Arg120stop nonsense mutation in the RP2 gene: mutational hotspot and germ line mosaicism?

Area of Science:

• Genetics
• Ophthalmology
• Molecular Biology

Background:

• X-linked recessive retinitis pigmentosa (XLRP) is a significant cause of inherited blindness.
• Mutations in the RP2 gene are responsible for up to 20% of XLRP cases.
• The Arg120stop mutation is the most common RP2 mutation identified to date.

Observation:

• A C-to-T transition at position 358 in the RP2 gene, resulting in the Arg120stop nonsense mutation, was identified in a South African family of German origin.
• This Arg120stop mutation was found to cosegregate with the disease in affected family members.
• Crucially, the Arg120stop mutation was not detected in the somatic cells of the obligate carrier female.

Findings:

• This study reports the first instance of germline mosaicism for an RP2 gene mutation in a family with XLRP.
• The identified Arg120stop mutation is a key genetic factor in this family's retinal degeneration.
• Germline mosaicism presents a challenge for carrier detection using standard molecular testing of somatic cells.

Implications:

• Accurate genetic counseling for families with X-linked retinitis pigmentosa is critical.
• The rare occurrence of germline mosaicism can lead to inaccurate risk assessments.
• Molecular testing should always guide genetic counseling for retinal degeneration to account for potential epigenetic events and mosaicism.