A commonly used anti-SOX15 antibody fails to demonstrate specificity in mouse embryos.

SOX15 is a broadly conserved transcription factor involved in many critical processes, including mammalian cell fate specification and pluripotency. We investigated the specificity of a commercially available, polyclonal anti-SOX15 antibody advertised as knockout-validated. We generated a new mouse line carrying a null allele of , and then evaluated anti-SOX15 activity in null mouse embryos. Nuclear signal was detected in both wild type and null embryos, even when potential maternally or paternally-contributed was eliminated. We conclude that this SOX15-detecting reagent may not be suitable for all applications, and caution the growing community of users accordingly.