The combined action of CTCF and its testis-specific paralog BORIS is essential for spermatogenesis

CTCF is a key organizer of the 3D genome. Its specialized paralog, BORIS, heterodimerizes with CTCF but is expressed only in male germ cells and in cancer states. Unexpectedly, BORIS-null mice have only minimal germ cell defects. To understand the CTCF-BORIS relationship, mouse models with varied CTCF and BORIS levels were generated. Whereas Ctcf+/+Boris+/+, Ctcf+/-Boris+/+, and Ctcf+/+Boris-/- males are fertile, Ctcf+/-Boris-/- (Compound Mutant; CM) males are sterile. Testes with combined depletion of both CTCF and BORIS show reduced size, defective meiotic recombination, increased apoptosis, and malformed spermatozoa. Although CM germ cells exhibit only 25% of CTCF WT expression, chromatin binding of CTCF is preferentially lost from CTCF-BORIS heterodimeric sites. Furthermore, CM testes lose the expression of a large number of spermatogenesis genes and gain the expression of developmentally inappropriate genes that are "toxic" to fertility. Thus, a combined action of CTCF and BORIS is required to both repress pre-meiotic genes and activate post-meiotic genes for a complete spermatogenesis program. Genome-wide mapping of CTCF and BORIS sites and mRNA expression profiles in Ctcf (+/+)Boris(+/+), Ctcf (+/-)Boris(+/+), Ctcf +/+Boris(-/-), and Ctcf (+/-)Boris(-/-) [also called 'DKO' or 'CM'] mouse whole testes, round spermatids , and spermatocytesCCCTC结合因子（CTCF）是三维基因组（3D genome）的关键组织者。其特异性旁系同源蛋白BORIS（Brother of the Regulator of Imprinted Sites）可与CTCF形成异二聚体，但仅在雄性生殖细胞与癌症状态下表达。令人意外的是，BORIS敲除（BORIS-null）小鼠仅表现出极轻微的生殖细胞缺陷。为解析CTCF与BORIS的调控关系，研究人员构建了CTCF与BORIS表达水平各异的小鼠模型。其中Ctcf+/+Boris+/+、Ctcf+/-Boris+/+与Ctcf+/+Boris-/-雄性小鼠均可正常生育，而Ctcf+/-Boris-/-（复合突变体；Compound Mutant，简称CM）雄性小鼠则不育。同时敲除CTCF与BORIS的睾丸组织体积减小、减数分裂重组异常、细胞凋亡水平升高，且精子形态畸形。尽管CM模型的生殖细胞中CTCF的表达量仅为野生型（WT）的25%，但CTCF的染色质结合偏好性却在CTCF-BORIS异二聚体结合位点处显著丢失。此外，CM模型的睾丸组织中大量精子发生相关基因表达下调，同时异常激活了一系列对生育能力具有‘毒性’的发育时序不符的基因。由此可见，完整的精子发生程序需要CTCF与BORIS协同作用，同时抑制减数分裂前基因的表达并激活减数分裂后基因的转录。本数据集包含了Ctcf(+/+)Boris(+/+)、Ctcf(+/-)Boris(+/+)、Ctcf+/+Boris(-/-)以及Ctcf(+/-)Boris(-/-)（亦称为‘DKO’或‘CM’）小鼠的全睾丸、圆形精子细胞与精母细胞的全基因组CTCF与BORIS结合位点图谱，以及mRNA表达谱数据。