Browsing by Author "Lazo, Pedro A."
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Item Dysfunctional Homozygous VRK1-D263G Variant Impairs the Assembly of Cajal Bodies and DNA Damage Response in Hereditary Spastic Paraplegia.(Neurology Genetics, 2021) Morejón García, Patricia; Keren, Boris; Marcos Alcalde, Íñigo; Gómez Puertas, Paulino; Mochel, Fanny; Lazo, Pedro A.Background and Objectives To conduct a genetic and molecular functional study of a family with members affected of hereditary spastic paraplegia (HSP) of unknown origin and carrying a novel pathogenic vaccinia-related kinase 1 (VRK1) variant. Methods Whole-exome sequencing was performed in 2 patients, and their parents diagnosed with HSP. The novel VRK1 variant was detected by whole-exome sequencing, molecularly modeled and biochemically characterized in kinase assays. Functionally, we studied the role of this VRK1 variant in DNA damage response and its effect on the assembly of Cajal bodies (CBs). Results We have identified a very rare homozygous variant VRK1-D263G with a neurologic phenotype associated with HSP and moderate intellectual disability. The molecular modeling of this VRK1 variant protein predicted an alteration in the folding of a loop that interferes with the access to the kinase catalytic site. The VRK1-D263G variant is kinase inactive and does not phosphorylate histones H2AX and H3, transcription factors activating transcription factor 2 and p53, coilin needed for assembly of CBs, and p53 binding protein 1, a DNA repair protein. Functionally, this VRK1 variant protein impairs CB formation and the DNA damage response. Discussion This report expands the neurologic spectrum of neuromotor syndromes associated with a new and rare VRK1 variant, representing a novel pathogenic participant in complicated HSP and demonstrates that CBs and the DNA damage response are impaired in these patients.Item Novel Dominant KCNQ2 Exon 7 Partial In-Frame Duplication in a Complex Epileptic and Neurodevelopmental Delay Syndrome.(International Journal of Molecular Sciences, 2020) Lazo, Pedro A.; García, Juan L.; Gómez-Puertas, Paulino; Marcos Alcalde, Íñigo; Arjona, Cesar; Villarroel, Alvaro; González-Sarmiento, Rogelio; Fons, CarmenComplex neurodevelopmental syndromes frequently have an unknown etiology, in which genetic factors play a pathogenic role. This study utilizes whole-exome sequencing (WES) to examine four members of a family with a son presenting, since birth, with epileptic-like crises, combined with cerebral palsy, severe neuromotor and developmental delay, dystonic tetraparexia, axonal motor affectation, and hyper-excitability of unknown origin. The WES study detected within the patient a de novo heterozygous in-frame duplication of thirty-six nucleotides within exon 7 of the human KCNQ2 gene. This insertion duplicates the first twelve amino acids of the calmodulin binding site I. Molecular dynamics simulations of this KCNQ2 peptide duplication, modelled on the 3D structure of the KCNQ2 protein, suggest that the duplication may lead to the dysregulation of calcium inhibition of this protein function.Item Pathogenic convergence of CNVs in genes functionally associated to a severe neuromotor developmental delay syndrome.(Human Genomics, 2021) García-Hernández, Juan L.; Corchete, Luis A.; Marcos Alcalde, Íñigo; Gómez Puertas, Paulino; Fons, Carmen; Lazo, Pedro A.Background Complex developmental encephalopathy syndromes might be the consequence of unknown genetic alterations that are likely to contribute to the full neurological phenotype as a consequence of pathogenic gene combinations. Methods To identify the additional genetic contribution to the neurological phenotype, we studied as a test case a boy, with a KCNQ2 exon-7 partial duplication, by single-nucleotide polymorphism (SNP) microarray to detect copy-number variations (CNVs). Results The proband presented a cerebral palsy like syndrome with a severe motor and developmental encephalopathy. The SNP array analysis detected in the proband several de novo CNVs, nine partial gene losses (LRRC55, PCDH9, NALCN, RYR3, ELAVL2, CDH13, ATP1A2, SLC17A5, ANO3), and two partial gene duplications (PCDH19, EFNA5). The biological functions of these genes are associated with ion channels such as calcium, chloride, sodium, and potassium with several membrane proteins implicated in neural cell-cell interactions, synaptic transmission, and axon guidance. Pathogenically, these functions can be associated to cerebral palsy, seizures, dystonia, epileptic crisis, and motor neuron dysfunction, all present in the patient. Conclusions Severe motor and developmental encephalopathy syndromes of unknown origin can be the result of a phenotypic convergence by combination of several genetic alterations in genes whose physiological function contributes to the neurological pathogenic mechanism.Item VRK1 (Y213H) homozygous mutant impairs Cajal bodies in a hereditary case of distal motor neuropathy.(Annals of Clinical and Translational Neurology, 2020) Marcos, Ana T.; Martín Doncel, Elena; Morejón García, Patricia; Marcos Alcalde, Íñigo; Gómez Puertas, Paulino; Segura Puimedon, María; Armengol, Lluis; Navarro Pando, José M.; Lazo, Pedro A.Background: Distal motor neuropathies with a genetic origin have a heterogeneous clinical presentation with overlapping features affecting distal nerves and including spinal muscular atrophies and amyotrophic lateral sclerosis. This indicates that their genetic background is heterogeneous. Patient and methods: In this work, we have identified and characterized the genetic and molecular base of a patient with a distal sensorimotor neuropathy of unknown origin. For this study, we performed whole-exome sequencing, molecular modelling, cloning and expression of mutant gene, and biochemical and cell biology analysis of the mutant protein. Results: A novel homozygous recessive mutation in the human VRK1 gene, coding for a chromatin kinase, causing a substitution (c.637T > C; p.Tyr213His) in exon 8, was detected in a patient presenting since childhood a progressive distal sensorimotor neuropathy and spinal muscular atrophy syndrome, with normal intellectual development. Molecular modelling predicted this mutant VRK1 has altered the kinase activation loop by disrupting its interaction with the C-terminal regulatory region. The p.Y213H mutant protein has a reduced kinase activity with different substrates, including histones H3 and H2AX, proteins involved in DNA damage responses, such as p53 and 53BP1, and coilin, the scaffold for Cajal bodies. The mutant VRK1(Y213H) protein is unable to rescue the formation of Cajal bodies assembled on coilin, in the absence of wild-type VRK1. Conclusion: The VRK1(Y213H) mutant protein alters the activation loop, impairs the kinase activity of VRK1 causing a functional insufficiency that impairs the formation of Cajal bodies assembled on coilin, a protein that regulates SMN1 and Cajal body formation.