Loss of DDRGK1 modulates SOX9 ubiquitination in spondyloepimetaphyseal dysplasia

J Clin Invest. 2017 Apr 3;127(4):1475-1484. doi: 10.1172/JCI90193. Epub 2017 Mar 6.


Shohat-type spondyloepimetaphyseal dysplasia (SEMD) is a skeletal dysplasia that affects cartilage development. Similar skeletal disorders, such as spondyloepiphyseal dysplasias, are linked to mutations in type II collagen (COL2A1), but the causative gene in SEMD is not known. Here, we have performed whole-exome sequencing to identify a recurrent homozygous c.408+1G>A donor splice site loss-of-function mutation in DDRGK domain containing 1 (DDRGK1) in 4 families affected by SEMD. In zebrafish, ddrgk1 deficiency disrupted craniofacial cartilage development and led to decreased levels of the chondrogenic master transcription factor sox9 and its downstream target, col2a1. Overexpression of sox9 rescued the zebrafish chondrogenic and craniofacial phenotype generated by ddrgk1 knockdown, thus identifying DDRGK1 as a regulator of SOX9. Consistent with these results, Ddrgk1-/- mice displayed delayed limb bud chondrogenic condensation, decreased SOX9 protein expression and Col2a1 transcript levels, and increased apoptosis. Furthermore, we determined that DDRGK1 can directly bind to SOX9 to inhibit its ubiquitination and proteasomal degradation. Taken together, these data indicate that loss of DDRGK1 decreases SOX9 expression and causes a human skeletal dysplasia, identifying a mechanism that regulates chondrogenesis via modulation of SOX9 ubiquitination.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Carrier Proteins / physiology*
  • Cartilage / growth & development
  • Cells, Cultured
  • Chondrogenesis
  • Collagen Type II / genetics
  • Collagen Type II / metabolism
  • Gene Expression
  • Genetic Association Studies
  • Genetic Predisposition to Disease
  • Homozygote
  • Humans
  • Mice, Knockout
  • Mutation
  • Osteochondrodysplasias / genetics*
  • Osteochondrodysplasias / metabolism
  • Pedigree
  • Protein Isoforms / physiology
  • Protein Stability
  • RNA Splice Sites
  • SOX9 Transcription Factor / metabolism*
  • Ubiquitination*
  • Zebrafish


  • Adaptor Proteins, Signal Transducing
  • COL2A1 protein, human
  • Carrier Proteins
  • Collagen Type II
  • DDRGK1 protein, human
  • Protein Isoforms
  • RNA Splice Sites
  • SOX9 Transcription Factor
  • SOX9 protein, human

Supplementary concepts

  • Spondyloepimetaphyseal Dysplasia, Shohat Type