Regional localisation of X chromosome short arm probes

Localization of X chromosome short arm markers relative to synovial sarcoma- and renal adenocarcinoma-associated translocation breakpoints

A series of thirteen different DNA markers was mapped relative to papillary renal cell carcinoma- and synovial sarcoma-associated translocation breakpoints in Xp11.2 using a panel of tumor-derived somatic cell hybrids in conjunction with Southern blot analysis. Our results indicate that the two translocation breakpoints differ from each other and that the chromosomal break in t(X;1)-positive papillary renal cell carcinoma is located between the markers PFC-TIMP-OATL1-SYP-TFE3 and DXS226-DXS146-DXS255-OATL2-DXS14. In addition, our current breakpoint analysis has resulted in a revision of the regional localization of the proximal Xp marker DXS226.

Translocation (X;1) in papillary renal cell carcinoma. A new cytogenetic subtype

We report a consistent t(X;1)(p11.2;q21) that was observed in four cases of papillary renal tumors. In one of the cases, two cells showed the cytogenetic abnormality as the only change, whereas the other cases showed additional chromosomal anomalies particularly involving chromosomes 7 and 17. One identical t(X;1) has been reported previously in a papillary renal cell carcinoma. To date, all of the patients carrying this translocation have been males.

The gene encoding human TFE3, a transcription factor that binds the immunoglobulin heavy-chain enhancer, maps to Xp11.22

TFE3, a member of the helix-loop-helix family of transcription factors, binds to the microE3 motif of the immunoglobulin heavy-chain enhancer and is expressed in many cell types. We have localized human TFE3 to the proximal short arm of the X chromosome using a somatic cell hybrid panel. A frequent RsaI RFLP detected by the TFE3 cDNA was found and used to confirm this location by linkage analysis in 20 pedigrees. Two-point and multipoint lod scores place TFE3 near markers in Xp11.22 with the most likely order DXS7-DXS255-TFE3-DXS146-DXS14.

Physical mapping of 60 DNA markers in the p21.1----q21.3 region of the human X chromosome

Using a panel of human/rodent somatic cell hybrids and human lymphoblast lines segregating 18 different human X-chromosome rearrangements and deletions, we have assigned 60 DNA markers to the physical map of the X chromosome from Xp21.1 to Xq21.3. Data from Southern blot hybridization and polymerase chain reaction (PCR) amplification assign these markers to 15 primary map intervals. This provides a basis for further long-range cloning and mapping of the pericentromeric region of the X chromosome.

Physical fine-mapping of a deletion spanning the Norrie gene

Norrie disease (ND), atrophia bulborum hereditaria, is caused by a gene defect on the proximal short arm of the X-chromosome. As shown by us and others, microdeletions spanning the DXS7 locus are not uncommon in this disorder, and there is recent evidence that, at least in some of the Norrie deletion patients, the monoamine oxidase (MAO) A and B genes are deleted as well. Molecular hybridization experiments with 19 cloned DNA fragments have enabled us to construct a preliminary long-range restriction map around DXS77, DXS7, MAO-A and MAO-B, and to localize the distal end point of an ND deletion between DXS77 and DXS7.

A method for generating hybrids containing nonselected fragments of human chromosomes

We have used an irradiation and fusion technique to generate somatic cell hybrids that contain human chromosomal fragments. As a model system, a human-hamster hybrid containing a single human X chromosome was gamma-irradiated and fused with a rodent line. Hybrids were obtained without imposing direct selection for human material. Analysis of 29 clones by in situ hybridization and Southern blotting revealed that human fragments were incorporated into the hybrid cell genomes in most lines. Like chromosome-mediated gene transfer (CMGT)-generated hybrids, these hybrids contained multiple human fragments and retained alphoid centromeric sequences with a high frequency. However, unlike the CMGT, human fragments (apart from alphoid sequences) of less than 10(7) bp showed no evidence for rearrangements. This technique provides a method for constructing hybrids that contain a limited number of small human fragments derived exclusively from any chromosome of choice without the need to impose selection. Such hybrids provide a valuable resource for high-resolution mapping over short distances and for the isolation of disease and other loci mapped genetically.

Xp21 DNA microdeletion in a patient with chronic granulomatous disease, retinitis pigmentosa, and McLeod phenotype

The clinical, biochemical, and molecular analysis of a patient with chronic granulomatous disease (CGD), retinitis pigmentosa (RP), and McLeod phenotype and of his parents demonstrated the X-linked transmission of these three traits in this family and a deletion of the entire X-CGD gene of the patient DNA. All but one other DNA markers tested, including those in Xp21, were present. These findings strongly suggest that the McLeod locus and at least one XL RP gene are closely linked to the X-CGD locus in the Xp21 region of the human X chromosome.

Fine mapping of glycerol kinase deficiency and congenital adrenal hypoplasia within Xp21 on the short arm of the human X chromosome

We have studied patients with Duchenne muscular dystrophy (DMD), DMD together with glycerol kinase (GK) deficiency, or DMD together with both GK deficiency and congenital adrenal hypoplasia (AHC). Analysis of deletions in these patients allows the mapping of these mutations in Xp21. The following order is proposed: Xpter - L1 - AHC - GK - DMD - Xcen. One of the boys with DMD, GK, and AHC is shown by pulsed-field-gel electrophoresis to have a deletion which has a proximal endpoint at least 500 kb distal from the pERT87 (DXS164) locus.

Mild and severe muscular dystrophy associated with deletions in Xp21 of the human X chromosome

We have analysed over 300 patients suffering from Duchenne or Becker muscular dystrophy (DMD or BMD). Deletions have been characterised which encompass either the pERT87 (DXS164) locus only, the XJ1.1 (DXS206) and HIP25 loci only, or all three loci. These loci have been shown to lie within the DMD region covering several hundred kilobases (kb) of DNA. One mildly affected BMD patient possesses a deletion of at least 110 kb including exons of the DMD gene. Other patients with similar exon deletions, or smaller deletions, show the more severe phenotype typical of DMD. We conclude from these studies that the severity of the clinical phenotype cannot be explained on the basis of the size of the deletion. We discuss this in the context of candidate gene sequences.

Molecular analysis of the Duchenne muscular dystrophy region using pulsed field gel electrophoresis

Genetic and molecular studies show that the Duchenne muscular dystrophy (DMD) locus at Xp21 is large and complex. We have analyzed this region using pulsed field gel electrophoresis (PFGE) and have determined physical distances between Xp21 probes. The sum of the sizes of the Sfil restriction fragments detected by these probes is greater than 4000 kb. The deletion endpoints in two DMD patients were detected by observing changes in these restriction fragments. In addition, the Xp21 breakpoint for the X;1 translocation in an affected female was mapped. These results demonstrate the applicability of PFGE for analysis of Xp21, and should facilitate the mapping of other translocations and deletions in this region, some of which lead to glycerol kinase deficiency and adrenal hypoplasia as well as DMD.