Zebrin II Expression in the Cerebellum of a Passerine Bird Species: Zebra Finch (Taeniopygia castanotis).

Abstract

Introduction: Zebrin II (ZII) is a glycolytic enzyme that is expressed in cerebellar Purkinje cells. In both mammals and birds, ZII is expressed heterogeneously, such that there are sagittal stripes of Purkinje cells with a high ZII expression (ZII+) alternating with stripes of Purkinje cells with little or no expression (ZII-). To date, ZII expression studies examined at least one species from most of the major branches of the avian phylogeny including Paleognatha (tinamous, kiwi), Galloanseres (chicken), Columbaves (pigeon) and Elementaves (hummingbird). In this regard, the most glaring omission is that a species from Telluraves, a clade that contains 75% of all avian species, has not been studied.

Methods: In this paper, we examined zebrin expression the zebra finch Taeniopygia castanotis (Order Passeriformes). Given that Telluraves have evolved sophisticated hindlimb movements associated with the jump to arboreality, we hypothesized that ZII expression would differ in those areas of the cerebellum that have a strong representation of the hindlimbs, namely folia II-V and IX.

Results: Contrary to our prediction, we found that the pattern of ZII expression in the cerebellum is highly similar to that observed in other bird species. In folium I all Purkinje cells are ZII+. In the rest of the anterior lobe (folia II-V) there are 4 pairs of ZII+/- stripes. In the posterior lobe, folia VI-VII all Purkinje cells are ZII+, in folia VIII-IXcd there are 5-7 pairs of ZII+/- stripes, and in folium X all Purkinje cells are ZII+. Moreover, the expression of ZII+ in Purkinje cell terminals in the cerebellar and vestibular nuclei was similar to that observed in other species.

Conclusion: These data indicate that the pattern of heterogeneous expression of ZII in cerebellar Purkinje is likely conserved across the entirety of the avian phylogenetic tree.