Microarray-based and next generation sequencing (NGS) technologies have revealed that segmental aneuploidy is frequently present in human oocytes, cleavage-stage embryos and blastocysts. However, very little research has analyzed the type, size, chromosomal distribution and topography of the chromosomal segments at the different stages of development. This is a retrospective study of 822 PGT-A (preimplantation genetic test for aneuploidies) performed on trophectoderm samples from 3565 blastocysts biopsied between January 2016 and April 2017. The cycles in question had been initiated for varying clinical indications. Samples were analyzed by next generation sequencing-based technology. Segmental aneuploidies were evaluated when fragment size was > 5 Mb. Blastocysts presenting a single segmental aneuploidy (SSA), without any additional whole-chromosome gain/loss, were statistically analyzed for incidence, type, size and chromosomal emplacement. Segment sizes relative to the whole chromosome or arm (chromosome- and arm-ratios) were also studied. 8.4% (299/3565) of blastocysts exhibited segmental aneuploidy for one or more chromosomes, some of which were associated with whole-chromosome aneuploidy while others were not. Nearly half of them (4.5%: 159/3565 of blastocysts) exhibited pure-SSA, meaning that a single chromosome was affected by a SSA. Segments were more frequent in medium-sized metacentric or submetacentric chromosomes and particularly in q-chrmosome arms, variables that were related to trophectoderm quality. SSA size was related to a greater extent to chromosome number and the arm affected than it was to SSA type. In absolute values (Mb), SSA size was larger in large chromosomes. However, the SSA:chromosome ratio was constant across all chromosomes and never exceeded 50% of the chromosome. SSA frequency is chromosome- and topographically dependent, and its incidence is not related to clinical or embryological factors, but rather to trophectoderm quality. SSA might be originated by chromosome instability in response to chromothripsis, bias introduced by the biopsy and/or iatrogenic effects. Retrospectively registered.

中文翻译：

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人类囊胚的节段性非整倍性：定性和定量概述

基于微阵列和下一代测序 (NGS) 技术表明，人类卵母细胞、卵裂期胚胎和囊胚中经常存在节段性非整倍性。然而，很少有研究分析不同发育阶段染色体片段的类型、大小、染色体分布和形态。这是一项对 2016 年 1 月至 2017 年 4 月期间活检的 3565 个囊胚的滋养外胚层样本进行的 822 PGT-A（非整倍体植入前遗传学检测）的回顾性研究。所讨论的周期是针对不同的临床适应症启动的。通过下一代测序技术对样品进行分析。当片段大小 > 5 Mb 时评估节段性非整倍性。对呈现单节段非整倍性（SSA）且没有任何额外的全染色体增益/丢失的囊胚的发生率、类型、大小和染色体位置进行统计分析。还研究了相对于整个染色体或臂的片段大小（染色体和臂比）。8.4% (299/3565) 的囊胚表现出一条或多条染色体的节段非整倍性，其中一些与全染色体非整倍性相关，而另一些则不然。其中近一半（4.5%：159/3565 的囊胚）表现出纯 SSA，这意味着单个染色体受到 SSA 的影响。片段在中等大小的中着丝粒或亚中着丝粒染色体中更为频繁，特别是在 q 染色体臂中，这些变量与滋养外胚层质量相关。SSA 大小与染色体数目和受影响手臂的关系比与 SSA 类型的关系更大。从绝对值 (Mb) 来看，大染色体中的 SSA 大小更大。然而，SSA：染色体比率在所有染色体上都是恒定的，并且从未超过染色体的 50%。SSA频率依赖于染色体和地形，其发生率与临床或胚胎学因素无关，而是与滋养外胚层质量有关。SSA 可能源于染色体不稳定对染色体碎裂的反应、活检和/或医源性效应引入的偏差。已追溯登记。