Map refinement of locus RP13 to human chromosome 17p13.3 in a second family with autosomal dominant retinitis pigmentosa.

In order to elucidate the genetic basis of autosomal dominant retinitis pigmentosa (adRP) in a large eight-generation family (UCLA-RP09) of British descent, we assessed linkage between the UCLA-RP09 adRP gene and numerous genetic loci, including eight adRP candidate genes, five anonymous adRP-linked DNA loci, and 20 phenotypic markers. Linkage to the UCLA-RP09 disease gene was excluded for all eight candidate genes analyzed, including rhodopsin (RP4) and peripherin/RDS (RP7), for the four adRP loci RP1, RP9, RP10 and RP11, as well as for 17 phenotypic markers. The anonymous DNA marker locus D17S938, linked to adRP locus RP13 on chromosome 17p13.1, yielded a suggestive but not statistically significant positive lod score. Linkage was confirmed between the UCLA-RP09 adRP gene and markers distal to D17S938 in the chromosomal region 17p13.3. A reanalysis of the original RP13 data from a South African adRP family of British descent, in conjunction with our UCLA-RP09 data, suggests that only one adRP locus exists on 17p but that it maps to a more telomeric position, at band 17p13.3, than previously reported. Confirmation of the involvement of RP13 in two presumably unrelated adRP families, both of British descent, suggests that this locus is a distinct adRP gene in a proportion of British, and possibly other, adRP families.     

Evidence for a major retinitis pigmentosa locus on 19q13.4 (RP11) and association with a unique bimodal expressivity phenotype.

Retinitis pigmentosa (RP) is the name given to a heterogeneous group of retinal degenerations mapping to at least 16 loci. The autosomal dominant form (ARP), accounting for approximately 25% of cases, can be caused by mutations in two genes, rhodopsin and peripherin/RDS, and by at least six other loci identified by linkage analysis. The RP11 locus for adRP has previously been mapped to chromosome 19q13.4 in a large English family. This linkage has been independently confirmed in a Japanese family, and we now report three additional unrelated linked U.K. families, suggesting that this is a major locus for RP. Linkage analysis in the U.K. families refines the RP11 interval to 5 cM between markers D19S180 and AFMc001yb1. All linked families exhibit incomplete penetrance; some obligate gene carriers remain asymptomatic throughout their lives, whereas symptomatic individuals experience night blindness and visual field loss in their teens and are generally registered as blind by their 30s. This "bimodal expressivity" contrasts with the variable-expressivity RP mapping to chromosome 7p (RP9) in another family, which has implications for diagnosis and counseling of RP11 families. These results may also imply that a proportion of sporadic RP, previously assumed to be recessive, might result from mutations at this locus.     

X-linked dominant cone-rod degeneration: linkage mapping of a new locus for retinitis pigmentosa (RP 15) to Xp22.13-p22.11.

Retinitis pigmentosa is the name given to a heterogeneous group of hereditary retinal degenerations characterized by progressive visual field loss, pigmentary changes of the retina, abnormal electroretinograms, and, frequently, night blindness. In this study, we investigated a family with dominant cone-rod degeneration, a variant form of retinitis pigmentosa. We used microsatellite markers to test for linkage to the disease locus and excluded all mapped autosomal loci. However, a marker from the short arm of the X chromosome, DXS989, showed 0% recombination to the disease locus, with a maximum lod (log-odds) score of 3.3. On the basis of this marker, the odds favoring X-linked dominant versus autosomal dominant inheritance are > 10(5):1. Haplotype analysis using an additional nine microsatellite markers places the disease locus in the Xp22.13-p22.11 region and excludes other X-linked disease loci causing retinal degeneration. The clinical expression of the retinal degeneration is consistent with X-linked dominant inheritance with milder, variable effects of Lyonization affecting expression in females. On the basis of these data we propose that this family has a novel form of dominant, X-linked cone-rod degeneration with the gene symbol "RP15."     

Mapping of locus for autosomal dominant retinitis pigmentosa on chromosome 6q23

Retinitis pigmentosa (RP) is a genetically heterogeneous group of retinal degenerative disorders resulting in severe visual loss and blindness that have remained incurable till date. We report the mapping of the disease locus in a 3-generation family of Indian origin with autosomal dominant RP (ADRP). Diagnosis of RP and recruitment was made after a complete clinical evaluation of all members. Manifestations of the disease included night blindness with blurred central vision in some cases, loss of peripheral vision, and diffuse degeneration of the retinal pigment epithelium. Linkage analysis using microsatellite markers was carried out on 34 members (14 affected). After testing for linkage to known retinal dystrophy loci as well as a subsequent genome-wide analysis, we detected linkage to markers on chromosome 6q23: D6S262 at 130 cM, D6S457 (130 cM) and D6S1656 (131 cM) gave significant 2-point LOD scores of 3.0–3.8. Multipoint LOD scores of ≥3.0 were obtained for markers between 121 and 130 cM. Haplotype analysis with several markers in the same region on chromosome 6 shows a disease-cosegregating region of about 25 Mb between 109 and 135 Mb. There are no known RP genes in this interval, which contains >100 genes. This study provides evidence for a novel ADRP locus on chromosome 6q23.     

Autosomal dominant retinitis pigmentosa: no evidence for nonallelic genetic heterogeneity on 3q.

Since the initial report of linkage of autosomal dominant retinitis pigmentosa (adRP) to the long arm of chromosome 3, several mutations in the gene encoding rhodopsin, which also maps to 3q, have been reported in adRP pedigrees. However, there has been some discussion as to the possibility of a second adRP locus on 3q. This suggestion has important diagnostic and research implications and must raise doubts about the usefulness of linked markers for reliable diagnosis of RP patients. In order to address this issue we have performed an admixture test (A-test) on 10 D3S47-linked adRP pedigrees and have found a likelihood ratio of heterogeneity versus homogeneity of 4.90. We performed a second A-test, combining the data from all families with known rhodopsin mutations. In this test we obtained a reduced likelihood ratio of heterogeneity versus homogeneity, of 1.0. On the basis of these statistical analyses we have found no significant support for two adRP loci on chromosome 3q. Furthermore, using 40 CEPH families, we have localized the rhodopsin gene to the D3S47-D3S20 interval, with a maximum lod score (Zm) of 20 and have found that the order qter-D3S47-rhodopsin-D3S20-cen is significantly more likely than any other order. In addition, we have mapped (Zm = 30) the microsatellite marker D3S621 relative to other loci in this region of the genome.     

A new locus (RP31) for autosomal dominant retinitis pigmentosa maps to chromosome 9p

Retinitis pigmentosa (RP) is a debilitating disease of the retina affecting ∼1.5 million people worldwide. RP shows remarkable heterogeneity both clinically and genetically, with more than 40 genetic loci implicated, 12 of which account for the autosomal dominant form (adRP) of inheritance. We have recently identified a French Canadian family that presents with early onset adRP. After exclusion of all known loci for adRP, a genome-wide search established firm linkage with a marker from the short arm of chromosome 9 (LOD score of 6.3 at recombination fraction θ=0). The linked region is flanked by markers D9S285 and D9S1874, corresponding to a genetic distance of 31 cM, in the region 9p22-p13.     

Further refinement of the location for autosomal dominant retinitis pigmentosa on chromosome 7p (RP9).

A form of autosomal dominant retinitis pigmentosa (adRP) mapping to chromosome 7p was recently reported by this laboratory, in a single large family from southeastern England. Further sampling of the family and the use a number of genetic markers from 7p have facilitated the construction of a series of multipoint linkage maps of the region with the most likely disease gene location. From this and haplotype data, the locus can now be placed between the markers D7S484 and D7S526, in an interval estimated to be 1.6-4 cM. Genetic distances between the markers previously reported to be linked to this region and those described in the recent whole-genome poly-CA map were estimated from data in this and other families. These data should assist in the construction of a physical map of the region and will help to identify candidate genes for the 7p adRP locus.     

Genetic mapping of RP1 on 8q11-q21 in an Australian family with autosomal dominant retinitis pigmentosa reduces the critical region to 4 cM between D8S601 and D8S285

The locus (RP1) for one form of autosomal dominant retinitis pigmentosa (adRP) was mapped on chromosome 8q11-q22 between D8S589 and D8S285, which are about 8 cM apart, by linkage analysis in an extended family ascertained in the USA. We have studied a multigeneration Australian family with adRP and found close linkage without recombination between the disease locus and D8S591, D8S566, and D8S166 (Z_max = 1.137– 4.650 at θ = 0.00), all mapped in the region known to harbor RP1. Assuming that the mutation of the same gene is responsible for the disease in both families, the analysis of multiply informative meioses in the American and Australian families places the adRP locus between D8S601 and D8S285, which reduces the critical region to about 4 cM, corresponding to approximately 4 Mb, which is completely covered by a yeast artificial chromosome contig assembled recently. Received: 23 April 1996 / Accepted: 3 July 1996     

Autosomal dominant retinitis pigmentosa (adRP; RP6): cosegregation of RP6 and the peripherin-RDS locus in a late-onset family of Irish origin.

We recently reported the localization of a gene for late-onset autosomal dominant retinitis pigmentosa (adRP; RP6), on the short arm of chromosome 6, by linkage analysis in a large family of Irish origin. It is notable that the gene encoding peripherin-RDS, a photoreceptor-specific protein, recently has been physically mapped on 6p. In our own analysis, an intrageneic marker derived from this gene cosegregated with the adRP disease locus with zero recombination (lod score 5.46 at q = .00). Using the CEPH reference panel, we now report the mapping of the peripherin-RDS gene relative to other 6p markers in the CEPH data base. Incorporation of these data into a multipoint analysis produced a lod score for adRP of 8.21, maximizing at the peripherin-RDS locus. This study provides strong evidence suggesting a role for peripherin-RDS in the etiology of one form of adRP.     

Retinitis pigmentosa locus on 17q (RP17): fine localization to 17q22 and exclusion of the PDEG and TIMP2 genes

This group has previously reported the mapping of a novel locus for autosomal dominant retinitis pigmentosa (adRP) in a South African kindred to 17q. Using a new series of microsatellite markers in this study, two-point and multipoint analysis provide evidence for the localization of the disease gene to the 17q22 region. In addition, a second South African adRP family is shown to be linked to this 17q22 locus. Disease-associated haplotypes constructed for both families and multipoint linkage analysis place the gene in the 10-cM interval between D17S1607 and D17S1874. Three candidate genes on 17q were investigated: PDEG, the gamma subunit of rod phosphodiesterase; TIMP2, tissue inhibitor of metalloproteinases-2; and PRKCA, protein kinase C alpha. Recombination events between the adRP locus and: (1) a single-stranded conformation polymorphism in PDEG; and (2) a restriction fragment length polymorphism in TIMP2 provided evidence for the exclusion of these candidate genes as being responsible for adRP in the South African kindred. Received: 6 December 1996 / Accepted: 19 July 1997     

Evidence that the penetrance of mutations at the RP11 locus causing dominant retinitis pigmentosa is influenced by a gene linked to the homologous RP11 allele.

A subset of families with autosomal dominant retinitis pigmentosa (RP) display reduced penetrance with some asymptomatic gene carriers showing no retinal abnormalities by ophthalmic examination or by electroretinography. Here we describe a study of three families with reduced-penetrance RP. In all three families the disease gene appears to be linked to chromosome 19q13.4, the region containing the RP11 locus, as defined by previously reported linkage studies based on five other reduced-penetrance families. Meiotic recombinants in one of the newly identified RP11 families and in two of the previously reported families serve to restrict the disease locus to a 6-cM region bounded by markers D19S572 and D19S926. We also compared the disease status of RP11 carriers with the segregation of microsatellite alleles within 19q13.4 from the noncarrier parents in the newly reported and the previously reported families. The results support the hypothesis that wild-type alleles at the RP11 locus or at a closely linked locus inherited from the noncarrier parents are a major factor influencing the penetrance of pathogenic alleles at this locus.     

Autosomal dominant retinitis pigmentosa: Localization of a disease gene (RP6) to the short arm of chromosome 6

DNA from members of an Irish pedigree presenting with late onset autosomal dominant retinitis pigmentosa (ADRP) have been typed with a series of genetic markers from chromosome 6p. Positive two-point lod scores have been obtained with five markers (D6S89: theta = 0.10, Z = 3.338; D6S109: theta = 0.10, Z = 3.932; D6S105: theta = 0.00, Z = 6.081; HLA-DRA: theta = 0.00, Z = 4.364; and RDS: theta = 0.00, Z = 5.376). In a series of overlapping multipoint analyses a lod score of 6.6 was obtained, maximizing at HLA-DRA and hence localizing the ADRP gene (RP5) segregating in this pedigree to 6p. These data provide direct evidence for an additional autosomal dominant RP locus and strongly implicate the human equivalent of the mouse retinal degeneration slow (rds) gene, peripherin-rds, as a candidate for autosomal dominant retinitis pigmentosa.     

An autosomal dominant retinitis pigmentosa family with close linkage to D7S480 on 7q

Retinitis pigmentosa is the most prevalent inherited disorder of the retina. It can be autosomal dominant (adRP), autosomal recessive (arRP) or X-linked (XLRP). A form of adRP mapping to chromosome 7q was reported in a large Spanish pedigree. We have typed DNA from the members of another Spanish family for polymorphic markers from the known candidate genes. Positive lod scores were obtained only for the markers located on 7q31-35, giving a maximum lod score of 2.98 (3.01 by multipoint analysis) at = 0.00 for D7S480. A brief clinical evaluation is given.     

Segregation of a mutation in CNGB1 encoding the β-subunit of the rod cGMP-gated channel in a family with autosomal recessive retinitis pigmentosa

Retinitis pigmentosa (RP) is a clinically and genetically heterogeneous group of retinal diseases leading to blindness. By performing full genome linkage analysis in a consanguineous French family affected with severe autosomal recessive RP, we have excluded linkage to known loci involved in RP and mapped a novel locus to chromosome 16q13-q21 (Zmax=2.83 at theta=0 at the D16S3089 locus). Two candidate genes KIFC3 and CNGB1 mapping to this critical interval have been screened for mutations. The CNGB1 gene, which encodes the beta-subunit of the rod cGMP-gated channel, is mutated in the family presented in this study.     

A locus for autosomal dominant "pure" hereditary spastic paraplegia maps to chromosome 19q13

Genetic loci for autosomal dominant pure hereditary spastic paraplegia (ADPHSP) have been mapped to chromosomes 2p, 8q, 12q, 14q, and 15q. We undertook a genomewide linkage screen of a large family with ADPHSP, for which linkage at all previously identified ADPHSP loci was excluded. Analysis of markers on chromosome 19q gave a peak pairwise LOD score of 3.72 at D19S420, allowing assignment of a novel ADPHSP locus (which we have termed "SPG12") to this region. Haplotype construction and analysis of recombination events narrowed the SPG12 locus to a 16.1-cM region between markers D19S868 and D19S902.     

Exclusion of chromosome 6 and 8 locations in nonrhodopsin autosomal dominant retinitis pigmentosa families: further locus heterogeneity in adRP.

Genetic studies have revealed that 25 to 30% of autosomal dominant retinitis pigmentosa (adRP) families have mutations in the rhodopsin gene, while the remainder do not. More recently linkage data and mutation detection have demonstrated two further loci implicated in adRP, at an as yet unidentified gene on chromosome 8p and at the human gene homologue of the mouse Rds (Retinal Degeneration Slow) gene on chromosome 6p. We have previously reported exclusion of adRP from the rhodopsin locus on 3q in two large adRP families. We now report exclusion data for both families, on chromosomes 6 and 8, demonstrating that the adRP phenotype results from mutations in at least four locations.     

Severe autosomal recessive retinitis pigmentosa maps to chromosome 1p13.3–p21.2 between D1S2896 and D1S457 but outside ABCA4

A severe form of autosomal recessive retinitis pigmentosa (arRP) was identified in a large Pakistani family ascertained in the Punjab province of Pakistan. All affected individuals in the family had night blindness in early childhood, early complete loss of useful vision, and typical RP fundus changes plus macular degeneration. After exclusion of known arRP loci, a genome-wide scan was performed using microsatellite markers at about 10 cM intervals and calculating two-point lod scores. PCR cycle dideoxynucleotide sequencing was used to sequence candidate genes inside the linked region for mutations. RP in this family shows linkage to markers in a 10.5 cM (8.9 Mbp) region of chromosome 1p13.3-p21.2 between D1S2896 and D1S457. D1S485 yields the highest lod score of 6.54 at theta=0. Sequencing the exons and intron-exon boundaries of five candidate genes and six ESTs in this region, OLFM3, GNAI3, LOC126987, FLJ25070, DKFZp586G0123, AV729694, BU662869, BU656110, BU171991, BQ953690, and CA397743, did not identify any causative mutations. This novel locus lies approximately 4.9 cM (7.1 Mbp) from ABCA4, which is excluded from the linked region. Identification and study of this gene may help to elucidate the phenotypic diversity of arRP mapping to this region.     

两个常染色体显性遗传寻常性鱼鳞病家系致病基因的定位

为了对寻常性鱼鳞病的致病基因进行定位, 收集了2个湖南寻常性鱼鳞病家系, 采集外周血, 提取基因组DNA, 采用1号染色体和10号染色体上2个已知寻常性鱼鳞病位点的微卫星标记对这两个家系进行基因分型和连锁分析。结果显示, 寻常性鱼鳞病家系1的致病基因位于D1S498(1q21)附近, 与已知定位区间重叠; 寻常性鱼鳞病家系2的致病基因位点与已知的寻常性鱼鳞病位点不连锁, 可能存在新的致病基因位点。     

Linkage mapping of autosomal dominant retinitis pigmentosa (RP1) to the pericentric region of human chromosome 8.

Linkage mapping in a large, seven-generation family with type 2 autosomal dominant retinitis pigmentosa (ADRP) demonstrates linkage between the disease locus (RP1) and DNA markers on the short arm of human chromosome 8. Five markers were most informative for mapping ADRP in this family using two-point linkage analysis. The markers, their maximum lod scores, and recombination distances were ANK1 (ankyrin)--2.0 at 16%; D8S5 (TL11)--5.3 at 17%; D8S87 [a(CA)n repeat]--7.2 at 14%; LPL (lipoprotein lipase)--1.5 at 26%; and PLAT (plasminigen activator, tissue)--10.6 at 7%. Multipoint linkage analysis, using a simplified pedigree structure for the family (which contains 192 individuals and two inbreeding loops), gave a maximum lod score of 12.2 for RP1 at a distance 8.1 cM proximal to PLAT in the pericentric region of the chromosome. Based on linkage data from the CEPH (Paris) reference families and physical mapping information from a somatic cell hybrid panel of chromosome 8 fragments, the most likely order for four of these five loci and the diseases locus is 8pter-LPL-D8S5-D8S87-PLAT-RP1. (The precise location of ANK1 relative to PLAT in this map is not established). The most likely location for RP1 is in the pericentric region of the chromosome. Recently, several families with ADRP with tight linkage to the rhodopsin locus at 3q21-q24 were reported and a number of specific rhodopsin mutations in families with ADRP have since been reported. In other ADRP families, including the one in this study, linkage to rhodopsin has been excluded. Thus mutations at two different loci, at least, have been shown to cause ADRP. There is no remarkable clinical disparity in the expression of disease caused by these different loci.     

Identification and functional characterization of a novel splicing mutation in RP gene PRPF31

A six-generation Chinese family with autosomal dominant retinitis pigmentosa (adRP) was identified and characterized. Genome-wide linkage analysis linked the family to markers D19S601 to D19S605, which span the PRPF31 gene on chromosome 19q13.33-13.43 (RP11) (LOD = 5.03). Direct DNA sequence analysis identified a novel splicing mutation (IVS1+1G>T) in affected family members and carriers, but not in unaffected family members and 200 normal controls. The splicing mutation occurs at the splicing donor of intron 1. Real time PCR with lymphoblastoid RNA samples from family members showed that in comparison to normal family members, the splicing mutation reduced the expression level of the PRPF31 mRNA by 57% in symptomatic patients and by 28% in clinically asymptomatic carriers. Our studies identify a novel splicing mutation in PRPF31 associated with adRP and suggest that the penetrance of RP11 mutations may be correlated with the expression level of the PRPF31 mRNA.