Sine oculis homeobox 1 (Six1) is an important factor for embryonic development and carcinoma malignancy. However, the localization of Six1 varies due to protein size and cell types in different organs. In this study, we focus on the expression and localization of Six1 in male reproductive organ via bioinformatics analysis and immunofluorescent detection. The potential interacted proteins with Six1 were also predicted by protein-protein interactions (PPIs) and Enrichr analysis. Bioinformatic data from The Cancer Genome Atlas and Genotype-Tissue Expression project databases showed that SIX1 was highly expressed in normal human testis, but low expressed in the testicular germ cell tumor sample. Human Protein Atlas examination verified that SIX1 level was higher in normal than that in cancer samples. The sub-localization of SIX1 in different reproductive tissues varies but specifically in the cytoplasm and membrane in testicular cells. In mouse cells, single cell RNA-sequencing data analysis indicated that Six1 expression level was higher in mouse spermatogonial stem cells (mSSCs) and differentiating spermatogonial than in other somatic cells. Immunofluorescence staining showed the cytoplasmic localization of Six1 in mouse testis and mSSCs. Further PPIs and Enrichr examination showed the potential interaction of Six1 with bone morphogenetic protein 4 (Bmp4) and catenin Beta-1 (CtnnB1) and stem cell signal pathways. Cytoplasmic localization of Six1 in male testis and mSSCs was probably associated with stem cell related proteins Bmp4 and CtnnB1 for stem cell development.

中文翻译：

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Six1 在男性睾丸和精原干细胞中的细胞质定位。

正弦眼同源框 1 (Six1) 是胚胎发育和癌症恶性肿瘤的重要因素。然而，Six1 的定位因不同器官中的蛋白质大小和细胞类型而异。本研究通过生物信息学分析和免疫荧光检测，重点研究Six1在男性生殖器官中的表达和定位。还通过蛋白质-蛋白质相互作用 (PPI) 和 Enrichr 分析预测了与 Six1 潜在相互作用的蛋白质。来自癌症基因组图谱和基因型组织表达项目数据库的生物信息数据表明，SIX1在正常人睾丸中高表达，但在睾丸生殖细胞肿瘤样本中低表达。人类蛋白质图谱检查证实，正常样本中的 SIX1 水平高于癌症样本中的水平。SIX1 在不同生殖组织中的亚定位各不相同，但特别是在睾丸细胞的细胞质和细胞膜中。在小鼠细胞中，单细胞 RNA 测序数据分析表明，小鼠精原干细胞 (mSSC) 和分化精原细胞中的Six1表达水平高于其他体细胞。免疫荧光染色显示了 Six1 在小鼠睾丸和 mSSC 中的细胞质定位。进一步的 PPI 和 Enrichr 检查显示 Six1 与骨形态发生蛋白 4 (Bmp4) 和连环蛋白 Beta-1 (CtnnB1) 以及干细胞信号通路之间的潜在相互作用。Six1 在男性睾丸和 mSSC 中的细胞质定位可能与干细胞发育的干细胞相关蛋白 Bmp4 和 CtnnB1 相关。