| Autor: |
B R, Migeon, M, Ausems, J, Giltay, C, Hasley-Royster, E, Kazi, T J, Lydon, J J, Engelen, G V, Raymond |
| Rok vydání: |
2000 |
| Předmět: |
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| Zdroj: |
American journal of medical genetics. 93(1) |
| ISSN: |
0148-7299 |
| Popis: |
Mental retardation and congenital malformations in individuals with small ring X chromosomes are often due to the functional disomy that results from failure of these chromosomes to undergo X inactivation. Such chromosomes either lack the XIST locus or do not express it. We have carried out genetic analysis of the ring X chromosomes from two girls with a 45,X/46,X,r(X) karyotype, mental retardation, and a constellation of abnormalities characteristic of the severe phenotype due to X disomy. In each case the ring X chromosome included an intact XIST locus which was expressed; the breakpoints were distal to DXS128, and therefore outside the XIC region; transcription analysis of alleles at the androgen receptor locus confirmed that these were inactive chromosomes. The characteristics of the XIST RNA were similar to the wild-type. Additional studies in cultured fibroblasts showed a second ring in a small percentage of the cells. The association of severe phenotype with an inactive X chromosome most likely reflects the presence of a second ring X chromosome which was active at least in some tissues during embryogenesis, but is no longer prominent in the tissues we analyzed. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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