No abstract

The single X chromosome of a girl with Turner syndrome (45,X) and typical Duchenne muscular dystrophy was investigated at the chromosomal and DNA levels. No visible abnormality of the residual X chromosome was found upon high-resolution R-banding. The DNA was analysed by Southern blotting and hybridization with seven cloned probes mapping in the Xp21 region where the Duchenne locus is thought to be located. A molecular deletion was detected with probes pERT 87.1, pERT 87.8, and pERT 87.15. The other probes (754, C7, 99.6, and RC8) gave a normal signal. The DNA alleles seen in the two parents indicated that the deletion found in the propositus had occurred de novo on a maternal X chromosome.

Retinal dystrophies are a complex set of hereditary diseases of the retina that result in the degeneration of photoreceptors. Recent studies have shown that mutations in RPE65, a gene that codes for a retinal pigment epithelium (RPE)-specific protein thought to be involved in the 11-cis-retinoid metabolism, a key process in vision, cause severe, early onset retinal dystrophy. We describe two novel missense RPE65 mutations, L22P and H68Y, in a compound heterozygote with autosomal recessive retinal dystrophy. The relatively mild phenotype associated with these mutations suggests a possible link between the severity of the disease and the type of mutations in the RPE65 gene.