title: Mutations in XLF/NHEJ1/Cernunnos gene results in downregulation of telomerase genes expression and telomere shortening.
abstract: NHEJ1-patients develop severe progressive lymphocytopenia and premature aging of hematopoietic stem cells (HSCs) at a young age. Here we show a patient with a homozygous-NHEJ1 mutation identified by whole exome-sequencing that developed severe pancytopenia and bone marrow aplasia correlating with the presence of short telomeres. The mutation resulted in a truncated protein. In an attempt to identify the mechanism behind the short telomere phenotype found in the NHEJ1-patient we downregulated NHEJ1 expression in 293T and CD34+cells. This downregulation resulted in reduced telomerase activity and decreased expression of several telomerase/shelterin genes. Interestingly, cell lines derived from two other NHEJ1-deficient patients with different mutations also showed increased p21 expression, inhibition in expression of several telomerase complex genes and shortened telomeres. Decrease in expression of telomerase/shelterin genes did not occur when we inhibited expression of other NHEJ genes mutated in SCID patients: DNA-PK, Artemis or LigaseIV. Because premature aging of HSCs is observed only in NHEJ1 patients, we propose that is the result of senescence induced by decreased expression of telomerase/shelterin genes that lead to an inhibition of telomerase activity. Previous reports failed to find this connection because of the use of patient´s cells immortalized by TERT expression or recombined telomeres by ALT pathway. In summary, defective regulation of telomere biology together with defective V(D)J recombination can negatively impact on the evolution of the disease in these patients. Identification of telomere shortening is important since it may open new therapeutic interventions for these patients by treatments aimed to recover the expression of telomerase genes.
authors.affiliation: Instituto Investigaciones Biomédicas (CSIC/UAM), Madrid, Spain.
authors.forename: Jaime
authors.initials: J
authors.lastname: Carrillo
authors.affiliation: Human Genetics Group, Spanish National Cancer Research Center (CNIO), Madrid, Spain.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.
authors.forename: Oriol
authors.initials: O
authors.lastname: Calvete
authors.affiliation: Instituto Investigaciones Biomédicas (CSIC/UAM), Madrid, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Pintado-Berninches
authors.affiliation: Instituto Investigaciones Biomédicas (CSIC/UAM), Madrid, Spain.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Manguan-García
authors.affiliation: Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.|Hospital Infantil Universitario Niño Jesus, Madrid, Spain.
authors.forename: Julian
authors.initials: J
authors.lastname: Sevilla Navarro
authors.affiliation: Advanced Medical Projects, Madrid, Spain.
authors.forename: Elena G
authors.initials: EG
authors.lastname: Arias-Salgado
authors.affiliation: Instituto Investigaciones Biomédicas (CSIC/UAM), Madrid, Spain.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.|IDIPaz, Biomarkers and New Therapies, Madrid, Spain.
authors.forename: Leandro
authors.initials: L
authors.lastname: Sastre
authors.affiliation: Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.|Division of Hematopoietic Innovative Therapies, Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain.|Advanced Therapies Unit, Instituto de Investigación Sanitaria Fundación Jiménez Díaz (IIS-FJD, UAM), Madrid, Spain.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Guenechea
authors.affiliation: Inmunology Department, Hospital La Paz, Madrid, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: López Granados
authors.affiliation: Genome Dynamics in the Immune System Laboratory, Institut National de la Santé et de la Recherche Médicale, UMR 1163, Institut Imagine, Université Paris Descartes, Sorbonne Paris Cité, Paris, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: de Villartay
authors.affiliation: Genome Dynamics in the Immune System Laboratory, Institut National de la Santé et de la Recherche Médicale, UMR 1163, Institut Imagine, Université Paris Descartes, Sorbonne Paris Cité, Paris, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Revy
authors.affiliation: Human Genetics Group, Spanish National Cancer Research Center (CNIO), Madrid, Spain.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Benitez
authors.affiliation: Instituto Investigaciones Biomédicas (CSIC/UAM), Madrid, Spain.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.|IDIPaz, Biomarkers and New Therapies, Madrid, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Perona
mesh_terms: D002460:Cell Line; D002648:Child; D045643:DNA Repair Enzymes / Q000097:blood / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000097:blood / Q000235:genetics* / Q000378:metabolism*; D015536:Down-Regulation; D015870:Gene Expression; D006801:Humans; D008297:Male; D009154:Mutation / Q000235:genetics; D019098:Telomerase / Q000235:genetics*; D016615:Telomere / Q000235:genetics / Q000378:metabolism; D059505:Telomere Homeostasis; D059506:Telomere Shortening / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; C508551:NHEJ1 protein, human; D019098:Telomerase; D045643:DNA Repair Enzymes