Abstract：
OBJECTIVE: Retrotransposons play important roles during early development when they are transiently de-repressed during epigenetic reprogramming. Long interspersed element-1 (L1), the only autonomous retrotransposon in humans, comprises 17% of the human genome. We applied the Single Cell Transposon Insertion Profiling by Sequencing (scTIPseq) to characterize and map L1 insertions in human embryos.
METHODS: Sixteen cryopreserved, genetically tested, human blastocysts, were accessed from consenting couples undergoing IVF at NYU Langone Fertility Center. Additionally, four trios (father, mother, and embryos) were also evaluated. scTIPseq was applied to map L1 insertions in all samples, using L1 locations reported in the 1000 Genomes as controls.
RESULTS: Twenty-nine unknown and unique insertions were observed in the sixteen embryos. Most were intergenic; no insertions were located in exons or immediately upstream of genes. The location or number of unknown insertions did not differ between euploid and aneuploid embryos, suggesting they are not merely markers of aneuploidy. Rather, scTIPseq provides novel information about sub-chromosomal structural variation in human embryos. Trio analyses showed a parental origin of all L1 insertions in embryos.
CONCLUSIONS: Several studies have measured L1 expression at different stages of development in mice, but this study for the first time reports unknown insertions in human embryos that were inherited from one parent, confirming no de novo L1 insertions occurred in parental germline or during embryogenesis. Since one-third of euploid embryo transfers fail, future studies would be useful for understanding whether these sub-chromosomal genetic variants or de novo L1 insertions affect embryo developmental potential.
METHODS: Sixteen cryopreserved, genetically tested, human blastocysts, were accessed from consenting couples undergoing IVF at NYU Langone Fertility Center. Additionally, four trios (father, mother, and embryos) were also evaluated. scTIPseq was applied to map L1 insertions in all samples, using L1 locations reported in the 1000 Genomes as controls.
RESULTS: Twenty-nine unknown and unique insertions were observed in the sixteen embryos. Most were intergenic; no insertions were located in exons or immediately upstream of genes. The location or number of unknown insertions did not differ between euploid and aneuploid embryos, suggesting they are not merely markers of aneuploidy. Rather, scTIPseq provides novel information about sub-chromosomal structural variation in human embryos. Trio analyses showed a parental origin of all L1 insertions in embryos.
CONCLUSIONS: Several studies have measured L1 expression at different stages of development in mice, but this study for the first time reports unknown insertions in human embryos that were inherited from one parent, confirming no de novo L1 insertions occurred in parental germline or during embryogenesis. Since one-third of euploid embryo transfers fail, future studies would be useful for understanding whether these sub-chromosomal genetic variants or de novo L1 insertions affect embryo developmental potential.
摘要：
目的：反转录转座子在表观遗传重编程过程中短暂去抑制，在早期发育过程中发挥重要作用。长散布元素-1(L1)，人类中唯一的自主反转录转座子，占人类基因组的17%。我们通过测序（scTIPseq）应用了单细胞转座子插入谱来表征和绘制人胚胎中的L1插入图。
方法：十六个冷冻保存，经过基因测试,人类胚泡，从纽约大学Langone生育中心接受IVF的同意夫妇那里获得。此外,四个三重奏(父亲，母亲,和胚胎）也进行了评估。将scTIPseq应用于所有样品中的图L1插入，使用1000个基因组中报告的L1位置作为对照。
结果：在16个胚胎中观察到29个未知和独特的插入。大多数是基因间的；没有插入位于外显子或基因上游。未知插入的位置或数量在整倍体和非整倍体胚胎之间没有差异，表明它们不仅仅是非整倍性的标记。相反，scTIPseq提供了有关人类胚胎亚染色体结构变异的新信息。三重奏分析显示胚胎中所有L1插入的亲本起源。
结论：一些研究测量了小鼠不同发育阶段的L1表达，但是这项研究首次报道了从父母一方遗传的人类胚胎中未知的插入，确认在亲本种系或胚胎发生过程中没有从头L1插入。由于三分之一的整倍体胚胎移植失败，未来的研究将有助于了解这些亚染色体遗传变异或L1从头插入是否会影响胚胎发育潜能.
方法：十六个冷冻保存，经过基因测试,人类胚泡，从纽约大学Langone生育中心接受IVF的同意夫妇那里获得。此外,四个三重奏(父亲，母亲,和胚胎）也进行了评估。将scTIPseq应用于所有样品中的图L1插入，使用1000个基因组中报告的L1位置作为对照。
结果：在16个胚胎中观察到29个未知和独特的插入。大多数是基因间的；没有插入位于外显子或基因上游。未知插入的位置或数量在整倍体和非整倍体胚胎之间没有差异，表明它们不仅仅是非整倍性的标记。相反，scTIPseq提供了有关人类胚胎亚染色体结构变异的新信息。三重奏分析显示胚胎中所有L1插入的亲本起源。
结论：一些研究测量了小鼠不同发育阶段的L1表达，但是这项研究首次报道了从父母一方遗传的人类胚胎中未知的插入，确认在亲本种系或胚胎发生过程中没有从头L1插入。由于三分之一的整倍体胚胎移植失败，未来的研究将有助于了解这些亚染色体遗传变异或L1从头插入是否会影响胚胎发育潜能.
