While chromosomal mosaicism in the embryo was observed already in the 1990s using both karyotyping and FISH technologies, the full extent of this phenomenon and the overall awareness of the consequences of chromosomal instability on embryo development has only come with the advent of sophisticated single-cell technologies. High-throughput techniques, such as DNA microarrays and massive parallel sequencing, have shifted single-cell genome research from evaluating a few loci at a time to the ability to perform comprehensive screening of all 24 chromosomes. The development of genome-wide single-cell haplotyping methods have also enabled for simultaneous detection of single-gene disorders and aneuploidy using a single universal protocol. Today, three decades later haplotyping-based embryo testing is performed worldwide to reliably detect virtually any Mendelian hereditary disease with a known cause, including autosomal-recessive, autosomal-dominant and X-linked disorders. At the same time, these single-cell assays have also provided unique insight into the complexity of embryo genome dynamics, by elucidating mechanistic origin, nature and developmental fate of embryonic aneuploidy. Understanding the impact of postzygotically acquired genomic aberrations on embryo development is essential to determine the still controversial diagnostic value of aneuploidy screening. For that reason, considerable efforts have been put into linking the genetic constitution of the embryo not only to its morphology and implantation potential, but more importantly to its transcriptome using single-cell RNA sequencing. Collectively, these breakthrough technologies have revolutionized single-cell research and clinical practice in assisted reproduction and led to unique discoveries in early embryogenesis.

中文翻译：

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处于 PGT 和胚胎研究前沿的单细胞技术

虽然在 1990 年代已经使用核型分析和 FISH 技术观察到胚胎中的染色体嵌合现象，但这种现象的全部范围以及对染色体不稳定性对胚胎发育后果的全面认识只是随着复杂的单细胞技术的出现而出现的. 高通量技术，如 DNA 微阵列和大规模平行测序，已将单细胞基因组研究从一次评估几个基因座转变为对所有 24 条染色体进行全面筛选的能力。全基因组单细胞单体型分析方法的发展也使得使用单一通用协议同时检测单基因疾病和非整倍性成为可能。今天，三十年后，基于单体型的胚胎测试在全球范围内进行，以可靠地检测几乎任何具有已知原因的孟德尔遗传性疾病，包括常染色体隐性遗传、常染色体显性遗传和 X 连锁疾病。同时，这些单细胞分析还通过阐明胚胎非整倍性的机制起源、性质和发育命运，为胚胎基因组动力学的复杂性提供了独特的见解。了解合子后获得的基因组畸变对胚胎发育的影响对于确定非整倍体筛查仍有争议的诊断价值至关重要。出于这个原因，人们付出了相当大的努力，将胚胎的遗传构成不仅与其形态和植入潜力联系起来，但更重要的是它的转录组使用单细胞 RNA 测序。总的来说，这些突破性技术彻底改变了辅助生殖的单细胞研究和临床实践，并在早期胚胎发生方面取得了独特的发现。