Nuclear/cytoplasmic transport defects in BBS6 underlie congenital heart disease through perturbation of a chromatin remodeling protein

PLoS Genet. 2017 Jul 28;13(7):e1006936. doi: 10.1371/journal.pgen.1006936. eCollection 2017 Jul.


Mutations in BBS6 cause two clinically distinct syndromes, Bardet-Biedl syndrome (BBS), a syndrome caused by defects in cilia transport and function, as well as McKusick-Kaufman syndrome, a genetic disorder characterized by congenital heart defects. Congenital heart defects are rare in BBS, and McKusick-Kaufman syndrome patients do not develop retinitis pigmentosa. Therefore, the McKusick-Kaufman syndrome allele may highlight cellular functions of BBS6 distinct from the presently understood functions in the cilia. In support, we find that the McKusick-Kaufman syndrome disease-associated allele, BBS6H84Y; A242S, maintains cilia function. We demonstrate that BBS6 is actively transported between the cytoplasm and nucleus, and that BBS6H84Y; A242S, is defective in this transport. We developed a transgenic zebrafish with inducible bbs6 to identify novel binding partners of BBS6, and we find interaction with the SWI/SNF chromatin remodeling protein Smarcc1a (SMARCC1 in humans). We demonstrate that through this interaction, BBS6 modulates the sub-cellular localization of SMARCC1 and find, by transcriptional profiling, similar transcriptional changes following smarcc1a and bbs6 manipulation. Our work identifies a new function for BBS6 in nuclear-cytoplasmic transport, and provides insight into the disease mechanism underlying the congenital heart defects in McKusick-Kaufman syndrome patients.

MeSH terms

  • Abnormalities, Multiple / genetics*
  • Abnormalities, Multiple / metabolism
  • Abnormalities, Multiple / pathology
  • Active Transport, Cell Nucleus / genetics
  • Animals
  • Animals, Genetically Modified / genetics
  • Bardet-Biedl Syndrome / genetics*
  • Bardet-Biedl Syndrome / metabolism
  • Bardet-Biedl Syndrome / pathology
  • Chromatin / genetics
  • Chromatin Assembly and Disassembly / genetics
  • Cilia / metabolism
  • Cilia / pathology
  • Cytoplasm / metabolism
  • Disease Models, Animal
  • Group II Chaperonins / genetics*
  • Heart Defects, Congenital / genetics*
  • Heart Defects, Congenital / metabolism
  • Heart Defects, Congenital / pathology
  • Humans
  • Hydrocolpos / genetics*
  • Hydrocolpos / metabolism
  • Hydrocolpos / pathology
  • Mice
  • Mutation
  • Polydactyly / genetics*
  • Polydactyly / metabolism
  • Polydactyly / pathology
  • Protein Transport / genetics
  • Transcription Factors / biosynthesis
  • Transcription Factors / genetics*
  • Uterine Diseases / genetics*
  • Uterine Diseases / metabolism
  • Uterine Diseases / pathology
  • Zebrafish / genetics


  • Chromatin
  • MKKS protein, human
  • SMARCC1 protein, human
  • Transcription Factors
  • Group II Chaperonins

Supplementary concepts

  • Bardet-Biedl Syndrome 6
  • McKusick Kaufman syndrome