Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Piecing together the problems in diagnosing lowlevel chromosomal mosaicism | Robberecht et al. Genome Medicine 2010 2 47 http content 2 7 47 Genome Medicine COMMENTARY L__ Piecing together the problems in diagnosing low-level chromosomal mosaicism Caroline Robberecht Jean-Pierre Fryns and Joris Robert Vermeesch Abstract Low-level somatic chromosomal mosaicism which usually arises from post-zygotic errors is a known cause of several well defined genetic syndromes and has been implicated in various multifactorial diseases. It is however not easy to diagnose as various physical and technical factors complicate its identification. Developmental origins of mosaicism Chromosomal mosaicism is defined as the presence of two or more karyotypically different cell lines in the same individual. Somatic mosaicism mostly results from post-zygotic errors in recombination or replication. Whole chromosomal aneuploidies in which there are more than or fewer than two copies of one or more chromosomes can arise by non-disjunction or anaphase lagging. Imbalances of chromosomal segments can originate from unrepaired breakages. Chromosome instability is common in human cleavagestage embryos that have been fertilized in vitro. This has become more apparent through the application of new techniques for the analysis of the chromosome content of single blastomeres. Recent array comparative genomic hybridization array CGH analysis 1 of normally developing good quality preimplantation embryos confirmed the presence of a high percentage of chromosomal abnormalities at cleavage stage. In addition this analysis 1 showed that all abnormal embryos were mosaic for the aberrations found and that not only could whole chromosome aneuploidies be detected but also a significant number of segmental aberrations. Most of these embryos are selected against during the first days and weeks of gestation. As a consequence mosaicism is observed in just 5 of aneuploid spontaneous miscarriages between 6 and 20 weeks 2 and in only 1 to 2 Correspondence .
