Behr R, Weinbauer G F
Institute of Reproductive Medicine of the University, Munster, Germany.
Endocrinology. 1999 Jun;140(6):2746-54. doi: 10.1210/endo.140.6.6764.
cAMP response element modulator (CREM) is an important component of the cAMP-mediated signaling pathway and is essential for differentiation of haploid male germ cells. In the rodent, testicular expression of CREM is believed to be controlled by FSH. We studied the expression pattern of CREM and gonadotropic control in the nonhuman primate and rodent testis. Adult cynomolgus monkeys (Macaca fascicularis) received daily either vehicle or the potent GnRH antagonist (ANT) cetrorelix for periods of 25 and 56 days. Rats were also exposed to vehicle or ANT for periods of 14 and 42 days. ANT treatment suppressed pituitary gonadotropin secretion, reduced testis size, and altered spermatogenesis. A rabbit polyclonal antibody raised against recombinant CREM tau and reacting with CREM alpha, -beta, -gamma, -tau1, and -tau2 at similar affinities was used for immunocytochemistry and Western blotting. CREM expression was seen in round spermatids, with highest levels during spermatogenic stages V-VII, but declined with progression of spermatid development in the primate. Similar observations were made for the rat testis. Thus, CREM expression was maximal at the onset of acrosome formation and was low or undetectable upon initiation of spermatid elongation in both species. A weak, but specific, CREM signal was seen in mid- to late pachytene spermatocytes and during meiotic division in both species. After ANT exposure, the germ cell- and stage-specific pattern of CREM expression was quantitatively retained at all time points and in both species. Northern and Western blot analysis confirmed the maintenance of testicular CREM expression despite 25 days of ANT treatment. A retrospective immunocytochemical analysis of rat testes 14 days posthypophysectomy revealed CREM signals in round spermatids. These findings demonstrate that the testicular expression of CREM is not entirely dependent on gonadotropic hormones but, rather, on the maturational stage of haploid round germ cells.
环磷酸腺苷反应元件调节因子（CREM）是环磷酸腺苷介导的信号通路的重要组成部分，对于单倍体雄性生殖细胞的分化至关重要。在啮齿动物中，CREM的睾丸表达被认为受促卵泡激素（FSH）控制。我们研究了非人灵长类动物和啮齿动物睾丸中CREM的表达模式及促性腺激素的调控作用。成年食蟹猴（猕猴属）每天接受溶剂或强效促性腺激素释放激素（GnRH）拮抗剂西曲瑞克，持续25天和56天。大鼠也接受溶剂或拮抗剂处理14天和42天。拮抗剂处理抑制了垂体促性腺激素的分泌，减小了睾丸大小，并改变了精子发生。使用针对重组CREM τ产生的兔多克隆抗体，该抗体以相似亲和力与CREM α、β、γ、τ1和τ2反应，用于免疫细胞化学和蛋白质印迹分析。在圆形精子细胞中可见CREM表达，在生精阶段V - VII水平最高，但在灵长类动物中随着精子细胞发育的进展而下降。在大鼠睾丸中也有类似观察结果。因此，在两个物种中，CREM表达在顶体形成开始时最高，在精子细胞伸长开始时较低或无法检测到。在两个物种的粗线期精母细胞中期至后期以及减数分裂期间可见微弱但特异的CREM信号。拮抗剂处理后，在所有时间点和两个物种中，CREM表达的生殖细胞和阶段特异性模式在数量上得以保留。Northern印迹和蛋白质印迹分析证实，尽管进行了25天的拮抗剂处理，睾丸中CREM表达仍得以维持。垂体切除术后14天大鼠睾丸的回顾性免疫细胞化学分析显示圆形精子细胞中有CREM信号。这些发现表明，CREM的睾丸表达并非完全依赖于促性腺激素，而是依赖于单倍体圆形生殖细胞的成熟阶段。
