A variety of morphological and molecular changes are required for spermatozoa formation. These steps are temporally guided by the transcription and translation of several testis-specific genes. SPERT (spermatid associated), also known as CBY2 (chibby homolog 2), spermatid flower-like structure protein or NURIT, is a 448 amino acid novel leucine-zipper protein belonging to the chibby family of proteins.Expressed uniquely in the spermatid flower-like structure, SPERT interacts with Nek1, a member of the NIMA-family kinase family that is associated centrosomal stability and ciliogenesis. Containing a leucine-zipper motif and two coiled-coil regions, SPERT is transcribed through the elongation stage of the spermatids. SPERT is absent from mature spermatozoa and is thought to be involved in transporting proteins that are to be discarded via the residual bodies.