Requirement of Notch 1 and its ligand Jagged 2 expressions for spermatogenesis in rat and human testes

It has already been demonstrated that the Notch signaling system is essenti al for gametogenesis in the adult germ line of Caenorhabditis elegans. Howe ver, the role of the Notch signaling system in mammalian spermatogenesis ha s not been well investigated. Recently, it has been revealed that this sign aling system is expressed in the mammalian testis by showing coexpression o f Jagged 2 and its receptor, Notch 1, is consistent with Notch 1 being a co gnate receptor for Jagged 2 in the mammalian testis. Therefore, we investig ated expressions of messenger RNAs of Notch 1 and Jagged 2 in the testicula r tissues of developing Sprague-Dawley rats by reverse transcription-polyme rase chain reaction and Northern blot analysis, expressions of their protei ns in the testicular tissues of developing rats, fertile human controls and infertile human patients with maturation arrest by immunohistochemistry, a nd effects of antibodies to this system by culturing rat testicular tissues with these antibodies. Transcripts of Notch 1 and Jagged 2 in the rat test is were positive throughout the examined period; these intensities became h igher at day 13 after birth, coincidence with the formation of spermatocyte s, and peaked at day 19 after birth. Expressions of Notch 1 and Jagged 2 we re recognized at first in the perinuclear regions of spermatocytes in the r at testis as a round structure at day 19 after birth and thereafter in furt her differentiated germ cells as meiosis proceeded. In the adult rat testis , positive staining was present as a round structure in spermatocytes, as a typical horses hoe-shaped, structure in round spermatids, and as a coverin g structure spreading around the nucleus of elongated spermatids, but not i n spermatozoa. Notch 1 was recognized in the vacuole of the Golgi complex o f primary spermatocytes and the acrosome of elongated spermatids with elect ron microscopy. When rat testicular tissues were cultured with anti-Notch 1 or anti-Jagged 2 antibody, round and elongated spermatids decreased after 5 and 7 days of culture, respectively, and disappeared at around 9 and 12 d ays of culture, respectively, with shrinkage of the diameter of seminiferou s tubules. Spermatocytes, however, increased after 11 days of culture. Expr essions of both proteins have been detected in the testicular tissues of hu man fertile controls as in the rat testicular tissues. However, Notch 1 exp ression has not been detected in testicular tissues of 11 patients with mat uration arrest, whereas Jagged 2 expression has been recognized in all of t hem. In conclusion, the results presented in this study offer the possibili ty that Notch Wagged 2 signaling system plays an important role for male ge rm cells to differentiate or at least to survive in the rat testis and fail s to express in the testis of spermatogenic maturation arrest patients.