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Manti F, Nardecchia F, De Leo S, Carducci C, Romani C, Palermo L, Angeloni A, Leuzzi V. Towards precision medicine for phenylketonuria: The effect of restoring a strict metabolic control in adult patients with early-treated phenylketonuria. Mol Genet Metab 2023; 140:107666. [PMID: 37549444 DOI: 10.1016/j.ymgme.2023.107666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Revised: 07/23/2023] [Accepted: 07/24/2023] [Indexed: 08/09/2023]
Abstract
BACKGROUND AND OBJECTIVE Neonatal screening and early treatment have changed the natural history of PKU, preventing severe neurological and intellectual disability. Nevertheless, the outcome of the disease in early-treated adult patients (ETPKU) is less than optimal, the predictive value of metabolic biomarkers is feeble, and the recommended levels of blood phenylalanine (Phe) for adulthood are controversial. A crucial question whose answer will improve our understanding and treatment of PKU is whether cognitive outcomes can be modulated by levels of Phe even in early-treated adults. To address this question, we carried out an interventional study in seven ETPKU women planning a pregnancy. METHODS They underwent an extensive neurocognitive assessment at baseline, and 3 and 6 months after having attained the blood Phe concentration recommended to prevent PKU fetopathy, but before pregnancy. RESULTS After 3 and 6 months with a stable blood Phe level of about 240 μmol/L, all participants experienced significant improvements in almost all neurocognitive domains and tasks. IQ also increased of 11 to 21 points from the last assessment before enrolment. This pattern remained strong and consistent after correction for multiple comparisons. CONCLUSION Our results indicate that a) strong cognitive improvement is possible even in adulthood and may be demonstrated by lowering Phe near normal levels; b) testing cognition under different metabolic conditions may unveil an individual vulnerability to Phe. These results pave the way for personalised treatment of the disease in adults with ETPKU.
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Affiliation(s)
- Filippo Manti
- Department of Human Neuroscience - Unit of Child Neurology and Psychiatry, Sapienza University of Rome, Rome, Italy
| | - Francesca Nardecchia
- Department of Human Neuroscience - Unit of Child Neurology and Psychiatry, Sapienza University of Rome, Rome, Italy
| | - Sabrina De Leo
- Department of Clinical Medicine, Azienda Ospedaliero Universitaria Policlinico Umberto I, Rome, Italy
| | - Claudia Carducci
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Cristina Romani
- School of Life and Health Sciences, Aston University, Birmingham, UK
| | - Liana Palermo
- Department of Medical and Surgical Sciences, Magna Graecia University of Catanzaro, Catanzaro, Italy
| | - Antonio Angeloni
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Vincenzo Leuzzi
- Department of Human Neuroscience - Unit of Child Neurology and Psychiatry, Sapienza University of Rome, Rome, Italy.
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Leuzzi V, Chiarotti F, Nardecchia F, van Vliet D, van Spronsen FJ. Predictability and inconsistencies of cognitive outcome in patients with phenylketonuria and personalised therapy: the challenge for the future guidelines. J Med Genet 2019; 57:145-150. [DOI: 10.1136/jmedgenet-2019-106278] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 07/06/2019] [Accepted: 08/11/2019] [Indexed: 11/04/2022]
Abstract
Phenylketonuria (PKU) is a prototypical model of a neurodevelopmental metabolic disease that follows a cascade of pathological events affecting brain maturation and functioning. Neonatal screening and early treatment have eradicated the classical PKU phenotype in patients with early and continuously treated phenylketonuria (ECTPKU). However, effort is required to optimise the treatment of the disease to minimise the risk of lifelong neurological, cognitive and behavioural impairment, and to solve issues on the variability in clinical outcome that are rather not understood and has yet hampered a more personalised approach to its treatment. The aim of the present review is to focus on the inconsistencies in the clinical outcome of adult patients with ECTPKU unexplained by the biochemical markers adopted for the monitoring of the disease to date. The interindividual variability of clinical outcome in late as well as in early treated patients under similar biochemical control suggests the existence of disease-independent determinants influencing the individual vulnerability to the neurotoxic effect of phenylalanine. This is further supported by the low predictive power of blood phenylalanine on the clinical outcome from the second decade of life onwards. In conclusion, individual vulnerability to the metabolic alterations of PKU contributes to the prognosis of PKU, also in patients with ECTPKU. The biological factors constitutive of this vulnerability are unknown (but have not been the object of many studies so far) and should be the target of further research as prerequisite for a personalised treatment aimed at avoiding burden and costs of overtreatment and clinical consequences and risks of undertreatment in patients with PKU.
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Bruinenberg VM, van der Goot E, van Vliet D, de Groot MJ, Mazzola PN, Heiner-Fokkema MR, van Faassen M, van Spronsen FJ, van der Zee EA. The Behavioral Consequence of Phenylketonuria in Mice Depends on the Genetic Background. Front Behav Neurosci 2016; 10:233. [PMID: 28066199 PMCID: PMC5167755 DOI: 10.3389/fnbeh.2016.00233] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Accepted: 11/28/2016] [Indexed: 12/31/2022] Open
Abstract
To unravel the role of gene mutations in the healthy and the diseased state, countless studies have tried to link genotype with phenotype. However, over the years, it became clear that the strain of mice can influence these results. Nevertheless, identical gene mutations in different strains are often still considered equals. An example of this, is the research done in phenylketonuria (PKU), an inheritable metabolic disorder. In this field, a PKU mouse model (either on a BTBR or C57Bl/6 background) is often used to examine underlying mechanisms of the disease and/or new treatment strategies. Both strains have a point mutation in the gene coding for the enzyme phenylalanine hydroxylase which causes toxic concentrations of the amino acid phenylalanine in blood and brain, as found in PKU patients. Although the mutation is identical and therefore assumed to equally affect physiology and behavior in both strains, no studies directly compared the two genetic backgrounds to test this assumption. Therefore, this study compared the BTBR and C57Bl/6 wild-type and PKU mice on PKU-relevant amino acid- and neurotransmitter-levels and at a behavioral level. The behavioral paradigms were selected from previous literature on the PKU mouse model and address four domains, namely (1) activity levels, (2) motor performance, (3) anxiety and/or depression-like behavior, and (4) learning and memory. The results of this study showed comparable biochemical changes in phenylalanine and neurotransmitter concentrations. In contrast, clear differences in behavioral outcome between the strains in all four above-mentioned domains were found, most notably in the learning and memory domain. The outcome in this domain seem to be primarily due to factors inherent to the genetic background of the mouse and much less by differences in PKU-specific biochemical parameters in blood and brain. The difference in behavioral outcome between PKU of both strains emphasizes that the consequence of the PAH mutation is influenced by other factors than Phe levels alone. Therefore, future research should consider these differences when choosing one of the genetic strains to investigate the pathophysiological mechanism underlying PKU-related behavior, especially when combined with new treatment strategies.
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Affiliation(s)
- Vibeke M Bruinenberg
- Molecular Neurobiology, Groningen Institute for Evolutionary Life Sciences, University of Groningen Groningen, Netherlands
| | - Els van der Goot
- Molecular Neurobiology, Groningen Institute for Evolutionary Life Sciences, University of Groningen Groningen, Netherlands
| | - Danique van Vliet
- Department of Pediatrics, Beatrix Children's Hospital, University Medical Center Groningen Groningen, Netherlands
| | - Martijn J de Groot
- Department of Pediatrics, Beatrix Children's Hospital, University Medical Center Groningen Groningen, Netherlands
| | - Priscila N Mazzola
- Molecular Neurobiology, Groningen Institute for Evolutionary Life Sciences, University of GroningenGroningen, Netherlands; Department of Pediatrics, Beatrix Children's Hospital, University Medical Center GroningenGroningen, Netherlands
| | | | - Martijn van Faassen
- Laboratory Medicine, University of Groningen, University Medical Center Groningen, Netherlands
| | - Francjan J van Spronsen
- Department of Pediatrics, Beatrix Children's Hospital, University Medical Center Groningen Groningen, Netherlands
| | - Eddy A van der Zee
- Molecular Neurobiology, Groningen Institute for Evolutionary Life Sciences, University of Groningen Groningen, Netherlands
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Abstract
Phenylketonuria (PKU) is an autosomal recessive disorder of phenylalanine (Phe) catabolism resulting from a deficiency of L-phenylalanine hydroxylase (PAH). An association between hyperphenylalaninaemia (HPA) and hypocholesterolaemia has been reported in children. However, controversy exists as to whether this is due to the low protein diet or to a disruption to cholesterol biosynthesis inherent to those with PKU. We investigated the relationship between blood Phe and plasma cholesterol in 41 apparently healthy adults with PKU (26 female, 15 male, age 18-57 years, median age 26 years) attending a PKU outpatient clinic at an adult tertiary care hospital. Of these patients, 33 (80%) were compliant with a Phe-restricted diet with amino acid supplementation, whereas eight (20%) were not. The PKU subjects had a mean body mass index (BMI) of 30.3 ± 1.8 kg/m; 72% were obese, 14% overweight, with only 14% having normal BMI. The mean blood Phe was 1194 ± 522 μmol/L with plasma total cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol and apolipoprotein (apo) B concentrations of 4.3 ± 0.8 mmol/L, 1.6 ± 0.8 mmol/L, 1.2 ± 0.3 mmol/L, 2.3 ± 0.8 mmol/L, and 0.83 ± 0.21 g/L, respectively. The mean LDL-cholesterol was 19% lower in PKU females than that of 8944 age-matched females from a community population (2.5 ± 0.8 mmol/L vs. 3.1 ± 0.9 mmol/L, p < 0.001). Similarly, the mean LDL-cholesterol was 32% lower in PKU males than 3786 age-matched males (2.1 ± 0.7 mmol/L vs. 3.1 ± 1.0 mmol/L, p < 0.0001). No correlations were observed between Phe and total cholesterol, LDL-cholesterol or apoB in the PKU cohort. Adults with PKU had low-normal cholesterol concentrations, with no correlation observed between Phe and cholesterol levels. Our findings support the concept that the HPA found in PKU, rather than an effect of a low-protein diet, leads to hypocholesterolaemia. Studies are required to determine whether this cholesterol-lowering effect confers cardioprotection.
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Camp KM, Parisi MA, Acosta PB, Berry GT, Bilder DA, Blau N, Bodamer OA, Brosco JP, Brown CS, Burlina AB, Burton BK, Chang CS, Coates PM, Cunningham AC, Dobrowolski SF, Ferguson JH, Franklin TD, Frazier DM, Grange DK, Greene CL, Groft SC, Harding CO, Howell RR, Huntington KL, Hyatt-Knorr HD, Jevaji IP, Levy HL, Lichter-Konecki U, Lindegren ML, Lloyd-Puryear MA, Matalon K, MacDonald A, McPheeters ML, Mitchell JJ, Mofidi S, Moseley KD, Mueller CM, Mulberg AE, Nerurkar LS, Ogata BN, Pariser AR, Prasad S, Pridjian G, Rasmussen SA, Reddy UM, Rohr FJ, Singh RH, Sirrs SM, Stremer SE, Tagle DA, Thompson SM, Urv TK, Utz JR, van Spronsen F, Vockley J, Waisbren SE, Weglicki LS, White DA, Whitley CB, Wilfond BS, Yannicelli S, Young JM. Phenylketonuria Scientific Review Conference: state of the science and future research needs. Mol Genet Metab 2014; 112:87-122. [PMID: 24667081 DOI: 10.1016/j.ymgme.2014.02.013] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 02/25/2014] [Accepted: 02/26/2014] [Indexed: 01/17/2023]
Abstract
New developments in the treatment and management of phenylketonuria (PKU) as well as advances in molecular testing have emerged since the National Institutes of Health 2000 PKU Consensus Statement was released. An NIH State-of-the-Science Conference was convened in 2012 to address new findings, particularly the use of the medication sapropterin to treat some individuals with PKU, and to develop a research agenda. Prior to the 2012 conference, five working groups of experts and public members met over a 1-year period. The working groups addressed the following: long-term outcomes and management across the lifespan; PKU and pregnancy; diet control and management; pharmacologic interventions; and molecular testing, new technologies, and epidemiologic considerations. In a parallel and independent activity, an Evidence-based Practice Center supported by the Agency for Healthcare Research and Quality conducted a systematic review of adjuvant treatments for PKU; its conclusions were presented at the conference. The conference included the findings of the working groups, panel discussions from industry and international perspectives, and presentations on topics such as emerging treatments for PKU, transitioning to adult care, and the U.S. Food and Drug Administration regulatory perspective. Over 85 experts participated in the conference through information gathering and/or as presenters during the conference, and they reached several important conclusions. The most serious neurological impairments in PKU are preventable with current dietary treatment approaches. However, a variety of more subtle physical, cognitive, and behavioral consequences of even well-controlled PKU are now recognized. The best outcomes in maternal PKU occur when blood phenylalanine (Phe) concentrations are maintained between 120 and 360 μmol/L before and during pregnancy. The dietary management treatment goal for individuals with PKU is a blood Phe concentration between 120 and 360 μmol/L. The use of genotype information in the newborn period may yield valuable insights about the severity of the condition for infants diagnosed before maximal Phe levels are achieved. While emerging and established genotype-phenotype correlations may transform our understanding of PKU, establishing correlations with intellectual outcomes is more challenging. Regarding the use of sapropterin in PKU, there are significant gaps in predicting response to treatment; at least half of those with PKU will have either minimal or no response. A coordinated approach to PKU treatment improves long-term outcomes for those with PKU and facilitates the conduct of research to improve diagnosis and treatment. New drugs that are safe, efficacious, and impact a larger proportion of individuals with PKU are needed. However, it is imperative that treatment guidelines and the decision processes for determining access to treatments be tied to a solid evidence base with rigorous standards for robust and consistent data collection. The process that preceded the PKU State-of-the-Science Conference, the conference itself, and the identification of a research agenda have facilitated the development of clinical practice guidelines by professional organizations and serve as a model for other inborn errors of metabolism.
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Affiliation(s)
- Kathryn M Camp
- Office of Dietary Supplements, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Melissa A Parisi
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | | | - Gerard T Berry
- Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Deborah A Bilder
- Department of Psychiatry, University of Utah, Salt Lake City, UT 84108, USA.
| | - Nenad Blau
- University Children's Hospital, Heidelberg, Germany; University Children's Hospital, Zürich, Switzerland.
| | - Olaf A Bodamer
- University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | - Jeffrey P Brosco
- University of Miami Mailman Center for Child Development, Miami, FL 33101, USA.
| | | | | | - Barbara K Burton
- Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, IL 60611, USA.
| | - Christine S Chang
- Agency for Healthcare Research and Quality, Rockville, MD 20850, USA.
| | - Paul M Coates
- Office of Dietary Supplements, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Amy C Cunningham
- Tulane University Medical School, Hayward Genetics Center, New Orleans, LA 70112, USA.
| | | | - John H Ferguson
- Office of Rare Diseases Research, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20982, USA.
| | | | | | - Dorothy K Grange
- Washington University School of Medicine, St. Louis Children's Hospital, St. Louis, MO 63110, USA.
| | - Carol L Greene
- University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Stephen C Groft
- Office of Rare Diseases Research, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Cary O Harding
- Oregon Health & Science University, Portland, OR 97239, USA.
| | - R Rodney Howell
- University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | | | - Henrietta D Hyatt-Knorr
- Office of Rare Diseases Research, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Indira P Jevaji
- Office of Research on Women's Health, National Institutes of Health, Bethesda, MD 20817, USA.
| | - Harvey L Levy
- Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Uta Lichter-Konecki
- George Washington University, Children's National Medical Center, Washington, DC 20010, USA.
| | | | | | | | | | - Melissa L McPheeters
- Vanderbilt Evidence-based Practice Center, Institute for Medicine and Public Health, Nashville, TN 37203, USA.
| | - John J Mitchell
- McGill University Health Center, Montreal, Quebec H3H 1P3, Canada.
| | - Shideh Mofidi
- Maria Fareri Children's Hospital of Westchester Medical Center, Valhalla, NY 10595, USA.
| | - Kathryn D Moseley
- University of Southern California Keck School of Medicine, Los Angeles, CA 90033, USA.
| | - Christine M Mueller
- Office of Orphan Products Development, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA.
| | - Andrew E Mulberg
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA.
| | - Lata S Nerurkar
- Office of Rare Diseases Research, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20982, USA.
| | - Beth N Ogata
- University of Washington, Seattle, WA 98195, USA.
| | - Anne R Pariser
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA.
| | - Suyash Prasad
- BioMarin Pharmaceutical Inc., San Rafael, CA 94901, USA.
| | - Gabriella Pridjian
- Tulane University Medical School, Hayward Genetics Center, New Orleans, LA 70112, USA.
| | | | - Uma M Reddy
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | | | | | - Sandra M Sirrs
- Vancouver General Hospital, University of British Columbia, Vancouver V5Z 1M9, Canada.
| | | | - Danilo A Tagle
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Susan M Thompson
- The Children's Hospital at Westmead, Sydney, NSW 2145, Australia.
| | - Tiina K Urv
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Jeanine R Utz
- University of Minnesota, Minneapolis, MN 55455, USA.
| | - Francjan van Spronsen
- University of Groningen, University Medical Center of Groningen, Beatrix Children's Hospital, Netherlands.
| | - Jerry Vockley
- University of Pittsburgh, Pittsburgh, PA 15224, USA.
| | - Susan E Waisbren
- Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Linda S Weglicki
- National Institute of Nursing Research, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Desirée A White
- Department of Psychology, Washington University, St. Louis, MO 63130, USA.
| | | | - Benjamin S Wilfond
- Seattle Children's Research Institute, University of Washington School of Medicine, Seattle, WA 98101, USA.
| | | | - Justin M Young
- The Young Face, Facial Plastic and Reconstructive Surgery, Cumming, GA 30041, USA.
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Sarkissian CN, Gámez A, Scriver CR. What we know that could influence future treatment of phenylketonuria. J Inherit Metab Dis 2009; 32:3-9. [PMID: 18668342 DOI: 10.1007/s10545-008-0917-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Revised: 06/10/2008] [Accepted: 06/11/2008] [Indexed: 11/25/2022]
Abstract
Phenylketonuria (PKU), a Mendelian autosomal recessive phenotype (OMIM 261600), is an inborn error of metabolism that can result in impaired postnatal cognitive development. The phenotypic outcome is multifactorial in origin, based both in nature, the mutations in the gene encoding the L-phenylalanine hydroxylase enzyme, and nurture, the nutritional experience introducing L-phenylalanine into the diet. The PKU story contains many messages including a framework to appreciate the complexity of this disease where phenotype reflects both locus-specific and genomic components. This knowledge is now being applied in the development of patient-specific therapies.
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Affiliation(s)
- C N Sarkissian
- Department of Biology, Human Genetics and Pediatrics, McGill University, Quebec, Canada.
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Williams RA, Mamotte CDS, Burnett JR. Phenylketonuria: an inborn error of phenylalanine metabolism. Clin Biochem Rev 2008; 29:31-41. [PMID: 18566668 PMCID: PMC2423317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine (Phe) metabolism resulting from deficiency of phenylalanine hydroxylase (PAH). Most forms of PKU and hyperphenylalaninaemia (HPA) are caused by mutations in the PAH gene on chromosome 12q23.2. Untreated PKU is associated with an abnormal phenotype which includes growth failure, poor skin pigmentation, microcephaly, seizures, global developmental delay and severe intellectual impairment. However, since the introduction of newborn screening programs and with early dietary intervention, children born with PKU can now expect to lead relatively normal lives. A better understanding of the biochemistry, genetics and molecular basis of PKU, as well as the need for improved treatment options, has led to the development of new therapeutic strategies.
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Affiliation(s)
- Robin A Williams
- Department of Core Clinical Pathology & Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital, Perth, WA 6847
- School of Biomedical Sciences, Curtin University of Technology, Bentley, WA 6001
| | - Cyril DS Mamotte
- School of Biomedical Sciences, Curtin University of Technology, Bentley, WA 6001
| | - John R Burnett
- Department of Core Clinical Pathology & Biochemistry, PathWest Laboratory Medicine, Royal Perth Hospital, Perth, WA 6847
- School of Medicine & Pharmacology, University of Western Australia, Nedlands, WA 6009, Australia
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Abstract
"Inborn errors of metabolism," first recognized 100 years ago by Garrod, were seen as transforming evidence for chemical and biological individuality. Phenylketonuria (PKU), a Mendelian autosomal recessive phenotype, was identified in 1934 by Asbjörn Fölling. It is a disease with impaired postnatal cognitive development resulting from a neurotoxic effect of hyperphenylalaninemia (HPA). Its metabolic phenotype is accountable to multifactorial origins both in nurture, where the normal nutritional experience introduces L-phenylalanine, and in nature, where mutations (>500 alleles) occur in the phenylalanine hydroxylase gene (PAH) on chromosome 12q23.2 encoding the L-phenylalanine hydroxylase enzyme (EC 1.14.16.1). The PAH enzyme converts phenylalanine to tyrosine in the presence of molecular oxygen and catalytic amounts of tetrahydrobiopterin (BH4), its nonprotein cofactor. PKU is among the first of the human genetic diseases to enter, through newborn screening, the domain of public health, and to show a treatment effect. This effect caused a paradigm shift in attitudes about genetic disease. The PKU story contains many messages, including: a framework on which to appreciate the complexity of PKU in which phenotype reflects both locus-specific and genomic components; what the human PAH gene tells us about human population genetics and evolution of modern humans; and how our interest in PKU is served by a locus-specific mutation database (http://www.pahdb.mcgill.ca; last accessed 20 March 2007). The individual Mendelian PKU phenotype has no "simple" or single explanation; every patient has her/his own complex PKU phenotype and will be treated accordingly. Knowledge about PKU reveals genomic components of both disease and health.
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Affiliation(s)
- Charles R Scriver
- Department of Human Genetics, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.
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Kahler SG, Fahey MC. Metabolic disorders and mental retardation. AMERICAN JOURNAL OF MEDICAL GENETICS. PART C, SEMINARS IN MEDICAL GENETICS 2003; 117C:31-41. [PMID: 12561056 DOI: 10.1002/ajmg.c.10018] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The metabolic and anatomical substrate of most forms of mental retardation is not known. Because the basis of normal brain function is not sufficiently understood, the basis of abnormal function is understood poorly. Even in disorders where the fundamental biochemical defect is known, such as phenylketonuria (PKU) and other enzyme defects, the exact basis for brain dysfunction is uncertain. The outcome for treated PKU, galactosemia, homocystinuria, and lysosomal disorders is not yet optimal. The various forms of nonketotic hyperglycinemia often respond poorly to current therapy. Less familiar disorders, with or without seizures, such as deficient synthesis of serine or creatine and impaired glucose transport into the brain, and disorders with variable malformations, such as Smith-Lemli-Opitz (SLO) syndrome and the congenital disorders of glycosylation (CDGs), may initially be thought to be a nonspecific form of developmental delay. Less familiar disorders, with or without seizures and disorders with variable malformations may initially be thought to be a nonspecific form of developmental delay. Simple tests of urine, blood, and cerebrospinal fluid may lead to a diagnosis, accurate genetic counseling, and better treatment. Metabolic brain imaging (magnetic resonance spectroscopy (MRS)) has also helped to reveal biochemical abnormalities within the brain.
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Affiliation(s)
- Stephen G Kahler
- Genetic Health Services, Victoria/Murdoch Children's Research Institute, Royal Children's Hospital, University of Melbourne, Parkville, Victoria, Australia.
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Scriver CR. Why mutation analysis does not always predict clinical consequences: explanations in the era of genomics. J Pediatr 2002; 140:502-6. [PMID: 12032513 DOI: 10.1067/mpd.2002.124316] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Charles R Scriver
- Department of Human Genetics, McGill University, Montréal, Québec, Canada.
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Urban M, Nieschlag A. The enigma of the old poet: did the child Wienke in Theodor Storm's novella "Der Schimmelreiter" (1888) have phenylketonuria? AMERICAN JOURNAL OF MEDICAL GENETICS 2001; 104:174-8. [PMID: 11746051 DOI: 10.1002/ajmg.1596] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We report a probable case of phenylketonuria in a figure from "Der Schimmelreiter", a novella by German author Theodor Storm (1817-1888), published in 1888. The child Wienke, daughter of the story's protagonist, Hauke Haien, displays symptoms of phenylketonuria. Storm's description of this child, its physiognomy, and increasing mental retardation, lead us to believe that Storm in fact described a case of phenylketonuria, a condition not reported until Følling's description in 1934.
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Affiliation(s)
- M Urban
- Institut für Medizinische Genetik, Universitätsklinikum Charité, Humboldt-Universität zu Berlin, Berlin, Germany
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Koch R, Güttler F. Benefits of mutation analysis and examination of brain phenylalanine levels in the management of phenylketonuria. Pediatrics 2000; 106:1136. [PMID: 11061787 DOI: 10.1542/peds.106.5.1136] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- R Koch
- Division of Medical Genetics, Department of Pediatrics, Children's Hospital, Los Angeles University of Southern California School of Medicine Los Angeles, CA 90027, USA.
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Greeves LG, Patterson CC, Carson DJ, Thom R, Wolfenden MC, Zschocke J, Graham CA, Nevin NC, Trimble ER. Effect of genotype on changes in intelligence quotient after dietary relaxation in phenylketonuria and hyperphenylalaninaemia. Arch Dis Child 2000; 82:216-21. [PMID: 10685924 PMCID: PMC1718236 DOI: 10.1136/adc.82.3.216] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Associations between genotype and intellectual outcome in patients with phenylketonuria are complicated because intelligence is influenced by many variables, including environmental factors and other genetic determinants. Intellectual changes with age, both on and after relaxation of diet, vary within the patient population. This study aims to determine whether a significant association exists between genotype and change in intelligence after relaxation of diet. METHODS 125 patients with hyperphenylalaninaemia and phenylketonuria whose diet was relaxed after 8 years of age. Verbal, performance, and full scale intelligence quotients at 8, 14, and 18 years were expressed as standard deviation scores (IQ-SDS), and genotype as predicted residual enzyme activity (PRA) of phenylalanine hydroxylase. RESULTS IQ-SDS at 8, 14, and 18 years were significantly below normal; no association was found between PRA and IQ-SDS. Significant reductions in verbal and full scale IQ-SDS occurred between 8 and 14 years and 8 and 18 years. There was a significant association between PRA and the reduction in verbal, performance, and full scale IQ between these years. Multiple regression analysis of 18 year results, using 8 year results as covariates, supported the association between PRA and IQ-SDS; after adjustment for phenylalanine control, both up to and after the age of 8 years, the full scale IQ-SDS at 14 and 18 years was 0.15 higher for each 10% increase in PRA. CONCLUSIONS Genotype might be useful in predicting the likelihood of intellectual change in patients with hyperphenylalaninaemia and phenylketonuria whose diet is relaxed after the age of 8 years.
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Affiliation(s)
- L G Greeves
- Royal Belfast Hospital for Sick Children, Belfast BT12 6BE, UK
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14
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Rivera I, Cabral A, Almeida M, Leandro P, Carmona C, Eusébio F, Tasso T, Vilarinho L, Martins E, Lechner MC, de Almeida IT, Konecki DS, Lichter-Konecki U. The correlation of genotype and phenotype in Portuguese hyperphenylalaninemic patients. Mol Genet Metab 2000; 69:195-203. [PMID: 10767174 DOI: 10.1006/mgme.2000.2971] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To understand the basis for the clinical heterogeneity of phenylalanine hydroxylase deficiency among Portuguese hyperphenylalaninemic patients, genotype-phenotype correlations were established. A group of 61 patients was completely genotyped, leading to the identification of 20 different mutant alleles in 36 different genotypic combinations, including a mutant allele not reported previously. The severity of those mutations found within this hyperphenylalaninemic population, which have not been previously expressed in vitro, were assessed. The results obtained by the present study exhibit a strong correlation between the predicted residual enzyme activity, as deduced from the genotype of the patients, and the biochemical phenotype represented by the diagnostic parameters (phenylalanine levels before the beginning of treatment and the dietary phenylalanine tolerance). It was observed that only a judicious follow-up and compliance with the appropriate diet permits the correct assessment of the clinical phenotype of the patients. Additionally, based upon the correlation observed between genotypes and diagnostic parameters, it was possible to predict the potential residual enzyme activity of those mutations (identified in our patients) which have not yet been studied in vitro.
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Affiliation(s)
- I Rivera
- Centro de Patogénese Molecular, Faculdade de Farmácia, University of Lisboa, Avenida das Forças Armadas, Lisboa, 1600, Portugal
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15
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Enns GM, Martinez DR, Kuzmin AI, Koch R, Wakeem CK, Woo SL, Eisensmith RC, Packman S. Molecular correlations in phenylketonuria: mutation patterns and corresponding biochemical and clinical phenotypes in a heterogeneous California population. Pediatr Res 1999; 46:594-602. [PMID: 10541324 DOI: 10.1203/00006450-199911000-00017] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We studied 133 California phenylketonuria (PKU) patients and one obligate heterozygote to delineate the molecular basis of PKU in a population with greater ethnic diversity than in previous studies, and to determine whether a correlation exists between genotype and clinical phenotype, with the latter defined by both the diagnostic pretreatment blood phenylalanine (PHE) level and cognitive (IQ) test scores. To determine PAH genotypes, we used PCR-mediated amplification, denaturing gradient gel electrophoresis, and direct sequencing on dried whole blood samples. Where possible, mutation severity was defined according to predicted in vitro PAH enzyme activity estimated by using Cos cell expression analysis for a given mutation. We then asked whether mutation severity, as defined by such expression analysis, correlated with pretreatment PHE levels or with IQ test results. A mutation was identified in 236 (88%) of 267 mutant alleles. Seventeen new mutant alleles were found; A47E, T81P, I102T, E182G, T328D, Y343P, K371R, Y387H, A389E, E422K, IVS9nt5, IVS11nt20, delS70, del364-368/del198-220, delF299, delT323, and -1C/T. In striking contrast to a number of studies in other populations, in this study, based on predicted PAH activity, we observed no correlation between mutation severity and pretreatment PHE levels. There was also no correlation between genotype and IQ. We conclude that in samples collected from an ethnically heterogeneous population, there is no correlation of mutation severity with either pretreatment PHE levels or IQ measurement in treated patients. We caution that genetic counseling in PKU should incorporate the notion that prognosis may not be predicted with precision based on mutation analysis in a given patient.
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Affiliation(s)
- G M Enns
- Department of Pediatrics, University of California, San Francisco 94143-0748, USA
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16
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Setianingsih I, Williamson R, Daud D, Harahap A, Marzuki S, Forrest S. Phenotypic variability of Filipino beta(o)-thalassemia/HbE patients in Indonesia. Am J Hematol 1999; 62:7-12. [PMID: 10467270 DOI: 10.1002/(sici)1096-8652(199909)62:1<7::aid-ajh2>3.0.co;2-s] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Three Indonesian patients with identical genotypes, each compound heterozygotes for Filipino beta(o)-thalassemia/HbE, expressed different clinical severities. One patient has mild disease and is transfusion independent, while the other two are severely affected and transfusion dependent. The size of the Filipino beta(o)-globin gene deletion was confirmed to be 45 kb, resolving conflicting values given in the literature. Neither ameliorating genetic factors such as alpha-globin gene deletions or the XmnI restriction site polymorphism at position -158 upstream of the (G)gamma-globin gene, nor differences in beta-globin gene haplotype, explain the phenotypic variation. These observations have implications for the development of antenatal diagnosis in Indonesia, as at present it is not possible to give an accurate prediction of severity of phenotype for this common genotype.
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Affiliation(s)
- I Setianingsih
- The Murdoch Institute, Royal Children's Hospital, Flemington Road, Parkville, Melbourne, Australia.
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17
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Güttler F, Azen C, Guldberg P, Romstad A, Hanley WB, Levy HL, Matalon R, Rouse BM, Trefz F, de la Cruz F, Koch R. Relationship among genotype, biochemical phenotype, and cognitive performance in females with phenylalanine hydroxylase deficiency: report from the Maternal Phenylketonuria Collaborative Study. Pediatrics 1999; 104:258-62. [PMID: 10429004 DOI: 10.1542/peds.104.2.258] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE To examine the relationship of phenylalanine hydroxylase (PAH) genotypes to biochemical phenotype and cognitive development in maternal phenylketonuria (PKU). METHODOLOGY PAH gene mutations were examined in 222 hyperphenylalaninemic females enrolled in the Maternal PKU Collaborative Study (MPKUCS). A total of 84 different mutations were detected, and complete genotype was obtained in 199 individuals. Based on previous knowledge about mutation-phenotype associations, 78 of the mutations could be assigned to one of four classes of severity (severe PKU, moderate PKU, mild PKU, and mild hyperphenylalaninemia [MHP]). Then, 189 MPKUCS subjects were grouped according to the various combinations of mutation classifications. The sample sizes were large enough for statistical testing in four groups with at least one mutation that completely abolishes enzyme activity. These patients are considered functionally hemizygous. RESULTS The biochemical phenotype predicted from the genotype in functionally hemizygous patients was related significantly to the assigned phenylalanine level. Cognitive performance (IQ) was also significantly related to genotype. The IQ of PAH-deficient mothers with a severe PKU mutation in combination with a MHP mutation or a mild PKU mutation was 99 and 96, respectively, whereas the IQ of PKU mothers with two severe PKU mutations or with one severe and one moderate PKU mutation was 83 and 84, respectively. Of the patients with PKU, 92% had been treated during childhood. Those who were untreated or treated late had lower than average IQ scores for their group of mutation combinations. Females with moderate or mild PKU who were treated early and treated for >6 years showed IQ scores 10 points above average for their group. CONCLUSIONS The reproductive outcome in maternal phenylketonuria is dependent on prenatal metabolic control and postnatal environmental circumstances. Both factors depend on the intellectual resources of the mother with PKU. The significant relationship among genotype, biochemical phenotype, and cognitive performance observed in the present study is of importance for the development of an optimal strategy for future treatment of females with PKU who plan pregnancy.
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Affiliation(s)
- F Güttler
- John F. Kennedy Institute, Glostrup, Denmark
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18
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Abstract
The classification of genetic disease into chromosomal, monogenic and multifactorial categories is an oversimplification. Phenylketonuria (PKU) is a classic 'monogenic' autosomal recessive disease in which mutation at the human PAH locus was deemed sufficient to explain the impaired function of the enzyme phenylalanine hydroxylase (enzymic phenotype), the attendant hyperphenylalaninemia (metabolic phenotype) and the resultant mental retardation (cognitive phenotype). In the era of molecular genetics, expectations for a consistently close correlation between the mutant genotype and variant phenotype have been somewhat disappointed, and PKU is used here to illustrate how and why this might be the case. So-called monogenic traits do, indeed, conform to long-accepted ideas about the expression of 'major' loci and their importance in determining parameters of phenotype, but the associated features are as complex, in their own ways, as those in so-called complex traits.
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Affiliation(s)
- C R Scriver
- DeBelle Laboratory for Biochemical Genetics, Montreal Children's Hospital, 2300 Tupper Street, Montreal, Quebec, Canada H3H 1P3.
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19
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Koch R, Moseley K, Ning J, Romstad A, Guldberg P, Guttler F. Long-term beneficial effects of the phenylalanine-restricted diet in late-diagnosed individuals with phenylketonuria. Mol Genet Metab 1999; 67:148-55. [PMID: 10356314 DOI: 10.1006/mgme.1999.2863] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The potential benefits to society of treating late-diagnosed mentally retarded persons with phenylketonuria were investigated. In order to ascertain the effects of late dietary intervention, the charts of 124 adults with PKU seen in the metabolic service at the Childrens Hospital of Los Angeles were reviewed. Fifty-nine were diagnosed later than 3 months of age and were over the age of 18 years. They were followed up with medical, psychological, and nutritional assessments. Genotyping was also performed. Twenty-eight have remained on a phenylalanine-restricted diet during the intervening years. All but 3 of the 28 late-diagnosed PKU persons who remained on a restricted diet showed significant intellectual improvement. Seven are able to attend college, 9 are employed, and 12 are attending workshops and/or day care programs. The result of treatment with the phenylalanine-restricted diet was that these individuals could participate in society and were able to arrest the neurodegenerative course characteristic of persons with mutations classified as severe in the phenylalanine hydroxylase gene. We conclude that society could benefit substantially by providing a phenylalanine-restricted diet for late-diagnosed mentally retarded persons with phenylketonuria. Eighteen of 28 such persons who otherwise would have required residential care are living independently.
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Affiliation(s)
- R Koch
- Department of Pediatrics, Research Institute, Childrens Hospital of Los Angeles, California 90027, USA.
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20
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Abstract
Previous studies have shown that genotype correlates with biochemical phenotype in treated phenylketonuria. If there is a strong correlation between genotype and intellectual phenotype of untreated patients, it would be possible to determine which individuals would have normal intelligence without treatment. In this study, 42 families with untreated phenylketonuria were analyzed to examine whether there was an association between genotype and untreated intellectual phenotype. Previously 12 of the 42 families were genotyped; now the genotyping of these patients is almost complete (40/42), a more thorough investigation was possible. Although the predicted phenylalanine hydroxylase (PAH) enzyme activity, based on genotype, showed an association with the patients' intellectual phenotype, the extensive overlap between the groups means the association is of little clinical value. Unrelated individuals with the same genotype and also siblings were found to have very different intellectual phenotypes. These phenotypic differences could not be explained by a difference in diet; therefore, we propose that another gene or genes may be modifying the intellectual phenotype of untreated patients. A preliminary search for possible modifying genes was performed. The possibility that a modifying gene was linked to the PAH gene on chromosome 12 was investigated using markers closely linked to the gene; however, no evidence for a modifying gene close to the PAH gene was found. Tyrosine hydroxylase was chosen as a candidate gene, because it can perform the same reaction as PAH. Using a common polymorphism within the gene, we found that this gene did not cause the discordant results and thus, did not modify the PAH phenotype.
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Affiliation(s)
- S J Ramus
- The Murdoch Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
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21
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Kayaalp E, Treacy E, Waters PJ, Byck S, Nowacki P, Scriver CR. Human phenylalanine hydroxylase mutations and hyperphenylalaninemia phenotypes: a metanalysis of genotype-phenotype correlations. Am J Hum Genet 1997; 61:1309-17. [PMID: 9399896 PMCID: PMC1716084 DOI: 10.1086/301638] [Citation(s) in RCA: 154] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We analyzed correlations between mutant genotypes at the human phenylalanine hydroxylase locus (gene symbol PAH) and the corresponding hyperphenylalaninemia (HPA) phenotypes (notably, phenylketonuria [OMIM 261600]). We used reports, both published and in the PAH Mutation Analysis Consortium Database, on 365 patients harboring 73 different PAH mutations in 161 different genotypes. HPA phenotypes were classified as phenylketonuria (PKU), variant PKU, and non-PKU HPA. By analysis both of homoallelic mutant genotypes and of "functionally hemizygous" heteroallelic genotypes, we characterized the phenotypic effect of 48 of the 73 different, largely missense mutations. Among those with consistent in vivo expression, 24 caused PKU, 3 caused variant PKU, and 10 caused non-PKU HPA. However, 11 mutations were inconsistent in their effect: 9 appeared in two different phenotype classes, and 2 (I65T and Y414C) appeared in all three classes. Seven mutations were inconsistent in phenotypic effect when in vitro (unit-protein) expression was compared with the corresponding in vivo phenotype (an emergent property). We conclude that the majority of PAH mutations confer a consistent phenotype and that this is concordant with their effects, when known, predicted from in vitro expression analysis. However, significant inconsistencies, both between in vitro and in vivo phenotypes and between different individuals with similar PAH genotypes, reveal that the HPA-phenotype is more complex than that predicted by Mendelian inheritance of alleles at the PAH locus.
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Affiliation(s)
- E Kayaalp
- DeBelle Laboratory, McGill University-Montreal Children's Hospital Research Institute, Quebec, Canada
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22
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Treacy EP, Delente JJ, Elkas G, Carter K, Lambert M, Waters PJ, Scriver CR. Analysis of phenylalanine hydroxylase genotypes and hyperphenylalaninemia phenotypes using L-[1-13C]phenylalanine oxidation rates in vivo: a pilot study. Pediatr Res 1997; 42:430-5. [PMID: 9380432 DOI: 10.1203/00006450-199710000-00002] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Hyperphenylalaninemia (HPA) resulting from deficient activity of phenylalanine hydroxylase (PAH) is caused by mutations in the human PAH gene (McKusick 261600). Herein, we report a noninvasive method to: 1) estimate whole-body phenylalanine oxidation in patients with HPA and 2) compare effects of mutant genotypes on phenotypes. We used oral L-[1-13C]phenylalanine as a substrate and measured 13CO2 formation in the first hour as an index of phenylalanine oxidation rates in: 1) patients with PKU (n = 6), variant phenylketonuria (PKU) (n = 7) and non-PKU HPA (n = 4); 2) obligate heterozygotes (n = 18); and 3) controls (n = 8). PAH mutations were identified by PCR, denaturing gradient gel electrophoresis, and DNA sequencing. Phenylalanine oxidation rates demonstrated a gene dosage effect; oxidation in heterozygotes was intermediate between probands and controls. The three classes of HPA had different mean oxidation rates (PKU < variant PKU < non-PKU HPA). The in vivo phenotype (HPA class or whole-body oxidation rate) did not always correspond to prediction from in vitro expression analysis of the mutation effect on enzyme activity. The findings indicate that the in vivo metrical trait (phenylalanine oxidation rate) is not a simple equivalent of phenylalanine hydroxylation activity (unit of protein phenotype) and, as expected, is an emergent property under the control of more than the PAH locus.
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Affiliation(s)
- E P Treacy
- DeBelle Laboratory for Biochemical Genetics, McGill University-Montreal, Children's Hospital Research Institute, Quebec, Canada
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23
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Tyfield LA. Phenylketonuria in Britain: genetic analysis gives a historical perspective of the disorder but will it predict the future for affected individuals? Mol Pathol 1997; 50:169-74. [PMID: 9350299 PMCID: PMC379622 DOI: 10.1136/mp.50.4.169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- L A Tyfield
- Molecular Genetics Unit, Lewis Laboratories, Southmead Hospital, Bristol
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24
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Koch R, Fishler K, Azen C, Guldberg P, Güttler F. The relationship of genotype to phenotype in phenylalanine hydroxylase deficiency. BIOCHEMICAL AND MOLECULAR MEDICINE 1997; 60:92-101. [PMID: 9169088 DOI: 10.1006/bmme.1997.2577] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Seventy-two adults with phenylketonuria were evaluated to investigate the genotypic relationship to phenotype. Patient data were collected by chart review and medical follow-up as well as current psychological evaluation. Nineteen diagnosed neonatally had remained on a phenylalanine-restricted diet all their lives, whereas 34 who were also diagnosed on newborn screening had discontinued dietary restriction during childhood. Nineteen others who were born prior to newborn screening were diagnosed later than the newborn period on clinical grounds but have remained on dietary restriction. Comparison between intellectual ability, academic achievement, and mental illness was made with degree of diet control as defined by range of blood phenylalanine levels over time. Diet discontinuation in childhood did not significantly lower IQ per se but appeared to diminish academic achievement. The lowest IQ scores were associated with poor dietary restriction of phenylalanine in the diet during childhood. While there appears to be a strong genotypic relationship to phenotypic metabolic parameters in phenylketonuria, there does not seem to be a similar relationship to intellectual ability in adults. Mutation R408W was not strongly related to the occurrence of mental illness in this sample. We conclude that dietary restriction of phenylalanine neonatally and good control contributed to normal intellectual development. Continuation of dietary treatment into adulthood appeared to improve academic achievement in patients with severe phenylalanine hydroxylase mutations.
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Affiliation(s)
- R Koch
- Division of Medical Genetics, Childrens Hospital Los Angeles, California 90027, USA
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25
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Burgard P, Schmidt E, Rupp A, Schneider W, Bremer HJ. Intellectual development of the patients of the German Collaborative Study of children treated for phenylketonuria. Eur J Pediatr 1996; 155 Suppl 1:S33-8. [PMID: 8828606 DOI: 10.1007/pl00014245] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In a multicentric and interdisciplinary approach the German Collaborative Study of Children Treated for Phenylketonuria (PKU) investigates prospectively the effects of early started strict dietary treatment on the growth and development of 140 patients. The present paper focuses on longitudinal intelligence data from 4, 5 and 9 years of age of 89 patients in relation to the quality of dietary control in comparison to 200 healthy children tested by the same protocol. Cluster analysis of phenylalanine (Phe) levels distinguished a cluster of good dietary control with Phe levels according to the recommendation of maintaining Phe levels below 360 mumol/l, a cluster of poor dietary control with Phe levels greater than 600 mumol/l after the age of 3 years, and a cluster of intermediate control. Intelligence quotients (IQ) and Phe clusters were inversely related with non-significant differences between the clusters good and intermediate. On average, all three clusters scored significantly lower than healthy age peers. Mean IQ scores decreased for patients as well as for healthy children due to different tests used at different measurement occasions. Patients with poor dietary control showed a steeper decrease between 4 and 5 years than patients with better dietary control. Between 5 and 9 years IQ differences between patients and healthy children remained stable. Verbal IQs were higher than performance IQs for patients as well as for healthy children. It is concluded that after early and strict treatment during the pre-school years Phe levels, in the range observed, do not influence IQ development until the age of 9 years. IQ subscale pattern indicate that PKU results in a generalized reduction of IQ instead of disturbing specific abilities. It remains to be investigated whether higher Phe levels are also innocuous and/or may result in late effects.
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Affiliation(s)
- P Burgard
- Department of General Pediatrics, University of Heidelberg, Germany
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26
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Güttler F, Guldberg P. The influence of mutations of enzyme activity and phenylalanine tolerance in phenylalanine hydroxylase deficiency. Eur J Pediatr 1996; 155 Suppl 1:S6-10. [PMID: 8828600 DOI: 10.1007/pl00014253] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The phenylalanine hydroxylase (PAH) deficiency trait is heterogeneous with a continuum of metabolic phenotypes ranging from classical phenylketonuria (PKU) to mild hyperphenylalaninaemia (MHP). More than 200 mutations in the PAH gene are associated with PAH deficiency. From theoretical considerations or in vitro expression studies each mutation has a particular influence on enzyme activity, which explains the variation in dietary tolerance for phenylalanine (Phe). This paper gives a summary of the effect of each type of mutation on PAH activity and illustrates how the combination of mutations (the genotype) is associated with the Phe tolerance (the metabolic phenotype). Mutations within a population generally include a few prevalent mutations and a high number of rare mutations. The particular distribution of mutations implies that many PAH-deficient patients carry the same mutation combination, enabling the establishment of genotype-phenotype correlations by comparing clinical parameters in patients with identical genotypes. Because certain mutations always cause MHP irrespective of the mutation on the second allele, mutation typing of hyperphenylalaninaemic neonates will differentiate between PKU and MHP. In addition, genotyping will provide a tool for precise diagnosis of the metabolic phenotype of the neonate with PKU and thereby permit earlier implementation of dietary therapy better tailored to each individual patient.
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Affiliation(s)
- F Güttler
- John F. Kennedy Institute, Glostrup, Denmark
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27
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Eiken HG, Knappskog PM, Motzfeldt K, Boman H, Apold J. Phenylketonuria genotypes correlated to metabolic phenotype groups in Norway. Eur J Pediatr 1996; 155:554-60. [PMID: 8831077 DOI: 10.1007/bf01957904] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
UNLABELLED In order to establish a genotype-phenotype relationship, we have identified both mutant phenylalanine hydroxylase (PAH) genes in 108 phenylketonuria (PKU) patients (27 different alleles, 54 different genotypes). One major group of patients with very high pretreatment phenylalanine values ("classical" PKU) exclusively comprised homozygotes of the PKU mutations I65T, G272X, F299C, Y356X, R408W, IVS12nt1, and compound heterozygotes of various combinations of these alleles with G46S, R261Q, R252W, A259T, R158Q, D143G, R243X, E280K, or Y204C. A second major group of patients with lower phenylalanine values ("mild" PKU) comprised mutations A300S, R408Q, Y414C in various compound heterozygous states, and R261Q, R408Q, Y414C in homozygotes. The phenylalanine values in these groups were non-overlapping. In addition, a smaller group of patients formed the transition between the two main groups. In sib pairs 4 of 15 had discordant pretreatment phenylalanine values. CONCLUSION Our results are consistent with the view that allelic heterogeneity at the PAH locus dominates the biochemical phenotype in PKU and that genotype information is able to predict the metabolic phenotype in PKU patients.
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Affiliation(s)
- H G Eiken
- Department of Medical Genetics, Haukeland Hospital, Bergen, Norway
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28
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Simonoff E, Bolton P, Rutter M. Mental retardation: genetic findings, clinical implications and research agenda. J Child Psychol Psychiatry 1996; 37:259-80. [PMID: 8707910 DOI: 10.1111/j.1469-7610.1996.tb01404.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The most important genetic advances in the field of mental retardation include the discovery of the novel genetic mechanism responsible for the Fragile X syndrome, and the imprinting involved in the Prader-Willi and Angelman syndromes, but there have also been advances in our understanding of the pathogenesis of Down syndrome and phenylketonuria. Genetic defects (both single gene Mendelizing disorders and cytogenetic abnormalities) are involved in a substantial proportion of cases of mild as well as severe mental retardation, indicating that the previous equating of severe mental retardation with pathology, and of mild retardation with normal variation, is a misleading over-simplication. Within the group in which no pathological cause can be detected, behaviour genetic studies indicate that genetic influences are important, but that their interplay with environmental factors, which are also important, is at present poorly understood. Research into the joint action of genetic and environmental influences in this group will be an important research area in the future.
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Affiliation(s)
- E Simonoff
- MRC Child Psychiatry Unit and Centre for Social, Genetic and Developmental Psychiatry, Institute of Psychiatry, London, U.K
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29
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Abstract
Since the early descriptions of sickle cell anemia, it has been clear that genotype at a single locus rarely completely predicts phenotype. This paper reviews explanations for phenotypic variability in some monogenic diseases. In cystic fibrosis, there is strong correlation between genotype and pancreatic phenotype but only weak association with respiratory phenotype, possibly due to differential inheritance of alleles at loci controlling susceptibility to respiratory infection. In addition, disease mutations have been shown to have more or less severe effect, depending on other variation within the cystic fibrosis gene. In phenylketonuria, genotype at the phenylalanine hydroxylase locus appears to explain the biochemical phenotype, but not the intellectual status. There may be genetically determined variation in flux through the minor metabolic pathways for phenylalanine, influencing levels of alternative metabolites involved in mental development. Phenotypic discordance in sickle cell anemia and beta-thalassemia has been associated with the co-inheritance of genes for hereditary persistence of fetal hemoglobin. A mouse locus has been identified that influences tumour number in mice with the multiple intestinal neoplasia gene. Understanding of the genetic interactions that determine phenotype in apparently monogenic diseases should lead to clarification of the role of different genes in polygenic diseases with complex inheritance patterns, as well as enhancing the ability to predict the outcome of a disease mutation.
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Affiliation(s)
- K M Summers
- Department of Medicine, University of Queensland, Prince Charles Hospital, Australia
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30
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Treacy E, Pitt JJ, Seller K, Thompson GN, Ramus S, Cotton RG. In vivo disposal of phenylalanine in phenylketonuria: a study of two siblings. J Inherit Metab Dis 1996; 19:595-602. [PMID: 8892014 DOI: 10.1007/bf01799832] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
Abstract
Mutation at the phenylalanine hydroxylase (PAH) locus is a cause of hyperphenylalaninaemia. Genotype-phenotype correlation relative to the predicted PAH activity may differ at the metabolite level and at the IQ level in untreated phenylketonuria. Discordant metabolic phenotypes have been noted in siblings; influences on transport and metabolism of phenylalanine determining homeostasis may account for differing metabolic phenotypes. We report two siblings of different sex and identical genotype at the PAH locus who demonstrate a difference in phenylalanine disposal. A stable isotope infusion of [2H5]phenylalanine was used to measure protein turnover, phenylalanine hydroxylation and excretion of phenylalanine transamination metabolites. The siblings were observed to have identical hydroxylation rates under the experimental conditions of the study while manifesting differences in renal excretion rates of phenylalanine transamination metabolites and protein accretion.
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Affiliation(s)
- E Treacy
- McGill University-Montreal Children's Hospital Research Institute, Canada
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31
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Romano V, Guldberg P, Güttler F, Meli C, Mollica F, Pavone L, Giovannini M, Riva E, Biasucci G, Luotti D, Palillo L, Calí F, Ceratto N, Anello G, Bosco P. PAH deficiency in Italy: correlation of genotype with phenotype in the Sicilian population. J Inherit Metab Dis 1996; 19:15-24. [PMID: 8830172 DOI: 10.1007/bf01799343] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The results of the neonatal screening for phenylalanine hydroxylase (PAH) deficiency in Sicily show that its incidence is higher than previously reported for mainland Italians and that non-PKU HPA is in excess of classical and mild PKU. The latter finding suggests that a high number of non-PKU HPA mutations would occur in the Sicilian population compared to populations with an inverted PKU/non-PKU HPA ratio. Previous studies have identified 40 mutations accounting for the majority (98%) of mutant alleles underlying PAH deficiency in Sicily. In order to study the molecular basis of the distribution of PAH deficiency phenotypes in the Sicilian population, we have correlated 31 of those mutations with clinical and metabolic phenotypes in 12 mentally retarded patients, 14 treated patients with classic or mild PKU, and 13 subjects presenting the non-PKU HPA phenotype. The present study proposes a tentative classification for a large number (26) of PAH gene mutations which may represent an additional tool for establishing a differential diagnosis for PAH deficiency in the Sicilian population.
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Affiliation(s)
- V Romano
- Laboratorio di Genetica Molecolare, Istituto per la Ricerca sul Ritardo Mentale e l'Involuzione Cerebrale (I.R.C.C.S.), Troina, Italy
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32
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Eiken HG, Knappskog PM, Apold J, Flatmark T. PKU mutation G46S is associated with increased aggregation and degradation of the phenylalanine hydroxylase enzyme. Hum Mutat 1996; 7:228-38. [PMID: 8829656 DOI: 10.1002/(sici)1098-1004(1996)7:3<228::aid-humu7>3.0.co;2-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The G46S mutation in the phenylalanine hydroxylase (PAH) gene was identified by fluorescence-based single-strand conformation polymorphism (F-SSCP) analysis on phenylketonuria (PKU) haplotype 5.9 alleles. DNA sequencing of PAH exon 2 revealed a G-to-A transition in cDNA position 136. G46S mutations were present on 17 of 236 Norwegian PKU alleles (7.2%) and on 8 of 176 Swedish PKU alleles (4.5%). Analysis of all 13 exons with the flanking regions further detected a 1316-35c > t polymorphism (PAH intron 12), associated with both G46S and haplotype 5.9. Three patients were homozygous for the G46S mutation, two were untreated and had mild and severe mental retardation, respectively. The G46S mutation was introduced in the PAH cDNA by site-directed mutagenesis and expressed in three different systems (the pMAL/Escherichia coli system, the pcDNA3/human embryonic kidney (A293) cells, and the pcDNA3/TnT coupled in vitro transcription-translation system). The mutant recombinant E. coli fusion protein was recovered in high yield and with a specific activity of the purified tetrameric form, which was higher than the wild-type activity. After transient expression in A293 cells, the amount of the G46S protein was only about 3% of the wild type at equal PAH mRNA levels. The fusion protein cleaved by restriction protease factor Xa, as well as the enzyme produced by in vitro transcription-translation, revealed an abnormal susceptibility to form catalytically inactive high-molecular-mass aggregates of the enzyme. This aggregation, followed by an increased cellular degradation of the G46S mutant enzyme, is compatible with the clinical/metabolic phenotype of the affected homozygous and compound heterozygous patients.
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Affiliation(s)
- H G Eiken
- Department of Medical Genetics, Haukeland Hospital, University of Bergen, Norway
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33
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Seim AR, Reichelt KL. An enzyme/brain-barrier theory of psychiatric pathogenesis: unifying observations on phenylketonuria, autism, schizophrenia and postpartum psychosis. Med Hypotheses 1995; 45:498-502. [PMID: 8748095 DOI: 10.1016/0306-9877(95)90230-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- A R Seim
- Department of General Practice, University of Oslo, Blindern, Norway
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34
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Tyfield LA, Zschocke J, Stephenson A, Cockburn F, Harvie A, Bidwell JL, Wood NA, Hunt LP. Discordant phenylketonuria phenotypes in one family: the relationship between genotype and clinical outcome is a function of multiple effects. J Med Genet 1995; 32:867-70. [PMID: 8592329 PMCID: PMC1051737 DOI: 10.1136/jmg.32.11.867] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Four members spanning three generations of one family have phenylketonuria of varying degrees of severity. Two first cousins were screened in the neonatal period and have had dietary phenylalanine restriction since diagnosis, the older patient having been classified as having more severe PKU and the younger one as having mild PKU. Their mutual grandfather and his older brother also have a significant hyperphenylalaninaemia and are of normal intelligence despite never having had restricted phenylalanine intake. Mutation analysis of the phenylalanine hydroxylase (PAH) gene has established that there are four different mutations, two in exon 2 (F39L and L48S) and two in exon 3 (R111X and S67P), which give rise to PKU in this family. In order to establish their relative severity, we screened the PKU populations of western Scotland and the south west of England for these mutations. The exon 3 mutations are rare; however, F39L is relatively common in Scotland and L48S in England. A comparison of diagnostic blood phenylalanine concentrations in subjects carrying L48S/null or F39L/null mutations with those carrying two null mutations suggest that these exon 2 mutations are less deleterious. Thus, in this family, the different biochemical phenotypes can be explained, in part, by different genotypes at the PAH locus but our results show that the relationship between genotype and clinical outcome is more complex and is a function of multiple effects.
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Affiliation(s)
- L A Tyfield
- Department of Clinical Chemistry, Southmead Hospital, Bristol, UK
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35
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Guldberg P, Mikkelsen I, Henriksen KF, Lou HC, Güttler F. In vivo assessment of mutations in the phenylalanine hydroxylase gene by phenylalanine loading: characterization of seven common mutations. Eur J Pediatr 1995; 154:551-6. [PMID: 7556322 DOI: 10.1007/bf02074833] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
UNLABELLED Mutations in the gene encoding phenylalanine hydroxylase (PAH) cause persistent hyperphenylalaninaemia. To date, more than 200 point mutations and microdeletions have been characterized. Each mutation has a particular quantitative effect on enzyme activity and recessive expression of different mutant alleles results in a marked interindividual heterogeneity of metabolic and clinical phenotypes. In this paper we demonstrate how a simple clinical test can be used to evaluate the correlation between mutation genotype and phenylalanine metabolism. In hyperphenylalaninaemic patients with known PAH mutation genotype, we have investigated phenylalanine turnover in vivo by measuring the ability to eliminate a test dose of L-phenylalanine. All patients could be considered functionally hemizygous for one of their mutant alleles by carrying on the other allele a mutation that is known to completely abolish PAH activity and encode a peptide with no immunoreactivity. Seven mutations (R408W, IVS-12nt1, R261Q, G46S, Y414C, A104D, and D415N) were characterized by oral phenylalanine loading, each mutation being represented by at least three patients. The elimination profile determined for a 3-day period provides a measure to compare residual activity of the mutant proteins and to assign each mutation to a particular metabolic phenotype. The established relation between genotype and phenotype may enable prediction of the severity of the disease by genotype determination in the newborn period. This will aid in the management of hyperphenylalaninaemia and may improve prognosis. CONCLUSION The possibility of predicting the residual enzyme activity by DNA analysis performed already in the newborn period allows the prompt implementation of a diet that is adjusted to the degree of PAH deficiency. This may improve management and prognosis of hyperphenylalaninaemia.
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Affiliation(s)
- P Guldberg
- John F. Kennedy Institute, Glostrup, Denmark
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36
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Ramus SJ, Treacy EP, Cotton RG. Characterization of phenylalanine hydroxylase alleles in untreated phenylketonuria patients from Victoria, Australia: origin of alleles and haplotypes. Am J Hum Genet 1995; 56:1034-41. [PMID: 7726156 PMCID: PMC1801443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Mutations in the phenylalanine hydroxylase (PAH) gene were identified in a group of untreated phenylketonuria patients from Victoria, Australia. Ninety-eight percent of the alleles were identified, and a total of 26 different mutations were detected on 83 independent chromosomes. The three most prevalent mutations--R408W, I65T, and IVS12nt1--together accounted for 54% of the alleles. A number of alleles were demonstrated, by genealogical studies, to be of Irish or Scottish origin, including a newly described mutation 1197/1198 del A. The distribution and relative frequencies of the more common alleles in this population parallel observed frequencies in the British Isles and are consistent with the known history of Caucasian settlement of this region of Australia. We have analyzed the haplotype and polymorphic short tandem-repeat allele of the mutant chromosomes and describe a number of new associations.
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Affiliation(s)
- S J Ramus
- Olive Miller Protein Laboratory, Murdoch Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
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37
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Abstract
The history of PKU is one of science in the discovery of an inborn error of metabolism and a chemical cause of mental retardation; and also one of technology with the development of methods to prevent disease. PKU is the classic example of success in the prevention of a genetic disease. Meanwhile, the science has continued to evolve over the 60 years since the discovery of PKU, generating new understanding of its clinical and metabolic phenotypes and about phenylalanine hydroxylation. At least five known genes are involved in hydroxylation of phenylalanine, synthesis of tetrahybrobiopterin and regeneration of this cofactor. The genes have been cloned and mutations characterized for several enzymes (GTPCH, 6-PTPS, PHS/DoCH, DHPR, PAH). A new animal model (the enu mouse) is contributing to knowledge about pathogenesis of brain disease and potential new treatments. The human phenylalanine hydroxylase gene (PAH) itself harbors 99% of the mutations causing hyperphenylalaninemia, over 170 different mutations have been identified at this locus. They cause loss of function; none affecting regulation has been identified. The aggregate PKU gene frequency at 1% is polymorphic in many human populations and mutations are highly stratified by region and population reflecting a variety of mechanisms (founder effect, genetic drift, hypermutability and, perhaps, selection) for their occurrence and distribution.
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Affiliation(s)
- C R Scriver
- Department of Pediatrics, McGill University, Montreal, Canada
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38
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Ramus SJ, Cotton RG. Mutations Ivs4nt1, 47delCT, and G148S identified in the phenylalanine hydroxylase gene by RT-PCR of illegitimate transcripts and chemical cleavage of mismatch. Hum Mutat 1995; 6:250-1. [PMID: 8535445 DOI: 10.1002/humu.1380060309] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- S J Ramus
- Olive Miller Protein Laboratory, Murdoch Institute, Royal Children's Hospital, Parkville, Melbourne, Victoria, Australia
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39
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Eisensmith RC, Woo SL. Molecular genetics of phenylketonuria: from molecular anthropology to gene therapy. ADVANCES IN GENETICS 1995; 32:199-271. [PMID: 7741023 DOI: 10.1016/s0065-2660(08)60206-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- R C Eisensmith
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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40
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Delineation of the catalytic core of phenylalanine hydroxylase and identification of glutamate 286 as a critical residue for pterin function. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32001-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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41
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Kaul R, Matalon R, Allen R, Fisch RO, Michals K, Petrosky A, Sullivan D. Frequency of 12 mutations in 114 children with phenylketonuria in the Midwest region of the USA. J Inherit Metab Dis 1994; 17:356-8. [PMID: 7807952 DOI: 10.1007/bf00711829] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- R Kaul
- Research Institute, Miami Children's Hospital, FL 33155
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