Data_Sheet_4_Expression of alternative transcription factor 4 mRNAs and protein isoforms in the developing and adult rodent and human tissues.xlsx

Transcription factor 4 (TCF4) belongs to the class I basic helix–loop–helix family of transcription factors (also known as E-proteins) and is vital for the development of the nervous system. Aberrations in the TCF4 gene are associated with several neurocognitive disorders such as schizophrenia, intellectual disability, post-traumatic stress disorder, depression, and Pitt-Hopkins Syndrome, a rare but severe autism spectrum disorder. Expression of the human TCF4 gene can produce at least 18 N-terminally distinct protein isoforms, which activate transcription with different activities and thus may vary in their function during development. We used long-read RNA-sequencing and western blot analysis combined with the analysis of publicly available short-read RNA-sequencing data to describe both the mRNA and protein expression of the many distinct TCF4 isoforms in rodent and human neural and nonneural tissues. We show that TCF4 mRNA and protein expression is much higher in the rodent brain compared to nonneural tissues. TCF4 protein expression is highest in the rodent cerebral cortex and hippocampus, where expression peaks around birth, and in the rodent cerebellum, where expression peaks about a week after birth. In human, highest TCF4 expression levels were seen in the developing brain, although some nonneural tissues displayed comparable expression levels to adult brain. In addition, we show for the first time that out of the many possible TCF4 isoforms, the main TCF4 isoforms expressed in the rodent and human brain and other tissues are TCF4-B, -C, -D, -A, and-I. Taken together, our isoform specific analysis of TCF4 expression in different tissues could be used for the generation of gene therapy applications for patients with TCF4-associated diseases.

转录因子4（Transcription factor 4, TCF4）属于I类碱性螺旋-环-螺旋（basic helix–loop–helix, bHLH）转录因子家族，亦称E蛋白（E-proteins），对神经系统发育至关重要。TCF4基因的异常变异与多种神经认知疾病密切相关，包括精神分裂症、智力障碍、创伤后应激障碍、抑郁症，以及皮特-霍普金斯综合征（Pitt-Hopkins Syndrome）——一种罕见且严重的自闭症谱系障碍。人类TCF4基因可产生至少18种N端序列各异的蛋白质同工型（protein isoforms），这些同工型以不同的转录激活活性发挥调控功能，因此在发育进程中的生物学作用可能存在显著差异。本研究采用长读长RNA测序（long-read RNA-sequencing）、蛋白质印迹分析（western blot analysis），结合公开可用的短读长RNA测序（short-read RNA-sequencing）数据，对啮齿类与人类神经及非神经组织中多种TCF4同工型的mRNA和蛋白质表达特征进行了全面解析。研究结果显示，相较于非神经组织，啮齿类大脑中TCF4的mRNA与蛋白质表达水平显著更高。其中，啮齿类大脑皮质与海马体的TCF4蛋白质表达量最高，其表达峰值出现在出生前后；而啮齿类小脑中的TCF4蛋白表达峰值则在出生后约一周出现。在人类组织中，发育中的大脑TCF4表达水平最高，尽管部分非神经组织的表达水平可与成人大脑相当。此外，本研究首次证实：在众多潜在的TCF4同工型中，啮齿类与人类大脑及其他组织中主要表达的TCF4同工型为TCF4-B、-C、-D、-A与-I。综上，本研究针对不同组织中TCF4同工型的特异性表达分析，可为TCF4相关疾病的基因治疗策略研发提供重要依据。