PDF(Pubmed)
Abstract：
Disrupted germline differentiation or compromised testis development can lead to subfertility or infertility and are strongly associated with testis cancer in humans. In mice, SRY and SOX9 induce expression of Fgf9, which promotes Sertoli cell differentiation and testis development. FGF9 is also thought to promote male germline differentiation but the mechanism is unknown. FGFs typically signal through mitogen-activated protein kinases (MAPKs) to phosphorylate ERK1/2 (pERK1/2). We explored whether FGF9 regulates male germline development through MAPK by inhibiting either FGF or MEK1/2 signalling in the foetal testis immediately after gonadal sex determination and testis cord formation, but prior to male germline commitment.
pERK1/2 was detected in Sertoli cells and inhibition of MEK1/2 reduced Sertoli cell proliferation and organisation and resulted in some germ cells localised outside of the testis cords. While pERK1/2 was not detected in germ cells, inhibition of MEK1/2 after somatic sex determination profoundly disrupted germ cell mitotic arrest, dysregulated a broad range of male germline development genes and prevented the upregulation of key male germline markers, DPPA4 and DNMT3L. In contrast, while FGF inhibition reduced Sertoli cell proliferation, expression of male germline markers was unaffected and germ cells entered mitotic arrest normally. While male germline differentiation was not disrupted by FGF inhibition, a range of stem cell and cancer-associated genes were commonly altered after 24 h of FGF or MEK1/2 inhibition, including genes involved in the maintenance of germline stem cells, Nodal signalling, proliferation, and germline cancer.
Together, these data demonstrate a novel role for MEK1/2 signalling during testis development that is essential for male germline differentiation, but indicate a more limited role for FGF signalling. Our data indicate that additional ligands are likely to act through MEK1/2 to promote male germline differentiation and highlight a need for further mechanistic understanding of male germline development.
pERK1/2 was detected in Sertoli cells and inhibition of MEK1/2 reduced Sertoli cell proliferation and organisation and resulted in some germ cells localised outside of the testis cords. While pERK1/2 was not detected in germ cells, inhibition of MEK1/2 after somatic sex determination profoundly disrupted germ cell mitotic arrest, dysregulated a broad range of male germline development genes and prevented the upregulation of key male germline markers, DPPA4 and DNMT3L. In contrast, while FGF inhibition reduced Sertoli cell proliferation, expression of male germline markers was unaffected and germ cells entered mitotic arrest normally. While male germline differentiation was not disrupted by FGF inhibition, a range of stem cell and cancer-associated genes were commonly altered after 24 h of FGF or MEK1/2 inhibition, including genes involved in the maintenance of germline stem cells, Nodal signalling, proliferation, and germline cancer.
Together, these data demonstrate a novel role for MEK1/2 signalling during testis development that is essential for male germline differentiation, but indicate a more limited role for FGF signalling. Our data indicate that additional ligands are likely to act through MEK1/2 to promote male germline differentiation and highlight a need for further mechanistic understanding of male germline development.
摘要：
背景：种系分化中断或睾丸发育受损可导致不育或不育，并与人类睾丸癌症密切相关。在老鼠身上,SRY和SOX9诱导Fgf9表达，促进支持细胞分化和睾丸发育。FGF9也被认为促进雄性种系分化,但其机制未知。FGF通常通过丝裂原激活的蛋白激酶（MAPK）发出信号以磷酸化ERK1/2（pERK1/2）。我们探讨了FGF9是否通过在性腺性别确定和睾丸形成后立即抑制胎儿睾丸中的FGF或MEK1/2信号通过MAPK调节男性种系发育。但是在男性生殖系承诺之前。
结果：在睾丸支持细胞中检测到pERK1/2，MEK1/2的抑制降低了睾丸支持细胞的增殖和组织，并导致一些生殖细胞位于睾丸外。虽然在生殖细胞中未检测到pERK1/2，体细胞性别决定严重破坏生殖细胞有丝分裂阻滞后MEK1/2的抑制，调节了广泛的男性种系发育基因，并阻止了关键男性种系标记的上调，DPPA4和DNMT3L。相比之下,而FGF抑制减少支持细胞增殖，雄性种系标记物的表达不受影响，生殖细胞正常进入有丝分裂停滞。虽然雄性种系分化没有被FGF抑制破坏，一系列干细胞和癌症相关基因通常在FGF或MEK1/2抑制24小时后发生改变，包括维持生殖干细胞的基因，节点信号,扩散,和种系癌症。
结论：一起，这些数据证明了MEK1/2信号在睾丸发育过程中的新作用，这对于雄性种系分化至关重要，但表明对FGF信号传导的作用更有限。我们的数据表明，其他配体可能通过MEK1/2起作用以促进雄性种系分化，并强调需要对雄性种系发育进行进一步的机械理解。
结果：在睾丸支持细胞中检测到pERK1/2，MEK1/2的抑制降低了睾丸支持细胞的增殖和组织，并导致一些生殖细胞位于睾丸外。虽然在生殖细胞中未检测到pERK1/2，体细胞性别决定严重破坏生殖细胞有丝分裂阻滞后MEK1/2的抑制，调节了广泛的男性种系发育基因，并阻止了关键男性种系标记的上调，DPPA4和DNMT3L。相比之下,而FGF抑制减少支持细胞增殖，雄性种系标记物的表达不受影响，生殖细胞正常进入有丝分裂停滞。虽然雄性种系分化没有被FGF抑制破坏，一系列干细胞和癌症相关基因通常在FGF或MEK1/2抑制24小时后发生改变，包括维持生殖干细胞的基因，节点信号,扩散,和种系癌症。
结论：一起，这些数据证明了MEK1/2信号在睾丸发育过程中的新作用，这对于雄性种系分化至关重要，但表明对FGF信号传导的作用更有限。我们的数据表明，其他配体可能通过MEK1/2起作用以促进雄性种系分化，并强调需要对雄性种系发育进行进一步的机械理解。
