CSTF2T encodes a tau variant of cleavage stimulation factor subunit 2 (τCstF-64), an RNA-binding protein involved in mRNA polyadenylation 1. The protein plays a significant role in AAUAAA-independent mRNA polyadenylation, particularly in germ cells, by binding directly to pre-mRNAs and participating in mRNA cleavage and polyadenylation 1. CSTF2T also regulates alternative polyadenylation (APA) in cancer contexts, where it mediates proximal poly(A) site usage—for example, promoting aberrant APA of DNM1L to increase colorectal cancer risk 2. In melanoma, CSTF2T binds ZEB1 mRNA to upregulate IGHG1 expression, promoting cell proliferation and invasion 3. The gene is primarily essential for spermatogenesis and male fertility; Cstf2t knockout mice display severe defects in sperm motility and morphology with reduced round spermatids and testosterone levels 4. CSTF2T also influences neurological function, with female Cstf2t-/- mice showing enhanced memory retention and males displaying altered anxiety-related behavior 5. Additionally, CSTF2T functions as an RNA-binding protein in hepatocellular carcinoma pathways and shows associations with cognitive function in breast cancer patients 67. CSTF2T is located at chromosome 10-q23, a region previously associated with male infertility and neurological disorders 1.