesting aspect of LNS is that it lacks progressive neurodegeneration. As yet there is no effective treatment. A possible solution is gene therapy, and recombinant adenoviruses have been proposed as vectors for gene transfer into postmitotic neuronal cells3.

Elevated UTP and CTP Content in Cultured Neurons from HPRT-Deficient Transgenic Mice

Hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8.; HPRT) catalyzes the salvage synthesis of inosine-5'-monophosphate (IMP) and guanosine-5'-monophosphate (GMP) from the purine bases hypoxanthine and guanine, respectively. Complete deficiency of HPRT activity is associated with the Lesch-Nyhan syndrome (LNS), characterized by excessive purine production and severe neurological manifestations. The etiology of the metabolic consequences of HPRT deficiency is clarified, but that of the neurological manifestations is not yet understood. HPRT-deficient mice represent an experimental animal model of LNS. In search for a possible metabolic abnormality in LNS brains, connecting the neurological deficit to HPRT deficiency, the purine and pyrimidine nucleotide content of cultured neurons, prepared from HPRT-deficient transgenic mice, was now determined. The HPRT-deficient neuronal cultures exhibited a significantly elevated content of the pyrimidine nucleotides UTP (1.33-fold the normal level, p = 0.0002) and CTP (1.28-fold the normal level, p = 0.02), but normal content of the purine nucleotides ATP and GTP. This abnormality in neuronal pyrimidine nucleotide content may be associated with the pathophysiology of the neurological deficit in LNS.

The spectrum of hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency.

Summary The enzyme hypoxanthine-guanine phosphoribo-syltransferase (HPRT) catalyzes the reutilization ofhypoxanthine and guanine to the purine nucleotidesIMP and GMP, respectively. HPRT deficiency is an X-linked disorder characterized by uric acid over-production and variable neurologic impairment. Thecomplete deficiency of HPRT is diagnostic of Lesch-Nyhan syndrome manifested by choreoathetosis,spasticity, mental retardation, and self-injurious be-havior. In some HPRT-deficient patients the enzymedefect appeared to be “partial” and the neurologicsymptoms mild to severe (Kelley-Seegmiller syn-drome). This has prompted the classification ofHPRT deficiency in 2 distinct groups: Lesch-Nyhansyndrome and Kelley-Seegmiller syndrome, whichhas created much confusion. A spectrum of clinicalconsequences of HPRT deficiency has been recog-nized in small series of patients, but the completespectrum of the neurologic disorder has not been de-scribed in a single series of patients examined by thesame observers.We analyzed our experience with 22 patients be-longing to 18 different families with HPRT deficiencydiagnosed at “La Paz” University Hospital in Madridover the past 16 years. The clinical spectrum of theseHPRT-deficient Spanish patients was similar to thedifferent phenotypes occasionally reported in the lit-erature, in some cases diagnosed as Lesch-Nyhan“variants.” The clinical, biochemical, enzymatic, andmolecular genetic studies on these 22 patients al-lowed us to delineate a new classification of HPRTdeficiency. Based on the neurologic symptoms, de-pendency for personal care, HPRT activity in he-molysate and in intact erythrocytes, and predictedprotein size, patients were classified into 4 groups:Group 1 (2 patients), normal development with noneurologic symptoms, HPRT activity was detectablein hemolysates and in intact erythrocytes, and themutation did not affect the predicted protein size.Group 2 (3 patients) mild neurologic symptoms thatdid not prevent independent lives, HPRT activity wasdetectable in intact erythrocytes, and the protein sizewas normal. Group 3 (2 patients), severe neurologicimpairment that precluded an independent life, noresidual HPRT activity, and normal protein size.Group 4 (15 patients), clinical characteristics ofLesch-Nyhan syndrome (some may not show self-injurious behavior), no residual HPRT activity, and inmost (7 of 8 patients in whom the mutation could bedetected) the mutation affected the predicted pro-tein size.This classification of HPRT deficiency into 4groups may be more useful in terms of accuracy, re-producibility, assessment for treatment trials andprognosis. The study of this Spanish series allows usto conclude that HPRT deficiency may be manifestedby a wide spectrum of neurologic symptoms; theoverall severity of the disease is associated with mu-tations permitting some degree of residual enzymeactivity; and mutation analysis provides a valuable

An unexpected female patient within a classical Lesch-Nyhan family

The Lesch-Nyhan (LN) disease is a genetic disorder of purine metabolism caused by defective activity of the enzyme Hypoxanthineguanine PhosphoRibosyl Transferase (HPRT). Affected individuals have a striking phenotype characterized by hyperuricemia and uricosuria, spasticity, involuntary movements, developmental disability and self-injurious behavior. The HPRT gene is located on the long arm of the X chromosome (Xq26) and the pattern of inheritance is X-linked recessive. The classical phenotype occurs exclusively in males, while heterozygous, carrier females are generally normal.We analyzed an Argentine family in which there were male and female siblings with clinically identical classic features of Lesch-Nyhan disease. The mother and an older daughter were carriers with normal phenotypes. We identified the HPRT mutation in the family. It is a C→T transition at position 508 of the cDNA that changes the CGA codon for Arg(169) to the TGA stop codon. The female patient was karyotypically normal and heterozygous for the mutation. She inherited the HPRT mutation from her mother, but she also had unexpected nonrandom inactivation of the paternal X chromosome carrying the normal HPRT gene. This additional genetic alteration is the cause of the clinical expression of the disease in this female patient.Three cases of female patients with classical LN clinical features have been previously reported. Each of them showed a different de novo molecular alteration that led to a specific HPRT enzyme defect, along with a mechanism of nonrandom inactivation of the X chromosome carrying the normal copy of the HPRT gene. Our family differs in that the HPRT mutation was inherited in at least three individuals, one of whom is our female case. Like the other affected females, she also shows nonrandom inactivation of the normal X chromosome.

Novel genetic mutations responsible for the HPRT deficiency and the clinical phenotypes in Japanese.

ConclusionWe have identified six novel mutations in Japanese families of HPRT deficiency manifesting different clinical phenotypes. A missense mutation (Y195C) was identified in a patient with hyperuricemia and gout (Case 1). In Cases 2 and 3 with mild neurological symptoms, missense mutations L147P and K159E were detected, respectively. A point mutation 532+2T>C causing splicing error was found in a severe form of partial HPRT deficiency (Case 4). Two mutations causing splicing error, 609+1delGT (Case 5) and 610-−1G>A (Case 6), resulted in the classic Lesch-Nyhan syndrome.

Identification of a new Lesch-Nyhan syndrome mutation (HPRTBrasil) and analysis of potentially heterozygous females.

The mutation in the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene has been determined in two brothers affected with Lesch-Nyhan syndrome. Female members of the family who are at risk for being heterozygous carriers of the HPRT mutation were also studied to determine whether they carry the mutation. DNA sequencing revealed that the boys' mother is heterozygous for the mutation in her somatic cells, but that three maternal aunts are not heterozygous. Such carrier information is important for the future pregnancy plans of at-risk females. The mutation, an A-->T transversion at cDNA base 590 (590A-->T), results in an amino acid change of glutamic acid to valine at codon 197, and has not been reported previously in a Lesch-Nyhan syndrome male. This mutation is designated HPRTBrasil.

Sex selection and preimplantation genetic diagnosis

Sex selection and preimplantation genetic diagnosis

Eighteen novel mutations in patients with Lesch-Nyhan syndrome or partial hypoxanthine phosphoribosyltransferase deficiency.

Eighteen novel mutations in patients with Lesch-Nyhan syndrome or partial hypoxanthine phosphoribosyltransferase deficiency.

Orthopedic Problems in Lesch-Nyhan Syndrome

Lesch-Nyhan syndrome is an X-linked disorder of purine metabolism. The orthopedic problems and results of treatment of nine Lesch-Nyhan patients are reviewed. Associated orthopedic problems included hip subluxation or dislocation (nine of 18 hips), fractures (three), autoamputation, infections (three), minor scoliosis, and contractures. Lesch-Nyhan patients can safely undergo orthopedic procedures and the results of surgery are satisfactory and similar to those of patients with spastic cerebral palsy. All of the seven operated-on hips maintained good reduction at 6-year mean follow-up. With adequate cast technique, fractures and hip subluxation/dislocation may be treated successfully. The treating orthopedist should be aware of the increased incidence of heterotopic ossification in this population, as well as the potential for serious complications such as hardware failure or femur fracture, if appropriate immobilization is not used.

Autopsy findings in umbilical cord blood transplant recipients.

Human umbilical cord blood stem cells have been used to reconstitute hematopoiesis in patients with malignant and nonmalignant diseases. The immunologic immaturity of cord blood cells confers peculiar characteristics to these hematopoietic precursors. Autopsy reports from January 1, 1988, through June 30, 1998, were searched for patients who had received an umbilical cord blood transplant (UCBT). Thirty-two patients (19 male, 13 female) were identified with a mean age at autopsy of 13.0 years with a range from 1 to 52 years. Most patients (24) underwent UCBT for treatment of a malignant neoplasm, while the remainder were treated for immunodeficiencies (4), Lesch-Nyhan syndrome (2), Hurler syndrome (1), and Diamond-Blackfan syndrome (1). Sixteen patients had at least 1 infectious complication, and 8 patients had multiple infections. Organisms included mycoses (7 patients), viruses (8 patients), bacteria (3 patients), and Toxoplasma (2 patients). Hemorrhagic complications, such as intra-alveolar hemorrhage and gastrointestinal tract hemorrhage, were found in 24 patients. Other frequent findings at autopsy included diffuse alveolar damage (15 patients), hepatic veno-occlusive disease (11 patients), and acute or chronic graft-vs-host disease (9 patients). Patients who have received UCBT represent a unique population of immunosuppressed patients. Infectious and hemorrhagic complications frequently are encountered at autopsy, and pathologists performing autopsies on these patients should be alert to unusual pathogens.

Orthopedic problems in Lesch-Nyhan syndrome.

Lesch-Nyhan syndrome is an X-linked disorder of purine metabolism. The orthopedic problems and results of treatment of nine Lesch-Nyhan patients are reviewed. Associated orthopedic problems included hip subluxation or dislocation (nine of 18 hips), fractures (three), autoamputation, infections (three), minor scoliosis, and contractures. Lesch-Nyhan patients can safely undergo orthopedic procedures and the results of surgery are satisfactory and similar to those of patients with spastic cerebral palsy. All of the seven operated-on hips maintained good reduction at 6-year mean follow-up. With adequate cast technique, fractures and hip subluxation/dislocation may be treated successfully. The treating orthopedist should be aware of the increased incidence of heterotopic ossification in this population, as well as the potential for serious complications such as hardware failure or femur fracture, if appropriate immobilization is not used.

Relationship of dopamine to serotonin in the neonatal 6-OHDA rat model of Lesch-Nyhan syndrome.

Rats were treated as neonates with either 6-hydroxydopamine (6-OHDA) 100 micrograms or vehicle intracisternally. Upon maturation, animals receiving 6-OHDA were assigned to four groups, with two of the four groups receiving intraventricular 5,7-dihydroxytryptamine (5,7-DHT) 75 micrograms bilaterally. At 94 days of age, animals were injected with either SKF-38393 (3.0 mg/kg, intraperitoneally (i.p.)), a dopamine D1 agonist, or m-chlorophenylpiperazine (m-CPP) (3.0 mg/kg, i.p.), a 5-HT2C agonist, in an attempt to evoke behaviors such as stereotypical chewing, head-nodding, self-biting and self-mutilation. Both SKF-38393 and m-CPP induced the target behaviors in animals receiving 6-OHDA alone. Animals receiving additional 5,7-DHT treatment did not show any of the target behaviors in response to SKF-38393, but exhibited a much higher sensitivity to m-CPP. Pre-treatment with SCH-23390 in animals receiving 6-OHDA alone was effective in preventing SKF-38393-induced target behaviors, but not those induced by m-CPP. Pre-treatment with mianserin partially antagonized the effects of both SKF-38393 and m-CPP in these same animals. In groups receiving both neonatal 6-OHDA and adult 5,7-DHT, mianserin was effective in reducing m-CPP-induced behaviors, while SCH-23390 was largely ineffective. These data provide evidence of a serial relationship between the D1 and 5-HT2C receptor systems in the neostriatum of animals receiving neonatal 6-OHDA lesions.

Gabapentin for self-injurious behavior in Lesch-Nyhan syndrome

Self-injurious behavior is a common clinical problem in children with Lesch-Nyhan syndrome, an X-linked disorder of purine metabolism. This behavior is not observed in other conditions associated with increased serum concentrations of uric acid, hypoxanthine, and xanthine. Various neurotransmitters appear to play a pivotal role in self-injurious behavior. The authors present a patient with Lesch-Nyhan syndrome, whose self-injurious behavior was effectively treated with gabapentin, and discuss possible mechanisms of action.

Cognitive functioning in Lesch–Nyhan syndrome: a 4‐year follow‐up study

Lesch–Nyhan syndrome (LNS) is a rare disorder of metabolism caused by a defective gene on the X chromosome. It is typically characterized by choreoathetosis, hypertonia, hyperreflexia, and self‐mutilation. The present study is a 4‐year follow‐up investigation of the cognitive status of six subjects with a mean age of 17 years 10 months (range 14 years 9 months to 23 years). The Stanford–Binet Intelligence Scale: IV was used. Each of the four domains assessed by this battery (verbal reasoning, abstract/visual reasoning, quantitative, and short‐term memory) was compared with previous findings of the same subjects at their initial test and 2‐year follow up; the aim being to gain further insight into the clinical course of LNS over time. The results suggest that while the subjects generally continued to acquire new information and skills over time, their standardized scores declined, indicating that a plateau was reached in their skill levels relative to their peers, as also seen in other developmental disabilities. Deficits were noted in working memory, particularly on tasks that involve considering multiple features simultaneously.