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A novel homozygous truncating GNAT1 mutation implicated in retinal degeneration
  1. Matthew Carrigan1,
  2. Emma Duignan2,
  3. Pete Humphries1,
  4. Arpad Palfi1,
  5. Paul F Kenna1,2,
  6. G Jane Farrar1
  1. 1School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland
  2. 2Research Foundation, Royal Victoria Eye & Ear Hospital, Dublin, Ireland
  1. Correspondence to Dr Matthew Carrigan, Smurfit Institute of Genetics, Trinity College Dublin, College Green, Dublin 2, Ireland; carrigma{at}


Background The GNAT1 gene encodes the α subunit of the rod transducin protein, a key element in the rod phototransduction cascade. Variants in GNAT1 have been implicated in stationary night-blindness in the past, but unlike other proteins in the same pathway, it has not previously been implicated in retinitis pigmentosa.

Methods A panel of 182 retinopathy-associated genes was sequenced to locate disease-causing mutations in patients with inherited retinopathies.

Results Sequencing revealed a novel homozygous truncating mutation in the GNAT1 gene in a patient with significant pigmentary disturbance and constriction of visual fields, a presentation consistent with retinitis pigmentosa. This is the first report of a patient homozygous for a complete loss-of-function GNAT1 mutation. The clinical data from this patient provide definitive evidence of retinitis pigmentosa with late onset in addition to the lifelong night-blindness that would be expected from a lack of transducin function.

Conclusion These data suggest that some truncating GNAT1 variants can indeed cause a recessive, mild, late-onset retinal degeneration in human beings rather than just stationary night-blindness as reported previously, with notable similarities to the phenotype of the Gnat1 knockout mouse.

  • Retina
  • Genetics
  • Degeneration

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