Fumel Betty, Froment Pascal, Holzenberger Martin, Livera Gabriel, Monget Philippe, Fouchécourt Sophie
INRA, UMR85 Physiologie de la Reproduction et des Comportements, F-37380, Nouzilly, France; CNRS, UMR7247 Physiologie de la Reproduction et des Comportements, F-37380, Nouzilly, France; Université François Rabelais de Tours, F-37041, Tours, France; IFCE, F-37380, Nouzilly, France.
INSERM and Sorbonne Universités-UPMC, UMRS 938, Hôpital Saint-Antoine, 75012, Paris, France.
PLoS One. 2015 Mar 20;10(3):e0119392. doi: 10.1371/journal.pone.0119392. eCollection 2015.
In the testis, thyroid hormone (T3) regulates the number of gametes produced through its action on Sertoli cell proliferation. However, the role of T3 in the regulation of steroidogenesis is still controversial.
The TRαAMI knock-in allele allows the generation of transgenic mice expressing a dominant-negative TRα1 (thyroid receptor α1) isoform restricted to specific target cells after Cre-loxP recombination. Here, we introduced this mutant allele in both Sertoli and Leydig cells using a novel aromatase-iCre (ARO-iCre) line that expresses Cre recombinase under control of the human Cyp19(IIa)/aromatase promoter.
We showed that loxP recombination induced by this ARO-iCre is restricted to male and female gonads, and is effective in Sertoli and Leydig cells, but not in germ cells. We compared this model with the previous introduction of TRαAMI specifically in Sertoli cells in order to investigate T3 regulation of steroidogenesis. We demonstrated that TRαAMI-ARO males exhibited increased testis weight, increased sperm reserve in adulthood correlated to an increased proliferative index at P3 in vivo, and a loss of T3-response in vitro. Nevertheless, TRαAMI-ARO males showed normal fertility. This phenotype is similar to TRαAMI-SC males. Importantly, plasma testosterone and luteinizing hormone levels, as well as mRNA levels of steroidogenesis enzymes StAR, Cyp11a1 and Cyp17a1 were not affected in TRαAMI-ARO.
CONCLUSIONS/SIGNIFICANCE: We concluded that the presence of a mutant TRαAMI allele in both Leydig and Sertoli cells does not accentuate the phenotype in comparison with its presence in Sertoli cells only. This suggests that direct T3 regulation of steroidogenesis through TRα1 is moderate in Leydig cells, and that Sertoli cells are the main target of T3 action in the testis.
在睾丸中，甲状腺激素（T3）通过对支持细胞增殖的作用来调节配子的产生数量。然而，T3在类固醇生成调节中的作用仍存在争议。
TRαAMI敲入等位基因使得在Cre-loxP重组后能够产生在特定靶细胞中表达显性负性TRα1（甲状腺受体α1）异构体的转基因小鼠。在此，我们使用一种新型的芳香化酶-iCre（ARO-iCre）品系，该品系在人Cyp19（IIa）/芳香化酶启动子的控制下表达Cre重组酶，将此突变等位基因导入支持细胞和间质细胞中。
我们发现，这种ARO-iCre诱导的loxP重组仅限于雄性和雌性性腺，在支持细胞和间质细胞中有效，但在生殖细胞中无效。为了研究T3对类固醇生成的调节作用，我们将该模型与之前仅在支持细胞中引入TRαAMI的情况进行了比较。我们证明，TRαAMI-ARO雄性小鼠的睾丸重量增加，成年期精子储备增加与其在出生后第3天体内增殖指数增加相关，并且在体外丧失了T3反应。然而，TRαAMI-ARO雄性小鼠的生育能力正常。这种表型与TRαAMI-SC雄性小鼠相似。重要的是，TRαAMI-ARO小鼠的血浆睾酮和促黄体生成素水平以及类固醇生成酶StAR、Cyp11a1和Cyp17a1的mRNA水平均未受影响。
结论/意义：我们得出结论，与仅在支持细胞中存在突变的TRαAMI等位基因相比，在间质细胞和支持细胞中同时存在该等位基因并不会使表型更加明显。这表明，通过TRα1对类固醇生成的直接T3调节在间质细胞中较为适度，并且支持细胞是睾丸中T3作用的主要靶细胞。
