**7. Conclusion**

In *D. melanogaster*, the evolutionarily conservative *sbr (Dm nxf1)* gene is characterized by the testis-specific gene products. The cytoplasmic localization of the SBR protein in meiotic cysts is quite impressive. Some *sbr* mutant alleles cause male sterility and the specific morphological defects of the spermatids at the individualization stage. Transcriptional activity during pre-meiotic and meiotic stages of spermatogenesis is crucial for the sperm motility in *D. melanogaster*. During these stages, the factors are formed that are able to affect the frequency of aneuploidy arising in the offspring after fertilization. The *sbr* gene is an attractive model for investigation of male sterility and the paternal effect on the embryonic development due to the RNAbinding protein SBR involvement in formation and fate of the long-lived RNAs.
