Abstract: 　Objective To screen stage-specific expression genes of plerocercoid of Spirometra erinacei-europaei. Methods RNA was extracted by the acid guanidinium thiocyanate-phenol-chloroform from plerocercoid and adult worm of Spirometra erinacei-europaei. Contaminated DNA in the RNA was digested by RNase-free DNase. cDNA was synthesized by using T₁₂MA, T₁₂MC, T₁₂MG and T₁₂MT primers, and PCR was then done using the same T₁₂MN and one random primers. The PCR products were fractionated on 8% denatured polyacrylamide gel, differential bands of plerocercoid found in the gel were cut out, amplified by PCR and sequenced after the gel was dried out and autoradiographed. Northern hybridization was conducted to identify the stage-specific expression genes. Results Eleven differential bands were selected from the gel and classified into 3 kinds of gene fragments by hybridization after they were amplified by PCR. The fragments 1 and 2 were confirmed to express specifically in plerocercoid by Northern hybridization, but the fragment 3 was expressed in both plerocercoid and adult worm. When the 3 gene fragments were homologically analyzed in GenBank, the sequence which was homologous with the fragments 1 and 2 was not found, but the fragment 3 had high homology with many kinds of 28S rRNA. Conclusion The gene expression of plerocercoid was different from that of adult worm probably because they live in different hosts. Two kinds of different gene fragments in plerocercoid were identified by mRNA differential display technique.

Key words: mRNA differential display, Spirometra erinacei europaei, PCR, gene, stage specific expression