The beta-tubulin multigene family is regulated during rat brain development as manifested by differential expression of at least three different genes. Hybridization of 3'-untranslated region subclones of different beta-tubulin cDNAs reveals that expression of two of these cDNAs is neural specific. RBT.1 is expressed abundantly during early postnatal brain development. RBT.2 corresponds to a mRNA which is prevalent between 7-15 days postnatal. A ubiquitous beta-tubulin gene is expressed throughout development and in all tissues. Preliminary studies in Dr. Berkowitz's laboratory have shown that this multigene family is composed of 12-14 unique EcoRI DNA fragments. Each cDNA subclone hybridizes to a subset of sequences within the family. At least one sequence within each subset is DNAase I sensitive and is, therefore, tentatively identified as a transcriptionally active gene. Dr. Berkowitz has isolated a genomic clone corresponding to RBT.2 . Nuclease studies in her laboratory indicate that this clone represents the transcriptionally active RBT.2 rather than its transcriptionally inert pseudogene. Dr. Berkowitz now intends to evaluate factors regulating the expression of this neural specific RBT.2 gene in rat cerebellar cortex and proposes the following experiments: the genomic clone for the pseudogene (and, if necessary, additional RBT.2 clones) will be isolated, subcloned, and sequenced. Using these subclones, an analysis of potential regulatory mechanisms will be performed, including mapping of hypersensitive sites, studying nucleosome distribution, and identifying nuclear regulatory factors. Additional studies on RBT.2 transcription and in situ hybridization will allow Dr. Berkowitz to identify factors involved in modulation of RBT.2 expression during postnatal cerebellar development.
