Pathogenic variants in IMPG1 cause autosomal dominant and autosomal recessive retinitis pigmentosa

J Med Genet. 2021 Aug;58(8):570-578. doi: 10.1136/jmedgenet-2020-107150. Epub 2020 Aug 17.


Background: Inherited retinal disorders are a clinically and genetically heterogeneous group of conditions and a major cause of visual impairment. Common disease subtypes include vitelliform macular dystrophy (VMD) and retinitis pigmentosa (RP). Despite the identification of over 90 genes associated with RP, conventional genetic testing fails to detect a molecular diagnosis in about one third of patients with RP.

Methods: Exome sequencing was carried out for identifying the disease-causing gene in a family with autosomal dominant RP. Gene panel testing and exome sequencing were performed in 596 RP and VMD families to identified additional IMPG1 variants. In vivo analysis in the medaka fish system by knockdown assays was performed to screen IMPG1 possible pathogenic role.

Results: Exome sequencing of a family with RP revealed a splice variant in IMPG1. Subsequently, the same variant was identified in individuals from two families with either RP or VMD. A retrospective study of patients with RP or VMD revealed eight additional families with different missense or nonsense variants in IMPG1. In addition, the clinical diagnosis of the IMPG1 retinopathy-associated variant, originally described as benign concentric annular macular dystrophy, was also revised to RP with early macular involvement. Using morpholino-mediated ablation of Impg1 and its paralog Impg2 in medaka fish, we confirmed a phenotype consistent with that observed in the families, including a decreased length of rod and cone photoreceptor outer segments.

Conclusion: This study discusses a previously unreported association between monoallelic or biallelic IMPG1 variants and RP. Notably, similar observations have been reported for IMPG2.

Keywords: eye diseases; genetics; ophthalmology; sequence analysis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Arthrogryposis / genetics
  • Exome / genetics
  • Exome Sequencing / methods
  • Extracellular Matrix Proteins / genetics*
  • Eye Proteins / genetics*
  • Female
  • Genes, Recessive / genetics*
  • Genetic Predisposition to Disease / genetics*
  • Humans
  • Inheritance Patterns / genetics
  • Macular Degeneration / genetics
  • Male
  • Middle Aged
  • Mutation / genetics*
  • Pedigree
  • Phenotype
  • Proteoglycans / genetics*
  • Retina / pathology
  • Retinitis Pigmentosa / genetics*
  • Retrospective Studies


  • Extracellular Matrix Proteins
  • Eye Proteins
  • IMPG1 protein, human
  • Proteoglycans

Supplementary concepts

  • Macular dystrophy, concentric annular
  • Multiple Pterygium Syndrome, Autosomal Dominant