Key Event Relationship Overview
AOPs Referencing Relationship
|AOP Name||Adjacency||Weight of Evidence||Quantitative Understanding|
|Histone deacetylase inhibition leading to testicular toxicity||adjacent||High||Not Specified|
|Mus musculus||Mus musculus||High||NCBI|
|Rattus norvegicus||Rattus norvegicus||High||NCBI|
Life Stage Applicability
|Adult, reproductively mature||High|
Key Event Relationship Description
Apoptosis results in spermatocyte depletion via cell death. HDAC inhibitor, MAA, induced apoptosis and spermatocyte depletion at stages IX-II [Brinkworwth, 1995]. Induced apoptosis during development of germ cells results in progressive depletion of spermatocyte.
Evidence Supporting this KER
In the mouse spermatocyte, spermatogenesis was inhibited by knockdown of Sucla2, a b subunit of succinyl coenzyme A synthase, via apoptosis [Huang, 2016]. The prolonged cryptorchidism leads to germs cell apoptosis and testicular sperm count decrease [Barqawi, 2004]. CD147 was reported to regulate apoptosis in mouse testis and spermatocyte cell line (GC-2 cells) via NFκB pathway [Wang, 2017].
MicroRNA-21 regulates the spermatogonial stem cell homeostasis, in which suppression of microRNA-21 with anti-miR-21 oligonucleotides led to apoptosis of spermatogonial stem cell-enriched germ cell cultures and the decrease in the number of spermatogonial stem cells [Niu, 2011].
Uncertainties and Inconsistencies
The process of apoptosis is necessary for the meitosis of the stem cell differentiation in the testis, which remains in question for the regulation of spermatocyte deletion and testis atrophy/weight loss [Dym, 1994].
Quantitative Understanding of the Linkage
The apoptotic germ cells occurred in the Stra8-Cre KO tubules were approximately 68%, whereas 46% of the cells were germ cells in WT tubules, as determined by double staining for Tra98, a germ cell marker, and cleaved caspase 3 [Bose, 2018].
Known modulating factors
Known Feedforward/Feedback loops influencing this KER
Domain of Applicability
The relationship between apoptosis and spermatocyte depletion is likely well conserved between species.
- Spermatogenesis was inhibited by knockdown of Sucla2 via apoptosis in the mouse spermatocyte (Mus musculus) [Huang, 2016].
- The suppression of microRNA-21 led to apoptosis of spermatogonial stem cell-enriched germ cell cultures and the decrease in the number of spermatogonial stem cells in mice (Mus musculus) [Niu Z, 2011].
- MAA induced apoptosis and depletion of spermatocytes in adult rats (Rattus norvegicus) [Brinkworth, 1995].
Brinkworth M et al. (1995) Identification of male germ cells undergoing apoptosis in adult rats. J Reprod Fertil 105: 25-33
Huang S et al. (2016) Knockdown of Sucla2 decreases the viability of mouse spermatocytes by inducing apoptosis through injury of the mitochondrial function of cells. Folia Histochem Cytobiol 54: 134-142
Barqawi A et al. (2004) Effect of prolonged cryptorchidism on germ cell apoptosis and testicular sperm count. Asian J Androl 6: 47-51.
Wang C et al. (2017) CD147 regulates extrinsic apoptosis in spermatocytes by modulating NFkB signaling pathways. Oncotarget 8: 3132-3143
Niu Z et al. (2011) microRNA-21 regulates the self-renewal of mouse spermatogonial stem cells. Proc Natl Acad Sci 108: 12740-12745
Dym M. (1994) Spermatogonial stem cells of the testis. Proc Natl Acad Sci USA 91: 11287-11289
Bose R et al. (2017) Ubiquitin ligase Huwe1 modulates spermatogenesis by regulating spermatogonial differentiation and entry into meiosis. Sci Rep 7: 17759