Molecular cytogenetic characterization of two Turner syndrome patients with mosaic ring X chromosome

Abstract

Purpose In the present study, we reported two cases of TS with mosaic ring X chromosome showing common clinical characteristics of TS like growth retardation and ovarian dysfunction. The purpose of the present study was to cytogenetically characterize both cases. Methods Whole blood culture and G-banding were performed for karyotyping the cases following standard protocol. Origin of the ring chromosome and degree of mosaicism were further determined by fluorescence in situ hybridization (FISH). Breakpoints and loss of genetic material in formation of different ring X chromosomes r (X) in cases were determined with the help of cytogenetic microarray. Results Cases 1 and 2 with ring chromosome were cytogenetically characterized as 45, X [114]/46Xr (X) (p22.11q21.32) [116] and 45, X [170]/46, Xr (X) (p22.2q21.33) [92], respectively. Sizes of these ring X chromosomes were found to be~7 5 and~95 Mb in cases 1 and 2, respectively, using visual estimation as part of cytogenetic observation. In both cases, we observed breakpoints on Xq chromosome were within relatively narrow region between Xq21.33 and Xq22.1 compared to regions in previously reported cases associated with ovarian dysgenesis. Conclusions Our observation agrees with the fact that despite of large heterogeneity, severity of the cases with intact Xinactive specific transcript (XIST) is dependent on degree of mosaicism and extent of Xq deletion having crucial genes involved directly or indirectly in various physiological involving ovarian cyclicity.

Genotype-phenotype correlation in 75 patients with small supernumerary marker chromosomes

“…The methyl-CpG binding protein-2 gene (MECP2 on Xq28) is located on the long arm of X. This gene correlates with RETT syndrome and the premature ovarian failure gene POF (POF1: Xq21→qter, POF2: Xq13.3→Xq21.1) [10]. As the min(X) from patient W09834 (:p11.2→q13.2:) and r(X) from patient 92568 (::p11.23→q21.1::) did not contain SHOX and MECP2, both patients had growth retardation and a high risk of RETT syndrome.…”

Coexistence of Growth Hormone Deficiency and Pituitary Microadenoma in a Child with Unique Mosaic Turner Syndrome: A Case Report and Literature Review

“…This case was cytogenetically characterized with a unique mosaicism for three types of cells with r(X), monosomy X, and psu dic r(X), which may have occurred as a process of dynamic mosaicism. The amount of Xq deletion and r(X) has been known to associated with phenotypic severity [ 30 ]. In particular, the presence of the XIST gene on Xq13.2 is important.…”

C-banding and AgNOR-staining were still effective complementary methods to indentify chromosomal heteromorphisms and some structural abnormalities in prenatal diagnosis

“…About 16% of the individuals with Tuner syndrome have an addtional cell line with 46 chromosomes due to the presence of an extra ring chromosome X [30]. Ring X chromosome, with different degree of mosaicism, showing common clinical characteristics of Turner syndrome had been reported, and karyotype-phenotype correlation related manifestation was dependent on the degree of genetic material lost in ring (X) formation as well as mosaicism [31]. Undoubtedly, for mosaic Tuner with mixed cell lines, FISH tests for Xcen and Ycen should be performed since ring X is more commonly seen in mosaic Turner and present of Y material will be clinically significant and requires intervention.…”