Lesch-Nyhan Syndrome: Models, Theories, and Therapies

Metabolic and neurobehavioral disturbances induced by purine recycling deficiency in Drosophila

Adenine phosphoribosyltransferase (APRT) and hypoxanthine-guanine phosphoribosyltransferase (HGPRT) are two structurally related enzymes involved in purine recycling in humans. Inherited mutations that suppress HGPRT activity are associated with Lesch-Nyhan disease (LND), a rare X-linked metabolic and neurological disorder in children, characterized by hyperuricemia, dystonia, and compulsive self-injury. To date, no treatment is available for these neurological defects and no animal model recapitulates all symptoms of LND patients. Here, we studied LND-related mechanisms in the fruit fly. By combining enzymatic assays and phylogenetic analysis, we confirm that no HGPRT activity is expressed in Drosophila melanogaster, making the APRT homolog (Aprt) the only purine-recycling enzyme in this organism. Whereas APRT deficiency does not trigger neurological defects in humans, we observed that Drosophila Aprt mutants show both metabolic and neurobehavioral disturbances, including increased uric acid levels, locomotor impairments, sleep alterations, seizure-like behavior, reduced lifespan, and reduction of adenosine signaling and content. Locomotor defects could be rescued by Aprt re-expression in neurons and reproduced by knocking down Aprt selectively in the protocerebral anterior medial (PAM) dopaminergic neurons, the mushroom bodies, or glia subsets. Ingestion of allopurinol rescued uric acid levels in Aprt-deficient mutants but not neurological defects, as is the case in LND patients, while feeding adenosine or N6-methyladenosine (m6A) during development fully rescued the epileptic behavior. Intriguingly, pan-neuronal expression of an LND-associated mutant form of human HGPRT (I42T), but not the wild-type enzyme, resulted in early locomotor defects and seizure in flies, similar to Aprt deficiency. Overall, our results suggest that Drosophila could be used in different ways to better understand LND and seek a cure for this dramatic disease.

Recurrent Fevers, Dysautonomia, and Dehydration in a Patient With Lesch-Nyhan Syndrome

Lesch-Nyhan syndrome (LNS) is a disease characterized by a reduced ability to recycle purines, leading to increased de novo purine synthesis and uric acid production. Patients classically present with an array of hyperuricemic, neurologic, and behavioral symptoms. In this report, we describe a 26-year-old male with a history of LNS and recurrent fevers of unknown origin who presented to the emergency department (ED) with a fever, hypotension, and hypernatremia. We suspect that our patient's presentation was caused by autonomic instability in the setting of LNS leading to excessive free water loss. This report highlights a rare but life-threatening manifestation of LNS.

Genetically modified mice as a tool for the study of human diseases

Modeling a human disease is an essential part of biomedical research. The recent advances in the field of molecular genetics made it possible to obtain genetically modified animals for the study of various diseases. Not only monogenic disorders but also chromosomal and multifactorial disorders can be mimicked in lab animals due to genetic modification. Even human infectious diseases can be studied in genetically modified animals. An animal model of a disease enables the tracking of its pathogenesis and, more importantly, to test new therapies. In the first part of this paper, we review the most common DNA modification technologies and provide key ideas on specific technology choices according to the task at hand. In the second part, we focus on the application of genetically modified mice in studying human diseases.

Naringin corrects renal failure related to Lesch-Nyhan disease in a rat model via NOS-cAMP-PKA and BDNF/TrkB pathways

This study explored the effect of naringin (NAR) on HGPRT1 deficiency and hyperuricemia through NOS-cAMP-PKA and BDNF/TrkB signaling pathways induced by caffeine (CAF) and KBrO3 in a rat model. Sixty-three adult male albino rats were randomly assigned into nine (n = 7) groups. Group I: control animals, Group II was treated with 100 mg/kg KBrO3 , Group III was treated with 250 mg/kg CAF, Group IV was treated with 100 mg/kg KBrO3  + 250 mg/kg CAF, Group V was administered with 100 mg/kg KBrO3  + 100 mg/kg haloperidol, Group VI was administered with 100 mg/kg KBrO3  + 50 mg/kg NAR, Group VII was administered with 500 mg/kg CAF + 50 mg/kg NAR, and Group VIII was administered with 100 mg/kg KBrO3  + 250 mg/kg CAF + 50 mg/kg NAR. Finally, group IX was treated with 50 mg/kg NAR. The exposure of rats to KBrO3 and CAF for 21 days induced renal dysfunction linked with Lesch-Nyhan disease. NAR obliterated renal dysfunction linked with Lesch-Nyhan disease by decreasing uric acid, renal malondialdehyde level, inhibiting the activities of arginase, and phosphodiesterase-51 (PDE-51) with corresponding upregulation of brain derived-neurotrophic factor and its receptor (BDNF-TrkB), Bcl11b, HGPRT1, and DARPP-32. Additionally, renal failure related to Lesch-Nyhan disease was remarkably corrected by NAR as shown by the reduced activities of AChE and enzymes of ATP hydrolysis (ATPase, AMPase, and ADA) with affiliated increase in the NO level. This study therefore validates NAR as nontoxic and effective chemotherapy against kidney-related Lesch-Nyhan disease by mitigating effects of toxic food additives and enzymes of ATP-hydrolysis via NOS-cAMP-PKA and BDNF/TrkB signaling pathways.

Red Blood Cells from Individuals with Lesch-Nyhan Syndrome: Multi-Omics Insights into a Novel S162N Mutation Causing Hypoxanthine-Guanine Phosphoribosyltransferase Deficiency

Lesch-Nyhan syndrome (LN) is an is an X-linked recessive inborn error of metabolism that arises from a deficiency of purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT). The disease manifests severely, causing intellectual deficits and other neural abnormalities, hypercoagulability, uncontrolled self-injury, and gout. While allopurinol is used to alleviate gout, other symptoms are less understood, impeding treatment. Herein, we present a high-throughput multi-omics analysis of red blood cells (RBCs) from three pediatric siblings carrying a novel S162N HPRT1 mutation. RBCs from both parents-the mother, a heterozygous carrier, and the father, a clinically healthy control-were also analyzed. Global metabolite analysis of LN RBCs shows accumulation of glycolytic intermediates upstream of pyruvate kinase, unsaturated fatty acids, and long chain acylcarnitines. Similarly, highly unsaturated phosphatidylcholines are also elevated in LN RBCs, while free choline is decreased. Intracellular iron, zinc, selenium, and potassium are also decreased in LN RBCs. Global proteomics documented changes in RBC membrane proteins, hemoglobin, redox homeostasis proteins, and the enrichment of coagulation proteins. These changes were accompanied by elevation in protein glutamine deamidation and methylation in the LN children and carrier mother. Treatment with allopurinol incompletely reversed the observed phenotypes in the two older siblings currently on this treatment. This unique data set provides novel opportunities for investigations aimed at potential therapies for LN-associated sequelae.

Lesch-Nyhan syndrome: a case report

Lesch-Nyhan syndrome (LNS) is a rare X-linked recessive disorder caused by a mutation in the hypoxanthine phosphoribosyltransferase 1 (HPRT1) gene. This syndrome is characterized by excessive production of uric acid, mental retardation, self-mutilation, choreoathetosis, and spasticity. The most distinctive symptom is compulsive self-mutilation. For patients with LNS, different methods have been tried to reduce self-biting behaviors including restraints, behavioral treatment, medications, deep brain stimulation, tooth extraction and botulinum toxin A injection. In this report, we present a case of LNS undergoing cheiloplasty due to self-mutilation and tooth extraction of the left deciduous maxillary canine.

The Role of Video-EEG Monitoring in Lesch-Nyhan Syndrome

Introduction: Lesch-Nyhan syndrome (LNS) is a rare genetic disease secondary to a HPRT1 mutation on chromosome X. It is characterized by dystonia, developmental delay, hyperuricemia and self-harming behaviours. The HPRT enzyme is implicated in the purine salvage pathway. The deficiency of HPRT results in accumulation of uric acid. There have been some cases associated with epilepsy, but it still remains a rare occurrence in LNS patients. Case presentation: We describe the case of a 20-month-old male patient with a heterozygous HPRT1 mutation c11_17del.p (Arg4Leufs*4) associated with LNS. The child associated epileptic seizures mistaken by his parents as non-epileptic sleep events associated with apnea. Seizures were discovered secondary to a polygraphic long-time sleep video-electroencephalography (EEG) monitoring. The dystonic movements and epileptic seizures responded to Levetiracetam, but the management of the behavioural disorder remained a challenge. Conclusion:Lesch-Nyhan syndrome is a rare inherited metabolic disease and its pathogenesis is not fully known, which makes the treatment management very difficult. Despite the fact that epilepsy is uncommon in LNS children, it should always be considered as part of the differential diagnosis in movement disorders. Therefore, long-term video-EEG monitoring is recommended as well as a detailed patient history to identify possible clinical/subclinical epileptic seizures that require treatment.

Treatment of neurometabolic epilepsies: Overview and recent advances

The rarity and heterogeneity of neurometabolic diseases make it challenging to reach evidence-based principles for their specific treatments. Indeed, current treatments for many of these diseases remain symptomatic and supportive. However, an ongoing scientific and medical revolution has led to dramatic breakthroughs in molecular sciences and genetics, revealing precise pathophysiologic mechanisms. Accordingly, this has led to significant progress in the development of novel therapeutic approaches aimed at treating epilepsy resulting from these conditions, as well as their other manifestations. We overview recent notable treatment advancements, from vitamins, trace minerals, and diets to unique medications targeting the elemental pathophysiology at a molecular or cellular level, including enzyme replacement therapy, enzyme enhancing therapy, antisense oligonucleotide therapy, stem cell transplantation, and gene therapy.

Amyloid A amyloidosis on medullary sponge kidney in a 28-year-old male with gout: A case report and literature review

Amyloidosis is a large group of diseases that occur through misfolding of extracellular proteins that accumulate in tissues and organs. Gout is the most common inflammatory arthritis worldwide and starts with the crystallization of uric acid within the joints and soft tissues. Although gouty arthritis is accompanied by inflammation, AA amyloidosis is rarely seen in patients with gout. Here we present a case of AA amyloidosis on the medullary sponge kidney in a 28-year-old man with gout. Our case had been diagnosed with gout 3 years previously, and his older brother was also diagnosed with early-onset gout. As a result of the hyperuricemic nephropathy clinic and familial history, a whole gene sequence analysis was performed on the HPRT1 gene and UMOD gene, but no pathogenic changes were detected. Renal ultrasound revealed a bilateral medullary sponge kidney and amyloidosis was detected in the renal needle biopsy performed for the etiology of proteinuria. In our literature review, we found 16 cases in which gout was accompanied by AA amyloidosis. We present a 17th case and compare it with the other 16 cases.

Research progress of risk factors and early diagnostic biomarkers of gout-induced renal injury

Gout renal injury has an insidious onset, no obvious symptoms, and laboratory abnormalities in the early stages of the disease. The injury is not easily detected, and in many cases, the patients have entered the renal failure stage at the time of diagnosis. Therefore, the detection of gout renal injury–related risk factors and early diagnostic biomarkers of gout renal injury is essential for the prevention and early diagnosis of the disease. This article reviews the research progress in risk factors and early diagnostic biomarkers of gout renal injury.

Case report: Early-onset renal failure as presenting sign of Lesch-Nyhan disease in infancy

Lesch-Nyhan disease (LND) is a rare X-linked recessive disease caused by pathogenic mutations of the HPRT1 gene. The typical clinical manifestations include cerebral palsy, intellectual disability, dysarthria, self-injurious behavior, and gouty arthritis in children. This report describes a Chinese boy aged 2 months and 7 days with a significantly elevated uric acid concentration accompanied by renal dysfunction and, notably, brain imaging changes. Whole-exome sequencing revealed a hemizygous mutation of HPRT1 in nucleotide 508 from cytosine to thymine (c.508C > T), resulting in a nonsense mutation (p.R170X). The incidence of LND is extremely low in China, and hyperuricemia is a common clinical manifestation. Therefore, the possibility of LND should be considered in children with increased uric acid in infancy accompanied by brain imaging changes or neurological dysfunction. Moreover, genetic testing is needed to provide adequate genetic counseling to the family, and should be conducted as early as possible in such children to avoid misdiagnosis or delayed diagnosis.

Chronic kidney disease and neurological disorders: are uraemic toxins the missing piece of the puzzle?

Chronic kidney disease (CKD) perturbs the crosstalk with others organs, with the interaction between the kidneys and the heart having been studied most intensively. However, a growing body of data indicates that there is an association between kidney dysfunction and disorders of the central nervous system. In epidemiological studies, CKD is associated with a high prevalence of neurological complications, such as cerebrovascular disorders, movement disorders, cognitive impairment and depression. Along with traditional cardiovascular risk factors (such as diabetes, inflammation, hypertension and dyslipidaemia), non-traditional risk factors related to kidney damage (such as uraemic toxins) may predispose patients with CKD to neurological disorders. There is increasing evidence to show that uraemic toxins, for example indoxyl sulphate, have a neurotoxic effect. A better understanding of factors responsible for the elevated prevalence of neurological disorders among patients with CKD might facilitate the development of novel treatments. Here, we review (i) the potential clinical impact of CKD on cerebrovascular and neurological complications, (ii) the mechanisms underlying the uraemic toxins' putative action (based on pre-clinical and clinical research) and (iii) the potential impact of these findings on patient care.

Connexin and gap junctions: perspectives from biology to nanotechnology based therapeutics

The concept of gap junctions and their role in intercellular communication has been known for around 50 years. Considerable progress has been made in understanding the fundamental biology of connexins in mediating gap junction intercellular communication (GJIC) and their role in various cellular processes including pathological conditions. However, this understanding has not led to development of advanced therapeutics utilizing GJIC. Inadequacies in strategies that target specific connexin protein in the affected tissue, with minimal or no collateral damage, are the primary reason for the lack of development of efficient therapeutic models. Herein, nanotechnology has a role to play, giving plenty of scope to circumvent these problems and develop more efficient connexin based therapeutics. AsODN, antisense oligodeoxynucleotides; BMPs, bone morphogenetic proteins; BMSCs, bone marrow stem cells; BG, bioglass; Cx, Connexin; CxRE, connexin-responsive elements; CoCr NPs, cobalt-chromium nanoparticles; cGAMP, cyclic guanosine monophosphate-adenosine monophosphate; cAMP, cyclic adenosine monophosphate; ERK1/2, extracellular signal-regulated kinase 1/2; EMT, epithelial-mesenchymal transition; EPA, eicosapentaenoic acids; FGFR1, fibroblast growth factor receptor 1; FRAP, fluorescence recovery after photobleaching; 5-FU, 5-fluorouracil; GJ, gap junction; GJIC, gap junctional intercellular communication; HGPRTase, hypoxanthine phosphoribosyltransferase; HSV-TK, herpes virus thymidine kinase; HSA, human serum albumin; HA, hyaluronic acid; HDAC, histone deacetylase; IRI, ischemia reperfusion injury; IL-6, interleukin-6; IL-8, interleukin-8; IONPs, iron-oxide nanoparticles; JNK, c-Jun N-terminal kinase; LAMP, local activation of molecular fluorescent probe; MSCs, mesenchymal stem cells; MMP, matrix metalloproteinase; MI, myocardial infarction; MAPK, mitogen-activated protein kinase; NF-κB, nuclear factor kappa B; NO, nitric oxide; PKC, protein kinase C; QDs, quantum dots; ROI, region of interest; RGO, reduced graphene oxide; siRNA, small interfering RNA; TGF-β1, transforming growth factor-β1; TNF-α, tumor necrosis factor-α; UCN, upconversion nanoparticles; VEGF, vascular endothelial growth factor. In this review, we discuss briefly the role of connexins and gap junctions in various physiological and pathological processes, with special emphasis on cancer. We further discuss the application of nanotechnology and tissue engineering in developing treatments for various connexin based disorders.

Urate Transporters in the Kidney: What Clinicians Need to Know

Urate is produced in the liver by the degradation of purines from the diet and nucleotide turnover and excreted by the kidney and gut. The kidney is the major route of urate removal and has a pivotal role in the regulation of urate homeostasis. Approximately 10% of the glomerular filtered urate is excreted in the urine, and the remainder is reabsorbed by the proximal tubule. However, the transport of urate in the proximal tubule is bidirectional: reabsorption and secretion. Thus, an increase in reabsorption or a decrease in secretion may induce hyperuricemia. In contrast, a decrease in reabsorption or an increase in secretion may result in hyperuricosuria. In the proximal tubule, urate reabsorption is mainly mediated by apical URAT1 (SLC22A12) and basolateral GLUT9 (SLC2A9) transporter. OAT4 (SLC22A11) also acts in urate reabsorption in the apical membrane, and its polymorphism is associated with the risk of hyperuricemia. Renal hypouricemia is caused by SLC22A12 or SLC2A9 loss-of-function mutations, and it may be complicated by exercise-induced acute kidney injury. URAT1 and GLUT9 are also drug targets for uricosuric agents. Sodium-glucose cotransporter inhibitors may induce hyperuricosuria by inhibiting GLUT9b located in the apical plasma membrane. Urate secretion is mediated by basolateral OAT1 (SLC22A6) and OAT3 (SLC22A8) and apical ATP-binding cassette super-family G member 2 (ABCG2), NPT1 (SLC17A1), and NPT4 (SLC17A3) transporter in the proximal tubule. NPT1 and NPT4 may be key players in renal urate secretion in humans, and deletion of SLC22A6 and SLC22A8 in mice leads to decreased urate excretion. Dysfunctional variants of ABCG2 inhibit urate secretion from the gut and kidney and may cause gout. In summary, the net result of urate transport in the proximal tubule is determined by the dominance of transporters between reabsorption (URAT1, OAT4, and GLUT9) and secretion (ABCG2, NPT1, NPT4, OAT1, and OAT3).

Lesch-Nyhan disease causes impaired energy metabolism and reduced developmental potential in midbrain dopaminergic cells

Mutations in HPRT1, a gene encoding a rate-limiting enzyme for purine salvage, cause Lesch-Nyhan disease which is characterized by self-injury and motor impairments. We leveraged stem cell and genetic engineering technologies to model the disease in isogenic and patient-derived forebrain and midbrain cell types. Dopaminergic progenitor cells deficient in HPRT showed decreased intensity of all developmental cell-fate markers measured. Metabolic analyses revealed significant loss of all purine derivatives, except hypoxanthine, and impaired glycolysis and oxidative phosphorylation. real-time glucose tracing demonstrated increased shunting to the pentose phosphate pathway for de novo purine synthesis at the expense of ATP production. Purine depletion in dopaminergic progenitor cells resulted in loss of RHEB, impairing mTORC1 activation. These data demonstrate dopaminergic-specific effects of purine salvage deficiency and unexpectedly reveal that dopaminergic progenitor cells are programmed to a high-energy state prior to higher energy demands of terminally differentiated cells.

The Influence of Serum Uric Acid Level on Alzheimer's Disease: A Narrative Review

As a powerful antioxidant in the human body, uric acid (UA) has been the subject of increasing research that focused on its influence on Alzheimer's disease (AD) in recent years. The latest literature was gathered to describe the influence of serum uric acid (SUA) level on the onset and progression of AD and to analyze the possibility that SUA is a biomarker of Alzheimer's disease. A large number of existing studies suggested that the SUA level was lower or tended to decrease in patients with AD, and increased SUA level may have a protective effect in AD, which could reduce the risk of onset and slowing the course of the disease. However, some Mendelian randomization analyses suggested that genetically determined uric acid was not associated with AD risk. Existing research results are contradictory due to the high inconsistency of the studies, the selection of subjects, and other factors. UA also showed a strong association with cognitive function, and there appeared to be a gender-selective neuroprotective action. Due to its potent antioxidant properties, the low uric acid level may contribute to oxidative stress to accelerate disease progression. But some preclinical data showed a possibility that in some special cases, UA had a prooxidant properties. The possibility was raised in the discussion of the underlying mechanism that both the low uric acid level and the rapidly progressive course of the disease were the consequence of malnutrition. This paper reviews recent advances in the study of SUA and AD which offers the possibility of new biomarker, new prevention, and treatment strategies for Alzheimer's disease.

Inborn Errors of Metabolism Associated With Autism Spectrum Disorders: Approaches to Intervention

Increasing evidence suggests that the autism spectrum disorder (ASD) may be associated with inborn errors of metabolism, such as disorders of amino acid metabolism and transport [phenylketonuria, homocystinuria, S-adenosylhomocysteine hydrolase deficiency, branched-chain α-keto acid dehydrogenase kinase deficiency, urea cycle disorders (UCD), Hartnup disease], organic acidurias (propionic aciduria, L-2 hydroxyglutaric aciduria), cholesterol biosynthesis defects (Smith-Lemli-Opitz syndrome), mitochondrial disorders (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes-MELAS syndrome), neurotransmitter disorders (succinic semialdehyde dehydrogenase deficiency), disorders of purine metabolism [adenylosuccinate lyase (ADSL) deficiency, Lesch-Nyhan syndrome], cerebral creatine deficiency syndromes (CCDSs), disorders of folate transport and metabolism (cerebral folate deficiency, methylenetetrahydrofolate reductase deficiency), lysosomal storage disorders [Sanfilippo syndrome, neuronal ceroid lipofuscinoses (NCL), Niemann-Pick disease type C], cerebrotendinous xanthomatosis (CTX), disorders of copper metabolism (Wilson disease), disorders of haem biosynthesis [acute intermittent porphyria (AIP)] and brain iron accumulation diseases. In this review, we briefly describe etiology, clinical presentation, and therapeutic principles, if they exist, for these conditions. Additionally, we suggest the primary and elective laboratory work-up for their successful early diagnosis.

Enzyme Replacement Therapy for Genetic Disorders Associated with Enzyme Deficiency

Mutations in human genes might lead to loss of functional proteins, causing diseases. Among these genetic disorders, a large class is associated with the deficiency in metabolic enzymes, resulting in both an increase in the concentration of substrates and a loss in the metabolites produced by the catalyzed reactions. The identification of therapeutic actions based on small molecules represents a challenge to medicinal chemists because the target is missing. Alternative approaches are biology-based, ranging from gene and stem cell therapy, CRISPR/Cas9 technology, distinct types of RNAs, and enzyme replacement therapy (ERT). This review will focus on the latter approach that since the 1990s has been successfully applied to cure many rare diseases, most of them being lysosomal storage diseases or metabolic diseases. So far, a dozen enzymes have been approved by FDA/EMA for lysosome storage disorders and only a few for metabolic diseases. Enzymes for replacement therapy are mainly produced in mammalian cells and some in plant cells and yeasts and are further processed to obtain active, highly bioavailable, less degradable products. Issues still under investigation for the increase in ERT efficacy are the optimization of enzymes interaction with cell membrane and internalization, the reduction in immunogenicity, and the overcoming of blood-brain barrier limitations when neuronal cells need to be targeted. Overall, ERT has demonstrated its efficacy and safety in the treatment of many genetic rare diseases, both saving newborn lives and improving patients' life quality, and represents a very successful example of targeted biologics.

Oxidopamine and oxidative stress: Recent advances in experimental physiology and pharmacology

Oxidopamine (6-hydroxydopamine, 6-OHDA) is a toxin commonly used for the creation of experimental animal models of Parkinson's disease, attention-deficit hyperactivity disorder, and Lesch-Nyhan syndrome. Its exact mechanism of action is not completely understood, although there are many indications that it is related to the generation of reactive oxygen species (ROS), primarily in dopaminergic neurons. In certain experimental conditions, oxidopamine may also cause programmed cell death via various signaling pathways. Oxidopamine may also have a significant impact on chromatin structure and nuclear structural organization in some cells. Today, many researchers use oxidopamine-associated oxidative damage to evaluate different antioxidant-based pharmacologically active compounds as drug candidates for various neurological and non-neurological diseases. Additional research is needed to clarify the exact biochemical pathways associated with oxidopamine toxicity, related ROS generation and apoptosis. In this short review, we focus on the recent research in experimental physiology and pharmacology, related to the cellular and animal experimental models of oxidopamine - mediated toxicity.

Reduction of self-mutilating behavior and improved oromotor function in a patient with Lesch-Nyhan syndrome following botulinum toxin injection: A case report

Lesch-Nyhan syndrome is a genetic metabolic disorder often involving dystonia and self-mutilating behavior. This case report describes a 13-year-old boy with Lesch-Nyhan syndrome and self-mutilating behavior who received botulinum toxin injections to his bilateral masseter muscles after failing multiple other treatments. Following injections, the patient had reduction in self-biting, along with improvements in speech, mastication and feeding observed in speech therapy. Botulinum toxin injections to the masseters may help to improve oromotor function and reduce self-mutilating behaviors in children with Lesch-Nyhan syndrome who have failed more conservative treatments, providing opportunity for improved functional status and patient safety. Further investigation is indicated to establish optimal dosing. Additionally, the mechanism for the reduction of self-mutilating behavior is unclear and justifies additional investigation.

Elevated salivary uric acid levels among adolescents with eating disorders

OBJECTIVE

Uric acid (UA) is increasingly recognized as having important physiological roles and associated with several peripheral and central pathophysiological outcomes, and might play a role in eating disorders (ED) pathogenesis. We investigated whether UA levels are altered among adolescents with ED.

METHODS

Morning salivary UA concentrations were compared between adolescents referred to treatment at the Herman Dana Center receiving a DSM-V diagnosis of an ED and matched healthy controls.

RESULTS

Salivary UA was significantly elevated among ED compared with control values (ED mean 3.9 ± 1.2 mg/dl, control mean 2.9 ± 1.9 mg/dl, t = - 3.13 df = 81, p = 0.003).

DISCUSSION

Salivary UA is elevated among adolescents with ED. Further studies are required to replicate and extend this finding and evaluate its generalizability as a state or trait marker as regards ED subtypes, other body fluids (plasma and cerebrospinal fluid), and recovery or premorbid stages, as well as its putative mechanistic relevance to ED.

LEVEL OF EVIDENCE

Level III, case-control analytic study.

Deep Brain Stimulation of the Internal Pallidum in Lesch-Nyhan Syndrome: Clinical Outcomes and Connectivity Analysis

BACKGROUND

Lesch-Nyhan syndrome (LNS) is a rare genetic disorder characterized by a deficiency of hypoxanthine-guanine phosphoribosyltransferase enzyme. It manifests during infancy with compulsive self-mutilation behavior associated with disabling generalized dystonia and dyskinesia. Clinical management of these patients poses an enormous challenge for medical teams and carers.

OBJECTIVES

We report our experience with bilateral deep brain stimulation (DBS) of the globus pallidus internus (GPi) in the management of this complex disorder.

MATERIALS AND METHODS

Preoperative and postoperative functional assessment data prospectively collected by a multidisciplinary pediatric complex motor disorders team, including imaging, neuropsychology, and neurophysiology evaluations were analyzed with regards to motor and behavioral control, goal achievement, and patient and caregivers' expectations.

RESULTS

Four male patients (mean age 13 years) underwent DBS implantation between 2011 and 2018. Three patients received double bilateral DBS electrodes within the posteroventral GPi and the anteromedial GPi, whereas one patient had bilateral electrodes placed in the posteroventral GPi only. Median follow-up was 47.5 months (range 22-98 months). Functional improvement was observed in all patients and discussed in relation to previous reports. Analysis of structural connectivity revealed significant correlation between the involvement of specific cortical regions and clinical outcome.

CONCLUSION

Combined bilateral stimulation of the anteromedial and posteroventral GPi may be considered as an option for managing refractory dystonia and self-harm behavior in LNS patients. A multidisciplinary team-based approach is essential for patient selection and management, to support children and families, to achieve functional improvement and alleviate the overall disease burden for patients and caregivers.

Animal Model Contributions to Congenital Metabolic Disease

Genetic model systems allow researchers to probe and decipher aspects of human disease, and animal models of disease are frequently specifically engineered and have been identified serendipitously as well. Animal models are useful for probing the etiology and pathophysiology of disease and are critical for effective discovery and development of novel therapeutics for rare diseases. Here we review the impact of animal model organism research in three examples of congenital metabolic disorders to highlight distinct advantages of model system research. First, we discuss phenylketonuria research where a wide variety of research fields and models came together to make impressive progress and where a nearly ideal mouse model has been central to therapeutic advancements. Second, we review advancements in Lesch-Nyhan syndrome research to illustrate the role of models that do not perfectly recapitulate human disease as well as the need for multiple models of the same disease to fully investigate human disease aspects. Finally, we highlight research on the GM2 gangliosidoses Tay-Sachs and Sandhoff disease to illustrate the important role of both engineered traditional laboratory animal models and serendipitously identified atypical models in congenital metabolic disorder research. We close with perspectives for the future for animal model research in congenital metabolic disorders.

New personalized genetic mouse model of Lesch-Nyhan syndrome for pharmacology and gene therapy

Introduction: Lesch-Nyhan syndrome is a clinical and laboratory disorder caused by X-linked disruption of the purine metabolism. The deletion in the HPRT1 gene leads to the disappearance of valine in the eighth position of the protein amino acid sequence. The disease occurs in males and is accompanied by an excess of uric acid, urate nephropathy and neurologic impairment.

Objective of the Study: Generation of the new personalized genetic mouse model of Lesch-Nyhan syndrome for preclinical study of new approaches to the pharmacological and gene therapy

Materials and Methods: For genomic editing, the sequence was synthesized the sequence of the matrix GACCGGTCCCGTCATGCCGACACGCAGTCCCAGCGTGGTGAGCCAAGGGGACTCCAGCAGAGCCCCACAG was synthesized. For the cultivation of viable mouse embryos after microinjection, KSOM media was used. Amplification and sequencing was performed by the standard methods.

Results: A boy with not previously described hemizygous variant in the HPRT1 gene, was observed in our clinic. The mutation was the deletion of 8Val in the first exon of the HPRT1 gene. To introduce this mutation, we used the CRISPR-Cas9 genomic editing system. The genetic construct for microinjections included a mixture of the vector for the expression of Cas9 and sgRNA (px330), as well as the matrix for homologous recombination (ssODN), in a ratio of 1 part Cas9 to 3 parts of the ssODN matrix. Four of the 12 obtained animals were mosaic transgenes. One of 4 mice mated with a male from the hybrid strain CBA x C57BL/6, and descendants of F2 have already been received from this mating.

Discussion: During the creation of HPRT1 genetically modified mice, we encountered certain difficulties. First, from 615 transplanted embryos, only 12 were able to complete full embryonic development. 9 recipients we observed abortions in the later stages. These data may indicate possible violations of embryonic development in animals carrying a mutant copy of the HPRT1 gene.

Conclusion: In the current study, we present the results of the generation of a genetically modified mouse strain carrying a deletion in the HPRT1 gene. These mice can be effectively used for the preclinical testing of new drugs aimed at the treatment of Lesch-Nyhan syndrome.

Cancer Connectors: Connexins, Gap Junctions, and Communication

Despite concerted clinical and research efforts, cancer is a leading cause of death worldwide. Surgery, radiation, and chemotherapy have remained the most common standard-of-care strategies against cancer for decades. However, the side effects of these therapies demonstrate the need to investigate adjuvant novel treatment modalities that minimize the harm caused to healthy cells and tissues. Normal and cancerous cells require communication amongst themselves and with their surroundings to proliferate and drive tumor growth. It is vital to understand how intercellular and external communication impacts tumor cell malignancy. To survive and grow, tumor cells, and their normal counterparts utilize cell junction molecules including gap junctions (GJs), tight junctions, and adherens junctions to provide contact points between neighboring cells and the extracellular matrix. GJs are specialized structures composed of a family of connexin proteins that allow the free diffusion of small molecules and ions directly from the cytoplasm of adjacent cells, without encountering the extracellular milieu, which enables rapid, and coordinated cellular responses to internal and external stimuli. Importantly, connexins perform three main cellular functions. They enable direct gap junction intercellular communication (GJIC) between cells, form hemichannels to allow cell communication with the extracellular environment, and serve as a site for protein-protein interactions to regulate signaling pathways. Connexins themselves have been found to promote tumor cell growth and invasiveness, contributing to the overall tumorigenicity and have emerged as attractive anti-tumor targets due to their functional diversity. However, connexins can also serve as tumor suppressors, and therefore, a complete understanding of the roles of the connexins and GJs in physiological and pathophysiological conditions is needed before connexin targeting strategies are applied. Here, we discuss how the three aspects of connexin function, namely GJIC, hemichannel formation, and connexin-protein interactions, function in normal cells, and contribute to tumor cell growth, proliferation, and death. Finally, we discuss the current state of anti-connexin therapies and speculate which role may be most amenable for the development of targeting strategies.

[Genetic and biochemical features of the monogenic hereditary urolithiasis]

Urolithiasis is a common urological problem. In most cases, this multifactorial pathology develops due to the combination of inherited low-penetrance gene variants and environment factors such as urinary tract infections and unbalanced diet. However, some cases are monogenic. These hereditary forms of urolithiasis manifest in childhood, and are characterized by multiple, bilateral and recurrent kidney stones and progress to chronic renal failure relatively early. Due to widening acceptance of exome and gene panel sequencing, substantially larger percentages of urolithiasis cases are now attributed to hereditary causes, up to 20% among patients of 18 years old or younger. Here we review genetic and biochemical mechanisms of urolithiasis, with an emphasis on its hereditary forms, including fermentopathies (primary hyperoxaluria, adenine phosphorobosyltransferase deficiency, phosphoribosyl-pyrophosphate-synthetase deficiency, xanthinuria, Lesch-Nihan syndrome) and these caused by membrane transport alterations (Dent's disease, familial hypomagnesia with hypercalciuria and nephrocalcinosis, hypophosphatemic urolithiasis, distal tubular acidosis, cystinuria, Bartter's syndrome). We suggest a comprehensive gene panel for NGS diagnostics of the hereditary urolithiasis. It is expected that accurate and timely diagnosis of hereditary forms of urolithiasis would enable the counselling of the carriers in affected families, and ensure personalized management of the patients with these conditions.

Uric Acid and Cognitive Function in Older Individuals

Hyperuricemia has been recognized as an independent cardiovascular risk factor in epidemiological studies. However, uric acid can also exert beneficial functions due to its antioxidant properties, which may be particularly relevant in the context of neurodegenerative diseases. In this paper, we critically revise the evidence on the relationship between serum uric acid levels and cognitive function in older individuals, focusing on the etiology of cognitive impairment (Alzheimer’s disease, Parkinson’s dementia, and vascular dementia) and on the interactive connections between uric acid, dementia, and diet. Despite high heterogeneity in the existing studies, due to different characteristics of studied populations and methods of cognitive dysfunction assessment, we conclude that serum uric acid may modulate cognitive function in a different way according to the etiology of dementia. Current studies indeed demonstrate that uric acid may exert neuroprotective actions in Alzheimer’s disease and Parkinson’s dementia, with hypouricemia representing a risk factor for a quicker disease progression and a possible marker of malnutrition. Conversely, high serum uric acid may negatively influence the disease course in vascular dementia. Further studies are needed to clarify the physio-pathological role of uric acid in different dementia types, and its clinical-prognostic significance.

The Role of Xist in X-Chromosome Dosage Compensation

In each somatic cell of a female mammal one X chromosome is transcriptionally silenced via X-chromosome inactivation (XCI), initiating early in development. Although XCI events are conserved in mouse and human postimplantation development, regulation of X-chromosome dosage in preimplantation development occurs differently. In preimplantation development, mouse embryos undergo imprinted form of XCI, yet humans lack imprinted XCI and instead regulate gene expression of both X chromosomes by dampening transcription. The long non-coding RNA Xist/XIST is expressed in mouse and human preimplantation and postimplantation development to orchestrate XCI, but its role in dampening is unclear. In this review, we discuss recent advances in our understanding of the role of Xist in X chromosome dosage compensation in mouse and human.

Lesch-Nyhan syndrome and its variants: examining the behavioral and neurocognitive phenotype

PURPOSE OF REVIEW

Lesch-Nyhan Syndrome (LNS) is a metabolic disorder involving mutations in the HGPRT1 gene that result in hyperuricemia, intellectual disability, a dystonic movement disorder, and compulsive self-injury with self-mutilation. The aim of this review is to summarize recent research that documents the extended behavioral, neurologic, and neurocognitive phenotype in classic LNS, to describe milder variants of HGprt deficiency that do not self-injure and have less severe neurological and cognitive deficits, and to provide an update on treatment for associated psychiatric and behavioral disorders.

RECENT FINDINGS

Psychiatric management utilizes combined behavioral and pharmacological treatment in conjunction with protective equipment and dental management to avert self-injury. Pharmacological management focuses on stabilization of mood and anxiety management. S-adenosylmethionine (SAMe), a physiological intermediate in methylation and transsulfuration, has shown beneficial effects in carefully selected patients who can tolerate the drug. Deep brain stimulation is shown in several case reports and series to reduce or eliminate self-injury and aggression, and in some cases, modify dystonia.

SUMMARY

This review highlights progress in our understanding of the behavioral and neurocognitive phenotype of Lesch-Nyhan syndrome (HGprt deficiency) and its variants, describes psychiatric and behavioral management, and discusses prospects for new therapies.

Leveraging Rational Protein Engineering to Improve mRNA Therapeutics

Messenger RNA (mRNA) is a promising new class of therapeutics that has potential for treatment of diseases in fields such as immunology, oncology, vaccines, and inborn errors of metabolism. mRNA therapy has several advantages over DNA-based gene therapy, including the lack of the need for nuclear import and transcription, as well as limited possibility of genomic integration. One drawback of mRNA therapy, especially in cases such as metabolic disorders where repeated dosing will be necessary, is the relatively short in vivo half-life of mRNA (∼6-12 h). We hypothesize that protein engineering designed to improve translation, yielding longer-lasting protein, or modifications that would increase enzymatic activity would be helpful in alleviating this issue. In this study, we present two examples where sequence engineering improved the expression and duration, as well as enzymatic activity of target proteins in vitro. We then confirmed these findings in wild-type mice. This work shows that rational engineering of proteins can lead to improved therapies in vivo.

[Rare metabolic disorders and urolithiasis]

Numerous metabolic anomalies, which often have no direct pathological relevance when considered individually, are found in all people. In most patients with urinary tract stones, it can be assumed that a specific combination or interaction of these anomalies occurs, thus, resulting in stone formation, but only after individual exogenous risk factors are triggered. Lithogenesis is the result of a cascade of different "events" that are temporally close to one another, but sometimes these events interact strong enough that significant stone growth occurs. Chronic metabolic disorders usually lead to permanently altered urine compositions. The occurrence of physiological urine constituents in nonnormal concentration ratios and/or the nonphysiological excretion of metabolic products can significantly increase the lithogenicity of urine, so that urolithiasis can manifest itself as a clinical symptom. In cases of urolithiasis of unknown origin, a potentially hidden rare metabolic anomaly should always be considered. In addition, if a patient has a known metabolic disease, then this should always be taken into account as a risk factor for stone formation and attempts should be taken to clarify its influence on urine composition. This also applies to the efficacy of a therapy. A distinct link between a metabolic disease and stone formation is generally rare and will likely remain so despite significant advances regarding differential diagnosis and etiopathology. This article focuses on very rare metabolic causes and/or genetic syndromes which may be associated with urolithiasis. Patients receiving symptomatic stone treatment should receive life-long follow-up care from a urologist because reducing the recurrence rate helps to improve the quality of life of the patients.

Oral Hemorrhage in a 3-year-old Boy Caused by Self-Mutilating Behavior

A 3-year-old boy referred for persistent tongue bleeding was diagnosed with a rare self-mutilating disease that had also affected his lip and fingers. He underwent multiple odontectomy and partial glossectomy and continues to undergo behavior therapy and on-demand splints and restraints. He has stopped self-biting and has gained appetite and weight. Lesch-Nyhan Syndrome can cause significant morbidity including self-inflicted oral hemorrhage and emergent measures are not easily decided. The long-term management of its neurobehavioral symptoms is problematic and multidisciplinary, and health providers remain challenged to find the best treatment, prolong lifespan and improve quality of life within their respective contexts.