Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier

Phenylketonuria (PKU) is an inborn error of metabolism caused by variants in the phenylalanine hydroxylase (PAH) gene and it is characterized by excessively high levels of phenylalanine in body fluids. PKU is a paradigm for a genetic disease that can be treated and majority of developed countries ha...

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Autores principales:	K. Klaassen, M. Djordjevic, A. Skakic, B. Kecman, R. Drmanac, S. Pavlovic, M. Stojiljkovic
Formato:	article
Lenguaje:	EN
Publicado:	Elsevier 2021
Materias:	Phenylketonuria Late-diagnosed Untreated Intellectual disability Modifier gene SHANK Medicine (General) R5-920 Biology (General) QH301-705.5
Acceso en línea:	https://doaj.org/article/d9f96c90fcf040fb8bfc5b302d89122c
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spelling	oai:doaj.org-article:d9f96c90fcf040fb8bfc5b302d89122c2021-11-20T05:06:19ZUntreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier2214-426910.1016/j.ymgmr.2021.100822https://doaj.org/article/d9f96c90fcf040fb8bfc5b302d89122c2021-12-01T00:00:00Zhttp://www.sciencedirect.com/science/article/pii/S2214426921001178https://doaj.org/toc/2214-4269Phenylketonuria (PKU) is an inborn error of metabolism caused by variants in the phenylalanine hydroxylase (PAH) gene and it is characterized by excessively high levels of phenylalanine in body fluids. PKU is a paradigm for a genetic disease that can be treated and majority of developed countries have a population-based newborn screening. Thus, the combination of early diagnosis and immediate initiation of treatment has resulted in normal intelligence for treated PKU patients. Although PKU is a monogenic disease, decades of research and clinical practice have shown that the correlation between the genotype and corresponding phenotype is not simple at all. Attempts have been made to discover modifier genes for PKU cognitive phenotype but without any success so far.We conducted whole genome sequencing of 4 subjects from unrelated non-consanguineous families who presented with pathogenic mutations in the PAH gene, high blood phenylalanine concentrations and near-normal cognitive development despite no treatment. We used cross sample analysis to select genes common for more than one patient. Thus, the SHANK gene family emerged as the only relevant gene family with variants detected in 3 of 4 analyzed patients. We detected two novel variants, p.Pro1591Ala in SHANK1 and p.Asp18Asn in SHANK2, as well as SHANK2:p.Gly46Ser, SHANK2:p.Pro1388_Phe1389insLeuPro and SHANK3:p.Pro1716Thr variants that were previously described. Computational analysis indicated that the identified variants do not abolish the function of SHANK proteins. However, changes in posttranslational modifications of SHANK proteins could influence functioning of the glutamatergic synapses, cytoskeleton regulation and contribute to maintaining optimal synaptic density and number of dendritic spines.Our findings are linking SHANK gene family and brain plasticity in PKU for the first time. We hypothesize that variant SHANK proteins maintain optimal synaptic density and number of dendritic spines under high concentrations of phenylalanine and could have protective modifying effect on cognitive development of PKU patients.K. KlaassenM. DjordjevicA. SkakicB. KecmanR. DrmanacS. PavlovicM. StojiljkovicElsevierarticlePhenylketonuriaLate-diagnosedUntreatedIntellectual disabilityModifier geneSHANKMedicine (General)R5-920Biology (General)QH301-705.5ENMolecular Genetics and Metabolism Reports, Vol 29, Iss , Pp 100822- (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Phenylketonuria Late-diagnosed Untreated Intellectual disability Modifier gene SHANK Medicine (General) R5-920 Biology (General) QH301-705.5
spellingShingle	Phenylketonuria Late-diagnosed Untreated Intellectual disability Modifier gene SHANK Medicine (General) R5-920 Biology (General) QH301-705.5 K. Klaassen M. Djordjevic A. Skakic B. Kecman R. Drmanac S. Pavlovic M. Stojiljkovic Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier
description	Phenylketonuria (PKU) is an inborn error of metabolism caused by variants in the phenylalanine hydroxylase (PAH) gene and it is characterized by excessively high levels of phenylalanine in body fluids. PKU is a paradigm for a genetic disease that can be treated and majority of developed countries have a population-based newborn screening. Thus, the combination of early diagnosis and immediate initiation of treatment has resulted in normal intelligence for treated PKU patients. Although PKU is a monogenic disease, decades of research and clinical practice have shown that the correlation between the genotype and corresponding phenotype is not simple at all. Attempts have been made to discover modifier genes for PKU cognitive phenotype but without any success so far.We conducted whole genome sequencing of 4 subjects from unrelated non-consanguineous families who presented with pathogenic mutations in the PAH gene, high blood phenylalanine concentrations and near-normal cognitive development despite no treatment. We used cross sample analysis to select genes common for more than one patient. Thus, the SHANK gene family emerged as the only relevant gene family with variants detected in 3 of 4 analyzed patients. We detected two novel variants, p.Pro1591Ala in SHANK1 and p.Asp18Asn in SHANK2, as well as SHANK2:p.Gly46Ser, SHANK2:p.Pro1388_Phe1389insLeuPro and SHANK3:p.Pro1716Thr variants that were previously described. Computational analysis indicated that the identified variants do not abolish the function of SHANK proteins. However, changes in posttranslational modifications of SHANK proteins could influence functioning of the glutamatergic synapses, cytoskeleton regulation and contribute to maintaining optimal synaptic density and number of dendritic spines.Our findings are linking SHANK gene family and brain plasticity in PKU for the first time. We hypothesize that variant SHANK proteins maintain optimal synaptic density and number of dendritic spines under high concentrations of phenylalanine and could have protective modifying effect on cognitive development of PKU patients.
format	article
author	K. Klaassen M. Djordjevic A. Skakic B. Kecman R. Drmanac S. Pavlovic M. Stojiljkovic
author_facet	K. Klaassen M. Djordjevic A. Skakic B. Kecman R. Drmanac S. Pavlovic M. Stojiljkovic
author_sort	K. Klaassen
title	Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier
title_short	Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier
title_full	Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier
title_fullStr	Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier
title_full_unstemmed	Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier
title_sort	untreated pku patients without intellectual disability: shank gene family as a candidate modifier
publisher	Elsevier
publishDate	2021
url	https://doaj.org/article/d9f96c90fcf040fb8bfc5b302d89122c
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Untreated PKU patients without intellectual disability: SHANK gene family as a candidate modifier

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