Fragile X syndrome (FXS) is one of the most common causes of mental retardation, but modern medicine has not yet produced a good therapeutic effect. Clinical practice and scientific studies have showed that acupuncture has a marked therapeutic effect on mental retardation, but researches on the mechanism of its action are still not mature. In view of this, this article will focus on the present situation of FXS study and expound the feasibility of NLGN-3 protein as a target for the mechanism of action of acupuncture on FXS.

AIM To construct a non-normalized cDNA library from Agkistrodon acutus venom gland as an imtial step to develop new and more effective venom by genetic engineering technique for screening and expressing target genes. METHODS The total RNA was extracted from fresh venom gland using Trizol. mRNA was reversely transcripted to cDNA using superscriptⅡ reverse transcriptase. Second-strand synthesis was performed using DNA polymeraseⅠ. After adding EcoRⅠ adaptor, phosphorylating the end and digesting with XhoⅠ, the cDNA was collected in five fractions (<0.25 kb, 0.25-0.5 kb, 0.5-1 kb, 1-2 kb and >2 kb) using the QIAquick Gel Extraction kit and ligated to pBluescriptⅡ vectors. The five libraries obtained were plated by infecting E.coli DH10B, constructing a cDNA library of Agkistrodon acutus venom gland. Sequencing clones at random, 8696 high quality 5′ end expressed sequenced tags (ESTs) were obtained and analyzed. The initial sequences were assembled into 2855 clusters. Among which, one of the clusters (Agkihagin) consisting of 74 ESTs was identified as a novel metalloprtoteinase based on RT-PCR and sequence analysis. RESULTSThe titers of library were 2.048×106. The novel metalloproteinase belonged to PⅢ type metalloproteinase. Its open reading frame was composed of 1827 nucleotides and coded a pre-zymogen of 608 amino acid with zinc-binding domain for metalloproteinase and Asp-Glu-Cys-Asp(DECD) domain for disintegrin. CONCLUSION The capacity of cDNA library of venom gland is above the general level of cDNA library. It would be a helpful platform to construct a catalog for transcripts in the venom gland of the Agkistrodon acutus. The sequence analysis indicates that the deduced amino acid sequence of the identified gene for metalloproteinase share the highest 87% identity with the metalloproteinase genes of other snakes in the GenBank. It lays a good foundation for the study of structure-function relationships of snake venom metalloproteinases.