Uterine Leiomyomas with an Apparently Normal Karyotype Comprise Minor Heteroploid Subpopulations Differently Represented in vivo and in vitro

In the present study, we aimed to check whether uterine leiomyomas (ULs) with an apparently normal karyotype in vitro comprise “hidden” cell subpopulations with numerical chromosome abnormalities (heteroploid cells). A total of 32 ULs obtained from 32 patients were analyzed in the study. Each UL was sampled for in vivo and in vitro cytogenetic studies. Karyotyping was performed on metaphase preparations from the cultured UL samples. A normal karyotype was revealed in 20 out of the 32 ULs, of which 9 were selected for further study based on the good quality of the interphase preparations. Then, using interphase FISH with centromeric DNA probes, we analyzed the copy number of chromosomes 7 and 16 in 1,000 uncultured and 1,000 cultured cells of each selected UL. All of the ULs included both disomic cells representing a predominant subpopulation and heteroploid cells reaching a maximum frequency of 21.6% (mean 9.8%) in vivo and 11.5% (mean 6.1%) in vitro. The spectrum of heteroploid cells was similar in vivo and in vitro and mostly consisted of monosomic and tetrasomic cells. However, their frequencies in the cultured samples differed from those in the uncultured ones: while the monosomic cells decreased in number, the tetrasomic cells became more numerous. The frequency of either monosomic or tetrasomic cells both in vivo and in vitro was not associated with the presence of <i>MED12</i> exon 2 mutations in the tumors. Our results suggest that ULs with an apparently normal karyotype consist of both karyotypically normal and heteroploid cells, implying that the occurrence of minor cell subpopulations with numerical chromosome abnormalities may be considered a characteristic of UL tumorigenesis. Different frequencies of heteroploid cells in vivo and in vitro suggest their dependence on microenvironmental conditions, thus providing a pathway for regulation of their propagation, which may be important for the UL pathogenesis.

Paternal Age and Numerical Chromosome Abnormalities in Human Spermatozoa

This study explores the relationship between numerical chromosome abnormalities in sperm and age in healthy men. We performed FISH in the spermatozoa of 10 donors from the general population: 5 men younger than 40 years of age and 5 fertile men older than 60 years of age. For each chromosome, 1,000 sperm nuclei were analyzed, with a total of 15,000 sperm nuclei for each donor. We used a single sperm sample per donor, thus minimizing intra-donor variability and optimizing consistent analysis. FISH with a TelVysion assay, which provides data on aneuploidy of 19 chromosomes, was used in order to gain a more genome-wide perspective of the level of aneuploidy. Aneuploidy and diploidy rates observed in the younger and older groups were compared. There were no significant differences in the incidence of autosomal disomy, sex chromosome disomy, total chromosome disomy, diploidy, nor total numerical abnormalities between younger and older men. This work confirms that aneuploidy of the sex chromosomes is more common than that of autosomes and that this does not change with age. Our results suggest that some probe combinations have a tendency to indicate higher levels of diploidy, thus potentially affecting FISH results and highlighting the limitations of FISH.