RESUMEN
BACKGROUND: Variegate porphyria (VP) is due to a partial deficiency of protoporphyrinogen oxidase (PPOX), the seventh enzyme in the haem biosynthetic pathway. Clinically, VP is characterized by photosensitivity and acute neurovisceral attacks that can manifest separately or together in affected individuals. The disease is inherited in an autosomal dominant fashion with incomplete penetrance and PPOX gene mutations associated with VP are usually unique to patients and their families. In South Africa, however, VP is highly prevalent as the result of a founder mutation, designated p.R59W. Previous genealogical and haplotype studies showed a link between South African and Dutch carriers of p.R59W and it was suggested that this mutation was introduced to South Africa by Dutch settlers at the end of the 17th century. OBJECTIVES: To perform extended haplotype analysis in six South African and Dutch VP families with the p.R59W mutation. METHODS: Haplotyping of 13 microsatellite markers flanking the PPOX gene on chromosome 1q22-23 and five informative single nucleotide polymorphisms within and around the gene. RESULTS: A core haplotype cosegregated in all families studied. CONCLUSIONS: Our data deliver further confirmation that the South African and Dutch VP families carrying mutation p.R59W shared a common ancestor.
Asunto(s)
Cromosomas Humanos Par 1/genética , Flavoproteínas/genética , Haplotipos/genética , Proteínas Mitocondriales/genética , Mutación/genética , Polimorfismo de Nucleótido Simple/genética , Porfiria Variegata/genética , Protoporfirinógeno-Oxidasa/genética , Frecuencia de los Genes/genética , Heterocigoto , Humanos , Repeticiones de Microsatélite/genética , Países Bajos/etnología , Linaje , Sudáfrica/etnologíaRESUMEN
Mutation analysis of genomic DNA samples obtained from 17 unrelated South African patients with variegate porphyria (VP) revealed three novel missense mutations in the protoporphyrinogen oxidase (PPOX) gene. A common C to T transition at nucleotide position 452 (R59W) was identified in 15 of the patients analysed, while base changes at positions 336 (H20P) and 779 (R168C) were identified in the remaining two patients. Using protein analysis software we were able to predict that all three mutations have a similar biophysical effect on the protein, being the disturbance of amphiphatic regions within the protein, which might result in misfolding of the protein. Mutation R59W, identified in the majority of South African VP families, was shown to create a Styl restriction site, while mutation R168C would abolish a Dsal restriction site in genomic DNA of affected individuals. As 100% of the index patients analysed were molecularly characterized, the combined use of restriction enzyme and single-strand conformation polymorphism (SSCP) analysis now allows a rapid and accurate diagnosis of VP in South Africa. Mutation R59W was furthermore shown to be in association with one of four potential haplotypes defined by two newly described polymorphisms in exon 1 of the PPOX gene. Our molecular data thus strongly support the founder hypothesis for VP in South Africa.
Asunto(s)
Haplotipos , Oxidorreductasas actuantes sobre Donantes de Grupo CH-CH , Oxidorreductasas/genética , Mutación Puntual/genética , Porfirias Hepáticas/genética , Análisis Mutacional de ADN , Exones/genética , Femenino , Flavoproteínas , Efecto Fundador , Humanos , Masculino , Proteínas Mitocondriales , Polimorfismo de Longitud del Fragmento de Restricción , Polimorfismo Conformacional Retorcido-Simple , Porfirias Hepáticas/diagnóstico , Porfirias Hepáticas/enzimología , Pliegue de Proteína , Protoporfirinógeno-Oxidasa , SudáfricaRESUMEN
The gene for variegate porphyria (VP), an autosomal dominant disease with a high prevalance in South Africa, evidently due to a founder effect, was previously mapped to chromosome 14q32. In the current study this localization was evaluated by linkage and haplotype analyses using microsatellite markers spanning a region of more than 20 cM on chromosome 14q32. In many recent studies linkage disequilibrium between disease and marker loci has been utilized to map genes in founder populations, but we could not find any association between VP and the markers used in this study. Our data suggest that the allocation of VP to chromosome 14q32 may be incorrect.
Asunto(s)
Cromosomas Humanos Par 14 , ADN Satélite/genética , Ligamiento Genético , Repeticiones de Microsatélite/genética , Porfirias Hepáticas/genética , Mapeo Cromosómico , Familia , Femenino , Genes Dominantes , Marcadores Genéticos , Genotipo , Humanos , Masculino , Porfirias Hepáticas/epidemiología , Prevalencia , Sudáfrica/epidemiologíaRESUMEN
In vitro activity of the new cyclic lipopeptide LY 146032 (daptomycin, Eli Lilly) was evaluated against 67 clinical isolates of Staphylococcus aureus, 15 clinical isolates of S. epidermidis and 80 clinical isolates of Streptococcus faecalis. Activity was best against methicillin-resistant S. epidermidis (minimal inhibitory concentrations of LY 146032 0.25-0.5 mg/l). Minimal inhibitory concentrations and minimal bactericidal concentrations were of similar value. LY 146032 requires physiological concentrations of Ca++ ion for the expression of antibacterial activity. Results of the time-kill curves indicated that exposure to a concentration of the antibiotic equivalent to the minimal inhibitory concentration abolished recovery in the strains of S. aureus and S. epidermidis investigated. Response by S. faecalis was less predictable although most S. faecalis strains were killed in vitro by LY 146032 concentrations of less than or equal to 8 mg/l which is within the predicted clinically achievable range.