Augmentation of progestin signaling rescues testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling.
Augmentation of progestin signaling rescues testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling.
复制标题
作者：
Zhai G;Shu T;Yu G;Tang H;Shi C;Jia J;Lou Q;Dai X;Jin X;He J;Xiao W;Liu X;Yin Z
雄激素信号的干扰已知会导致斑马鱼的睾丸畸形和精子发生缺陷。然而，在雄性斑马鱼中，负责雄激素合成的关键酶--CYP17A1的基因敲除却矛盾地导致睾丸肥大和精子生成增加。由于细胞色素P17A1在孕烯醇酮和孕酮(P4)的羟化过程中起关键作用，并将17α-羟孕烯醇酮转化为脱氢表雄酮和17α-羟孕酮转化为雄烯二酮，我们推测，细胞色素P17A1-/-；雄激素受体(AR)-/-斑马鱼的意外表型可能是通过孕激素/核孕激素受体(NPGR)信号的增强而介导的。为了支持这一假说，我们发现CyP17A1的敲除导致17α，20β-二羟基-4-孕烯-3-酮和P4的积累。此外，给予孕激素(一种合成的DHP模拟物)足以挽救Ar-/-斑马鱼的睾丸发育和精子发生，而敲除npgr则取消了CYP17A1-/-；Ar-/-双突变体中的CYP17A1-/-的拯救作用。对睾丸组织和精子发生缺陷的突变体(Ar-/-、Ar-/-；npgr-/-和cyp17a-/-；Ar-/-；npgr-/-)、表型正常的突变体(对照和CYP17A1-/-)以及被挽救的表型(CYP17A1-/-；Ar-/-)的转录分析表明，在cyp17a-/-；ar-/-；npgr-/-斑马鱼中，INSL3的表达下调与其下游相关基因之间存在共同的联系。综上所述，我们的数据表明，在雄激素信号缺失的情况下，孕激素/nPGR途径的遗传或药物增强足以恢复斑马鱼的睾丸组织和精子发生。
Disruption of androgen signaling is known to cause testicular malformation and defective spermatogenesis in zebrafish. However, knockout of cyp17a1, a key enzyme responsible for the androgen synthesis, in ar-/- male zebrafish paradoxically causes testicular hypertrophy and enhanced spermatogenesis. Because Cyp17a1 plays key roles in hydroxylation of pregnenolone and progesterone (P4), and converts 17α-hydroxypregnenolone to dehydroepiandrosterone and 17α-hydroxyprogesterone to androstenedione, we hypothesize that the unexpected phenotype in cyp17a1-/-;androgen receptor (ar)-/- zebrafish may be mediated through an augmentation of progestin/nuclear progestin receptor (nPgr) signaling. In support of this hypothesis, we show that knockout of cyp17a1 leads to accumulation of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and P4. Further, administration of progestin, a synthetic DHP mimetic, is sufficient to rescue testicular development and spermatogenesis in ar-/- zebrafish, whereas knockout of npgr abolishes the rescue effect of cyp17a1-/- in the cyp17a1-/-;ar-/- double mutant. Analyses of the transcriptomes among the mutants with defective testicular organization and spermatogenesis (ar-/-, ar-/-;npgr-/- and cyp17a-/-;ar-/-;npgr-/-), those with normal phenotype (control and cyp17a1-/-), and rescued phenotype (cyp17a1-/-;ar-/-) reveal a common link between a downregulated expression of insl3 and its related downstream genes in cyp17a-/-;ar-/-;npgr-/- zebrafish. Taken together, our data suggest that genetic or pharmacological augmentation of the progestin/nPgr pathway is sufficient to restore testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling.