A retrospective study of registered retinitis pigmentosa patients in The Netherlands

A retrospective study was performed of patients with retinitis pigmentosa (RP) registered at the Department of Ophthalmogenetics of the Netherlands Ophthalmic Research Institute. The aim was to establish the relative frequencies of the genetic modes and to attempt a clinical subclassification. Of the 575 RP patients, 10.4% were X-linked, 22.4% autosomal dominant, 30.1% autosomal recessive, and 37.1% simplex cases. Clinical classification was inconclusive, and consequently correlation of phenotype to genotype impossible in most cases. One exception was the occurrence of a tapetal reflex, which seemed to differentiate between RP2 and RP3. Gene defects have not been detected so far in Dutch families with either autosomal dominant or autosomal recessive RP. In the future, simplex cases will have to be classified according to their genetic defects. It is probable that results of DNA studies may prove a better basis for classification of RP than clinical dat

Refinement of the chromosomal position of the X linked juvenile retinoschisis gene.

Linkage analysis was carried out in seven X linked juvenile retinoschisis (XLRS) families using four DNA probes and four CA repeat polymorphisms from the Xp22 region. Close linkage was observed between the XLRS locus and DXS207 (theta max = 0.04, Zmax = 3.71), DXS999 (theta max = 0.00, Zmax = 4.59), DXS365 (theta max = 0.07, Zmax = 2.22), and DXS451 (theta max = 0.05, Zmax = 3.26). The analysis of recombination breakpoints and multipoint linkage analysis suggests the order Xpter-DXS16-(DXS43, DXS207)-RS-DXS365-(DXS451, DXS41)-Xcen, thereby refining the position of the XLRS locus to an interval of approximately 3-4 cM. These results improve the feasibility of diagnosis in XLRS considerably, since carriers of this disease cannot be identified clinically

Assignment of a gene for autosomal recessive retinitis pigmentosa (RP12) to chromosome 1q31-q32.1 in an inbred and genetically heterogeneous disease population

Linkage analysis was carried out in a large family segregating for autosomal recessive retinitis pigmentosa (arRP), originating from a genetically isolated population in The Netherlands. Within the family, clinical heterogeneity was observed, with a major section of the family segregating arRP with characteristic para-arteriolar preservation of the retinal pigment epithelium (PPRPE). In the remainder of the ar-RP-patients no PPRPE was found. Initially, all branches of the family were analyzed jointly, and linkage was found between the marker F13B, located on 1q31-q32.1, and RP12 (zmax = 4.99 at 8% recombination). Analysis of linkage heterogeneity between five branches of the family yielded significant evidence for nonallelic genetic heterogeneity within this family, coinciding with the observed clinical differences. Multipoint analysis, carried out in the branches that showed linkage, favored the locus order 1cen-D1S158-(F13B, RP12)-D1S53-1qter (zmax = 9.17). The finding of a single founder allele associated with the disease phenotype supports this localization. This study reveals that even in a large family, apparently segregating for a single disease entity, genetic heterogeneity can be detected and resolved successfull

Evidence for nonallelic genetic heterogeneity in autosomal recessive retinitis pigmentosa

Recent evidence suggesting the involvement of mutant rhodopsin proteins in the pathogenesis of autosomal recessive retinitis pigmentosa has prompted us to investigate whether this form of the disease shows non-allelic genetic heterogeneity, as has previously been shown to be the case in autosomal dominant retinitis pigmentosa. The availability of a unique inbred Dutch pedigree has enabled us to address this question. We have used an intragenic polymorphism to exclude the possibility that a mutation in the rhodopsin gene is responsible for the disease in this patient population. These data provide evidence for the involvement of at least two loci in autosomal recessively inherited retinitis pigmentos

Molecular basis of choroideremia (CHM): mutations involving the rab escort protein 1 (rep 1) gene

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