The Effect Of Nicotine On Meiosis Recombination In Spermatogenesis

Cigarette smoking can affect male fertility via the quality of semen.To explore the effects of nicotine,a major component of cigarettes,on meiotic recombination during spermatogenesis,C57BL/6J male mice were injected with nicotine at a dosage of 0.2 mg/100 g body weight daily for 35 days(nicotine-treated group);mice in the control group were injected with isopycnic normal saline.According to previous expression profiles of mouse sperm,a subset of meiosis-related genes was pooled using bioinformatic analysis.Protein expression was compared between the two groups using by Western blotting and immunohistochemistry.Recombination frequency during the meiosis phase of spermatogenesis was estimated by combined use of chromosome spread and immunofluorescence staining in mouse testes.Data mining analysis indicated that 4 genes that express meiotic topoisomerase-like protein SPO11,MutS protein homolog 4(MSH4),strand exchange protein RAD51 and MutL protein homologue 1(MLH1),were associated with the meiosis recombination process.The results of Western blotting and immunohistochemistry further showed that the protein expression of SPO11(0.73-fold)and MSH4(0.73-fold)was downregulated in murine testes after nicotine treatment,whereas the protein expression of both RAD51(2.06-fold)and MLH1(1.40-fold)was upregulated.Unexpectedly,we did not detect a significant difference in recombination frequency in meiosis during spermatogenesis in the nicotine-treated group as compared to the control.Taken together,these results indicate that nicotine can affect the expression profile of restructuring-related genes,but it does not significantly change the recombination frequency during male meiosis.These findings suggest there is a self-regulating mechanism during meiotic chromosome restructuring in male mice that responds to environmental stress.