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目的：从人牙髓细胞内克隆转化生长因子－β特异的细胞内信号转导基因Ｓｍａｄ２的功能性结构域———ＭＨ２结构域。方法：原代培养人牙髓细胞，从培养的细胞中提取总ＲＮＡ，逆转录合成ｃＤＮＡ第１条链；设计内、外侧两对引物，进行巢式ＰＣＲ，扩增Ｓｍａｄ２基因ＭＨ２结构域的基因片段；将所获得的基因片段定向插入ｐＢｌｕｓｃｒｉｐｔⅡＳＫ（＋）载体；转化大肠杆菌ＪＭ１０９，挑选阳性克隆并鉴定；用ＰＥ３１７－Ａ型自动测序仪进行核苷酸序列测定分析。结果：测序结果与国外从人肾ｃＤＮＡ文库中克隆的基因序列完全一致。结论：首次从人牙髓细胞中克隆成功Ｓｍａｄ２基因的ＭＨ２结构域，证实了Ｓｍａｄ２基因在人牙髓细胞中的表达；提示人牙髓细胞内存在Ｓｍａｄ２信号转导途径，ＴＧＦ－β对人牙髓细胞分化的调节可能是通过Ｓｍａｄ２信号转导途径实现的。
OBJECTIVE: To clone the MH2 domain, the functional domain of transforming growth factor-β-specific intracellular signal transduction gene Smad2, from human dental pulp cells. Methods: Human dental pulp cells were cultured in primary culture. The total RNA was extracted from cultured cells and the first strand of cDNA was reverse transcribed. Two pairs of primers were designed to carry out nested PCR to amplify the gene of Smad2 MH2 domain The fragment was inserted into pBluscriptⅡSK (+) vector. The recombinant plasmid was transformed into E.coli JM109 and positive clones were selected and identified. The nucleotide sequence was analyzed by PE317-A automated sequencer. Results: The sequencing results were identical with those cloned from human kidney cDNA library. Conclusion: The MH2 domain of Smad2 gene was successfully cloned from human dental pulp cells for the first time, which confirmed the expression of Smad2 gene in human dental pulp cells. It suggests that there is Smad2 signal transduction pathway in human dental pulp cells. TGF- Modulation of myeloid differentiation may be through the Smad2 signaling pathway.