Through selective splicing, CARM1 manifests in several isoforms, including the full-length variant (referred to as CARM1) that is predominantly expressed in healthy heart, brain, testis, and skeletal muscle, and the truncated CARM1 lacking exon 15 (CARM1ΔE15) that prevails in breast cancers. The gene discussed is CARM1; the disease is breast cancer.