TTC21B contributes both causal and modifying alleles across the ciliopathy spectrum

Nat Genet. 2011 Mar;43(3):189-96. doi: 10.1038/ng.756. Epub 2011 Jan 23.


Ciliary dysfunction leads to a broad range of overlapping phenotypes, collectively termed ciliopathies. This grouping is underscored by genetic overlap, where causal genes can also contribute modifier alleles to clinically distinct disorders. Here we show that mutations in TTC21B, which encodes the retrograde intraflagellar transport protein IFT139, cause both isolated nephronophthisis and syndromic Jeune asphyxiating thoracic dystrophy. Moreover, although resequencing of TTC21B in a large, clinically diverse ciliopathy cohort and matched controls showed a similar frequency of rare changes, in vivo and in vitro evaluations showed a significant enrichment of pathogenic alleles in cases (P < 0.003), suggesting that TTC21B contributes pathogenic alleles to ∼5% of ciliopathy cases. Our data illustrate how genetic lesions can be both causally associated with diverse ciliopathies and interact in trans with other disease-causing genes and highlight how saturated resequencing followed by functional analysis of all variants informs the genetic architecture of inherited disorders.

Publication types

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

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Alleles*
  • Animals
  • Ciliary Motility Disorders / genetics*
  • Genetic Variation
  • Humans
  • Mice
  • Mutation
  • Pedigree
  • Photoreceptor Cells / physiology
  • Zebrafish / genetics


  • Adaptor Proteins, Signal Transducing
  • Ttc21b protein, mouse

Associated data

  • RefSeq/NM_001128258
  • RefSeq/NM_024753
  • RefSeq/NP_079029