Dynamic Expression and New Functions of Early B Cell Factor 2 in Cerebellar Development
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The collier/Olf1/EBF family genes encode helix-loop-helix transcription factors (TFs) highly conserved in evolution, initially characterized for their roles in the immune system and in various aspects of neural development. The Early B cell Factor 2 (Ebf2) gene plays an important role in the establishment of cerebellar cortical topography and in Purkinje cell (PC) subtype specification. In the adult cerebellum, Ebf2 is expressed in zebrin II (ZII)-negative PCs, where it suppresses the ZII+ molecular phenotype. However, it is not clear whether Ebf2 is restricted to a PC subset from the onset of its expression or is initially distributed in all PCs and silenced only later in the prospective ZII+ subtype. Moreover, the dynamic distribution and role of Ebf2 in the differentiation of other cerebellar cells remain unclarified. In this paper, by genetic fate mapping, we determine that Ebf2 mRNA is initially found in all PC progenitors, suggesting that unidentified upstream factors silence its expression before completion of embryogenesis. Moreover we show Ebf2 activation in an early born subset of granule cell (GC) precursors homing in the anterior lobe. Conversely, Ebf2 transcription is repressed in other cerebellar cortex interneurons. Last, we show that, although Ebf2 only labels the medial cerebellar nuclei (CN) in the adult cerebellum, the gene is expressed prenatally in projection neurons of all CN. Importantly, in Ebf2 nulls, fastigial nuclei are severely hypocellular, mirroring the defective development of anterior lobe PCs. Our findings further clarify the roles of this terminal selector gene in cerebellar development.
KeywordsEbf2 gene COE transcription factors Cerebellar development Purkinje cell development Purkinje cell subtype specification Cerebellar cortex topography Cerebellar nuclei development Fastigial nuclei development Cerebellar granule cell subtypes
Oocyte injections were performed at the Center for Conditional Mutagenesis (CFCM), San Raffaele Scientific Institute. Image analysis was carried out at ALEMBIC, an advanced microscopy laboratory established by the San Raffaele Scientific Institute and University.
G.G.C.’s research was funded by the Italian Telethon Foundation, grant GGP13146. O.C. was the recipient of a grant from the Italian Ministry of Health (Ministero della Salute Ricerca Finalizzata 2011-PE-2011-02347716). R.H. was supported by an award from the Canadian Institutes of Health Research.
Compliance with Ethical Standards
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. The experimental plan was designed in agreement with the stipulations of the San Raffaele Institutional Animal Care and Use Committee (permit number 336).
Conflict of Interest
The authors declare that they have no conflicts of interest.
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