Spetex-1: A new component in the middle piece of flagellum in rodent spermatozoa

Abstract

Spetex-1 has recently been isolated by differential display and screening of cDNA library. It encodes a protein of 556 amino acid residues possessing coiled-coil motifs. In the rat seminiferous tubules (ST), Spetex-1 was expressed in the cytoplasm of elongating spermatids. To examine the subcellular distribution of Spetex-1 in mature spermatozoa, we performed biochemical and immunocytochemical approaches. We found that Spetex-1 that was synthesized in the cytoplasm of elongating spermatids was subsequently integrated as a middle piece component into spermatozoa during spermiogenesis. After integration, the majority of Spetex-1 in spermatozoa could be extracted by 6M urea under reduced condition but not released by the treatment of 1% Triton X-100. Immunoelectron microscopy demonstrated that Spetex-1 seemed to locate at the inner side of outer dense fibers (ODFs) in the middle piece or the narrow space between ODFs and axoneme. Spetex-1 might be involved in the stability of the structural complexity comprising axoneme and ODFs in the middle piece of sperm flagellum.

SPATA18, a Spermatogenesis-Associated Gene, Is a Novel Transcriptional Target of p53 and p63

“…Accordingly, the mRNA of Spetex-1, the rat ortholog of SPATA18, is detected at 3 weeks of postnatal development and reaches peak levels at 6 weeks (27). The combined results of in situ hybridization, immunocytochemical analysis, and immunoelectron microscopy show that Spetex-1 is highly expressed in elongating spermatids and in spermatozoa (26,27).…”

“…SPATA18 rat ortholog, Spetex-1, is highly expressed during spermatogenesis in spermatids, and its protein localizes at defined regions, such as the cytoplasm of spermatids, residual bodies, and the flagella (26,27,30). Accordingly, two distinct non-mutually exclusive suggestions were raised regarding its function in spermatogenesis, being involved either in the process of spermatid maturation or constituting a flagellar component.…”

“…In situ hybridization and immunohistochemical analyses revealed that Spetex-1 mRNA and protein are expressed in the cytoplasm of haploid spermatids and in residual bodies (27). Further subcellular analysis revealed that Spetex-1 protein also localizes at satellite fibrils associated with outer dense fibers in the middle piece of the flagella in spermatozoa (26,30).…”

“…In addition, Iida et al showed that a portion of Spetex-1 protein is retained in spermatozoa as a flagellar component after spermiation. Thus, Spetex-1 might serve as a structural constituent in the flagella (26,30).…”

Germ cell-less like-2 protein is a new component of outer dense fibers in rat sperm flagella

“…The antiserum was collected within 2 weeks after the third injection. Affinity purification of the antibody was carried out over a matrix of the peptide coupled to Formyl-Cellulofine (Seikagaku Kougyo, Nagoya, Japan), as described previously (Matsuyama et al 2005, Iida et al 2006a). …”