Distribution of the class II beta-tubulin in developmental and adult rat tissues.

Abstract

During a screen of monoclonal antibodies raised against a cytoskeletal preparation of neonatal rat cerebrum, we have identified a monoclonal antibody, MAb58A, that is specific for the class II beta-tubulin isotype. Immunoscreening of a rat brain cDNA library using MAb58A yielded the cDNA retaining a class II-specific nucleotide sequence. The specificity of MAb58A to the class II beta-tubulin isotype was confirmed by immunoreactivity to synthetic peptides corresponding to isotype-specific sequence of class I, II, III, IVa, or IVb. Further, the results of an immunoassay against a series of overlapping octapeptides derived from a class II-specific region revealed that the antibody epitope was a heptapeptide that consists of Glu-Glu-Glu-Glu-Gly-Glu-Asp (EEEEGED). Immunoblot analysis revealed that the class II isotype represented a significant portion of beta-tubulin present in the adrenal gland, brain, and testis of adult rats. In fetal tissues, this isotype was detected in skeletal muscle, as well as in the brain. Immunohistochemically, MAb58A reacted predominantly with components of the developing rat nervous system, such as migrating neuroblasts, peripheral nerves and ganglion cells, and sensory organs. MAb58A-immunoreactivity was also found in developing skeletal and smooth muscle cells, chondrocytes, and vascular endothelia. In adults, MAb58A-immunoreactivity was remarkably diminished, but persisted in peripheral nerves and ganglion cells, chondrocytes, and capillary components. Together, our results demonstrate that MAb58A is specific for the class II beta-tubulin isotype, which may retain an embryonic nature in both neuronal and non-neuronal tissues.