Expression of the Hamster Sperm Protein P26h During Spermatogenesis1

Abstract

P26h is a hamster sperm protein of 26 kDa that has been previously characterized as a surface protein covering the acrosome acquired during epididymal transit. P26h is involved in sperm-egg interactions. Recently, it has been shown that the P26h transcript is highly expressed in the testis, and the P26h cDNA has been cloned from a hamster testicular cDNA library. Herein we report the production of a fusion protein (maltose binding protein-P26h) with the whole P26h cDNA encoding sequence and the production of a polyclonal antiserum against it. In Western blots, this antiserum recognized both the P26h extracted from cauda epididymal spermatozoa and the MBP-P26h. We also determined the age of appearance of P26h and which germ cell types express P26h mRNA and its translational product. Northern blots and in situ hybridization analysis showed that P26h transcripts appear at 3 wk of age, within the first round of spermatogenesis in the golden hamster. In situ hybridization showed that P26h transcripts are expressed in spermatocytes and round spermatids, whereas immunostaining revealed the presence of P26h in the cytoplasm of round spermatids and elongated spermatids. P26h was undetectable in testicular spermatozoa. Both in situ hybridization and immunostaining showed P26h expression to be dependent of the testicular cell type and the epithelium cycle. The implications for P26h in sperm-egg interaction and the testicular origin of P26h are discussed.

Effects of Vasectomy on Gene Expression Profiling along the Human Epididymis1

“…They are known to encode highly abundant gene products of the human epididymis, or gene products enriched in specific regions that provide important functional clues [41]. These data complete the list of the two fundamental epididymal human genes, DCXR and NPC2, known to be affected by vasectomy [17,64].…”

Identification and validation of mouse sperm proteins correlated with epididymal maturation

“…In most cases, the disappearance of sperm surface proteins is caused by a specific proteolytic mechanism [10]. P26h, a member of the short-chain dehydrogenase/reductase superfamily, is not detected in caput epididymal hamster sperm, but appears on the acrosomal region in corpus epididymal sperm and accumulates on the acrosomal cap of cauda epididymal sperm [26]. Similarly, P25b is transferred to the sperm head during epididymal transit in the bull [27].…”

Identification of a Hamster Sperm 26-Kilodalton Dehydrogenase/Reductase That Is Exclusively Localized to the Mitochondria of the Flagellum1

“…It was proposed that P26h is anchored to the membrane through a phosphaditylinositol linkage and that prostasome-like particles may be involved in the transfer of P26h from the epididymal fluid to the sperm plasma membrane [25]. Later, the same group of investigators cloned a cDNA from a hamster testicular cDNA library and reported that P26h is a member of the shortchain dehydrogenase/reductase superfamily [31]. They also found the predominant expression of P26h transcript in the seminiferous tubules of the testis, not the epididymis, and proposed that the epididymal luminal fluid P26h is secreted by the seminiferous tubules of the testis [31].…”

“…Later, the same group of investigators cloned a cDNA from a hamster testicular cDNA library and reported that P26h is a member of the shortchain dehydrogenase/reductase superfamily [31]. They also found the predominant expression of P26h transcript in the seminiferous tubules of the testis, not the epididymis, and proposed that the epididymal luminal fluid P26h is secreted by the seminiferous tubules of the testis [31]. They also proposed that P26h may have two different functions, as observed for other moonlighting proteins [32]: first in the testis, as an alcohol dehydrogenase, and then in the epididymis, where it adsorbs on the sperm surface and plays a role during fertilization.…”