Molecular Characteristics and Differentiation Control Mechanisms of Bergmann Glia-Like Progenitors in the Postnatal Mouse Cerebellum.

In the mammalian cerebellum, three types of astroglial cells-Bergmann glial cells (BGs), inner granule cell layer (IGL) astrocytes, and white matter (WM) astrocytes-arise in postnatal timing from two types of progenitors: Bergmann glia-like progenitors (BGLPs) and astrocyte-like progenitors (AsLPs). In contrast to AsLPs, which are commonly observed in other brain regions, BGLPs have not been well studied. Here, we investigate differentiation abilities, gene expression profiles and differentiation control mechanisms of BGLPs at postnatal stages. BGLPs and AsLPs decrease in number as development progresses from postnatal day 0 (P0), and are almost absent by P10. By utilizing an electroporation-based method to BGLPs, we found that P6 BGLPs differentiate into BGs and IGL astrocytes, but not into WM astrocytes, consistent with a previous report. However, P0 BGLPs were observed to differentiate into not only BGs and IGL astrocytes, but also WM astrocytes and a small number of molecular layer inhibitory neurons. By conducting spatial transcriptomic analysis with over 5000 probes (Xenium), we successfully identified distinct clusters corresponding to BGLPs at P0 and P6, respectively, and genes preferentially expressed in P0 and P6 BGLPs. In addition, upstream regulatory analysis using Enrichr identified Foxm1 and Nfia as candidate regulators that affect stage-specific properties of BGLPs. in vivo knockdown and overexpression experiments further demonstrated that precise regulation of Foxm1 and Nfia expression is important for proper progeny production from postnatal BGLPs. This study gives insights into understanding molecular nature and differentiation ability control of BGLPs during postnatal cerebellar development.