Rannals Matthew D, Page Stephanie Cerceo, Campbell Morganne N, Gallo Ryan A, Mayfield Brent, Maher Brady J
Department of Neurobiology, School of Medicine, University of Pittsburgh , Pittsburgh, PA, USA.
Lieber Institute for Brain Development, Johns Hopkins Medical Campus , Baltimore, MD, USA.
Rare Dis. 2016 Aug 5;4(1):e1220468. doi: 10.1080/21675511.2016.1220468. eCollection 2016.
The clinically pleiotropic gene, Transcription Factor 4 (TCF4), is a broadly expressed basic helix-loop-helix (bHLH) transcription factor linked to multiple neurodevelopmental disorders, including schizophrenia, 18q deletion syndrome, and Pitt Hopkins syndrome (PTHS). suppression of by shRNA or mutation by CRISPR/Cas9 in the developing rat prefrontal cortex resulted in attenuated action potential output. To explain this intrinsic excitability deficit, we demonstrated that haploinsufficiency of TCF4 lead to the ectopic expression of two ion channels, and . These targets of TCF4 regulation were identified through molecular profiling experiments that used translating ribosome affinity purification to enrich mRNA from genetically manipulated neurons. Using a mouse model of PTHS (), we observed a similar intrinsic excitability deficit, however the underlying mechanism appeared slightly different than our rat model - as expression was similarly increased but expression was decreased. Here, we show that the truncated TCF4 protein expressed in our PTHS mouse model binds to wild-type TCF4 protein, and we suggest the difference in expression levels between these two rodent models appears to be explained by a dominant-negative function of the truncated TCF4 protein. Despite the differences in the underlying molecular mechanisms, we observed common underlying intrinsic excitability deficits that are consistent with ectopic expression of . The converging molecular function of TCF4 across two independent rodent models indicates SCN10a is a potential therapeutic target for Pitt-Hopkins syndrome.
临床上具有多效性的基因——转录因子4（TCF4），是一种广泛表达的碱性螺旋-环-螺旋（bHLH）转录因子，与多种神经发育障碍有关，包括精神分裂症、18q缺失综合征和皮特-霍普金斯综合征（PTHS）。在发育中的大鼠前额叶皮层中，通过短发夹RNA（shRNA）抑制或通过CRISPR/Cas9突变TCF4，导致动作电位输出减弱。为了解释这种内在兴奋性缺陷，我们证明了TCF4单倍剂量不足会导致两种离子通道——SCN10a和KCNQ2的异位表达。通过分子谱实验确定了这些TCF4调控的靶点，该实验使用翻译核糖体亲和纯化从基因操作的神经元中富集mRNA。使用PTHS的小鼠模型（TCF4+/−），我们观察到了类似的内在兴奋性缺陷，然而其潜在机制似乎与我们的大鼠模型略有不同——SCN10a的表达同样增加，但KCNQ2的表达却降低。在这里，我们表明在我们的PTHS小鼠模型中表达的截短型TCF4蛋白与野生型TCF4蛋白结合，并且我们认为这两种啮齿动物模型之间KCNQ2表达水平的差异似乎可以用截短型TCF4蛋白的显性负功能来解释。尽管潜在的分子机制存在差异，但我们观察到了共同的潜在内在兴奋性缺陷，这与SCN10a的异位表达一致。TCF4在两个独立的啮齿动物模型中的趋同分子功能表明，SCN10a是皮特-霍普金斯综合征的一个潜在治疗靶点。
