Lysine demethylase 6A (KDM6A), also known as UTX, belongs to the KDM6 family of 
histone H3 lysine 27 (H3K27) demethylases, which also includes UTY and KDM6B 
(JMJD3). The KDM6A protein contains six tetratricopeptide repeat (TPR) domains 
and an enzymatic Jumonji C (JmjC) domain that catalyzes the removal of di- and 
trimethylation on H3K27. KDM6A physically associates with histone H3 lysine 4 
monomethyltransferases MLL3 (KMT2C) and MLL4 (KMT2D). Since its identification 
as an H3K27 demethylase in 2007, studies have reported KDM6A's critical roles in 
cell differentiation, development, and cancer. KDM6A is important for 
differentiation of embryonic stem cells and development of various tissues. 
Mutations of KDM6A cause Kabuki syndrome. KDM6A is frequently mutated in cancers 
and functions as a tumor suppressor. KDM6A is redundant with UTY and functions 
largely independently of its demethylase activity. It regulates gene expression, 
likely through the associated transcription factors and MLL3/4 on enhancers. 
However, KDM6A enzymatic activity is required in certain cellular contexts. 
Functional redundancy between H3K27 demethylase activities of KDM6A and KDM6B in 
vivo has yet to be determined. Further understanding of KDM6A functions and 
working mechanisms will provide more insights into enhancer regulation and may 
help generate novel therapeutic approaches to treat KDM6A-related diseases.