Mutations in the β-subunit of rod phosphodiesterase identified in consanguineous Pakistani families with autosomal recessive retinitis pigmentosa

PURPOSE: This study was designed to identify pathogenic mutations causing autosomal recessive retinitis pigmentosa (RP) in consanguineous Pakistani families. METHODS: Two consanguineous families affected with autosomal recessive RP were identified from the Punjab Province of Pakistan. All affected individuals underwent a thorough ophthalmologic examination. Blood samples were collected, and genomic DNAs were extracted. Exclusion analysis was completed, and two-point LOD scores were calculated. Bidirectional sequencing of the β subunit of phosphodiesterase 6 (PDE6β) was completed. RESULTS: During exclusion analyses both families localized to chromosome 4p, harboring PDE6β, a gene previously associated with autosomal recessive RP. Sequencing of PDE6β identified missense mutations: c.1655G>A (p.R552Q) and c.1160C>T (p.P387L) in families PKRP161 and PKRP183, respectively. Bioinformatic analyses suggested that both mutations are deleterious for the native three-dimensional structure of the PDE6β protein. CONCLUSIONS: These results strongly suggest that mutations in PDE6β are responsible for the disease phenotype in the consanguineous Pakistani families.