Changes in Otx2 and Parvalbumin Immunoreactivity in the Superior Colliculus in the Platelet-Derived Growth Factor Receptor-β Knockout Mice

The superior colliculus (SC), a relay nucleus in the subcortical visual pathways, is implicated in socioemotional behaviors. Homeoprotein Otx2 and beta subunit of receptors of platelet-derived growth factor (PDGFR-beta) have been suggested to play an important role in development of the visual system and development and maturation of GABAergic neurons. Although PDGFR-beta knockout (KO) mice displayed socio-emotional deficits associated with parvalbumin (PV-) immunoreactive (IR) neurons, their anatomical bases in the SC were unknown. In the present study, Otx2 and PV-immunolabeling in the adult mouse SC were investigated in the PDGFR-beta KO mice. Although there were no differences in distribution patterns of Otx2 and PV-IR cells between the wild type and PDGFR-beta KO mice, the mean numbers of both of the Otx2- and PV-IR cells were significantly reduced in the PDGFR-beta KOmice. Furthermore, average diameters of Otx2- and PV-IR cells were significantly reduced in the PDGFR-beta KOmice. These findings suggest that PDGFR-beta plays a critical role in the functional development of the SC through its effects on Otx2- and PV-IR cells, provided specific roles of Otx2 protein and PV-IR cells in the development of SC neurons and visual information processing, respectively.