MPP10 (M-phase phosphoprotein 10), also known as MPHOSPH10, is a 681 amino acid protein that localizes to the fibrillar region of the nucleolus. Phosphorylated in the M (mitotic) phase of the cell cycle, MPP10 is a component of the 60-80S U3 small nucleolar ribonucleoprotein (U3 snoRNP) complex and is required for the early cleavages during pre-18S ribosomal RNA processing. MPP10 forms a heterotrimeric complex with IMP-3 and IMP-4, which may be required for its association with nucleolar components. The gene encoding MPP10 is localized to human chromosome 2, which houses over 500 genes and is the second smallest human chromosome. Mutations in several of the genes that map to chromosome 22 are involved in the development of Phelan-McDermid syndrome, Neurofibromatosis type 2, autism and schizophrenia.