Molecular cytogenetic studies towards the full karyotype analysis of human blastocysts and cytotrophoblasts

Abstract

Numerical chromosome aberrations in gametes typically lead to failed fertilization, spontaneous abortion or a chromosomally abnormal fetus. By means of preimplantation genetic diagnosis (PGD), we now can screen human embryos in vitro for aneuploidy before transferring the embryos to the uterus. PGD allows us to select unaffected embryos for transfer and increases the implantation rate in in vitro fertilization programs. Molecular cytogenetic analyses using multi-color fluorescence in situ hybridization (FISH) of blastomeres have become the major tool for preimplantation genetic screening of aneuploidy. However, current FISH technology can test for only a small number of chromosome abnormalities and hitherto failed to increase the pregnancy rates as expected. We are in the process of developing multi-color FISH-based technologies to score all 24 chromosomes in single cells within a three-day time limit, which we believe is vital to the clinical setting. Also, human placental cytotrophoblasts (CTBs) at the fetal-maternal interface acquire aneuploidies as they differentiate to an invasive phenotype. About 20–50% of invasive CTB cells from uncomplicated pregnancies were found to be aneuploid, suggesting that the acquisition of aneuploidy is an important component of normal placentation, perhaps limiting the proliferative and invasive potential of CTBs. Since most invasive CTBs are interphase cells and possess extreme heterogeneity, we applied multi-color FISH and repeated hybridizations to investigate the feasibility of a full karyotype analysis of individual CTBs. In summary, this study demonstrates the strength of Spectral Imaging analysis and repeated hybridizations, which provides a basis for full karyotype analysis of single interphase cells.

Genetic Basis for Dosage Sensitivity in A. thaliana

“…For example, segmental aneuploidy is frequent in yeast deletion mutants [39] and can confer a growth advantage to the aneuploid cells compared to the euploid ones [39]. In humans, aneuploid cells have recently been found to be an integral part of the functional pool of neurons and in placental trophoblasts, consistent with a functional role for aneuploidy in these contexts [12][13][14][15]. In plants, it is believed that aneuploidy can play a role in speciation and phenotype evolution [40].…”

“…For example, aneuploid cells are normally found in certain tissues such as the brain and the placenta, where they appear to play a functional role [12][13][14][15]. Aneuploidy has been associated with invasive cancer [16,17] and controversially proposed to play a causal role in malignancy [18].…”

Genomic Instability in the Brain: Etiology, Pathogenesis and New Biological Markers of Psychiatric Disorders

“…До 50-70% эмбрионов явля-ются анеуплоидными, представляя, таким образом, случаи нестабильного генома в результате мейотиче-ского нерасхождения [4,10,[32][33][34][35]. Однако подавля-ющее большинство анеуплоидных эмбрионов, веро-ятно, спонтанно абортируются на последующих стадиях развития [9,23,35].…”

“…До 50-70% эмбрионов явля-ются анеуплоидными, представляя, таким образом, случаи нестабильного генома в результате мейотиче-ского нерасхождения [4,10,[32][33][34][35]. Однако подавля-ющее большинство анеуплоидных эмбрионов, веро-ятно, спонтанно абортируются на последующих стадиях развития [9,23,35]. Тем не менее, исследование преим-плантационных эмбрионов, которые демонстрируют геномную нестабильность на следующих онтогенетиче-ских стадиях, выявляет почти во всех образцах возникно-вение анеуплоидии или хромосомных аберраций, затра-гивающих не менее 20-50% клеток [8,32,36].…”

Somatic genomic variations in extra-embryonic tissues

“…In our studies of uncomplicated pregnancies, we did find that a majority of iCTBs identified as human leukocyte antigen -G (HLA-G) positive cells [21] were chromosomally abnormal [38][39][40]. Please note that this population is rarely studied by any means, because of the difficulty of obtaining these samples.…”