Cloning and studies of the mouse cDNA encoding Smad3

Following stimulation by the transforming growth factor-beta (TGF-beta) fam ily in the cytoplasm, the Smad family is phosphorylated and translocated to the nucleus and activates several gene transcriptions. In this study, the mouse Smad3 cDNA including the open reading frame (ORF) was cloned from the mouse brain using a RACE (rapid amplification of cDNA ends) technique, and its expression pattern was analyzed in mouse tissue using northern blot. T he predicted amino acid (aa) sequences of mouse Smad3 showed a high homolog y with human Smad3 (99.3%) and mouse Smad2 (85.4%). It revealed that this p rotein may be highly conserved in different species of mammals. Northern bl ot analyses revealed that Smad3 was highly expressed in the brain and ovary , and that the size of major transcript was about 5.7 kb. In situ hybridiza tion analyses revealed the high expression of Smad3 was detected in the pyr amidal cells of the hippocampus, the granule cells of the dentate gyrus, th e granular cells of the cerebral cortex and the granulosa cells of the ovar y. Smad3 may be essential transducer of signals from TGF-beta and activin i n these cells.