A novel Pah-exon1 deleted murine model of phenylalanine hydroxylase (PAH) deficiency.
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ABSTRACT:
SUBMITTER: Richards DY
PROVIDER: S-EPMC8173763 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Aromatic amino acid hydroxylases (AAAH) typically use tetrahydrobiopterin (H(4)B) as the cofactor. The protozoan parasite Leishmania major requires biopterin for growth and expresses strong salvage and regeneration systems to maintain H(4)B levels. Here we explored the consequences of genetic manipulation of the sole L. major phenylalanine hydroxylase (PAH) to explore whether it could account for the Leishmania H(4)B requirement. L. major PAH resembles AAAHs of other organisms, bearing eukaryotic-type domain organization, and conservation of key catalytic residues including those implicated in pteridine binding. A pah(-) null mutant and an episomal complemented overexpressing derivative (pah-/+PAH) were readily obtained, and metabolic labeling studies established that PAH was required to hydroxylate Phe to Tyr. Neither WT nor overexpressing lines were able to hydroxylate radiolabeled tyrosine or tryptophan, nor to synthesize catecholamines. WT but not pah(-) parasites showed reactivity with an antibody to melanin when grown with l-3,4-dihydroxyphenylalanine (L-DOPA), although the reactive product is unlikely to be melanin sensu strictu. WT was auxotrophic for Phe, Trp and Tyr, suggesting that PAH activity was insufficient to meet normal Tyr requirements. However, pah(-) showed an increased sensitivity to Tyr deprivation, while the pah(-)/+PAH overexpressor showed increased survival and could be adapted to grow well without added Tyr. pah(-) showed no alterations in H(4)B-dependent differentiation, as established by in vitro metacyclogenesis, or survival in mouse or macrophage infections. Thus Leishmania PAH may mitigate but not alleviate Tyr auxotrophy, but plays no essential role in the steps of the parasite infectious cycle. These findings suggest PAH is unlikely to explain the Leishmania requirement for biopterin.
| S-EPMC2987234 | biostudies-literature
Project description:BACKGROUND:Phenylalanine hydroxylase (PAH) deficiency is one of 31 targeted inherited metabolic diseases (IMD) for the Canadian Inherited Metabolic Diseases Research Network (CIMDRN). Early diagnosis and initiation of treatment through newborn screening has gradually shifted treatment goals from the prevention of disabling complications to the optimization of long term outcomes. However, clinical evidence demonstrates that subtle suboptimal neurocognitive outcomes are present in the early and continuously diet-treated population with PAH deficiency. This may be attributed to variation in blood phenylalanine levels to outside treatment range and this, in turn, is possibly due to a combination of factors; disease severity, dietary noncompliance and differences in practice related to the management of PAH deficiency. One of CIMDRN's goals is to understand current practices in the diagnosis and management of PAH deficiency in the pediatric population, from the perspective of both health care providers and patients/families. OBJECTIVES:We investigated Canadian metabolic dietitians' perspectives on the nutritional management of children with PAH deficiency, awareness of recently published North American treatment and nutritional guidelines in relation to PAH deficiency, and nutritional care practices within and outside these guidelines. METHODS:We invited 33 dietitians to participate in a survey, to ascertain their use of recently published guidelines and their practices in relation to the nutritional care of pediatric patients with PAH deficiency. RESULTS:We received 19 responses (59% response rate). All participants reported awareness of published guidelines for managing PAH deficiency. To classify disease severity, 89% of dietitians reported using pre-treatment blood phenylalanine (Phe) levels, alone or in combination with other factors. 74% of dietitians reported using blood Phe levels ?360??mol/L (6?mg/dL) as the criterion for initiating a Phe-restricted diet. All respondents considered 120-360??mol/L (2-6?mg/dL) as the optimal treatment range for blood Phe in children 0-9?years old, but there was less agreement on blood Phe targets for older children. Most dietitians reported similar approaches to diet assessment and counseling: monitoring growth trends, use of 3?day diet records for intake analysis, individualization of diet goals, counseling patients to count grams of dietary natural protein or milligrams of dietary Phe, and monitoring blood Phe, tyrosine and ferritin. CONCLUSION:While Canadian dietitians' practices in managing pediatric PAH deficiency are generally aligned with those of the American College of Medical Genetics and Genomics (ACMG), and with the associated treatment and nutritional guidelines from Genetic Metabolic Dietitians International (GMDI), variation in many aspects of care reflects ongoing uncertainty and a need for robust evidence.
| S-EPMC6323774 | biostudies-literature
Project description:Phenylalanine hydroxylase (PAH) regulates phenylalanine (Phe) levels in mammals to prevent neurotoxicity resulting from high Phe concentrations as observed in genetic disorders leading to hyperphenylalaninemia and phenylketonuria. PAH senses elevated Phe concentrations by transient allosteric Phe binding to a protein-protein interface between ACT domains of different subunits in a PAH tetramer. This interface is present in an activated PAH (A-PAH) tetramer and absent in a resting-state PAH (RS-PAH) tetramer. To investigate this allosteric sensing mechanism, here we used the GROMACS molecular dynamics simulation suite on the Folding@home computing platform to perform extensive molecular simulations and Markov state model (MSM) analysis of Phe binding to ACT domain dimers. These simulations strongly implicated a conformational selection mechanism for Phe association with ACT domain dimers and revealed protein motions that act as a gating mechanism for Phe binding. The MSMs also illuminate a highly mobile hairpin loop, consistent with experimental findings also presented here that the PAH variant L72W does not shift the PAH structural equilibrium toward the activated state. Finally, simulations of ACT domain monomers are presented, in which spontaneous transitions between resting-state and activated conformations are observed, also consistent with a mechanism of conformational selection. These mechanistic details provide detailed insight into the regulation of PAH activation and provide testable hypotheses for the development of new allosteric effectors to correct structural and functional defects in PAH.
| S-EPMC6314134 | biostudies-literature
Project description:The effectiveness of a phenylalanine-restricted diet to improve the outcome of individuals with phenylalanine hydroxylase deficiency (OMIM no. 261600) has been recognized since the first patients were treated 60 years ago. However, the treatment regime is complex, costly, and often difficult to maintain for the long term. Improvements and refinements in the diet for phenylalanine hydroxylase deficiency have been made over the years, and adjunctive therapies have proven to be successful for certain patients. Yet evidence-based guidelines for managing phenylalanine hydroxylase deficiency, optimizing outcomes, and addressing all available therapies are lacking. Thus, recommendations for nutrition management were developed using evidence from peer-reviewed publications, gray literature, and consensus surveys. The areas investigated included choice of appropriate medical foods, integration of adjunctive therapies, treatment during pregnancy, monitoring of nutritional and clinical markers, prevention of nutrient deficiencies, providing of access to care, and compliance strategies. This process has not only provided assessment and refinement of current nutrition management and monitoring recommendations but also charted a direction for future studies. This document serves as a companion to the concurrently published American College of Medical Genetics and Genomics guideline for the medical treatment of phenylalanine hydroxylase deficiency.
| S-EPMC3918542 | biostudies-literature
Project description:In phenylalanine hydroxylase (PAH) deficiency, an easily feasible method to access the progression of neurodegeneration is warranted to contribute to current discussions on treatment indications and targets. The objective of the present study was to investigate whether optical coherence tomography (OCT) measures as markers of neurodegeneration differ between patients with PAH deficiency and healthy controls (HCs) according to phenotype and metabolic control. In this single-center cross-sectional study, 92 patients with different phenotypes of PAH deficiency [PAH deficiency not requiring treatment, early treated phenylketonuria (ETPKU), and late-diagnosed phenylketonuria (PKU)] compared with 76 HCs were examined using spectral-domain OCT. Indices of phenylalanine elevation and variability were correlated with OCT parameters. Late-diagnosed PKU patients showed reduced peripapillary retinal nerve fiber layer (pRNFL) thickness and combined ganglion cell and inner plexiform layer (GCIPL) volume. Adult ETPKU patients were found to have lower GCIPL volume (p = 0.016), which correlated with the indices of phenylalanine control. In pediatric ETPKU patients with poor metabolic control, pRNFL was significantly reduced (p = 0.004). Patients with PAH deficiency not requiring treatment did not exhibit retinal degeneration. Inner nuclear layer (INL) was significantly increased in the pediatric ETPKU patients, driven by those with current poor metabolic control (p = 0.006). Our data provide evidence of retinal neuroaxonal degeneration and INL swelling, depending on the phenotype, current age, and metabolic control. These findings suggest that OCT is suitable to investigate neurodegeneration in PKU and we propose OCT as a sensitive, reliable, safe, low-burden, and low-cost examination for future multicenter studies.
| S-EPMC8703042 | biostudies-literature
Project description:BACKGROUND: Phenylalanine hydroxylase (PAH) is the enzyme that metabolizes phenylalanine, an essential amino acid required for catecholamine synthesis. Rare mutations in PAH are causal to phenylketonuria (PKU), an autosomal recessive disease characterized by neuropsychiatric symptoms including intellectual disability. We examined whether there is an association between common single nucleotide polymorphisms (SNPs) of PAH and memory performance in the Japanese population. METHODS: Subjects were 599 healthy adults (166 males and 433 females; mean age 43.8?±?15.5 years). The Wechsler Memory Scale-Revised (WMS-R) was administered to all participants to assess memory performance. Genotyping was performed for 6 selected tagging SNPs of PAH (rs1722387, rs3817446, rs1718301, rs2037639, rs10860936 and rs11111419). RESULTS: Analyses of covariance controlling for sex and education years, indicated a significant association between a SNP (rs2037639) and age-corrected verbal memory index of WMS-R (nominal p?=?0.0013) which remained significant after correction for multiple testing ( p?=?0.0013?<?0.0017?=?0.05/30tests). Individuals with the GG genotype showed a significantly lower mean verbal memory score, compared with those individuals carrying the AA/AG genotype (106.0?±?16.0 vs. 111.7?±?13.4; p?=?0.00099). A haplotype block containing two markers of rs2037639 and rs10860936 was associated with verbal memory index (permutation global p?=?0.0091). CONCLUSIONS: Our findings suggest that common genetic variations in PAH are associated with verbal memory in healthy adults. Unknown functional polymorphisms in PAH or those in other genes nearby might affect memory performance.
| S-EPMC3733818 | biostudies-literature
Project description:Phenylketonuria (PKU) is caused by autosomal recessive variants in phenylalanine hydroxylase (PAH), leading to systemic accumulation of L-phenylalanine (L-Phe) that may reach neurotoxic levels. A homozygous Pah-R261Q mouse, with a highly prevalent misfolding variant in humans, reveals the expected hepatic PAH activity decrease, systemic L-Phe increase, L-tyrosine and L-tryptophan decrease, and tetrahydrobiopterin-responsive hyperphenylalaninemia. Pah-R261Q mice also present unexpected traits, including altered lipid metabolism, reduction of liver tetrahydrobiopterin content, and a metabolic profile indicative of oxidative stress. Pah-R261Q hepatic tissue exhibits large ubiquitin-positive, amyloid-like oligomeric aggregates of mutant PAH that colocalize with selective autophagy markers. Together, these findings reveal that PKU, customarily considered a loss-of-function disorder, can also have toxic gain-of-function contribution from protein misfolding and aggregation. The proteostasis defect and concomitant oxidative stress may explain the prevalence of comorbid conditions in adult PKU patients, placing this mouse model in an advantageous position for the discovery of mutation-specific biomarkers and therapies.
| S-EPMC8024259 | biostudies-literature
Project description:In the Plain Community, there is an increased frequency of genetic disorders including phenylalanine hydroxylase (PAH) deficiency. Common pathogenic variants have been observed due to founder effect and closed community. This study obtained genotypes of 12 Plain individuals with PAH deficiency, identified through newborn screen or diagnosed by symptomatic presentation, who are receiving medical care at the University of Wisconsin metabolic clinic. Genotype and phenotypic data were evaluated to characterize genotype-phenotype correlations. Results can inform the need for confirmatory testing for the disorder and provide a better understanding of the biochemical phenotype, which may help with management.
| S-EPMC5857495 | biostudies-literature
Project description:Phenylalanine hydroxylase deficiency (PAHD), one of the genetic disorders resulting in hyperphenylalaninemia, has a complex phenotype with many variants and genotypes among different populations. Here, we describe the mutational and phenotypic spectrum of PAHD in a cohort of 420 patients from neonatal screening between 1999 and 2016. The observed phenotypes comprised 43.57% classic phenylketonuria, 33.10% mild PKU, and 23.33% mild hyperphenylalaninemia, with an overall PAHD incidence of 1 in 20,445. Genetic testing was performed for 209 patients and 72 variants including seven novel variants were identified. These included two synonymous and five pathogenic nonsynonymous variants (p.S36*, p.T186I, p.L255W, p.F302V and p.R413H). The most common variant among all patients was p.R243Q, followed by p.R241C, p.Y204C, p.R111* and c.442-1G > A. Variants p.R53H and p.F392I occurred only in MHP with 19.3% and 8.0% of the observed alleles respectively. The genotypes p.[R241C];[R243Q], p.[R243Q];[R243Q], and p.[Y204C];[R243Q] were abundant across all PAHD patients. The distributions of the null allele and the three defined genotypes, null/null, null/missense, and missense/missense, were significantly different between the cPKU and mPKU patients. However, no significant differences were found between mPKU and MHP patients, indicating that other modifier factors influence the phenotypic outcome in these patients. The data presented here will provide a valuable tool for improved genetic counseling and management of future cases of PAHD in China.
| S-EPMC6244417 | biostudies-literature
Project description:Because defects in the phenylalanine hydroxylase gene (PAH) cause phenylketonuria (PKU), PAH was studied for normal polymorphisms and linkage disequilibrium soon after the gene was cloned. Studies in the 1980s concentrated on European populations in which PKU was common and showed that haplotype-frequency variation exists between some regions of the world. In European populations, linkage disequilibrium generally was found not to exist between RFLPs at opposite ends of the gene but was found to exist among the RFLPs clustered at each end. We have now undertaken the first global survey of normal variation and disequilibrium across the PAH gene. Four well-mapped single-nucleotide polymorphisms (SNPs) spanning approximately 75 kb, two near each end of the gene, were selected to allow linkage disequilibrium across most of the gene to be examined. These SNPs were studied as PCR-RFLP markers in samples of, on average, 50 individuals for each of 29 populations, including, for the first time, multiple populations from Africa and from the Americas. All four sites are polymorphic in all 29 populations. Although all but 5 of the 16 possible haplotypes reach frequencies >5% somewhere in the world, no haplotype was seen in all populations. Overall linkage disequilibrium is highly significant in all populations, but disequilibrium between the opposite ends is significant only in Native American populations and in one African population. This study demonstrates that the physical extent of linkage disequilibrium can differ substantially among populations from different regions of the world, because of both ancient genetic drift in the ancestor common to a large regional group of modern populations and recent genetic drift affecting individual populations.
| S-EPMC1378054 | biostudies-other