Presence of XIST specific sequences and apparent failure of X dosage compensation by inactivation in a patient with a severe Turner phenotype and mosaicism for X chromosome abnormalities
- Univ. of Florida, Gainesville, FL (United States); and others
An XIST FISH analysis and a late replication chromosome study was performed for a 10 year old female with Turner stigmata, mental retardation, multiple congenital anomalies and a cytogenetic mosaicism of 45,X,inv(9)(p11q13)/46,X,del(X)(q22),inv(9)(p11q13)/46,X,+mar,inv(9)(p11q13). The X chromosomes from a cell line in which one was deleted for the distal long arm segment (breakpoint of Xq22), observed in 6% of metaphase cells from peripheral blood and 23.3% of metaphase cells from skin fibroblasts, did not demonstrate an asynchronous or differential staining pattern by BrDU techniques. However, both the normal X chromosome and the deleted X chromosome were demonstrated to contain XIST specific sequences by FISH analysis. A very small marker chromosome, observed in 6% of metaphase cells from peripheral blood and 3.3% of metaphase cells from skin fibroblasts, appeared to consist exclusively of X chromosome alpha satellite centromeric material (DXZ1). This finding was consistent with the morphology of the marker chromosome as observed by conventional G-banding. Due to its small size and low level frequency, analysis by late replication BrDU techniques was not possible. The predominate cell line containing a signal X chromosome was observed in 88% of metaphase cells from peripheral blood and 73.3% of metaphase cells from skin fibroblasts. This case is significant because: (1) it represents another case of an X chromosome abnormality in which XIST is apparently present but not expressed; and (2) the more severe phenotype expressed is probably attributable to the failure of X gene dosage compensation by inactivation.
- OSTI ID:
- 133648
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0378
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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