A Survey of the Metabolic Landscape of the Developing Cerebellum at Single-Cell Resolution.

The use of cell-culture models to investigate development and disease of the cerebellum is a recent advance, facilitated by the discovery that patterning of precursors is capable of giving rise to cells with specific neuronal identity. Pluripotent stem cell-derived organoids, which exhibit self-organisational characteristics reminiscent of early cerebellar tissue, present a number of challenges including recapitulation of conditions resembling the mature brain. An understanding of the processes driving fetal and postnatal maturation is required to reproduce these conditions in vitro and advance the capability of the system to model adult-onset disease. A key tool for achieving this is single-cell RNA sequencing, which enables visualisation of key transcriptional features of subpopulations comprising tissues. Here, we explore and compare available single-cell RNA sequencing data derived from the developing human cerebellum and its synthetic, in vitro counterpart (stem cell-derived cerebellar organoids). We focus on performing a qualitative assessment of the expression of key metabolic pathway genes, given recent findings exemplifying tissue-specific metabolic activity, including hypoxia and metabolic shifts associated with neuronal expansion. Signatures indicative of known cell type-specific metabolic differences, such as the astrocyte-neuron lactate shuttle and glutamate-glutamine cycle were evident at a transcriptional level. Cerebellar tissue and cerebellar organoids showed a number of behavioural similarities, including HIF1 signalling, which may serve to drive expansion of granule cell progenitors in both settings. We further highlight numerous differences between cultured organoids and native tissue which may provide clarity on the state of metabolic state following differentiation of organoids, providing the future framework to test and further hypotheses regarding promoting maturation. Overall, this analysis provides insight into understanding the state of in vitro models of the cerebellum, a critical factor required for modelling susceptibility of various cell types to cerebellar disease.