Developmental expression of the cyclin D2 splice variant in postnatal Purkinje cells of the mouse cerebellum.

In the present study, we compared the expression of cyclin D2 and D2SV, the cyclin D2 splice variant, in mouse cerebellum at postnatal day 1 (P1), P7, P14 and P28. Western blotting revealed that cyclin D2 levels (34kDa) peaked at P7 and then decreased to levels near the limit of detection at P28. To detect D2SV, we generated a rabbit polyclonal antibody directed against a C-terminal motif unique to this protein that recognizes two D2SV immunoreactive bands at 20 and 25kDa. Western blotting indicated that levels of the 20kDa band remained constant from P1 to P28 while the intensity of the 25kDa band decreased gradually over this period of time. At P7, cyclin D2 immunoreactivity was evident throughout the cerebellum where it was located in nestin-positive cells. By contrast, at P28, cyclin D2 immunoreactivity was restricted to Bergmann glia whose cell bodies are located in the Purkinje cell layer and processes extend into the molecular layer. Unlike cyclin D2, D2SV immunoreactivity was restricted to Purkinje cells at both P7 and P28. Our observations that D2SV immunoreactivity is localized to Purkinje cells and reflects changing levels of at least two D2SV immunoreactive proteins suggests that this splice variant may play an important role in the postnatal development of these neurons.