Four polymorphic variations in the PEDF gene identified during the mutation screening of patients with Leber congenital amaurosis

PURPOSE: Leber congenital amaurosis (LCA) has been mapped to chromosome 17p 13.1. From the candidate genes mapped to this region, thus far, only Retina l Guanylate Cyclase (RetGC), has been found to have pathogenic LCA mutation s, in families from North African origin. However, early reports, demonstra ted eight LCA families linked to 17p13.1, but only four of them showed muta tions in RetGC. Mapped in proximity to this locus is the candidate gene Pig ment Epithelium Derived actor (PEDF), a factor implicated in photoreceptor differentiation and neuronal survival. Our purpose in this study was to ide ntify mutations and polymorphisms in the PEDF gene in LCA patients of diver se ethnic origin. METHODS: Automated genotyping with four 17p13.1 markers flanking the PEDF g ene was performed to assess homozygosity and PCR-SSCP combined with direct sequencing was used to detect mutations in the PEDF gene in 17 LCA patients . RESULTS: Homozygosity of markers D17S796 and D17S804 was found and four new intragenic basepair alterations were discovered: a Met72Thr polymorphism i n exon 3 (T331C), a Thr130Thr polymorphism in exon 4 (T506C), a G to A tran sition in intron 5 (nine base pairs upstream from splice acceptor site), an d a Tyr321Tyr polymorphism in exon 7 (C1079T) were detected. CONCLUSIONS: We report the discovery of four new polymorphic alterations in the PEDF gene in LCA patients and exclude by RFLP analysis the PEDF gene a s a common cause of Leber congenital amaurosis. These single nucleotide pol ymorphisms will aid in future linkage analysis of complex multifactorial di seases involving retinal and RPE dysfunctions.