E2f4 is required for intestinal and otolith development in zebrafish

E2f4 is a multifunctional transcription factor that is essential for many cellular processes. Although the role of E2f4 during cell cycle progression has been investigated in great detail, less is known about E2f4 during embryonic development. Here, we investigated the role of E2f4 during zebrafish development. Zebrafish e2f4 mutants displayed ectopic otolith formation due to abnormal ciliary beating in the otic vesicle. The beating defects of motile cilia were caused by abnormal expression of ciliary motility genes. The expression of two genes, lrrc23 and ccdc151, were significantly decreased in the absence of E2f4. In addition to that, e2f4 mutants also displayed growth retardation both in the body length and body weight and mostly died at around 6 months old. Although food intake was normal in the mutants, we found that the microvilli of the intestinal epithelia were significantly affected in the mutants. Finally, the intestinal epithelia of e2f4 mutants also displayed reduced cell proliferation, together with an increased level of cell apoptosis. Our data suggested a tissue-specific role of E2f4 during zebrafish development, which is distinct from the traditional views of this protein as a transcription repressor.