Kimberlie Vandenburgh

A single EFEMP1 mutation associated with both Malattia Leventinese and Doyne honeycomb retinal dystrophy

Malattia Leventinese (ML) and Doyne honeycomb retinal dystrophy (DHRD) refer to two autosomal dominant diseases characterized by yellow-white deposits known as drusen that accumulate beneath the retinal pigment epithelium (RPE). Both loci were mapped to chromosome 2p16-21 (Refs 5,6) and this genetic interval has been subsequently narrowed. The importance of these diseases is due in large part to their close phenotypic similarity to age-related macular degeneration (AMD), a disorder with a strong genetic component that accounts for approximately 50% of registered blindness in the Western world. Just as in ML and DHRD, the early hallmark of AMD is the presence of drusen. Here we use a combination of positional and candidate gene methods to identify a single non-conservative mutation (Arg345Trp) in the gene EFEMP1 (for EGF-containing fibrillin-like extracellular matrix protein 1) in all families studied. This change was not present in 477 control individuals or in 494 patients with age-related macular degeneration. Identification of this mutation may aid in the development of an animal model for drusen, as well as in the identification of other genes involved in human macular degeneration.

Allelic variation in ABCR associated with Stargardt disease but not age-related macular degeneration.

Allelic variation in ABCR associated with Stargardt disease but not age-related macular degeneration

Retinitis Pigmentosa Associated With a Dominant Mutation in Codon 46 of the Peripherin/RDS Gene (Arginine-46-Stop)

PURPOSE We identified genetic mutations and characterized their associated phenotypes in patients with retinitis pigmentosa. METHODS Patients with retinitis pigmentosa were prospectively examined and screened for genetic mutations. RESULTS A 46-year-old man with retinitis pigmentosa was found to have a heterozygous mutation in the peripherin/RDS gene (arginine-46-stop). He had late onset of symptoms and demarcated peripheral retinal atrophy. All five first-degree relatives including his parents had no detectable mutations or retinitis pigmentosa. Genotypic data were consistent with reported family structure. CONCLUSIONS This study shows that new dominant mutations are a rare cause of isolated, or simplex, cases of retinitis pigmentosa. Identification of these mutations is helpful for genetic counseling.

Clinical Features of a Previously Undescribed Codon 216 (proline to serine) Mutation in the Peripherin/Retinal Degeneration Slow Gene in Autosomal Dominant Retinitis Pigmentosa

BACKGROUND Mutations in the human peripherin/retinal degeneration slow (rds) gene have been found in patients with macular dystrophies as well as in those with autosomal dominant retinitis pigmentosa. The authors studied the clinical features in members of two families with autosomal dominant retinitis pigmentosa and a previously unreported mutation in the peripherin/rds gene. METHODS Affected family members underwent a clinical ophthalmic examination and electrophysiologic and psychophysical testing. Available family members were evaluated for a mutation in the peripherin/rds gene. RESULTS A mutation in codon 216 of the peripherin/rds gene, resulting in a substitution of the amino acid serine for proline, was found to segregate with retinitis pigmentosa in these two families. Ocular features of this mutation include a later onset of more notable ophthalmoscopic, electrophysiologic, and psychophysical abnormalities of the retina, an atrophic-appearing foveal lesion, and extrafoveal atrophic and hyperpigmented degenerative retinal changes, which were found more posteriorly than usually seen in patients with retinitis pigmentosa. Visual field testing showed a partial ring scotoma or pear-shaped configuration of the remaining portions of the peripheral fields. CONCLUSION A previously undescribed mutation in the peripherin/rds gene is responsible for an autosomal dominant retinitis pigmentosa phenotype. This phenotype tends to be associated with the development of an atrophic-appearing foveal lesion, more posterior distribution of pigmentary changes involving the vascular arcades, the presence of a partial ring scotoma or a pear-shaped configuration of the peripheral visual field, and a later onset of more extensive retinal structural and functional impairment.

27 – Identification of Rhodopsin Gene Mutations Using GC-Clamped Denaturing Gradient Gel Electrophoresis

Publisher Summary Several techniques have been developed that make it possible to detect single base changes in DNA. These techniques include allele-specific oligonucleotide (ASO) hybridization, RNase cleavage, chemical cleavage, single-stranded conformation polymorphism (SSCP) analysis, heteroduplex analysis, and denaturing gradient gel electrophoresis (DGGE). Some of these techniques are not suitable for screening DNA for mutations. GC-clamped DGGE makes it possible to detect nearly 100% of single-base changes in DNA fragments of about 500 bp in length. This chapter describes the use of GC-clamped DGGE for the detection of rhodopsin coding sequence mutations. These methods are also applicable to the study of other candidate genes that may be involved in human retinal degeneration. DGGE can physically separate fragments differing by a single-base substitution on the basis of a difference in melting temperature (T m ) of the two molecules. A single-base change alters the T m of a given DNA melting domain by up to 2°C. Melting of a domain changes the conformation of the DNA molecule and, thus, affects its rate of migration through a polyacrylamide gel matrix.