| Objective: Microsporum canis is a kind of fungus that infect skin,hair and nail of human and animal, which is characterized by prominent invasion of the stratum corneum and cause superficial skin infection. It is not opportu- nistic but really pathogenic fungi. As living level improving,people get in touch with house pet more closely, the frequency of M. canis infection especially kerion is going up year by year. There is evidence that the secretory activity of protease in their invasive play an important role, but the role of in addition to factors other than protease in tinea capitis remains unclear. Early trials have been induced M. canis from different culture medium ,which were induction medium strains in children scalp (tester);in children smooth skin (driver1) and in adult scalp (driver2),and have been used suppression subtractive hybridization (SSH) to build two positive differences in gene library : tester and driver1(SSH1), tester and driver2 (SSH2),and processed separately library clone.In this study , Using dot-blot hybridization and real time PCR technique to screen and verify the differentially expressed genes and homology search was performed on GenBank using BLAST. On the basis of these results, we will study the pathogenesis of tinea capitis caused by M. canis, which may be helpful for infection in the guinea pig model.Methods:1.Using dot-blot hybridization to screen positive clones in library of SSH1 and SSH2,each which have 250 differentially clones.2. Positive clones screened were sequenced and homology search was performed on database of GenBank and Clusters of Orthologous Groups of proteins (COG) using BLAST. 3. Using real time PCR technique to detect differentially genes.Results:1. 110 positive clones in libraries were obtained by used the dot-blot hybridization .2. Positive clones sequence: 62 effective sequence were aquired in SSH1 library and 44 in SSH2 library. Database analysis: removal of intermi- xture gene (Human gene homology with> 98%, linear scores> = 200; and fungal gene linear scores <40), 13 differentially expressed sequences were obtained from SSH libraries of M.canis and eight of those had homologous genes and six had functions ,five were new unknown sequence which may be new genes of tester.3. Real time PCR test results: the expression levels of FSH1 and PQ-LRP genes were 44.6-fold and 117-fold separately in tester than in driver1, while P-GAL4 and NADH1 genes were 78.2-fold and 9.8-fold separately in tester than in driver2.Conclusion:1. Five homologous genes were obtained in SSH1 library,which were FSH1, PQ-LRP, multidrug resistance protein MDR, RING zinc finger protein and RING zinc finger protein, putative. Three homologous genes were aquired in SSH2 library , which were P-GAL4, NADH1 and DNA-directed RNA polymerase I subunit.2. FSH1 and PQ-LRP genes shown up-regulated expression in chil- dren's scalp induction medium strains than in children's smooth skin tissue induction medium strains suggest that the above-mentioned genes in M.canis may play an important role in infection scalp tissue and demand further study.3. P-GAL4 and NADH1 genes are up-regulated in M.canis in children's scalp induction medium than that in adult's scalp induction medium reve- aled that the two genes may be associated with M.canis infection children, which can serve as candidate genes of M.canis'pathogenicity.
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