Testis-specific DNA binding protein responsible for insulator function, nuclear architecture and transcriptional control, which probably acts by recruiting epigenetic chromatin modifiers. Plays a key role in gene imprinting in male germline, by participating in the establishment of differential methylation at the IGF2/H19 imprinted control region (ICR). Directly binds the unmethylated H19 ICR and recruits the PRMT7 methyltransferase, leading to methylate histone H4 'Arg-3' to form H4R3sme2. This probably leads to recruit de novo DNA methyltransferases at these sites (By similarity). Seems to act as tumor suppressor. In association with DNMT1 and DNMT3B, involved in activation of BAG1 gene expression by binding to its promoter. Required for dimethylation of H3 lysine 4 (H3K4me2) of MYC and BRCA1 promoters. Interacts with histones, PRMT7 and SETD1A. Interacts (via N-terminus) with BAG6/BAT3. Testis specific. Specifically expressed in primary spermatocytes. Is up-regulated in primary spermatocytes (expression overlapping with the genome-wide erasure of methylation) to become silenced on activation of CTCF in post-meiotic germline cells (expression corresponding to DNA remethylation). Belongs to the CTCF zinc-finger protein family.