sentence: This suggests that there is likely to have a selective advantage for rs140685149 in / del heterozygote , although further work needs to reveal the underlying mechanism of this observation.According to an online gene expression dataset ( GSE740 ) 33 in the NCBI website , at least 7 defensin genes ( DEFB126 , DEFB103A , DEFA4 , DEFB1 , DEFB4A , DEFA5 and DEFA6 ) are expressed in epididymis .