Differential expression of thymosins β4 and β10 during rat cerebellum postnatal development

The β-thymosins are a family of actin monomer-sequestering proteins widely distributed among vertebrate classes. The most abundant β-thymosins in mammalian species are thymosin β₄ (Tβ₄) and thymosin β₁₀ (Tβ₁₀), two small peptides (43 amino acids) sharing a high degree of sequence homology. In the present work, we have analyzed the distribution of Tβ₄ and Tβ₁₀ in the developing and adult rat cerebellum using in situ hybridization and immunohistochemistry techniques. Our results show that the temporal and cellular patterns of expression of both β-thymosins are different. In the young (7 and 18 postnatal days) and adult (1 and 4 months old) rat cerebellum, Tβ₄ was mainly expressed in the glia (microglia, Golgi epithelial cells and oligodendrocytes), neurons (granule cells and Purkinje cells), and in the capillaries. In 14-month-old rats, the Tβ₄ immunoreactivity was only detected in some microglia cells. In young and adult animals, most of the Tβ₁₀ immunoreactivity was localized in several types of neuronal cells including granule cells, Golgi neurons and Purkinje cells. In old animals, a faint Tβ₁₀ signal could be detected in a few Purkinje cells. Our results suggest that each β-thymosin could play a different function in the control of actin dynamics.