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(Reference retrieved automatically from SciELO through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Cryptic mosaicism involving a second chromosome X in patients with Turner syndrome

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Author(s):
A. Araújo [1] ; E.S. Ramos [2]
Total Authors: 2
Affiliation:
[1] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Genética - Brasil
[2] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Genética - Brasil
Total Affiliations: 2
Document type: Journal article
Source: Brazilian Journal of Medical and Biological Research; v. 41, n. 5, p. 368-372, 2008-05-00.
Abstract

The high abortion rate of 45,X embryos indicates that patients with Turner syndrome and 45,X karyotype could be mosaics, in at least one phase of embryo development or cellular lineage, due to the need for the other sex chromosome presence for conceptus to be compatible with life. In cases of structural chromosomal aberrations or hidden mosaicism, conventional cytogenetic techniques can be ineffective and molecular investigation is indicated. Two hundred and fifty patients with Turner syndrome stigmata were studied and 36 who had female genitalia and had been cytogenetically diagnosed as having "pure" 45,X karyotype were selected after 100 metaphases were analyzed in order to exclude mosaicism and the presence of genomic Y-specific sequences (SRY, TSPY, and DAZ) was excluded by PCR. Genomic DNA was extracted from peripheral blood and screened by the human androgen receptor (HUMARA) assay. The HUMARA gene has a polymorphic CAG repeat and, in the presence of a second chromosome with a different HUMARA allele, a second band will be amplified by PCR. Additionally, the CAG repeats contain two methylation-sensitive HpaII enzyme restriction sites, which can be used to verify skewed inactivation. Twenty-five percent (9/36) of the cases showed a cryptic mosaicism involving a second X and approximately 14% (5/36), or 55% (5/9) of the patients with cryptic mosaicism, also presented skewed inactivation. The laboratory identification of the second X chromosome and its inactivation pattern are important for the clinical management (hormone replacement therapy, and inclusion in an oocyte donation program) and prognostic counseling of patients with Turner syndrome. (AU)

FAPESP's process: 05/00616-5 - Differential development of XX and XY preimplantation embryos and TSPX and SRY gene expression pattern
Grantee:Ester Silveira Ramos
Support Opportunities: Regular Research Grants