Transcriptomic changes induced by Gsk-3-deletion in cerebellar progenitors

Cerebellar development requires regulated proliferation of cerebellar granule neuron progenitors (CGNPs). Inadequate CGNP proliferation causes cerebellar hypoplasia while excessive CGNP proliferation can cause medulloblastoma, the most common malignant pediatric brain tumor. Although Sonic Hedgehog (SHH) signaling is known to activate CGNP proliferation, the mechanisms down-regulating proliferation are less defined. We investigated CGNP regulation by GSK-3, which down-regulates proliferation in the forebrain, gut and breast by suppressing mitogenic WNT signaling. In striking contrast, we found that co-deleting Gsk-3α and Gsk-3β blocked CGNP proliferation, causing severe cerebellar hypoplasia. Transcriptomic analysis showed activated WNT signaling and up-regulated Cdkn1a in Gsk-3-deleted CGNPs. These data show that a GSK-3/WNT axis modulates the developmental proliferation of CGNPs and the pathologic growth of SHH-driven medulloblastoma. The requirement for GSK-3 in SHH-driven proliferation suggests that GSK-3 may be targeted for SHH-driven medulloblastoma therapy. In this experiment, we dissociated cells from whole cerebella collected from postnatal day 1 (P1) mice with the indicated genotypes. Whole cerebella were collected from P1 mice with both isoforms of Gsk-3 deleted, Gsk-3b deleted, or Gsk-3 intact. Cells were dissociated and CGNPs were enriched through a density gradient before isolating RNA. 5 replicates of each indicated genotype were included in the study. Gsk-3-deleted samples (Gsk-3 DKO) were compared to either Cre-containing Math1-Cre/GSKa+/- controls or controls with no Cre and Gsk-3 intact.