Chromatin remodeling enzyme Brg1 is required for mouse lens fiber cell terminal differentiation and its denucleation.
Chromatin remodeling enzyme Brg1 is required for mouse lens fiber cell terminal differentiation and its denucleation.
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DOI：
10.1186/1756-8935-3-21
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发表时间：
2010-11-30
影响因子：
3.9
通讯作者：
Cvekl A
中科院分区：
文献类型：
--
作者：
He S;Pirity MK;Wang WL;Wolf L;Chauhan BK;Cveklova K;Tamm ER;Ashery-Padan R;Metzger D;Nakai A;Chambon P;Zavadil J;Cvekl A
Brahma 相关基因 1（Brg1，也称为 Smarca4 和 Snf2β）编码（开关/蔗糖不可发酵）(SWI/SNF) 染色质重塑复合物的腺苷 5'-三磷酸 (ATP) 依赖性催化亚基。 SWI/SNF 复合物通过多种机制被招募到染色质，包括特定的 DNA 结合因子（例如，热休克转录因子 4 (Hsf4) 和配对盒基因 6 (Pax6)）、染色质结构蛋白（例如，高迁移率 A1 (HMGA1)）和/或乙酰化核心组蛋白。先前的研究表明，Brg1 ATPase 结构域中的单个氨基酸取代 (K798R) 通过显性失活 (dn) 机制发挥作用。遗传学研究表明，Brg1 是早期（即植入前）小鼠胚胎发育的必需基因。 Brg1 还控制神经干细胞的维持、多种细胞谱系和器官（包括 T 细胞、神经胶质细胞和四肢）的终末分化。为了研究 Brg1 在小鼠晶状体发育中的作用，使用晶状体特异性 αA-晶状体蛋白启动子在有丝分裂后晶状体纤维细胞中表达 dnBrg1 转基因构建体。形态学研究揭示转基因晶状体中晶状体纤维细胞分化异常，导致白内障。电子显微镜研究显示晶状体缝线形成异常，晶状体纤维细胞核解不完全（即去核）。为了鉴定受 Brg1 调节的基因，在胚胎第 15.5 天 (E15.5) 野生型和 dnBrg1 转基因晶状体中进行了 RNA 表达谱分析。此外，比较dnBrg1转基因、Pax6杂合子和Hsf4纯合子晶状体中差异表达的基因，发现了由Brg1、Hsf4和Pax6共同调控的多个基因。 DNase IIβ 是晶状体纤维细胞脱核所需的关键酶，在 Pax6、Brg1 和 Hsf4 模型系统中被发现下调。使用条件基因靶向对 Brg1 进行晶状体特异性删除表明，Brg1 是晶状体纤维细胞分化、DNase IIβ 表达、晶状体纤维细胞去核以及间接视网膜发育所必需的。这些研究证明了 Brg1 在晶状体纤维细胞终末分化中的细胞自主作用，并确定 DNase IIβ 是 SWI/SNF 复合物的潜在直接靶点。 Brg1 直接或间接参与晶状体纤维细胞染色质降解过程。细胞核和其他细胞器的存在会产生不符合晶状体光学要求的散射光。
Brahma-related gene 1 (Brg1, also known as Smarca4 and Snf2β) encodes an adenosine-5'-triphosphate (ATP)-dependent catalytical subunit of the (switch/sucrose nonfermentable) (SWI/SNF) chromatin remodeling complexes. SWI/SNF complexes are recruited to chromatin through multiple mechanisms, including specific DNA-binding factors (for example, heat shock transcription factor 4 (Hsf4) and paired box gene 6 (Pax6)), chromatin structural proteins (for example, high-mobility group A1 (HMGA1)) and/or acetylated core histones. Previous studies have shown that a single amino acid substitution (K798R) in the Brg1 ATPase domain acts via a dominant-negative (dn) mechanism. Genetic studies have demonstrated that Brg1 is an essential gene for early (that is, prior implantation) mouse embryonic development. Brg1 also controls neural stem cell maintenance, terminal differentiation of multiple cell lineages and organs including the T-cells, glial cells and limbs. To examine the roles of Brg1 in mouse lens development, a dnBrg1 transgenic construct was expressed using the lens-specific αA-crystallin promoter in postmitotic lens fiber cells. Morphological studies revealed abnormal lens fiber cell differentiation in transgenic lenses resulting in cataract. Electron microscopic studies showed abnormal lens suture formation and incomplete karyolysis (that is, denucleation) of lens fiber cells. To identify genes regulated by Brg1, RNA expression profiling was performed in embryonic day 15.5 (E15.5) wild-type and dnBrg1 transgenic lenses. In addition, comparisons between differentially expressed genes in dnBrg1 transgenic, Pax6 heterozygous and Hsf4 homozygous lenses identified multiple genes coregulated by Brg1, Hsf4 and Pax6. DNase IIβ, a key enzyme required for lens fiber cell denucleation, was found to be downregulated in each of the Pax6, Brg1 and Hsf4 model systems. Lens-specific deletion of Brg1 using conditional gene targeting demonstrated that Brg1 was required for lens fiber cell differentiation, for expression of DNase IIβ, for lens fiber cell denucleation and indirectly for retinal development. These studies demonstrate a cell-autonomous role for Brg1 in lens fiber cell terminal differentiation and identified DNase IIβ as a potential direct target of SWI/SNF complexes. Brg1 is directly or indirectly involved in processes that degrade lens fiber cell chromatin. The presence of nuclei and other organelles generates scattered light incompatible with the optical requirements for the lens.
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影响因子：
3.1
作者：
Duncan, Beverly;Zhao, Keji
通讯作者：
Zhao, Keji
影响因子：
3.7
作者：
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作者：
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10.5
作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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