[The expression pattern of the chick pleiotrophin and its possible role in early embryogenesis]

I investigated the expression pattern of the Pleiotrophin (PTN), a heparin-binding multifunctional protein, to investigate its role in early embryogenesis. The PTN expression dynamically changed during somitogenesis, which seemed to be affected by the interaction of axial (neural tube and notochord) and paraxial structures. In the middle stage (i.e. the hind limb bud level), coordinated expression between somite and neural tube was remarkable in the dorsal part. Separation experiments demonstrated that the PTN expression in dorsal somite depends on some factor secreted by the neural tube. The factor was not the PTN itself, since its forced expression in the neural tube did not affect its somite expression. Other secretory factors in the neural tube that are reported to affect somite development were also examined but failed to change the expression. On the contrary, forced expression of PTN in the neural tube enhanced only the Pax3 expression in somite. These results indicate the complexity of the PTN role in somitogenesis, which might possibly explain the phenotype of Pax3 mutant mouse, Sploch (Sp).