Mammalian cerebellum development module

A mammalian developmental program that builds the cerebellum from dorsal rhombomere 1. The program begins with allocation of the cerebellar anlage by the midbrain-hindbrain (isthmic) organizer, followed by segregation of two principal germinal-zone programs: an ATOH1-positive rhombic-lip program that generates glutamatergic lineages and a PTF1A-positive ventricular-zone program that generates GABAergic lineages. Reelin-dependent reorientation of an early/posterior-born Purkinje-cell subset initiates early plate formation. As Purkinje cells differentiate, they provide Sonic hedgehog (SHH) to expand granule-cell precursors in the transient external granule layer. Partly overlapping granule-neuron migration and Bergmann-glial differentiation assemble the cortical layers, while Engrailed-dependent regional patterning coordinates foliation of the vermis and hemispheres. The module ends with formation of the layered, foliated cerebellum; mature synaptic physiology, motor learning, adult homeostasis, and tumorigenesis are outside its boundary.

This is a mammalian scaffold, with most causal evidence coming from mouse. Reviewed human UniProt proteins are used as concrete orthologous exemplars; they do not imply that every mechanism was tested directly in human or that cerebellum development is the protein's core function. Detailed receptor and intracellular machinery is factored into the existing fgfr_signaling and hedgehog_signaling modules. An initial study proposed a noncanonical DNER-NOTCH1 mechanism in Bergmann glia, but a later direct replication found that DNER neither bound nor activated NOTCH1. The supported Dner loss-of-function phenotype is therefore retained without a molecular Notch edge. Purkinje-cell development, granule-cell-precursor proliferation, granule-neuron migration, and Bergmann-glial differentiation partially overlap in developmental time; their order records causal organization, not completion of one program before the next begins. The current definitions of GO:0021695 through GO:0021699 incorrectly describe a six-layered cerebral cortex rather than the three-layered cerebellar cortex, so those definitions were not used to organize this module. Deep cerebellar nuclei are represented as outputs of the early ATOH1/PTF1A lineage split but are not yet decomposed into nucleus-specific submodules. The explicit macro-process -> cell-process -> reusable-pathway layering, and the use of SHH to connect Purkinje-cell development to granule-cell-precursor proliferation, follow the "Decomposition of macro biological processes" Google Slides deck (presentation 1q7PE8VGRGYWyohbLMwpiYpd6dnCJQVuomyzsK5dC9bc, accessed through gog/Drive export on 2026-07-14). ModuleReview has no arbitrary module-include field, so the receiving context points to hedgehog_signaling and anchors it with SMO instead of copying the generic PTCH1-SMO-SUFU-GLI topology or misusing template conformance.