Summary Answer: Most primordial/primary oocytes were found to have a 46,XX karyotype. Chromosome patterns of the ovarian cells were different from that observed in other tissues.
Background: TS is a chromosomal condition associated with partial or complete absence of one of the two X-chromosomes. Females with TS have a limited reproductive lifespan due to an accelerated loss of germ cells. It has been hypothesized that viable oocytes arise from 46,XX germ cells and that 45,X0 germ cells are eliminated. However, primordial follicles have been found in females with an 45,X karyotype. It is currently unknown if the karyotype found in lymphocytes, buccal cells or urine cells is representative for the karyotype in ovarian cells. Furthermore, it is unknown if oocytes in these patients have a normal karyotype.
Design: Prospective experimental study using fluorescent in situ hybridization (FISH) of single ovarian cortical cells from young females with classic TS (45,X; n=5) or mosaic TS (45,X/ 46,XX; n=5). FISH signals were evaluated in stromal cells, oocytes and their corresponding granulosa cells, and compared to the karyotype of lymphocytes, buccal cells and urine cells of the same patient.
Methods: Intact ovaries from 10 females with TS (aged 2-18 years) were obtained by unilateral ovariectomy for fertility preservation purposes after informed consent was given. One fragment per patient was digested with a mix of proteases/DNase to obtain a cell suspension containing intact follicles and stromal cells. Stromal cells and primordial/primary follicles were transferred to coated microscope slides and prepared for FISH with chromosome X and chromosome 18 (control) specific centromere probes.
Results: In patients with 45,X karyotype in lymphocytes, buccal cells and urine cells, all ovarian stromal cells were 45,X and no follicles were found. In mosaic TS patients, the level of mosaicism of the ovarian stromal cells was very different from that observed in lymphocytes, buccal cells and urine cells. Analysis of follicles of these TS patients revealed that granulosa cells also display mosaicism that was different from the other cell types. Furthermore, individual follicles from the same ovary may have very different levels of mosaicism in their granulosa cells. While most oocytes of TS patients were found to have a 46,XX karyotype, we identified 4 oocytes in two patients with reduced X-chromosome content. Interestingly, some 46,XX oocytes were surrounded exclusively by 45,X granulosa cells.
19 - 21 Sep 2019
European Society for Paediatric Endocrinology