RESUMO
Retinitis pigmentosa (RP) is a group of progressive hereditary disorders of the retina in which various modes of inheritance have been described. Here, we report on X linked RP in nine families with constant and severe expression in carrier females. In our series, however, the phenotype was milder and delayed in carrier females compared to hemizygous males. This form of X linked RP could be regarded therefore as partially dominant. The disease gene maps to chromosome Xp2.1 in the genetic interval encompassing the RP3 locus (Zmax=13.71 at the DXS1100 locus). Single strand conformation polymorphism and direct sequence analysis of the retinitis pigmentosa GTPase regulator (RPGR) gene, which accounts for RP3, failed to detect any mutation in our families. Future advances in the identification of X linked RP genes will hopefully help to elucidate the molecular basis of this X linked dominant RP.
Assuntos
Proteínas de Transporte/genética , Proteínas do Olho , Ligação Genética , Heterozigoto , Retinose Pigmentar/genética , Cromossomo X , Adolescente , Adulto , Arginina , Criança , Pré-Escolar , Mapeamento Cromossômico , Feminino , Marcadores Genéticos , Humanos , Isoleucina , Masculino , Pessoa de Meia-Idade , Linhagem , Polimorfismo Genético , Polimorfismo Conformacional de Fita SimplesRESUMO
The availability of more and more reliable obstetrical echographies makes now possible to screen fetuses for microphtalmies and anophtalmies. More over, by mean of linkage studies with DNA markers within a family, we can identify the women who will transmit X-linked diseases, and realize a prenatal diagnosis. This technology can be applied to the following ophthalmological diseases: the X-linked retinoschisis, the choroideremia, the ocular albinism, the Noorie disease, and recently the retinoblastoma. From now on, the use of such a technology which makes it possible to detect ophthalmological diseases in the fetuses, is posing ethical problems especially in case of diseases without any survival prognosis involvement.
Assuntos
Oftalmopatias Hereditárias/diagnóstico , Diagnóstico Pré-Natal/métodos , Anoftalmia/diagnóstico , Anoftalmia/genética , Cegueira/prevenção & controle , Feminino , Humanos , Masculino , Microftalmia/diagnóstico , Microftalmia/genética , Linhagem , GravidezRESUMO
Autosomal dominant forms of retinitis pigmentosa appear among the most frequent types of retinal degenerations. Two clinical subtypes have been recognized, namely the early onset, severe form (type I) and the late onset, moderate form (type II). A linkage between the D3S47 probe (C17) with the gene of the type I has been recently demonstrated by Humphries et al., 1989. Here, two families with type II of the disease have been tested for possible allelism at the D3S47 locus. A negative lod-score was found with this probe and a linkage with this region could be excluded. These results support the hypothesis of a genetic heterogeneity in autosomal dominant forms of retinitis pigmentosa.