Purkinje cell diversification: A blueprint for cerebellar development, patterning, and evolution.

Purkinje cells (PCs) are the linchpins of cerebellar development and function. As the sole output neurons of the cerebellar cortex, PCs play a key role in integrating input and transmitting cerebellar output. In addition, PCs influence the development of other cell populations through the secretion of morphogens and region-specific activity. PCs emerge as a molecularly heterogeneous population early in development, and their migration, spatial reorganization, and subtype-dependent roles sculpt the cerebellar architecture. In this review, we synthesize the current knowledge of PC ontogenesis and diversification, including recent single-cell transcriptomic findings that reveal embryonic subtype diversity and its spatial logic. We examine how combinatorial expression of key transcription factors, notably the FOXP family, drives PC subtype identity, and how their loss disrupts cerebellar regionalization. We also discuss how PC subtype diversification integrates developmental timing, circuit formation, and evolutionary expansion of the cerebellar hemisphere, highlighting its importance in both cerebellar morphogenesis and the emergence of higher cognitive functions.