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Compound Heterozygosis in AADC Deficiency and Its Complex Phenotype in Terms of AADC Protein Population

Aromatic amino acid decarboxylase (AADC) deficiency is a rare monogenic disease due to mutations in the ddc gene producing AADC, a homodimeric pyridoxal 5′-phosphate-dependent enzyme. The disorder is often fatal in the first decade and is characterized by profound motor impairments and developmental...

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Autores principales: Bisello, Giovanni, Bertoldi, Mariarita
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9570296/
https://www.ncbi.nlm.nih.gov/pubmed/36232540
http://dx.doi.org/10.3390/ijms231911238
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author Bisello, Giovanni
Bertoldi, Mariarita
author_facet Bisello, Giovanni
Bertoldi, Mariarita
author_sort Bisello, Giovanni
collection PubMed
description Aromatic amino acid decarboxylase (AADC) deficiency is a rare monogenic disease due to mutations in the ddc gene producing AADC, a homodimeric pyridoxal 5′-phosphate-dependent enzyme. The disorder is often fatal in the first decade and is characterized by profound motor impairments and developmental delay. In the last two years, there has been a net rise in the number of patients and variants identified, maybe also pushed by the ongoing gene therapy trials. The majority of the identified genotypes are compound heterozygous (about 70%). Efforts are underway to reach early diagnosis, find possible new markers/new fast methods, and predict clinical outcome. However, no clear correlation of genotype-to-phenotype exists to date. Nevertheless, for homozygous patients, reliable results have been obtained using genetic methods combined with available computational tools on crystal structures corroborated by biochemical investigations on recombinant homodimeric AADC variants that have been obtained and characterized in solution. For these variants, the molecular basis for the defect has been suggested and validated, since it correlates quite well with mildness/severity of the homozygous phenotype. Instead, prediction for compound heterozygous patients is more difficult since complementation effects could happen. Here, by analyzing the existing literature on compound heterozygosity in AADC deficiency and other genetic disorders, we highlight that, in order to assess pathogenicity, the measurement of activity of the AADC heterodimeric variant should be integrated by bioinformatic, structural, and functional data on the whole protein constellation theoretically present in such patients. A wider discussion on symptomatic heterozygosity in AADC deficiency is also presented.
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spelling pubmed-95702962022-10-17 Compound Heterozygosis in AADC Deficiency and Its Complex Phenotype in Terms of AADC Protein Population Bisello, Giovanni Bertoldi, Mariarita Int J Mol Sci Review Aromatic amino acid decarboxylase (AADC) deficiency is a rare monogenic disease due to mutations in the ddc gene producing AADC, a homodimeric pyridoxal 5′-phosphate-dependent enzyme. The disorder is often fatal in the first decade and is characterized by profound motor impairments and developmental delay. In the last two years, there has been a net rise in the number of patients and variants identified, maybe also pushed by the ongoing gene therapy trials. The majority of the identified genotypes are compound heterozygous (about 70%). Efforts are underway to reach early diagnosis, find possible new markers/new fast methods, and predict clinical outcome. However, no clear correlation of genotype-to-phenotype exists to date. Nevertheless, for homozygous patients, reliable results have been obtained using genetic methods combined with available computational tools on crystal structures corroborated by biochemical investigations on recombinant homodimeric AADC variants that have been obtained and characterized in solution. For these variants, the molecular basis for the defect has been suggested and validated, since it correlates quite well with mildness/severity of the homozygous phenotype. Instead, prediction for compound heterozygous patients is more difficult since complementation effects could happen. Here, by analyzing the existing literature on compound heterozygosity in AADC deficiency and other genetic disorders, we highlight that, in order to assess pathogenicity, the measurement of activity of the AADC heterodimeric variant should be integrated by bioinformatic, structural, and functional data on the whole protein constellation theoretically present in such patients. A wider discussion on symptomatic heterozygosity in AADC deficiency is also presented. MDPI 2022-09-23 /pmc/articles/PMC9570296/ /pubmed/36232540 http://dx.doi.org/10.3390/ijms231911238 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Review
Bisello, Giovanni
Bertoldi, Mariarita
Compound Heterozygosis in AADC Deficiency and Its Complex Phenotype in Terms of AADC Protein Population
title Compound Heterozygosis in AADC Deficiency and Its Complex Phenotype in Terms of AADC Protein Population
title_full Compound Heterozygosis in AADC Deficiency and Its Complex Phenotype in Terms of AADC Protein Population
title_fullStr Compound Heterozygosis in AADC Deficiency and Its Complex Phenotype in Terms of AADC Protein Population
title_full_unstemmed Compound Heterozygosis in AADC Deficiency and Its Complex Phenotype in Terms of AADC Protein Population
title_short Compound Heterozygosis in AADC Deficiency and Its Complex Phenotype in Terms of AADC Protein Population
title_sort compound heterozygosis in aadc deficiency and its complex phenotype in terms of aadc protein population
topic Review
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9570296/
https://www.ncbi.nlm.nih.gov/pubmed/36232540
http://dx.doi.org/10.3390/ijms231911238
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