内鞘細胞アイデンティティー決定の分子機構

我一直在筛选决定乳腺癌周细胞身份的关键转录因子。我的筛选发现了两个基本的螺旋-环-受阻（bHLH）家族转录因子的进化枝，以No.17（包括No.17、No.17H、No.17H2和No.17H3）和No.51（包括No.51、No.36、No.14、No.14L等）为代表，在调节牙周膜细胞特性中起关键作用。酵母双杂交筛选证实了这两个蛋白分支之间的相互作用。No.51在周细胞中特异性表达。No.51过表达（No.51-OE）引起XPP标记GFP的异位表达。重要的是，No.51-OE引起根中的异位细胞分裂。外源生长素促进了51号-OE根的异位细胞分裂，表明51号赋予了进行生长素诱导的细胞分裂的能力。No.17-OE引起的表型与No.51相似，但比No.51温和。No.17在包括周环在内的多种细胞类型中广泛表达，No.51调控No.17的转录，而No.51不调控No.17的转录。51号也是自动调节的。这样的反馈强化了他们自己的转录。No.51-OE根的转录谱分析表明，No.51-OE上调了许多周环特异基因的表达，提示No.51是周环细胞身份的正调控因子。通过对51-OE/51-SRDX根转录谱的分析，为bHLH转录因子下游效应子的鉴定奠定了基础。

I have been screening for the key transcription factors that determine pericycle cell Identity. My screening has revealed two clades of basic Helix-Loop-Helix (bHLH) family transcription factors, represented by No.17 (including No.17, No.17H, No.17H2, and No.17H3) and No. 51 (including No.51, No. 36, No.14, No.14L etc.), that play key roles in regulation pericycle cell identity. A Yeast-Two-Hybrid screening confirmed the interaction between the two clades of proteins.No.51 is expressed specifically in pericycle cells. No.51 overexpression (No.51-OE) causes ectopic expression of XPP-marker GFP. Importantly, No.51-OE caused ectopic cell division in the root. Exogenous auxin increased the ectopic cell division in No.51-OE root, demonstrating that No.51 confers the competency to undergo auxin-induced cell division. No.17-OE caused similar but milder phenotype than that of No.51. No.17 is broadly expressed in several cell types including pericycle.No.51 regulate No.17's transcription, but not vice versa. No.51 is also auto-regulated. Such feedback reinforces their own transcription. No.51’s specific expression pattern confines this network in the pericycle, which constitutes a master regulation of pericycle cell’s identity.Transcriptional profiling of No.51-OE root shows that many pericycle-specific genes are up-regulated by No.51-OE, suggesting No.51’s role as a positive regulator of pericycle cell identity. Detailed analysis on the obtained transcriptional profile of No.51-OE/ No.51-SRDX roots will shed light on the identification of the bHLH TFs’ downstream effectors.