Expression of vascular endothelial growth factor receptor-3 mRNA in the developing rat cerebellum.

Vascular endothelial growth factor receptor (VEGFR)-3, a receptor for VEGF-C and VEGF-D, has recently been suggested to play an important role during neuronal development. To characterize its potential role in CNS ontogenesis, we investigated the spatiotemporal and cellular expression of VEGFR-3 in developing and mature rat cerebellum using in situ hybridization. VEGFR-3 expression appeared as early as E15, and was restricted to the ventricular zone of the cerebellar primordium, the germinative neuroepithelium, but was absent by E20. Instead, the expression area of VEGFR-3 in the cerebellum grew in parallel with cerebellar development. From E20 on, two populations of VEGFR-3-expressing cells can be clearly distinguished in the developing cerebellum: a population of differentiating and postmitotic neurons and the Bergmann glia. VEGFR-3 expression in neurons occurred during the period of neuronal differentiation, and increased with maturation. In particular, the expression of VEGFR-3 mRNA revealed different temporal patterns in different neuronal populations. Neurons generated early, Purkinje cells, and deep nuclear neurons expressed VEGFR-3 mRNA during late embryonic stages, whereas VEGFR-3 transcription in local interneurons appeared by P14 with weaker expression. In addition, Bergmann glia expressed VEGFR-3 throughout cerebellar maturation into adulthood. However, receptor expression was absent in the progenitors in the external granular layer and during further migration. The results of this study suggest that VEGFR-3 has even broader functions than previously thought, regulating both developmental processes and adult neuronal function in the cerebellum.