|dc.description.abstract||Forkhead transcription factors constitute a family that share a conserved DNA binding domain, the Forkhead box. Members of the subfamily O, including FoxO1, FoxO3, FoxO4, and FoxO6, are involved in many physiological processes, such as cell cycle arrest, DNA damage repair, cell differentiation and apoptosis. Among these FoxOs, the expression and function of the recently discovered FoxO6 in most physiological processes has not been studied before. Therefore, we want to delineate the expression of FoxO6 at mRNA and protein levels respectively in developing muscles in utero and in various post-natal mature muscles. So we detected FoxO6 mRNA in mouse tissues by Q-PCR and observed that the heart, liver, kidney have lower FoxO6 expression than brain and muscle. The highest expression of FoxO6 was found in pituitary. We also found that FoxO6 expression decreased with increasing age. It is also of interest to know the Foxo6 localization at the different stages of myoblasts. To achieve these goals, we used FoxO6-speific domain (amino acid 229~492) as antigen to produce FoxO6 polyclonal antibody in rabbits. After titering, we are sure that this antibody can recognize FoxO6 specifically without cross-reacting with other FoxOs. Using immunofluorescence, we demonstrated that FoxO6 accumulated mostly in nucleus of proliferating myoblasts, and this nuclear localization was further increased when myoblasts became confluent. After terminal differentiation, homogeneous distribution of FoxO6 was detected in the cytoplasm and nucleus of myotubes. Since the expression pattern of FoxO6 is similar to other FoxOs, it suggests that the role played by FoxO6 in myogenesis is probably the same as other FoxOs do. After the delineation of its expression, we will perform promoter assay to find out how FoxO6 expression is regulated in muscle.