The Variation of Aneuploidy Frequency in the Developing and Adult Human Brain Revealed by an Interphase FISH Study

Abstract

and Institute of Pediatrics and Children's Surgery, Russian Ministry of Health, Moscow, Russia (SGV) S U M M A R Y Despite the lack of direct cytogenetic studies, the neuronal cells of the normal human brain have been postulated to contain normal (diploid) chromosomal complement. Direct proof of a chromosomal mutation presence leading to large-scale genomic alterations in neuronal cells has been missing in the human brain. Large-scale genomic variations due to chromosomal complement instability in developing neuronal cells may lead to the variable level of chromosomal mosaicism probably having a substantial effect on brain development. The aim of the present study was the pilot assessment of chromosome complement variations in neuronal cells of developing and adult human brain tissues using interphase multicolor fluorescence in situ hybridization (mFISH). Chromosome-enumerating DNA probes from the original collection (chromosomes 1, 13 and 21, 18, X, and Y) were used for the present pilot FISH study. As a source of fetal brain tissue, the medulla oblongata was used. FISH studies were performed using uncultured fetal brain samples as well as organotypic cultures of medulla oblongata tissue. Cortex tissues of postmortem adult brain samples (Brodmann area 10) were also studied. In cultured in vitro embryonic neuronal brain cells, an increased level of aneuploidy was found (mean rate in the range of 1.3-7.0% per individual chromosome, in contrast to 0.6-3.0% and 0.1-0.8% in uncultured fetal and postmortem adult brain cells, respectively). The data obtained support the hypothesis regarding aneuploidy occurrence in normal developing and adult human brain. T he human brain is the control center that stores, computes, integrates, and transmits information. It contains ‫ف‬ 10 12 neurons, each forming as many as a thousand connections with other neurons (Lodish et al. 2000). There have been no direct studies of large-scale genomic variations and chromosomal complement in the human central nervous system. Without experimental proof, the neuronal cells of the normal brain were postulated to contain normal (diploid) chromosome complement. However, indirect evidence for some forms of somatic, genomic, and chromosomal alterations in the neurons of mouse brain has been obtained. By means of fluorescence in situ hybridization (FISH) and spectral karyotype analysis of mouse embryonic cerebral cortical neuroblasts in the developing and adult nervous system, more than 30% of neuroblasts were found to be aneuploid (Rehen et al. 2001). Visualization of metaphase chromosomes by a nuclear transfer technique in mouse cortical neurons has indicated that the majority are characterized by an abnormal karyotype (Osada et al. 2002). Therefore, there is evidence for genomic variation at the level of whole chromosomes in developing and adult mouse neurons.There are only a limited number of molecular cytogenetic studies of the human brain using interphase FISH. The use of FISH was reported for examination of the interphase nuclei chromosomal co...

Single-walled carbon nanotube-induced mitotic disruption

“…1c, Table 1). The frequency of the aneuploid cells in the controls was within the range reported in adult human cells in culture [46,47]. In contrast, the SWCNT-treated SAEC had a level of aneuploidy that was as high as the effect that was observed in the vanadium pentoxidetreated positive control cells (Fig.…”

Somatic genomic variations in extra-embryonic tissues

“…This is in contrast to reports of genomic variations in other organs such as the reproductive system, the human brain or in hematological disorders [44,[53][54][55][56], where an association between aneuploidy and disease could be established [54,[56][57][58]. While it seems that all human tissues are affected by somatic genomic variations [59], albeit to a greatly varying extent, aneuploidy might be missed when present in rare cells [60,61]. This low frequency of genomic variants marks a demand for highly sensitive technologies-of-scale that offer the high throughput necessary to detect such rare events.…”

Extensive genetic variation in somatic human tissues

“…Somatic mosaicism is well known to occur in normal germline cells as the process of meiotic recombination and in cells of the immune system within Ig and T-cell receptor genes as a result of V(D)J recombination that provides diversity in immune responses. Other studies have revealed age-related structural variation in human blood cells (14), aneuploidy and retrotransposition in the human brain (15,16), and aneuploidy in human preimplantation embryos (17). Evidence of copy number variation (CNV) in monozygotic twins (18) also reveals the presence of somatic mosaicism in tissues arising from the same zygote.…”