title: Nonketotic hyperglycinemia: Functional assessment of missense variants in GLDC to understand phenotypes of the disease.
abstract: The rapid analysis of genomic data is providing effective mutational confirmation in patients with clinical and biochemical hallmarks of a specific disease. This is the case for nonketotic hyperglycinemia (NKH), a Mendelian disorder causing seizures in neonates and early-infants, primarily due to mutations in the GLDC gene. However, understanding the impact of missense variants identified in this gene is a major challenge for the application of genomics into clinical practice. Herein, a comprehensive functional and structural analysis of 19 GLDC missense variants identified in a cohort of 26 NKH patients was performed. Mutant cDNA constructs were expressed in COS7 cells followed by enzymatic assays and Western blot analysis of the GCS P-protein to assess the residual activity and mutant protein stability. Structural analysis, based on molecular modeling of the 3D structure of GCS P-protein, was also performed. We identify hypomorphic variants that produce attenuated phenotypes with improved prognosis of the disease. Structural analysis allows us to interpret the effects of mutations on protein stability and catalytic activity, providing molecular evidence for clinical outcome and disease severity. Moreover, we identify an important number of mutants whose loss-of-functionality is associated with instability and, thus, are potential targets for rescue using folding therapeutic approaches.
authors.affiliation: Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Bravo-Alonso
authors.affiliation: Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Navarrete
authors.affiliation: Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Arribas-Carreira
authors.affiliation: SmartLigs S.L., Parque Científico de Madrid, Madrid, Spain.
authors.forename: Almudena
authors.initials: A
authors.lastname: Perona
authors.affiliation: Servicio de Bioinformática, Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Abia
authors.affiliation: Unit of Diagnosis and Treatment of Congenital Metabolic Diseases, Service of Neonatology, Department of Pediatrics, Hospital Clínico Universitario de Santiago, CIBERER, Health Research Institute of Santiago de Compostela (IDIS), Santiago de Compostela, Spain.
authors.forename: María Luz
authors.initials: ML
authors.lastname: Couce
authors.affiliation: Institut de Recerca Pediàtrica-Hospital Sant Joan de Déu (IRP-HSJD), Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain.
authors.forename: Angels
authors.initials: A
authors.lastname: García-Cazorla
authors.affiliation: Unidad de Nutrición Infantil y Enfermedades Metabólicas, Hospital Universitario Infantil La Paz, Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Morais
authors.affiliation: Servicio de Pediatría, Hospital Virgen de la Arrixaca, Murcia, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Domingo
authors.affiliation: Servicio de Genética, Hospital B del Complejo Hospitalario de Navarra, Pamplona, Navarra, Spain.
authors.forename: María Antonia
authors.initials: MA
authors.lastname: Ramos
authors.affiliation: Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado, Aurora, Colorado.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Swanson
authors.affiliation: Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado, Aurora, Colorado.
authors.forename: Johan L K
authors.initials: JLK
authors.lastname: Van Hove
authors.affiliation: Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Ugarte
authors.affiliation: Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain.
authors.forename: Belén
authors.initials: B
authors.lastname: Pérez
authors.affiliation: Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain.
authors.forename: Celia
authors.initials: C
authors.lastname: Pérez-Cerdá
authors.affiliation: Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa, CBM-CSIC, Departamento de Biología Molecular, Universidad Autónoma Madrid, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), IDIPAZ, Madrid, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Rodríguez-Pombo
mesh_terms: D005091:Exons / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D005998:Glycine / Q000378:metabolism; D050841:Glycine Dehydrogenase (Decarboxylating) / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D020158:Hyperglycinemia, Nonketotic / Q000235:genetics* / Q000473:pathology; D007231:Infant, Newborn; D008968:Molecular Conformation; D020125:Mutation, Missense / Q000235:genetics*; D010641:Phenotype; D055550:Protein Stability; D013329:Structure-Activity Relationship
chemical_list: D050841:Glycine Dehydrogenase (Decarboxylating); D005998:Glycine
keywords: GCS P-protein; GLDC gene; nonketotic hyperglycinemia; structure function and phenotype correlations in GLDC