Required for correct axoneme development in spermatozoa (PubMed:16549801, PubMed:19889948). Important for normal development of the manchette and sperm head morphology. Essential for male fertility. Plays a role in localization of the intraflagellar transport protein IFT20 to the manchette, suggesting function as an adapter for dynein-mediated protein transport during spermatogenesis. Also plays a role in bone growth where it seems to be required for normal osteoblast differentiation (By similarity). Interacts (via C-terminus) with IFT20. Interacts with DYNC1I2. Shows dynamic localization in developing spermatozoa. Localizes to the manchette in step 10-12 elongating spermatids. Detected in the basal body and neck area of step 13-14 spermatids. Localizes to the midpiece of the sperm tail in step 15-16 spermatids. During the epididymal transport of spermatozoa, expression in the sperm tail reduces and becomes concentrated at the distal part of the midpiece. Detected in the Golgi apparatus of late spermatocytes and round spermatids. Detected in the cytoplasm of Sertoli cells. Predominantly expressed in ciliated tissues. Mainly expressed in testis, followed by trachea. Also expressed at lower level in lung, kidney and liver. Defects in SPEF2 are a cause of immotile short-tail sperm defects, an autosomal recessive disease only found in the Finnish Yorkshire pig population (PubMed:16549801, PubMed:17610085, PubMed:19889948). It specifically affects the axoneme structure of sperm flagella, whereas cilia in other tissues appear unaffected (PubMed:16549801, PubMed:17610085, PubMed:19889948). Sperm flagella are short and malformed, with disorganized mitochondria and loss or disorganization of the outer fibrous sheath (PubMed:19889948).