ODF1, sperm flagelar protein is expressed in kidney collecting ducts of rats.

ODF1 has been described as an exclusively expressed testicular protein and is located in the outer dense fibers along the sperm tail. ODF1 has been involved in the sperm motility and in the development of the flagellum, but the function of ODF1 is not already clear. Other ODF proteins, such as ODF2 have been characterized in other tissues like the basal body of the kidney primary cilium, but so far only the mRNA of ODF1 has been described in other tissues.

Thiols of flagellar proteins are essential for progressive motility in human spermatozoa.

Male infertility is a disorder of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse. The presence of low-motile or immotile spermatozoa is one of many causes of infertility; however, this observation provides little or no information regarding the pathogenesis of the malfunction. Good sperm motility depends on correct assembly of the sperm tail in the testis and efficient maturation during epididymal transit.

Protein fraction isolated from epididymal fluid re-associates sperm in vitro: possible role of serpins in rat rosettes assembly.

In many mammalian species, sperm associate as a consequence of the epididymal transit. From the classic Rouleaux in guinea pig to the most recent work in mouse and echidna, authors have focused mainly on a detailed morphological description of this phenomenon. Some of these articles have also begun to describe the nature of the material present between sperm heads.