Loss of heterozygosity at chromosome segment Xq25-26.1 in advanced human ovarian carcinomas

To determine whether a tumor suppressor gene of importance to epithelial ovarian cancer resides on the X chromosome, we examined loss of heterozygosity (LOH) in 123 epithelial ovarian cancer cases. In 54 such cases, we examined LOH at 26 loci on the human X chromosome. In eight cases, we examined LOH in 14 loci and in 61 cases we examined LOH in 13 loci. Matched DNA samples from tumors and corresponding normal tissues were analyzed by polymerase chain reaction (PCR) amplification of microsatellite markers. Frequent losses were found in epithelial carcinomas at the Xq25-26.l region, including DXS1206 (34.5% loss in informative cases), DXS1047 (27.7%), HPRT (24.1%), and DXS1062 (33.3%). The minimum overlapping region of LOH was approximately 5 megabases (Mb), flanked by DXS1206 (Xq25) and HPRT (Xq26.1). The methylation status of the remaining allele of the androgen receptor gene in the tumors exhibiting LOH at the Xq25-26.1 region suggested that the loss was exclusively in the inactive X chromosome. We next determined whether a significant relationship exists between Xq LOH and other parameters, including histologic grade and/or clinical stage of the tumors and LOH at TP53. The Xq LOH had a significant association with grade 2 to 3 tumors at stages II to IV. Sixteen of 18 cases that showed Xq LOH revealed LOH at the TP53 locus, and 45% of tumors exhibiting LOH at TP53 showed Xq LOH. These results suggest that there may be a tumor suppressor gene or genes which escape inactivation of the X chromosome at Xq25-26.1, and that the loss of the gene(s) at Xq25-26.1 is frequently accompanied by loss of the TP53 or loss of another gene on chromosome 17. These losses may contribute to the progression from a well-differentiated to a more poorly differentiated state or to metastatic aggressiveness.     

A novel locus (RP24) for X-linked retinitis pigmentosa maps to Xq26-27

Two genetic loci, RP2 and RP3, for X-linked retinitis pigmentosa (XLRP) have been localized to Xp11.3-11.23 and Xp21.1, respectively. RP3 appears to account for 70% of XLRP families; however, mutations in the RPGR gene (isolated from the RP3 region) are identified in only 20% of affected families. Close location of XLRP loci at Xp and a lack of unambiguous clinical criteria do not permit assignment of genetic subtype in a majority of XLRP families; nonetheless, in some pedigrees, both RP2 and RP3 could be excluded as the causative locus. We report the mapping of a novel locus, RP24, by haplotype and linkage analysis of a single XLRP pedigree. The RP24 locus was identified at Xq26-27 by genotyping 52 microsatellite markers spanning the entire X chromosome. A maximum LOD score of 4.21 was obtained with DXS8106. Haplotype analysis assigned RP24 within a 23-cM region between the DXS8094 (proximal) and DXS8043 (distal) markers. Other chromosomal regions and known XLRP loci were excluded by obligate recombination events between markers in those regions and the disease locus. Hemizygotes from the RP24 family have early onset of rod photoreceptor dysfunction; cone receptor function is normal at first, but there is progressive loss. Patients at advanced stages show little or no detectable rod or cone function and have clinical hallmarks of typical RP. Mapping of the RP24 locus expands our understanding of the genetic heterogeneity in XLRP and will assist in development of better tools for diagnosis.     

Isolation and characterization of three microsatellite markers in the proximal long arm of the human X chromosome

Three microsatellites have been identified in cosmids from the human X chromosome. The cosmids have been assigned locus numbers DXS554, DXS559, and DXS566 and have been localized to Xq12-q13 (DXS554 and DXS559) and Xq13 (DXS566). In addition, they have been genetically mapped in relation to the androgen receptor (AR), phosphoglycerate kinase 1, pseudogene 1 (PGK1P1), and phosphoglycerate kinase (PGK1) loci in the proximal long arm. Genetically, the localization of microsatellites at DXS554 and DXS566 is indistinguishable from PGK1, whereas that at DXS559 maps between AR and PGK1, close to PGK1P1. DXS566 is identical to the independently identified DXS441 marker. These markers should be useful for physical and genetic mapping in this region.     

A high-resolution map of genes, microsatellite markers, and new dinucleotide repeats from UBE1 to the GATA locus in the region Xp11.23

Several new genes and markers have recently been identified on the proximal short arm of the human X chromosome in the area of Xp11.23. We had previously generated a YAC contig in this region extending from UBE1 to the OATL1 locus. In this report two polymorphic dinucleotide repeats, DXS6949 and DXS6950, were isolated and characterized from the OATL1 locus. A panel of YAC deletion derivatives from the distal portion of the contig was used in conjunction with the rest of the YAC map to position the new microsatellites and order other markers localizing to this interval. The marker order was determined to be DXS1367-ZNF81-DXS6849-ZNF21-DXS6616-DXS 6950-DXS6949. In the proximal region below OATL1, we have isolated a pair of YACs from the GATA locus, B1026 and C01160. Mapping within these YACs indicates the orientation of DXS1126 and DXS1240, while a cosmid near the OATL1 region reveals the overlap between the YAC contigs from the two loci. This cosmid contains the gene responsible for Wiskott-Aldrich syndrome (WAS) and localizes the disease gene between OATL1 and GATA. These data enable the expansion of the present physical map of the X chromosome from UBE1 to the GATA locus, covering a large portion of the Xp11.23 region. Genetic cross-overs in Xp11.23 support the marker orientation and the position of WAS, contrary to previous reports. With the integration of both physical and genetic maps we have predicted the following marker order: Xpter-UBE1-SYN1/ARAF1/ TIMP1-DXS1367-ZNF81-DXS.6849-ZNF21-DXSy6616++ +-(OATL1, DXS6950-DXS6949)- WAS-(GATA, DXS1126)-DXS1240-Xcen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fine mapping of the dyskeratosis congenita locus in Xq28

Dyskeratosis congenita (DC) is characterised by reticulate skin pigmentation, mucosal leucoplakia, and nail dystrophy. Bone marrow failure occurs in 50% of patients and is the principal cause of early mortality. In the majority of families the pattern of inheritance of DC is compatible with an X linked recessive trait. The locus for the X linked recessive form of DC has been linked to Xq28. We have now extended our earlier studies by investigating five families with additional Xq28 polymorphic markers; analysis of recombination events in these families has located the DC1 locus between GABRA3 and DXS1108, an interval of approximately 4 Mb.     

Localization of CSNBX (CSNB4) between the retinitis pigmentosa loci RP2 and RP3 on proximal Xp

PURPOSE: Proximal Xp harbors many inherited retinal disorders, including retinitis pigmentosa (RP) and congenital stationary night blindness, both of which display genetic heterogeneity. X-linked congenital stationary night blindness (CSNBX) is a nonprogressive disease causing night blindness and reduced visual acuity. Distinct genetic loci have been reported for CSNBX at Xp21.1, which is potentially allelic with the RP3 gene, and at Xp11.23, which is potentially allelic with the RP2 gene. The study to identify the RP2 gene led to an extended study of families with potentially allelic diseases that include CSNBX. METHODS: Haplotype analysis of a family diagnosed with CSNBX was performed with 17 polymorphic markers on proximal Xp covering previously identified loci for CSNBX and XLRP. Two-point and multipoint lod scores were calculated. RESULTS: Informative recombinations in this family define a locus for CSNBX (CSNB4) with flanking markers DXS556 and DXS8080 on Xp11.4 to Xp11.3, an interval spanning approximately 5 to 6 cM. A maximum lod score of 3.2 was calculated for the locus order DXS556-1 cM-(CSNB4-DXS993)-2 cM-DXS1201. CONCLUSIONS: The results describe a new localization for CSNBX (CSNB4) between the RP2 and RP3 loci on proximal Xp. CSNB4 is not allelic with any previously reported XLRP loci; however, the interval overlaps the locus reported to contain the cone dystrophy (COD1) gene, and both diseases are nonrecombinant with DXS993. Because mutations in the RPGR gene to date account for disease in only a small proportion of RP3 families, the possibility that this new locus (CSNB4) also segregates with an as yet unidentified XLRP locus cannot be excluded.     

Localization of the gene for Wieacker-Wolff syndrome in the pericentromeric region of the X chromosome

The Wieacker-Wolff syndrome (WWS, MIM* 314580), first described clinically in 1985, is an X-linked recessive disorder. In earlier studies, linkage between the WWS gene and DXYS1 at Xq21.2 and DXS1 at Xq11 as well as AR at Xq12 was reported. Here we report on a linkage analysis using highly polymorphic, short terminal repeat markers located in the segment from Xp21 to Xq24. No recombination between the WWS locus and ALAS2 or with AR (z = 4.890 at theta = 0.0) was found. Therefore, the WWS locus was assigned to a segment of approximately 8 cM between PFC (Xp11.3-Xp 11.23) and DXS339 (Xq11.2-Xq13).     

Actin-binding protein (ABP-280) filamin gene (FLN) maps telomeric to the color vision locus (R/GCP) and centromeric to G6PD in Xq28

Actin-binding protein-280 (ABP-280) is a dimeric actin filament crosslinking protein that promotes orthogonal branching of actin filaments and links actin filaments to membrane glycoproteins. We have mapped the ABP-280 filamin gene (FLN) to Xq28 by Southern blot analysis of somatic cell hybrid lines, by fluorescence in situ hybridization, and through identification of portions of the FLN gene within cosmids and YACs mapped to Xq28. The FLN gene is found within a 200-kb region centromeric to the G6PD locus and telomeric to DSX52 and the color vision locus.     

A family with mental retardation, variable macrocephaly and macro-orchidism, and linkage to Xq12-q21

A family with X linked inheritance of mental retardation (XLMR) is presented. There are 10 mentally retarded males and two affected females in two generations. There are four obligatory carriers, one of whom is described as "slow". Most affected males show macrocephaly and macro-orchidism, which are typical signs of the fragile X syndrome, but have been tested cytogenetically and by analysis of the FMR1 gene and do not have this syndrome. However, some normal males in the family also exhibit macro-orchidism and macrocephaly. Linkage analysis using markers derived from the X chromosome indicates that the causative gene in this family is located in the proximal long arm of the X chromosome, in the interval Xp11-q21. Maximum lod scores of 2.96 with no recombination were found at three loci in Xq13-q21: DXS1111, DXS566, and DXS986. Recombination was observed with DXS1002 (Xq21.31) and DXS991 (Xp11.2), loci separated by about 30 Mb. Although isolation of the gene in this family will be difficult because of the size of the region involved, the localisation should be helpful in investigating other similar families with XLMR, macrocephaly, and macro-orchidism not attributable to FMR1.     

Continuous nebulization with terbutaline sulfate under tent inhalation. Evaluation of the efficacy in children 2 to 5 years of age in asthmatic crises

X-linked mental retardation (XLMR) includes distinct entities in which mental deficiency is either associated with specific abnormalities (syndromal) or not (nonsyndromal). We report on the clinical, neuropsychological, and laboratory findings and linkage analysis in one family with XLMR and isolated growth hormone deficiency (IGHD). Mental retardation was associated in 3 males and 5 females with short stature, microcephaly, and particular facial traits, i.e., high curved forehead, midface hypoplasia, and concave nasal bridge with nasal end of normal size and broad traits. Significant lod scores (Zmax >2) at a recombination fraction of theta = 0 were detected for 6 marker loci between DXS178 (Xq22.1) and DXS292 (Xq27.2). This mapping region overlaps that of XLMR with IGHD, recently reported by Hamel et al. [1996: Am J Med Genet 64:35-41] (Xq24-q27.3), and that of agammaglobulinemia with IGHD (Xq21.33-q22.2). This observation may confirm the suspicion of a gene involved in growth hormone regulation being localized in Xq.     

Mechanical gastritis as cause of upper gastrointestinal hemorrhage

The gene responsible for X linked agammaglobulinaemia (XLA) lies in Xq22 and has recently been identified as atk. DXS101 is a polymorphic locus which is closely linked to the disease locus. In this report we describe the identification, by pulsed field gel electrophoresis, of a new polymorphism at the DXS101 locus with a predicted heterozygosity of 4.9%. Despite this low value, we show how this polymorphism has been important in carrier status determination in a family with XLA where assessment was not possible by other means.     

Characterization of pigmented granules in minocycline-induced cutaneous pigmentation: observations using fluorescence microscopy and high-performance liquid chromatography

Ambiguous abdominal situs, asplenia/polysplenia and severe cardiac malformations characterize heterotaxy in humans. These anomalies result from the inability of the developing embryo to establish normal left-right asymmetry. We have studied an interesting family in which the heterotaxy phenotype segregates as an X-linked recessive trait. In order to map the heterotaxy locus (HTX), we have analysed 39 family members using highly-polymorphic microsatellite markers from the X chromosome. One of these markers, DXS994, shows no recombination with the disease locus in 20 informative meioses. Linkage analysis results in a maximum lod score of 6.37. Current genetic and physical mapping data assign the order of loci in Xq24-q27.1 as cen-DXS1001-(DXS994, HTX)-DXS984-tel. These results establish the first mapping assignment of situs abnormalities in humans.     

Linkage analysis of candidate genes in autoimmune thyroid disease. II. Selected gender-related genes and the X-chromosome. International Consortium for the Genetics of Autoimmune Thyroid Disease

Hashimoto's thyroiditis (HT) and Graves' disease (GD) are autoimmune thyroid diseases (AITD) in which multiple genetic factors are suspected to play an important role. Until now, only a few minor risk factors for these diseases have been identified. Susceptibility seems to be stronger in women, pointing toward a possible role for genes related to sex steroid action or mechanisms related to genes on the X-chromosome. We have studied a total of 45 multiplex families, each containing at least 2 members affected with either GD (55 patients) or HT (72 patients), and used linkage analysis to target as candidate susceptibility loci genes involved in estrogen activity, such as the estrogen receptor alpha and beta and the aromatase genes. We then screened the entire X-chromosome using a set of polymorphic microsatellite markers spanning the whole chromosome. We found a region of the X-chromosome (Xq21.33-22) giving positive logarithm of odds (LOD) scores and then reanalyzed this area with dense markers in a multipoint analysis. Our results excluded linkage to the estrogen receptor alpha and aromatase genes when either the patients with GD only, those with HT only, or those with any AITD were considered as affected. Linkage to the estrogen receptor beta could not be totally ruled out, partly due to incomplete mapping information for the gene itself at this time. The X-chromosome data revealed consistently positive LOD scores (maximum of 1.88 for marker DXS8020 and GD patients) when either definition of affectedness was considered. Analysis of the family data using a multipoint analysis with eight closely linked markers generated LOD scores suggestive of linkage to GD in a chromosomal area (Xq21.33-22) extending for about 6 cM and encompassing four markers. The maximum LOD score (2.5) occurred at DXS8020. In conclusion, we ruled out a major role for estrogen receptor alpha and the aromatase genes in the genetic predisposition to AITD. Estrogen receptor beta remains a candidate locus. We found a locus on Xq21.33-22 linked to GD that may help to explain the female predisposition to GD. Confirmation of these data in HT may require study of an extended number of families because of possible heterogeneity.     

X-linked juvenile retinoschisis: localization between (DXS1195, DXS418) and AFM291wf5 on a single YAC

We studied 17 pedigrees with 108 affected males with X-linked juvenile retinoschisis (RS; McKusick No. 31270) and have analyzed all of the known polymorphic markers in the RS region of Xp22.1-p22.2 between DXS987 and DXS41. By haplotype analyses we found 7 individuals who showed crossovers in this interval surrounding RS. We previously reported AFM291wf5 as the centromeric boundary, and this remains unchanged in the present study. A new recombination was identified on the telomeric side at (DXS1195, DXS418). Our data support the locus order Xpter--(DXS987, DXS207, DXS1053, DXS43)--(DXS1195, DXS418)--(RS, DXS257, DXS999)--(AFM291wf5, DXS443)--DXS1052--(DXS1226, DXS274, DXS41)--Xcen; loci grouped in parentheses could not be mutually ordered by our genetic data. Physical mapping has indicated a distance of at most 900-1,000 kb between (DXS1195, DXS418) and AFM291wf5. No recombination was observed between RS and DXS257 which lies in our new interval of interest, but one critical individual was not informative with this marker. Our data now define the smallest RS inclusion interval. This interval is contained on a single YAC from which we have identified expressed sequences as candidate genes for RS.     

The relation between immunoglobulin G antibodies to Chlamydia trachomatis and poor ovarian response to gonadotropin stimulation before in vitro fertilization

Although several genes for mental retardation and epilepsy, including double cortex/X-linked lissencephaly (DC/XLIS), have been localized to Xq21.3-q23, there has been no complete physical map of this region available. We constructed a YAC/STS contig map by initiating two yeast artificial chromosome (YAC) walks from the markers that flanked the DC/XLIS candidate gene region. We report an approximately 4-Mb contig extending from DXS287 to DXS8088, encompassing DXS1072 and DXS1059, and composed of 52 YACs identified with 15 previously published STSs and 19 novel YAC-end STSs. This contig also contains two brain-specific genes, doublecortin (HGMW-approved symbol DCX), responsible for DC/XLIS, and PAK3, which may be responsible for neurological diseases localized to this region. The new contig extends and incorporates several previously published contigs, providing a total overlapping contig extending approximately 34 Mb from DXS441 in Xq13.1 to DXS8088 in Xq23.     

Malignant splenic lymphoma: sonographic patterns, diagnosis and follow-up

In 1972, Fried described a large Scottish family affected by X linked mental retardation (XLMR), hydrocephalus, and mild facial dysmorphism. The phenotype has considerable similarity to the MASA syndrome, which results from mutations of the L1CAM gene in Xq28, and this family has since been assumed to be an example of this condition. We have reinvestigated the family for linkage to X chromosome markers, and obtained additional clinical information on surviving affected subjects. The phenotype in these patients has evolved into a distinctive syndrome, with severe mental retardation (MR), spastic diplegia, ventricular dilatation, and calcification of the basal ganglia. Linkage to Xq28 markers has been excluded, suggesting that Fried syndrome is not allelic with MASA syndrome. Two point and multipoint linkage analysis indicates that the gene for this condition lies within the interval KAL-DXS989 in Xp22. We propose the designation Fried syndrome to emphasise the disorder's distinctive phenotype.     

A c-rasHa mutation in the metastasis of a human papillomavirus (HPV)-18 positive penile squamous cell carcinoma suggests a cooperative effect between HPV-18 and c-rasHa activation in malignant progression

Progressive X-linked cone-rod dystrophy (COD1) is a retinal disease affecting primarily the cone photoreceptors. The COD1 locus originally was localized, by the study of three independent families, to a region between Xp11.3 and Xp21.1, encompassing the retinitis pigmentosa (RP) 3 locus. We have refined the COD1 locus to a limited region of Xp11.4, using two families reported elsewhere and a new extended family. Genotype analysis was performed by use of eight microsatellite markers (tel-M6CA, DXS1068, DXS1058, DXS993, DXS228, DXS1201, DXS1003, and DXS1055-cent), spanning a distance of 20 cM. Nine-point linkage analysis, by use of the VITESSE program for X-linked disorders, established a maximum LOD score (17.5) between markers DXS1058 and DXS993, spanning 4.0 cM. Two additional markers, DXS977 and DXS556, which map between DXS1058 and DXS993, were used to further narrow the critical region. The RP3 gene, RPGR, was excluded on the basis of two obligate recombinants, observed in two independent families. In a third family, linkage analysis did not exclude the RPGR locus. The entire coding region of the RPGR gene from two affected males from family 2 was sequenced and was found to be normal. Haplotype analysis of two family branches, containing three obligate recombinants, two affected and one unaffected, defined the COD1 locus as distal to DXS993 and proximal to DXS556, a distance of approximately 1.0 Mb. This study excludes COD1 as an allelic variant of RP3 and establishes a novel locus that is sufficiently defined for positional cloning.     

Genetic analysis of a kindred with X-linked mental handicap and retinitis pigmentosa

A kindred is described in which X-linked nonspecific mental handicap segregates together with retinitis pigmentosa. Carrier females are mentally normal but may show signs of the X-linked retinitis pigmentosa carrier state and become symptomatic in their later years. Analysis of polymorphic DNA markers at nine loci on the short arm of the X chromosome shows that no crossing-over occurs between the disease and Xp11 markers DXS255, TIMP, DXS426, MAOA, and DXS228. The 90% confidence limits show that the locus is in the Xp21-q21 region. Haplotype analysis is consistent with the causal gene being located proximal to the Xp21 loci DXS538 and 5'-dystrophin on the short arm of the X chromosome. The posterior probability of linkage to the RP2 region of the X chromosome short arm (Xp11.4-p11.23) is .727, suggesting the possibility of a contiguous-gene-deletion syndrome. No cytogenetic abnormality has been identified.