Developmental expression of the cell cycle and apoptosis controlling gene, Lot1, in the rat cerebellum and in cultures of cerebellar granule cells

The Lot1 gene encodes a zinc finger protein that, in vitro, concurrently regulates apoptosis and cell cycle arrest and belongs to a recently identified family of proteins with oncogenic and tumor-supressor functions. The present study, based on the development of the first antibody reportedly produced against rat Loll, examines protein expression during normal development of the rat cerebellum and following methylazoxymethanol (MAM) administration, which results in hypoplasia of the cerebellar granule cell population. Using light microscopic immumocytochemistry, specific immunostaining for the Loll protein was observed at postnatal days 2 to 7 in the superficial external granule layer composed primarily of proliferating neuronal precursor cells. Purkinje cells showed distinct nuclear labeling at P7 In the adult cerebellum, the overall low Lot1 level was essentially associated with Purkinje cells. Experimentally altered developmental conditions, such as those obtained through MAM-induced microencephaly, did not drastically affect the pattern of Lot1 expression. In particular, Purkinje cells continued to show normal levels of immunoreactivity notwithstanding the altered cerebellar architecture. Primary cultures of cerebellar granule cells showed a temporal pattern of Loll expression resembling that of in vivo development, with mRNA and protein levels progressively decreasing with differentiation. When cerebellar granule cells were exposed to different neurotoxic challenges, Loll appeared not affected by purely apoptotic cell death, while transitorily induced by mixed necrotic-apoptotic cell death. (C) 2003 Elsevier Science B.V. All rights reserved.