2. Academic Validation
  3. Nonketotic hyperglycinemia: Functional assessment of missense variants in GLDC to understand phenotypes of the disease

Nonketotic hyperglycinemia: Functional assessment of missense variants in GLDC to understand phenotypes of the disease

  • Hum Mutat. 2017 Jun;38(6):678-691. doi: 10.1002/humu.23208.
Irene Bravo-Alonso 1,  Rosa Navarrete 1,  Laura Arribas-Carreira 1,  Almudena Perona 2,  David Abia 3,  María Luz Couce 4,  Angels García-Cazorla 5,  Ana Morais 6,  Rosario Domingo 7,  María Antonia Ramos 8,  Michael A Swanson 9,  Johan L K Van Hove 9,  Magdalena Ugarte 1,  Belén Pérez 1,  Celia Pérez-Cerdá 1,  Pilar Rodríguez-Pombo 1
Affiliations

Affiliations

  • 1 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.
  • 2 SmartLigs S.L., Parque Científico de Madrid, Madrid, Spain.
  • 3 Servicio de Bioinformática, Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.
  • 4 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.
  • 5 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.
  • 6 Unidad de Nutrición Infantil y Enfermedades Metabólicas, Hospital Universitario Infantil La Paz, Madrid, Spain.
  • 7 Servicio de Pediatría, Hospital Virgen de la Arrixaca, Murcia, Spain.
  • 8 Servicio de Genética, Hospital B del Complejo Hospitalario de Navarra, Pamplona, Navarra, Spain.
  • 9 Department of Pediatrics, Section of Clinical Genetics and Metabolism, University of Colorado, Aurora, Colorado.
PMID: 28244183 DOI: 10.1002/humu.23208
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.

Keywords

GCS P-protein; GLDC gene; nonketotic hyperglycinemia; structure function and phenotype correlations in GLDC.

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