Supplementary Material for: Early Crypt Formation Defects in the Uterine Epithelia of <b><i>Sox17</i></b> Heterozygous Mice

SOX17 activity in the uterine epithelium is essential for the implantation of mouse embryos. Previously, we demonstrated that female <i>Sox17</i> heterozygous mutant mice are subfertile, and 2 active copies of <i>Sox17</i> are required for the proper implantation of mouse embryos. To understand which implantation step is most sensitive to the <i>Sox17</i> gene dosage, we comprehensively investigated the phenotypes and RNA transcriptomes of <i>Sox17</i> heterozygous mutant mice. Uterine <i>Sox17</i> expression drastically changed according to estrous cycle and during early pregnancy. The highest <i>Sox17</i> expression was observed during the receptive period for blastocyst implantation. <i>Sox17</i> heterozygous uterine epithelia showed ectopic high-level expression of SOX9, another SOX factor that is normally expressed in the uterine gland. Three-dimensional analysis of the uterus on day 5 of pregnancy revealed no crypt formation near the healthy blastocysts in the <i>Sox17</i> heterozygous uterine epithelium, suggesting that early defects in embryo homing had occurred. Global transcriptional analysis revealed that the expression of Amphiregulin (<i>Areg</i>), a gene encoding a heparin-binding epidermal growth factor receptor ligand, was decreased drastically in <i>Sox17</i>^+/− uterine epithelia. These data imply that full <i>Sox17</i> activity is required to promote early crypt formation through proper regulation of SOX9 and AREG expression at the implantation site.子宫上皮细胞中的SOX17活性对于小鼠胚胎着床至关重要。此前本研究团队已证实，雌性*Sox17*杂合突变小鼠呈现亚生育表型，且小鼠胚胎正常着床需要两份具有活性的*Sox17*等位基因。 为明确胚胎着床过程中哪个步骤对*Sox17*基因剂量最为敏感，本研究对*Sox17*杂合突变小鼠的表型与RNA转录组（RNA transcriptome）进行了全面分析。子宫*Sox17*的表达会随发情周期及妊娠早期发生显著改变，其表达峰值出现在胚泡着床接受期。*Sox17*杂合子宫上皮细胞出现了SOX9的异位高表达——SOX9是另一种通常仅在子宫腺体中表达的SOX家族转录因子。妊娠第5天的子宫三维成像分析显示，*Sox17*杂合子宫上皮的健康胚泡附近未形成着床隐窝，提示胚胎归巢过程已出现早期缺陷。 全局转录组分析发现，编码肝素结合型表皮生长因子受体配体的双调蛋白（Amphiregulin, *Areg*）在*Sox17*^+/-子宫上皮中的表达水平显著下调。上述数据表明，完整的*Sox17*活性可通过精准调控着床部位的SOX9与AREG表达，进而促进早期着床隐窝的形成。