21-03-2018, 02:33 PM
https://pdfs.semanticscholar.org/92cf/d8ce49992073f865ffcf8465308c5b769bb8.pdf
eLife digest
In female mammals, granulosa cells in the ovaries help egg cells to grow and develop by secreting nutrients and estrogens—the female sex hormones. A protein called FOXL2 helps granulosa cells to develop and functions by binding to the DNA of the cells to switch certain genes either on or off. In humans, mutations in the gene that codes for the FOXL2 protein are associated with granulosa cell tumors and with a loss of female fertility in early adulthood. In addition, if the amount of FOXL2 is artificially reduced in granulosa cells in female mice, the cells take on many of the characteristics of supporting cells found in the testes of males. To investigate in more detail how FOXL2 works, Georges et al. grew mouse granulosa cells in the laboratory to identify the DNA sequences where FOXL2 will bind, and to uncover how this binding affects gene expression. Georges et al. conclude that FOXL2 orchestrates a network involving many different proteins that allows estrogen to be produced and used by granulosa cells; and in doing so these cells maintain their identity as ovarian cells. FOXL2 was also shown to work closely with the receptor proteins that detect the sex hormones, and which help to control whether particular sex-specific genes are switched on or off. One particularly important role of FOXL2 in granulosa cells is that it represses a gene called Sox9. By repressing Sox9, the granulosa cells do not transform into their counterparts normally found in testes. Although FOXL2 was previously reported to directly regulate the Sox9 gene, Georges et al. find that it also acts through other molecules, and that there are alternative ways in which it can do so. Although Georges et al. have established some of the ways that FOXL2 functions, this protein can work via other pathways; these will require further investigation to be fully understood.
FOXL2 is required for efficient estrogen signaling.The above-mentioned findings support our hypothesis that FOXL2 plays an important role in estrogen signaling. We therefore analyzed the transcriptomic changes following a 10 hr 17β-estradiol (E2) treatment of primary granulosa cells pre-treated for 24 hr with either anti-FOXL2 or control siRNAs. We considered as potential targets those genes in the microarrays whose expression displayed a foldchange >2 in the presence of E2. We found 41 genes responding to estradiol according to our inclusion threshold, 39 of which were activated and only 2 were repressed. This is in agreement with previous reports suggesting that ERs are mainly transcriptional activators
A feed-forward loop reinforces the impact of FOXL2 on granulosa cell identity To better understand the combined effect of FOXL2 and ESR2 on granulosa cell maintenance, we analyzed SOX9 expression at the protein level 48 hr after Foxl2 and/or Esr2 knockdown. As expected considering our transcriptomic analyses, we observed that SOX9 expression was upregulated in the absence of either FOXL2 or ESR2 (Figure 5A). SOX9 expression was much higher in the absence of both ESR2 and FOXL2. This confirms that estrogen receptors and FOXL2 co-regulate SOX9 expression (Uhlenhaut et al., 2009). Interestingly, our transcriptomic analyses indicate that FOXL2 is required for the expression of Cyp19a1 (encoding the rate-limiting enzyme in estradiol production) both in the presence (Figure 5B) and in the absence of hormones (Figure 5C). Thus, FOXL2 may allow both estradiol production and enable estrogen signaling in the same cells. These data suggest the existence of a coherent feed-forward loop in which FOXL2 stimulates both estradiol production and receptivity (i.e., ESR2 expression) that might be responsible at least in part for the maintenance of granulosa cell identity by repressing the testis determinant Sox9.
So: if we can upregulate the FOXL2 to suppress the Sox9, creating a feed-forward loop, can this in fact convert the testes into ovaries or ovotestes, and thereby create a self sufficient estrogen producing organ , and delete the reliance on external estrogens? i.e. synthetic hormones?
eLife digest
In female mammals, granulosa cells in the ovaries help egg cells to grow and develop by secreting nutrients and estrogens—the female sex hormones. A protein called FOXL2 helps granulosa cells to develop and functions by binding to the DNA of the cells to switch certain genes either on or off. In humans, mutations in the gene that codes for the FOXL2 protein are associated with granulosa cell tumors and with a loss of female fertility in early adulthood. In addition, if the amount of FOXL2 is artificially reduced in granulosa cells in female mice, the cells take on many of the characteristics of supporting cells found in the testes of males. To investigate in more detail how FOXL2 works, Georges et al. grew mouse granulosa cells in the laboratory to identify the DNA sequences where FOXL2 will bind, and to uncover how this binding affects gene expression. Georges et al. conclude that FOXL2 orchestrates a network involving many different proteins that allows estrogen to be produced and used by granulosa cells; and in doing so these cells maintain their identity as ovarian cells. FOXL2 was also shown to work closely with the receptor proteins that detect the sex hormones, and which help to control whether particular sex-specific genes are switched on or off. One particularly important role of FOXL2 in granulosa cells is that it represses a gene called Sox9. By repressing Sox9, the granulosa cells do not transform into their counterparts normally found in testes. Although FOXL2 was previously reported to directly regulate the Sox9 gene, Georges et al. find that it also acts through other molecules, and that there are alternative ways in which it can do so. Although Georges et al. have established some of the ways that FOXL2 functions, this protein can work via other pathways; these will require further investigation to be fully understood.
FOXL2 is required for efficient estrogen signaling.The above-mentioned findings support our hypothesis that FOXL2 plays an important role in estrogen signaling. We therefore analyzed the transcriptomic changes following a 10 hr 17β-estradiol (E2) treatment of primary granulosa cells pre-treated for 24 hr with either anti-FOXL2 or control siRNAs. We considered as potential targets those genes in the microarrays whose expression displayed a foldchange >2 in the presence of E2. We found 41 genes responding to estradiol according to our inclusion threshold, 39 of which were activated and only 2 were repressed. This is in agreement with previous reports suggesting that ERs are mainly transcriptional activators
A feed-forward loop reinforces the impact of FOXL2 on granulosa cell identity To better understand the combined effect of FOXL2 and ESR2 on granulosa cell maintenance, we analyzed SOX9 expression at the protein level 48 hr after Foxl2 and/or Esr2 knockdown. As expected considering our transcriptomic analyses, we observed that SOX9 expression was upregulated in the absence of either FOXL2 or ESR2 (Figure 5A). SOX9 expression was much higher in the absence of both ESR2 and FOXL2. This confirms that estrogen receptors and FOXL2 co-regulate SOX9 expression (Uhlenhaut et al., 2009). Interestingly, our transcriptomic analyses indicate that FOXL2 is required for the expression of Cyp19a1 (encoding the rate-limiting enzyme in estradiol production) both in the presence (Figure 5B) and in the absence of hormones (Figure 5C). Thus, FOXL2 may allow both estradiol production and enable estrogen signaling in the same cells. These data suggest the existence of a coherent feed-forward loop in which FOXL2 stimulates both estradiol production and receptivity (i.e., ESR2 expression) that might be responsible at least in part for the maintenance of granulosa cell identity by repressing the testis determinant Sox9.
So: if we can upregulate the FOXL2 to suppress the Sox9, creating a feed-forward loop, can this in fact convert the testes into ovaries or ovotestes, and thereby create a self sufficient estrogen producing organ , and delete the reliance on external estrogens? i.e. synthetic hormones?