Il pattern spaziotemporale di maturazione delle cellule di Purkinje durante lo sviluppo fetale cerebellare umano

The cerebellum is characterized by a unique morphology and structure, which is the result of a complex developmental program widely described in mice: two embryonal germinative zones, the ventricular zone and the rhombic lip, are responsible of the production of inhibitory and excitatory phenotypes. Newly generated neurons migrate following a specific temporal schedule, where an intense interrelationship between these cells highly influence their maturation and positioning in the final cerebellar architecture. Purkinje cells are the sole output of the cerebellar cortex and exert a pivotal role in cerebellar development and during adult life. Purkinje cells are fundamental in the correct functioning of the organ: their importance is highlighted in ataxia, where loss of voluntary movement is associated with Purkinje cells impairment and degeneration. In humans, cerebellar development has been so far poorly described: at the actual state of art, events described are conserved from murine development, even though more protracted in time. However, much information is still missing. In this study, we wanted to investigate the morphological maturation of Purkinje cells by analysing the vermis of 24, 30 and 32 gestational weeks old human cerebella. In particular, we focused on their morphological changes by taking as parameters the Purkinje cells density and the length of their dendritic tree. These analyses were coupled with the analysis of PCs axons myelination: increasing morphological complexity and myelination were assumed to reveal progressive cell maturation. To do so, we considered the anteroposterior subdivision of the cerebellum in anterior, posterior and central lobe. We found that Purkinje cells maturation follows a spatial pattern where posterior Purkinje cells are the first to reach maturity, followed by anterior and central ones; intralobular, cells maturate following fissures elongation. Results obtained from the myelination analyses showed that also here a similar trend within and across lobules is detectable, especially at older ages, probably reflecting functional maturity. Finally, we performed a clustering analysis on an adult murine single cell RNAseq dataset of PCs, that revealed that differences between anterior, central and posterior PCs are maintained also in the adult expression profile of these cells. Position of Purkinje cells in the cerebellum is thus critical in their development, and further investigation will be required to understand if some molecular or functional interactions might be the cause of this high but consistent heterochronic progression.