Diagnostic strategy in segmentation defect of the vertebrae: a retrospective study of 73 patients

J Med Genet. 2018 Jun;55(6):422-429. doi: 10.1136/jmedgenet-2017-104939. Epub 2018 Feb 19.

Abstract

Background: Segmentation defects of the vertebrae (SDV) are non-specific features found in various syndromes. The molecular bases of SDV are not fully elucidated due to the wide range of phenotypes and classification issues. The genes involved are in the Notch signalling pathway, which is a key system in somitogenesis. Here we report on mutations identified in a diagnosis cohort of SDV. We focused on spondylocostal dysostosis (SCD) and the phenotype of these patients in order to establish a diagnostic strategy when confronted with SDV.

Patients and methods: We used DNA samples from a cohort of 73 patients and performed targeted sequencing of the five known SCD-causing genes (DLL3, MESP2, LFNG, HES7 and TBX6) in the first 48 patients and whole-exome sequencing (WES) in 28 relevant patients.

Results: Ten diagnoses, including four biallelic variants in TBX6, two biallelic variants in LFNG and DLL3, and one in MESP2 and HES7, were made with the gene panel, and two diagnoses, including biallelic variants in FLNB and one variant in MEOX1, were made by WES. The diagnostic yield of the gene panel was 10/73 (13.7%) in the global cohort but 8/10 (80%) in the subgroup meeting the SCD criteria; the diagnostic yield of WES was 2/28 (8%).

Conclusion: After negative array CGH, targeted sequencing of the five known SCD genes should only be performed in patients who meet the diagnostic criteria of SCD. The low proportion of candidate genes identified by WES in our cohort suggests the need to consider more complex genetic architectures in cases of SDV.

Keywords: diagnostic strategy; gene panel; segmentation defect of the vertebrae; spondylocostal dysostosis; whole exome sequencing.

MeSH terms

  • Adolescent
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Bone Diseases, Developmental / genetics*
  • Bone Diseases, Developmental / physiopathology
  • Child
  • Child, Preschool
  • Exome Sequencing*
  • Female
  • Glycosyltransferases / genetics
  • Humans
  • Infant
  • Intracellular Signaling Peptides and Proteins / genetics
  • Male
  • Membrane Proteins / genetics
  • Mutation
  • Pedigree
  • Phenotype
  • Spine / metabolism
  • Spine / pathology
  • T-Box Domain Proteins / genetics

Substances

  • Basic Helix-Loop-Helix Transcription Factors
  • DLL3 protein, human
  • HES7 protein, human
  • Intracellular Signaling Peptides and Proteins
  • MESP2 protein, human
  • Membrane Proteins
  • T-Box Domain Proteins
  • TBX6 protein, human
  • Glycosyltransferases
  • LFNG protein, human