ID #481 Loss of EOMES disrupts neuronal migration and alters Group 3/4 medulloblastoma cell-of-origin identity in early cerebellum development

Abstract

Transcription factors (TFs) are central regulators of gene expression programs governing cerebellar development and specification of distinct neural lineages. Among these, the glutamatergic granule cell/unipolar brush cell (GC/UBC) lineage arises from progenitors in the rhombic lip, a region also implicated as the cellular origin of pediatric medulloblastoma subtype Group 3/4. Notably, these tumors share transcriptional similarities with UBCs and express TFs associated with normal UBC development; however, the mechanisms by which these TFs contribute to tumor initiation and progression remain poorly understood. Eomesodermin (Eomes), a T-box transcription factor and defining marker of UBC identity, represents a key candidate mediating these shared developmental and tumor-associated transcriptional programs.

In this study, we used single-cell RNA sequencing (scRNA-seq) to characterize UBC development in murine models. We generated a conditional Eomes knockout mouse lacking the DNA-binding T-box domain responsible for TF activity and isolated UBC lineage cells at two critical developmental stages: embryonic day 16 (E16), when EOMES expression peaks in rhombic lip progenitors, and postnatal day 0 (P0), when mature UBCs are present. Loss of Eomes disrupted UBC identity beginning at E16. By P0, a subset of UBC-like cells persisted in a partially differentiated state; however, these cells failed to express gene signatures characteristic of mature UBC receptors. Instead, they exhibited upregulation of migration-associated genes and pathways, despite displaying a cellular-level migratory defect.

Collectively, these findings provide new insights into EOMES function and underscore its essential role in early UBC specification and cerebellar development. By integrating transcriptomic and epigenomic datasets, we aim to identify direct targets and regulatory networks controlled by EOMES during development and determine how their dysregulation contributes to medulloblastoma pathogenesis. This work establishes a detailed molecular framework for GC/UBC lineage progression and reveals how developmental gene regulatory programs may be co-opted during tumorigenesis.