2. Academic Validation
  3. Functional analysis of TLK2 variants and their proximal interactomes implicates impaired kinase activity and chromatin maintenance defects in their pathogenesis

Functional analysis of TLK2 variants and their proximal interactomes implicates impaired kinase activity and chromatin maintenance defects in their pathogenesis

  • J Med Genet. 2022 Feb;59(2):170-179. doi: 10.1136/jmedgenet-2020-107281.
Lisa Pavinato 1 2,  Marina Villamor-Payà 3,  Maria Sanchiz-Calvo 3,  Cristina Andreoli 4,  Marina Gay 3,  Marta Vilaseca 3,  Gianluca Arauz-Garofalo 3,  Andrea Ciolfi 5,  Alessandro Bruselles 6,  Tommaso Pippucci 7,  Valentina Prota 4,  Diana Carli 8,  Elisa Giorgio 1 9,  Francesca Clementina Radio 5,  Vincenzo Antona 10,  Mario Giuffrè 10,  Kara Ranguin 11,  Cindy Colson 11,  Silvia De Rubeis 12 13 14 15,  Paola Dimartino 16,  Joseph D Buxbaum 12 13 14 15 17 18,  Giovanni Battista Ferrero 8,  Marco Tartaglia 5,  Simone Martinelli 19,  Travis H Stracker # 3 20,  Alfredo Brusco # 21 22
Affiliations

Affiliations

  • 1 Department of Medical Sciences, University of Turin, Torino, Italy.
  • 2 Institute of Human Genetics and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.
  • 3 The Barcelona Institute of Science and Technology, Institute for Research in Biomedicine, Barcelona, Spain.
  • 4 Department of Environment and Health, Istituto Superiore di Sanità, Roma, Italy.
  • 5 Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù IRCCS, Roma, Italy.
  • 6 Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy.
  • 7 Medical Genetics Unity, Sant'Orsola-Malpighi University Hospital, Bologna, Italy.
  • 8 Department of Pediatrics and Public Health and Pediatric Sciences, University of Turin, Torino, Italy.
  • 9 Department of Molecular Medicine, University of Pavia, Pavia, Italy.
  • 10 Department of Sciences for Health Promotion and Mother and Child Care "G. D'Alessandro", University of Palermo, Palermo, Italy.
  • 11 Department of Genetics, Reference center for Rare Diseases and Developmental Anomalies, Caen, France.
  • 12 Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York City, New York, USA.
  • 13 Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York City, New York, USA.
  • 14 The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York City, New York, USA.
  • 15 Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York City, New York, USA.
  • 16 Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy.
  • 17 Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York City, New York, USA.
  • 18 Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York City, New York, USA.
  • 19 Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Roma, Italy.
  • 20 Radiation Oncology Branch, National Cancer Institute, Bethesda, Maryland, USA.
  • 21 Department of Medical Sciences, University of Turin, Torino, Italy alfredo.brusco@unito.it.
  • 22 Unit of Medical Genetics, "Città della Salute e della Scienza" University Hospital, Torino, Italy.
  • # Contributed equally.
PMID: 33323470 DOI: 10.1136/jmedgenet-2020-107281
Abstract

Introduction: The Tousled-like kinases 1 and 2 (TLK1 and TLK2) are involved in many fundamental processes, including DNA replication, cell cycle checkpoint recovery and chromatin remodelling. Mutations in TLK2 were recently associated with 'Mental Retardation Autosomal Dominant 57' (MRD57, MIM# 618050), a neurodevelopmental disorder characterised by a highly variable phenotype, including mild-to-moderate intellectual disability, behavioural abnormalities, facial dysmorphisms, microcephaly, epilepsy and skeletal anomalies.

Methods: We re-evaluate whole exome Sequencing and array-CGH data from a large cohort of patients affected by neurodevelopmental disorders. Using spatial proteomics (BioID) and single-cell gel electrophoresis, we investigated the proximity interaction landscape of TLK2 and analysed the effects of p.(Asp551Gly) and a previously reported missense variant (c.1850C>T; p.(Ser617Leu)) on TLK2 interactions, localisation and activity.

Results: We identified three new unrelated MRD57 families. Two were sporadic and caused by a missense change (c.1652A>G; p.(Asp551Gly)) or a 39 kb deletion encompassing TLK2, and one was familial with three affected siblings who inherited a nonsense change from an affected mother (c.1423G>T; p.(Glu475Ter)). The clinical phenotypes were consistent with those of previously reported cases. The tested mutations strongly impaired TLK2 kinase activity. Proximal interactions between TLK2 and Other factors implicated in neurological disorders, including CHD7, CHD8, BRD4 and NACC1, were identified. Finally, we demonstrated a more relaxed chromatin state in lymphoblastoid cells harbouring the p.(Asp551Gly) variant compared with control cells, conferring susceptibility to DNA damage.

Conclusion: Our study identified novel TLK2 pathogenic variants, confirming and further expanding the MRD57-related phenotype. The molecular characterisation of missense variants increases our knowledge about TLK2 function and provides new insights into its role in neurodevelopmental disorders.

Keywords

genetic research; genetics; loss of function mutation; medical; missense; molecular biology; mutation.

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