Functions of block of proliferation 1 during anterior development in Xenopus laevis

Abstract

Block of proliferation 1 (Bop1) is a nucleolar protein known to be necessary for the assembly of the 60S subunit of ribosomes. Here, we show a specificbop1expression in the developing anterior tissue of the South African clawed frogXenopus laevis. Morpholino oligonucleotide-mediated knockdown approaches demonstrated that Bop1 is required for proper development of the cranial cartilage, brain, and the eyes. Furthermore, we show thatbop1knockdown leads to impaired retinal lamination with disorganized cell layers. Expression of neural crest-, brain-, and eye-specific marker genes was disturbed. Apoptotic and proliferative processes, which are known to be affected during ribosomal biogenesis defects, are not hindered uponbop1knockdown. Because earlyXenopusembryos contain a large store of maternal ribosomes, we considered if Bop1 might have a role independent ofde novoribosomal biogenesis. At early embryonic stages,pax6expression was strongly reduced inbop1morphants and synergy experiments indicate a common signaling pathway of the two molecules, Bop1 and Pax6. Our studies imply a novel function of Bop1 independent of ribosomal biogenesis.