Component of a nucleolar small nuclear ribonucleoprotein particle (snoRNP) thought to participate in the processing and modification of pre-ribosomal RNA. Regulation of cell size by ribosome synthesis is an important parameter for stem cell maintenance and function. Component of U3 snoRNP complex. Asymmetric segregation of expression upon mitosis both in germline stem cells (GSCs) and dividing larval neural stem cells (NSCs) (at protein level). Induces premature differentiation of germline stem cells (GSCs). Belongs to the WD repeat UTP18 family.