MRPL3 (mitochondrial ribosomal protein L3) is a nuclear-encoded component of the mitochondrial large ribosomal subunit that serves as a structural constituent essential for mitochondrial protein synthesis. The protein is critical for early embryonic development, as MRPL3 knockout results in successful implantation but severe developmental delay and failure to initiate gastrulation by embryonic day 7.5, accompanied by significantly reduced ATP production and compromised mitochondrial function 1. MRPL3 functions in mitochondrial translation and is involved in the expression of electron transport chain components 2. Disease associations include combined oxidative phosphorylation deficiency 9, and structural variants in MRPL3 can cause adult-onset neurodegeneration with memory impairment and stereotypical limbic system progression patterns 3. Clinically, MRPL3 shows promise as a biomarker in multiple cancers, being upregulated in pancreatic adenocarcinoma where it promotes cell growth and proliferation 2, and serving as a diagnostic and prognostic marker in breast cancer and hepatocellular carcinoma 45. In pediatric critical illness, MRPL3 expression changes are associated with recovery from multiple organ dysfunction syndrome 6, highlighting its broader clinical relevance beyond mitochondrial disorders.