LAUSR

The cerebellum plays a pivotal role in the control and regulation of motor functions, contributing to the coordination, precision and timing of movements; in addition, recent evidence suggests its involvement also in cognitive and emotional functions, such as attention, memory, language and responses to fear or pleasure (Schmahmann, 2019). In humans, cerebellar development begins during early embryonic stages and persists for several months after birth. Granule cell precursors (GCPs) proliferate postnatally in the external granule layer (EGL), in response to Sonic Hedgehog (Shh) stimulus provided by underlying Purkinje cells; then, GCPs migrate inward to the molecular and internal granule layers (ML and IGL, respectively) and differentiate in mature granule neurons (Ruiz i Altaba et al., 2002). Abnormalities in cerebellar development are responsible for several disorders and cancer (Farioli-Vecchioli et al., 2012). Medulloblastoma (MB) is the most common malignant childhood brain tumor, arising in the posterior cranial fossa during early brain development. It is a heterogeneous disease, comprising four molecular variants (Wnt, Shh, Group 3, and Group 4) with different cells of origin, age of onset and prognosis. The current MB treatment includes maximal safe resection, chemotherapy and radiotherapy; however, survivors suffer devastating side effects, such as neurological cognitive and behavioral deficits (Juraschka and Taylor, 2019). Thus, this Research Topic has focused on the discovery of signaling pathways or genetic mutations with significant impact on both the physiological and pathological cerebellar development, for the identification of new molecular targets/biomarkers of diseases and the generation of advanced preclinical models for the study of cerebellar pathologies. Xiao et al. demonstrated that abnormal development of the cerebellum can lead to significant impairments in motor coordination and learning, deficits commonly observed in patients with autism spectrum disorders (ASD). Specifically, the authors observed that in a BTBR T Itpr3/J mouse model of autism, severe dystonia-like behavior and motor disfunctions were closely related with increased proliferation of GCPs in EGL and enhanced cerebellar foliation. Furthermore, in the BTBR cerebellum, Purkinje cells, the only efferent cerebellar neurons with a key role in motor function, showed morphological OPEN ACCESS