LSM1 is a core component of the cytoplasmic Lsm1-7-Pat1 complex that functions primarily in mRNA degradation 1. The protein localizes to discrete cytoplasmic P-bodies where it colocalizes with decapping enzymes (Dcp1/2) and the exonuclease Xrn1, forming a functional mRNA degradation machinery 1. LSM1 plays a specialized role in degrading histone mRNAs, the only non-polyadenylated eukaryotic mRNAs, and participates in general mRNA decay through deadenylation-dependent decapping 2. In reproductive biology, LSM1 is critical for maternal RNA degradation during zygotic genome activation, with paternally-specific expression facilitating early human embryonic development 3. Clinically, LSM1 variants, particularly the homozygous splice-site variant c.231+4A>C causing exon 3 skipping, are causative for a novel autosomal recessive syndromic neurodevelopmental disorder characterized by dysmorphic facial features, developmental delay, and multisystemic involvement 4. In breast cancer, elevated LSM1 expression serves as a diagnostic and prognostic marker for advanced disease with poor survival, associated with tumor-promoting metabolic reprogramming and increased macrophage infiltration 5. LSM1 inactivation sensitizes breast cancer cells to MEK inhibitors, suggesting therapeutic potential 6.