Cell formation in the cortical layers of the developing human cerebellum

Cell proliferation has been studied in the human cerebellar cortex between the 24th gestational week and the 12th postnatal month. Intensive cell form ation has been found in the external granular layer (EGL) of the human cere bellum, where the highest cell proliferation rate occurs between the 28th a nd 34th gestational weeks. This is followed by a gradual decrease that last s up to the eighth postnatal month. As late in development as the fifth pos tnatal month, still 30% of cells of the EGL are labeled with the monoclonal antibody Ki-67, which is specific for dividing cells. The width of the EGL remained unchanged from the 28th gestational week to the end of the first postnatal month, when it starts to decrease and completely disappears by th e 11th postnatal month. Large number of Ki-67 labeled cells occurs in the i nternal granular layer (IGL) between the 24th and 28th gestational weeks. F rom the 36th week onwards, the labeling index is less than 1%, although a f ew labeled cells have always been found in this layer even in the late post natal period. Labeled cells are distributed in the entire width of the IGL. However, from the 34th gestational week, almost all labeled cells are foun d among and directly below the Purkinje cells. Their position, the nuclear features, and their occasionally stained cell processes suggest that those are Bergmann glial cells. There are few Ki-67 labeled cells in the molecula r layer (ML) and in the white matter (WM) of the cerebellum throughout the examined period. It is likely that most of these are glial cells. Pyknotic index has been found to be small in all layers of the cerebellum during the examined period. (C) 2001 International Society for Developmental Neurosci ence (C) 2001 ISDN. Published by Elsevier Science Ltd. All rights reserved.