Mutation analysis of 272 Spanish families affected by autosomal recessive retinitis pigmentosa using a genotyping microarray

Abstract

Purpose: Retinitis pigmentosa (RP) is a genetically heterogeneous disorder characterized by progressive loss of vision. The aim of this study was to identify the causative mutations in 272 Spanish families using a genotyping microarray.

Methods: 272 unrelated Spanish families, 107 with autosomal recessive RP (arRP) and 165 with sporadic RP (sRP), were studied using the APEX genotyping microarray. The families were also classified by clinical criteria: 86 juveniles and 186 typical RP families. Haplotype and sequence analysis were performed to identify the second mutated allele.

Results: At least one-gene variant was found in 14% and 16% of the juvenile and typical RP groups respectively. Further study identified four new mutations, providing both causative changes in 11% of the families. Retinol Dehydrogenase 12 (RDH12) was the most frequently mutated gene in the juvenile RP group, and Usher Syndrome 2A (USH2A) and Ceramide Kinase-Like (CERKL) were the most frequently mutated genes in the typical RP group. The only variant found in CERKL was p.Arg257Stop, the most frequent mutation.

Conclusions: The genotyping microarray combined with segregation and sequence analysis allowed us to identify the causative mutations in 11% of the families. Due to the low number of characterized families, this approach should be used in tandem with other techniques.

Figure 1

Haplotype analysis of the chromosome segments encompassing arRP genes in those arRP families (A-H) in which the microarray detected one mutated allele. For the RP-1292 (E) the haplotype analysis shows the studied gene does not co-segregate with the disease. ►Where the gene is located.

Figure 2

Family pedigrees in which the co-segregation of the detected mutations was performed. “+” wild type allele, “m, m1 and m2” mutated alleles. A: Pedigrees of families with RP mutations. B: Pedigrees of families with RP mutations.