SPP2 Mutations Cause Autosomal Dominant Retinitis Pigmentosa

Area of Science:

• Genetics
• Ophthalmology
• Molecular Biology

Background:

• Retinitis pigmentosa (RP) is a group of inherited retinal diseases characterized by progressive photoreceptor degeneration.
• RP has a complex genetic basis with numerous causative genes identified.
• The genetic etiology of RP in certain populations remains incompletely understood.

Purpose of the Study:

• To identify the genetic cause of autosomal dominant RP in a Chinese family.
• To investigate the functional consequences of a novel SPP2 gene variant in retinal degeneration.
• To elucidate the role of secreted phosphoprotein 2 (Spp-24) in photoreceptor health.

Main Methods:

• Exome sequencing and linkage analysis were performed on a Chinese family with autosomal dominant RP.
• A novel variant (p.Gly97Arg) in the SPP2 gene was identified and validated.
• In vitro overexpression studies and zebrafish models were used to assess the pathogenicity of SPP2 mutations.

Main Results:

• A pathogenic variant, p.Gly97Arg, in the SPP2 gene was identified as the cause of autosomal dominant RP in the studied family.
• The identified SPP2 variant was absent in control cohorts, indicating its rarity.
• Mutations in SPP2 exhibited dominant negative effects, leading to cellular retention of Spp-24 and affecting rod photoreceptors in zebrafish, mimicking RP phenotypes.

Conclusions:

• The study identifies SPP2 as a novel causative gene for retinitis pigmentosa.
• SPP2 mutations, particularly p.Gly97Arg, induce dominant negative effects and cellular accumulation of Spp-24, leading to photoreceptor toxicity.
• These findings highlight a new mechanism of retinal degeneration involving SPP2 and Spp-24 in the context of RP.