Smarcd1, also known as BAF60a, is a member of the SWI/SNF chromatin-remodeling complex family. It regulates the transcription of target genes by altering chromatin structure, and is involved in multiple biological processes such as cell differentiation, development, and senescence-associated lipid accumulation [5]. It plays a crucial role in determining cell fate, and genetic models like KO/CKO mouse models are valuable for studying its functions.

In murine adult hematopoiesis, acute deletion of Smarcd1 leads to lymphopenia, with a near-complete absence of early lymphoid progenitors and mature B and T cells, while myeloid and erythroid lineages remain unaffected. This indicates that Smarcd1 is essential for the specification of lymphoid cell fate from multipotent progenitors, achieved by interacting with the E2a transcription factor at proximal promoters and regulating distal enhancer activity [1].

In glioblastoma cell lines and high-grade glioma patients, low expression of Smarcd1 was observed. Depletion of Smarcd1 promoted cell proliferation, invasion, and chemoresistance, while enhanced expression inhibited tumor-malignant phenotypes. There is a crosstalk between Smarcd1 and Notch1 forming a feedback loop, which is crucial in regulating glioblastoma malignant phenotypes [4].

In breast cancer, both high and low expression of Smarcd1 correlate with positive clinical outcomes, while intermediate expression significantly reduces the probability of survival. Small perturbations in Smarcd1 expression can significantly reduce metastasis in mouse models and alter splicing programs relevant to the ER+/HER2-enriched breast cancer subtype [2,3].

In conclusion, Smarcd1 is an essential chromatin remodeler that governs lymphoid cell fate, and its dysregulation is associated with various diseases including glioblastoma and breast cancer. Studies using KO/CKO mouse models have provided valuable insights into its role in these disease conditions, helping to understand the underlying mechanisms and potentially guiding the development of new treatment strategies.