Abstract
Purpose :
Mutations in the Retinitis Pigmentosa GTPase Regulator (RPGR) gene are associated with X-chromosomal recessive Retinitis Pigmentosa (RP) and lead to ciliary mis-localization of the RPGR protein. Hemizygous males of an RPGR mutation are affected by RP. Suprisingly, carrier females may also present with severe phenotypes of RP. The underlying pathomechanism of RP in carrier females is not yet fully understood.
Methods :
We analyzed a three-generation family co-segregating a non-sense mutation in the RPGR gene using genomic DNA extraction, X-chromosomal inactivation assays, as well as immunocytochemistry of primary cilia of cultured human patient- and control-derived fibroblast. Patients and control clinical phenotypes were analyzed in detail.
Results :
The male index patient was severely affected by RP. Two of the three female carriers in the pedigree were also affected by RP. In patient-derived cell lines, we found that the loss of RPGR causes shortening of the lengths of primary cilia. In several cell lines derived from carrier females, we found that RPGR transcript expression, primary cilia localization of RPGR proteins, and primary cilia length are tightly correlated with X-chromosome inactivation (XCI) patterns. Skewed XCI disturbed the localization of RPGR along primary cilia and led to reduced cilium length.
Conclusions :
We conclude that skewed XCI can cause RP in affected female carriers of RPGR mutations. Our study will support currently developed gene therapies with the aim to help patients affected by RPGR mutations.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.