Differentiation of zebrafish melanophores depends on transcription factors AP2 alpha and AP2 epsilon.
Differentiation of zebrafish melanophores depends on transcription factors AP2 alpha and AP2 epsilon.
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DOI：
10.1371/journal.pgen.1001122
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发表时间：
2010-09-16
期刊：
影响因子：
4.5
通讯作者：
Cornell RA
中科院分区：
文献类型：
--
作者：
Van Otterloo E;Li W;Bonde G;Day KM;Hsu MY;Cornell RA
通过对小鼠毛色突变和黑色素瘤细胞系的研究，出现了一个控制黑素细胞生长、存活和分化的基因调控网络(GRN)模型。在这个模型中，转录因子激活蛋白2α(TFAP2A)通过激活编码受体酪氨酸激酶Kit的基因的表达而促进黑素细胞的发育。接下来，配体结合试剂盒刺激激活转录因子小眼症(MITF)的途径，通过激活酪氨酸酶家族成员Bcl2和其他基因的表达来促进黑素细胞的分化和存活。该模型预测，在TFAP2A和Kit缺失突变体中都会有黑素细胞减少的表型，并且由于TFAP2A作用于Kit上游，与Kit缺失突变体相比，这种表型将比TFAP2A缺失突变体更严重，或者至少与Kit缺失突变体一样严重。出乎意料的是，斑马鱼或老鼠的情况并非如此。由于许多Tfap2家族成员具有相同的DNA结合特异性，我们推测另一个Tfap2家族成员可能与TFAP2A在促进Kit表达方面存在冗余作用。我们报道了TFAP2E在斑马鱼胚胎的黑素母细胞和黑素载体中表达，其同源基因TFAP2E在人类黑素细胞中表达。我们提供的证据表明，Tfap2e与TFAP2a在斑马鱼胚胎黑素载体中具有冗余功能，以维持KITA的表达。此外，我们表明，与KITA突变体中胚胎黑素细胞似乎正常分化相反，在TFAP2A/e双缺陷胚胎黑素细胞中，尽管它们保留了mitfa的表达，但它们很小且黑化不足。有趣的是，在TFAP2a/e双缺陷胚胎中强制表达mitfa可以部分恢复黑素载体的分化。这些发现表明，Tfap2活性由TFAP2a和Tfap2e冗余地介导，通过Kit以外的效应器促进黑素细胞分化，与MITF平行。这项工作说明了对单基因突变的分析可能无法识别GRN中受相关蛋白质冗余活性影响的步骤。神经脊衍生的色素细胞，又称黑色素细胞，对生物体的生存很重要，因为它们保护皮肤细胞免受紫外线辐射，伪装生物体免受捕食者的伤害，并有助于性选择。调控蛋白网络控制黑素细胞发育的各个步骤，包括谱系指定、迁移、存活和分化。我们对这些网络的理解上的差距阻碍了有效预防和治疗黑素细胞疾病的进展，包括转移性黑色素瘤和白癜风。在组织培养细胞和小鼠胚胎中进行的研究表明，包括转录因子TFAP2A、生长因子受体试剂盒和转录因子MITF在内的调节蛋白在黑素细胞发育的多个步骤中起重要作用。黑色素瘤中TFAP2A、KIT和MITF表达的异常突出了这一途径在人类疾病中的重要性。在这里，我们发现与TFAP2a密切相关的基因tfap2e在斑马鱼胚胎黑素细胞和人类黑素细胞中表达。我们提供了Tfap2e与TFAP2a协同促进斑马鱼kita在胚胎黑素细胞中表达的证据。此外，我们还证明了除KITA外，TFAP2A/e活性的效应子对于黑素细胞的分化是必需的，并且该效应子作用于Mitfa活性的上游或平行。这些发现揭示了控制黑素细胞分化的基因调控网络出人意料的复杂性。
A model of the gene-regulatory-network (GRN), governing growth, survival, and differentiation of melanocytes, has emerged from studies of mouse coat color mutants and melanoma cell lines. In this model, Transcription Factor Activator Protein 2 alpha (TFAP2A) contributes to melanocyte development by activating expression of the gene encoding the receptor tyrosine kinase Kit. Next, ligand-bound Kit stimulates a pathway activating transcription factor Microphthalmia (Mitf), which promotes differentiation and survival of melanocytes by activating expression of Tyrosinase family members, Bcl2, and other genes. The model predicts that in both Tfap2a and Kit null mutants there will be a phenotype of reduced melanocytes and that, because Tfap2a acts upstream of Kit, this phenotype will be more severe, or at least as severe as, in Tfap2a null mutants in comparison to Kit null mutants. Unexpectedly, this is not the case in zebrafish or mouse. Because many Tfap2 family members have identical DNA–binding specificity, we reasoned that another Tfap2 family member may work redundantly with Tfap2a in promoting Kit expression. We report that tfap2e is expressed in melanoblasts and melanophores in zebrafish embryos and that its orthologue, TFAP2E, is expressed in human melanocytes. We provide evidence that Tfap2e functions redundantly with Tfap2a to maintain kita expression in zebrafish embryonic melanophores. Further, we show that, in contrast to in kita mutants where embryonic melanophores appear to differentiate normally, in tfap2a/e doubly-deficient embryonic melanophores are small and under-melanized, although they retain expression of mitfa. Interestingly, forcing expression of mitfa in tfap2a/e doubly-deficient embryos partially restores melanophore differentiation. These findings reveal that Tfap2 activity, mediated redundantly by Tfap2a and Tfap2e, promotes melanophore differentiation in parallel with Mitf by an effector other than Kit. This work illustrates how analysis of single-gene mutants may fail to identify steps in a GRN that are affected by the redundant activity of related proteins. Neural crest-derived pigment cells, known as melanocytes, are important to an organism's survival because they protect skin cells from ultraviolet radiation, camouflage the organism from predators, and contribute to sexual selection. Networks of regulatory proteins control the steps of melanocyte development, including lineage specification, migration, survival, and differentiation. Gaps in our understanding of these networks hamper progress in effective prevention and treatment of diseases of melanocytes, including metastatic melanoma and vitiligo. Studies conducted in tissue-culture cells and mouse embryos implicate regulatory proteins including the transcription factor TFAP2A, the growth factor receptor KIT, and the transcription factor MITF as being important for multiple steps in melanocyte development. Abnormalities in TFAP2A, KIT, and MITF expression in melanoma highlight the importance of this pathway in human disease. Here we show that a gene closely related to TFAP2A, tfap2e, is expressed in zebrafish embryonic melanocytes and human melanocytes. We provide evidence that Tfap2e cooperates with Tfap2a to promote expression of zebrafish kita in embryonic melanocytes. Further we show that an effector of Tfap2a/e activity other than Kita is required for melanocyte differentiation and that this effector acts upstream or in parallel with Mitfa activity. These findings reveal unexpected complexity to the gene-regulatory network governing melanocyte differentiation.
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DOI：
10.1002/jez.b.21189
发表时间：
2007-09-15
影响因子：
2.2
作者：
Hoffman, Trevor L.;Javier, Anna L.;Schilling, Thomas F.
通讯作者：
Schilling, Thomas F.
影响因子：
4.3
作者：
Braasch, Ingo;Liedtke, Daniel;Schartl, Manfred
通讯作者：
Schartl, Manfred
影响因子：
64.8
作者：
Carreira, S;Goodall, J;Goding, CR
通讯作者：
Goding, CR
影响因子：
4.6
作者：
Elworthy, S;Lister, JA;Kelsh, RN
通讯作者：
Kelsh, RN
影响因子：
6
作者：
Hsu, MY;Shih, DT;Herlyn, M
通讯作者：
Herlyn, M