BAHD1, or bromo adjacent homology domain-containing protein 1, is a heterochromatinization factor that associates with histone deacetylases HDAC1/2. It plays a role in chromatin-dependent gene regulation, which is crucial for various biological processes. The protein is involved in pathways related to nervous system development, cell proliferation, and steroid metabolism [1,2,3].

In male Bahd1 knockout (KO) mice, although there were no detectable brain anatomical defects, RNA sequencing showed about 2500 deregulated genes, mainly related to nervous system functions, behavior, metabolism, and immunity. Bahd1 heterozygous male mice exhibited anxiety-like behavior and reduced prepulse inhibition of the startle response, suggesting BAHD1's role in psychiatric-related behaviors [1].

In breast cancer, BAHD1 was found to be predictive of lymph node metastasis and prognosis, and in vitro studies showed it affects breast cancer cell proliferation, migration, and invasion, with its down-regulation inducing cell cycle arrest in the G1 phase [2].

Ablation of the Bahd1 gene in mice also led to hypocholesterolemia, hypoglycemia, decreased body fat, placental growth restriction, and high neonatal mortality, indicating its role in placental development and regulation of steroid metabolism [3].

In conclusion, BAHD1 is essential for chromatin-dependent gene regulation. Studies using KO mouse models have revealed its significance in nervous system-related behaviors, breast cancer progression, and placental development. Understanding BAHD1's functions provides insights into the mechanisms of related diseases and may offer potential therapeutic targets.