Carlos Alberto Longui, Mylene Neves Rocha, Liana Carla Albuquerque Peres Martinho, Gustavo Gir Gomes, Ricardo Eustachio de Miranda, Thomas Alves de Souza Lima, Mônica Barbosa Melo, Osmar Monte
Published: September 23, 2002
Genet. Mol. Res. 1 (3) : 266-270
Cite this Article:
C.Alberto Longui, M.Neves Rocha, L.Carla Albu Martinho, G.Gir Gomes, R.Eustachio de Miranda, T.Alves de S. Lima, M.Barbosa Melo, O. Monte (2002). Molecular detection of XO – Turner syndrome. Genet. Mol. Res. 1(3): 266-270.
About the Authors
Carlos Alberto Longui, Mylene Neves Rocha, Liana Carla Albuquerque Peres Martinho, Gustavo Gir Gomes, Ricardo Eustachio de Miranda, Thomas Alves de Souza Lima, Mônica Barbosa Melo, Osmar Monte
Corresponding author: C.A. Longui
E-mail: fisiolab@santacasasp.org.br
ABSTRACT
Turner syndrome is caused by haploinsufficiency of the short arm of X-chromosome, and is usually diagnosed by karyotyping. This procedure is time-consuming, expensive and unfeasible for population screening. We propose molecular detection of 45XO Turner patients based on the ability of HpaII, a methylation sensitive endonuclease, to induce the cleavage of non-methylated DNA in the active X-allele. Genomic DNA was obtained from 22 patients with Turner syndrome confirmed by karyotype (45XO, N = 18; 45XO/46XX, N = 4). After digestion, DNA was amplified with primers directed to exon 1 of the androgen receptor (AR) gene and to the GAPDH control gene. Normal control females or mosaic patients, with a second methylated X-chromosome, escaped from HpaII digestion and produced a band corresponding to AR gene amplification. 45XO patients have just one active non-methylated X-chromosome, completely digested by HpaII, thus preventing the amplification of the AR gene. Three of the 45XO cases gave amplified bands, suggesting low-frequency mosaicisms that are not detected by karyotyping. Compared to classical karyotype studies for the detection of 45XO Turner patients, this new molecular method is simpler, faster and less expensive.
Turner syndrome is caused by haploinsufficiency of the short arm of X-chromosome, and is usually diagnosed by karyotyping. This procedure is time-consuming, expensive and unfeasible for population screening. We propose molecular detection of 45XO Turner patients based on the ability of HpaII, a methylation sensitive endonuclease, to induce the cleavage of non-methylated DNA in the active X-allele. Genomic DNA was obtained from 22 patients with Turner syndrome confirmed by karyotype (45XO, N = 18; 45XO/46XX, N = 4). After digestion, DNA was amplified with primers directed to exon 1 of the androgen receptor (AR) gene and to the GAPDH control gene. Normal control females or mosaic patients, with a second methylated X-chromosome, escaped from HpaII digestion and produced a band corresponding to AR gene amplification. 45XO patients have just one active non-methylated X-chromosome, completely digested by HpaII, thus preventing the amplification of the AR gene. Three of the 45XO cases gave amplified bands, suggesting low-frequency mosaicisms that are not detected by karyotyping. Compared to classical karyotype studies for the detection of 45XO Turner patients, this new molecular method is simpler, faster and less expensive.
Keywords: Molecular diagnosis, Turner syndrome, X-Chromosome methylation