Human Genetics

, Volume 87, Issue 4, pp 498–502 | Cite as

Isodicentric X chromosome in a patient with Turner syndrome — implications for localization of the X-inactivation center

  • Anjana Lal Pettigrew
  • Edward R. B. McCabe
  • David H. Ledbetter
  • Frederick F. B. Elder
Short Communications
Received:
Revised:

Summary

Cytogenetic analyses have previously shown that the region Xq11.2–q21 is retained in all structurally abnormal X chromosomes. From these observations the conclusion has been drawn that this “critical region” on the proximal long arm of the X chromosome contains the locus controlling X-inactivation. Structurally abnormal X chromosomes without the X-inactivation center would allow nullisomy, disomy, or trisomy for genes on the X chromosome, and this condition is presumed nonviable. We studied a 28-year-old woman with primary amenorrhea and features of Turner syndrome who had an unusual isodicentric chromosome of the short arm of X. This patient provided us with the opportunity to more closely define the location of the X-inactivation center. High resolution chromosome analysis showed a 46,X,idic(X)(pter→q13.2::q13.2→pter) chromosome pattern in 94% of her cells and a 45,X complement in 6%. Replication studies showed this derivative X chromosome to be late-replicating (inactive) in all cells analyzed. DNA analysis confirmed the breakpoint of the isodicentric chromosome to be proximal to PGK1. Based on these results, the locus for the X-inactivation center can be refined to be within Xq11.2–q13.2.

Keywords

Internal Medicine High Resolution Metabolic Disease Critical Region Cytogenetic Analysis 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Anjana Lal Pettigrew
    • 1
  • Edward R. B. McCabe
    • 2
  • David H. Ledbetter
    • 2
  • Frederick F. B. Elder
    • 3
  1. 1.Departments of Pathology, Pediatrics, and Obstetrics-GynecologyUniversity of Kentucky Medical SchoolLexingtonUSA
  2. 2.Institute for Molecular Genetics, Baylor College of MedicineHoustonUSA
  3. 3.Department of PediatricsUniversity of Texas Medical SchoolHoustonUSA

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