SPEF2 is expressed in all ciliated cells and is essential for correct sperm tail development and male fertility. We have previously identified a mutation within the SPEF2 gene as the cause for infertility because of immotile and malformed sperm tails in pigs. This mutation in pigs alters the testis-specific long SPEF2 isoform and exclusively affects the sperm tail development. In infertile boars, axonemal and all accessory structures of the sperm tail are affected; thus, SPEF2 seems to participate in the organization of these structures. In the present study, we have investigated the expression of SPEF2 during mouse spermatogenesis. SPEF2 mRNA and protein products appear to be localized both in germ cells and in Sertoli cells. In differentiating germ cells, SPEF2 protein is localized in the Golgi complex, manchette, basal body, and midpiece of the sperm tail. In mature murine sperm, SPEF2 is present in the distal part of the sperm tail midpiece. Using yeast two-hybrid assay and coimmunoprecipitation experiments, we identified an interaction between SPEF2 and the intraflagellar transport protein IFT20 in the testis. Furthermore, these two proteins colocalize in differentiating male germ cells. These results support the crucial importance of SPEF2 in sperm differentiation and involvement of SPEF2 in structuring of the sperm tail.

MicroRNAs (miRNA) are short single-stranded RNA molecules that regulate gene expression post-transcriptionally by binding to complementary sequences in the 3' untranslated region (3' UTR) of target mRNAs. MiRNAs participate in the regulation of myogenesis, and identification of the complete set of miRNAs expressed in muscles is likely to significantly increase our understanding of muscle growth and development. To determine the identity and abundance of miRNA in porcine skeletal muscle, we applied a deep sequencing approach. This allowed us to identify the sequences and relative expression levels of 212 annotated miRNA genes, thereby providing a thorough account of the miRNA transcriptome in porcine muscle tissue. The expression levels displayed a very large range, as reflected by the number of sequence reads, which varied from single counts for rare miRNAs to several million reads for the most abundant miRNAs. Moreover, we identified numerous examples of mature miRNAs that were derived from opposite sides of the same predicted precursor stem-loop structures, and also observed length and sequence heterogeneity at the 5' and 3' ends. Furthermore, KEGG pathway analysis suggested that highly expressed miRNAs are involved in skeletal muscle development and regeneration, signal transduction, cell-cell and cell-extracellular matrix communication and neural development and function.

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