RMP64 (ribonuclease MRP subunit p64), also known as NEPRO, is a metazoan-specific protein subunit of the ribonuclease MRP (RNase MRP) ribonucleoprotein complex 1. As an integral component of RNase MRP, RMP64 stabilizes the catalytic RNA and is essential for pre-rRNA processing at internal transcribed spacer 1 (ITS1) site 2, with particular importance for 40S ribosome biogenesis 23. RMP64 is structurally and functionally distinct from the related RNase P complex, which processes tRNA precursors 1. The protein employs a unique 'double-anchor' substrate-binding mechanism that enables specific recognition of rRNA substrates 4. RMP64 is required for cell proliferation, protein synthesis, and chondrogenesis 4. Disease-associated mutations in RMP64 impair its association with other RNase MRP subunits, resulting in defective ribosome biogenesis 2. RMP64 mutations are associated with anauxetic dysplasia 3, highlighting the clinical significance of this conserved ribosomal processing factor in human development and skeletal formation.