TBX6-associated congenital scoliosis (TACS) as a clinically distinguishable subtype of congenital scoliosis: further evidence supporting the compound inheritance and TBX6 gene dosage model

Genet Med. 2019 Jul;21(7):1548-1558. doi: 10.1038/s41436-018-0377-x. Epub 2019 Jan 14.


Purpose: To characterize clinically measurable endophenotypes, implicating the TBX6 compound inheritance model.

Methods: Patients with congenital scoliosis (CS) from China(N = 345, cohort 1), Japan (N = 142, cohort 2), and the United States (N = 10, cohort 3) were studied. Clinically measurable endophenotypes were compared according to the TBX6 genotypes. A mouse model for Tbx6 compound inheritance (N = 52) was investigated by micro computed tomography (micro-CT). A clinical diagnostic algorithm (TACScore) was developed to assist in clinical recognition of TBX6-associated CS (TACS).

Results: In cohort 1, TACS patients (N = 33) were significantly younger at onset than the remaining CS patients (P = 0.02), presented with one or more hemivertebrae/butterfly vertebrae (P = 4.9 × 10‒8), and exhibited vertebral malformations involving the lower part of the spine (T8-S5, P = 4.4 × 10‒3); observations were confirmed in two replication cohorts. Simple rib anomalies were prevalent in TACS patients (P = 3.1 × 10‒7), while intraspinal anomalies were uncommon (P = 7.0 × 10‒7). A clinically usable TACScore was developed with an area under the curve (AUC) of 0.9 (P = 1.6 × 10‒15). A Tbx6-/mh (mild-hypomorphic) mouse model supported that a gene dosage effect underlies the TACS phenotype.

Conclusion: TACS is a clinically distinguishable entity with consistent clinically measurable endophenotypes. The type and distribution of vertebral column abnormalities in TBX6/Tbx6 compound inheritance implicate subtle perturbations in gene dosage as a cause of spine developmental birth defects responsible for about 10% of CS.

Keywords: 16p11.2/TBX6; compound inheritance model; congenital scoliosis (CS); gene dosage; genotype-phenotype correlation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cohort Studies
  • Disease Models, Animal
  • Gene Dosage*
  • Humans
  • Inheritance Patterns*
  • Mice
  • Models, Genetic
  • Scoliosis / classification
  • Scoliosis / congenital*
  • Scoliosis / genetics*
  • Scoliosis / pathology
  • Spine / pathology
  • T-Box Domain Proteins / genetics*


  • T-Box Domain Proteins
  • TBX6 protein, human
  • Tbx6 protein, mouse