Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, UK; The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, EH25 9RG, UK.
Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, UK.
Gen Comp Endocrinol. 2019 Nov 1;283:113227. doi: 10.1016/j.ygcen.2019.113227. Epub 2019 Jul 23.
Water temperature is a critical external factor influencing gonadal development in fish. This research aimed to study the impact of elevated temperature on testicular germ cell survival and reproductive capacity of Nile tilapia. Male Nile tilapia were exposed to high temperatures of either 36 (HT1) or 37 °C (HT2) for 3000 degree-days (DD) and thereafter returned to the control temperature of 27 °C (CT) for 2200 DD. The deleterious effects on testicular germ and somatic cells were observed histologically, characterised by vacuolisation, atrophy and the loss of spermatogenic cells in testes with a more severe impact of HT2 compared to HT1. Interestingly, serum 11-ketotestosterone (11-KT) and testosterone (T) levels tended to be higher during the heat treatments than CT. Expression levels of germline-specific genes piwil1, piwil2 and nanos2 and Bcl-2 family genes, bcl-xLb and baxa were significantly reduced during the heat treatment compared to CT, more so in the HT2, while the levels of nanos3 and gfra1 transcripts were only significantly reduced in HT2, implying a significant loss of spermatogonial stem cell (SSC) and spermatogonia in HT2. The effect of HT2 is further evidenced by the significantly reduced sperm density and fertilisation rate compared to CT and HT1 at the end of the recovery period but complete sterility was not induced by HT2. Overall, the present study showed significant effects of HT2 on germ cell survival with histological changes in testes, reduced milt quality, increased 11-KT, and decreased expression of germline-specific genes, SSC marker genes and Bcl-2 family genes in testes which could therefore be potential target genes for sterilisation by genome editing.
水温是影响鱼类性腺发育的关键外部因素。本研究旨在研究高温对尼罗罗非鱼睾丸生殖细胞存活和生殖能力的影响。雄性尼罗罗非鱼暴露于 36°C（HT1）或 37°C（HT2）的高温下 3000 度日（DD），然后返回 27°C（CT）的对照温度 2200 DD。睾丸生殖和体细胞的损伤作用通过组织学观察，表现为空泡化、萎缩和生殖细胞丢失，与 HT1 相比，HT2 对睾丸的影响更严重。有趣的是，血清 11-酮睾酮（11-KT）和睾酮（T）水平在热处理期间往往高于 CT。与 CT 相比，热处理期间生殖细胞特异性基因 piwil1、piwil2 和 nanos2 以及 Bcl-2 家族基因 bcl-xLb 和 baxa 的表达水平显著降低，HT2 更为明显，而 nanos3 和 gfra1 转录本的水平仅在 HT2 中显著降低，这意味着 HT2 中显著丧失了精原干细胞（SSC）和精原细胞。HT2 的影响还进一步表现在恢复期末与 CT 和 HT1 相比，精子密度和受精率显著降低，但 HT2 并未完全导致不育。总体而言，本研究表明 HT2 对生殖细胞存活有显著影响，睾丸组织学发生变化，精液质量下降，11-KT 增加，睾丸中生殖细胞特异性基因、SSC 标记基因和 Bcl-2 家族基因的表达降低，这些基因可能成为基因组编辑绝育的潜在靶基因。
