The histone demethylase KDM6A controls the mammary luminal lineage through enzyme-independent mechanisms

Mammary ducts and alveoli are composed of basal and luminal cells, with the fate and differentiation of secreting cells being controlled by hormones through specific transcription factors. This study establishes the essential role of the histone H3 lysine 27 trimethylation (H3K27me3) demethylase KDM6A (UTX) in a balanced basal and luminal cell compartment. Disproportionate formation of basal cells in the absence of KDM6A resulted in disorganized mammary ducts and alveoli and lactation failure. Mutant luminal progenitors lost their distinctive transcription factor expression pattern and acquired basal characteristics leading to a preferential expansion of this lineage. The structure of mammospheres obtained from mutant progenitors suggested they were derived from basal progenitors. The genomic H3K27me3 landscape was unaltered in the absence of KDM6A suggesting demethylase-independent mechanisms. In support of this, mammary tissue developed normally in mice expressing a catalytically inactive KDM6A. This study demonstrated that mammary luminal progenitor cells rely on UTX to stably maintain their identity and thereby establish a balance of basal and luminal cells required for a functional mammary gland. mRNA-seq in WT;MMTV-Cre (Control) and Kdm6af/f;MMTV-Cre(Kdm6a KO) at virgin. ChIP-seq for KDM6A, and NFIB in mammary tissues at virgin and KDM6A KO H3K27me3, H3K4me1, PR, and ER in mammary tissues at p13.乳腺导管与腺泡由基底细胞和腔细胞组成，分泌细胞的命运与分化过程受激素通过特定转录因子调控。本研究明确了组蛋白H3赖氨酸27三甲基化（H3K27me3）去甲基化酶KDM6A（UTX）在维持基底细胞与腔细胞室平衡中的核心作用。当KDM6A缺失时，基底细胞异常增殖，进而导致乳腺导管与腺泡结构紊乱、泌乳功能障碍。突变的腔系祖细胞会丧失其特有的转录因子表达模式，并获得基底细胞特性，最终引发该细胞谱系的优先扩增。从突变祖细胞中获取的乳腺球（mammospheres）结构特征提示，其起源于基底祖细胞。在KDM6A缺失的情况下，基因组的H3K27me3修饰全景未发生显著改变，表明该调控过程不依赖于去甲基化酶的催化活性。这一结论得到实验佐证：表达催化失活型KDM6A的小鼠，其乳腺组织发育完全正常。本研究证实，乳腺腔系祖细胞依赖UTX以稳定维持自身细胞身份，进而建立功能性乳腺所需的基底细胞与腔细胞平衡。本数据集包含以下测序数据：未生育状态下野生型（WT）、MMTV-Cre（对照组）以及Kdm6a^f/f;MMTV-Cre（Kdm6a基因敲除，KO）小鼠的mRNA测序（mRNA-seq）数据；未生育状态下乳腺组织中KDM6A与NFIB的染色质免疫沉淀测序（ChIP-seq）数据；以及妊娠第13天（p13）乳腺组织中H3K27me3、H3K4me1、孕激素受体（PR）与雌激素受体（ER）的ChIP-seq数据。