Pitt–Hopkins syndrome is an underdiagnosed neurodevelopmental disorder which is characterized by specific facial features, early-onset developmental delay, and moderate to severe intellectual disability. The genetic cause, a deficiency of the TCF4 gene, has been established; however, the underlying pathological mechanisms of this disease are still unclear. Herein, we report four unrelated children with different de novo mutations (T606A, K607E, R578C, and V617I) located at highly conserved sites and with clinical phenotypes which present variable degrees of developmental delay and intellectual disability. Three of these four missense mutations have not yet been reported. The patient with V617I mutation exhibits mild intellectual disability and has attained more advanced motor and verbal skills, which is significantly different from other cases reported to date. Molecular dynamics simulations are used to explore the atomic level mechanism of how missense mutations impair the functions of TCF4. Mutations T606A, K607E, and R578C are found to affect DNA binding directly or indirectly, while V617I only induces subtle conformational changes, which is consistent with the milder clinical phenotype of the corresponding patient. The study expands the mutation spectrum and phenotypic characteristics of Pitt–Hopkins syndrome, and reinforces the genotype–phenotype correlation and strengthens the understanding of phenotype variability, which is helpful for further investigation of pathogenetic mechanisms and improved genetic counseling.

Pitt-Hopkins 综合征是一种诊断不足的神经发育障碍，其特征是特定的面部特征、早发性发育迟缓和中度至重度智力障碍。遗传原因，TCF4基因的缺陷，已经确定；然而，这种疾病的潜在病理机制仍不清楚。在这里，我们报告了四个不相关的儿童，它们具有不同的从头突变（T606A、K607E、R578C 和 V617I），它们位于高度保守的位点，临床表型呈现出不同程度的发育迟缓和智力障碍。这四种错义突变中的三种尚未被报道。V617I 突变患者表现出轻度智力障碍，并获得了更高级的运动和语言技能，这与迄今为止报告的其他案例有很大不同。分子动力学模拟用于探索错义突变如何损害 TCF4 功能的原子级机制。发现突变 T606A、K607E 和 R578C 直接或间接影响 DNA 结合，而 V617I 仅诱导细微的构象变化，这与相应患者的较温和临床表型一致。该研究扩展了Pitt-Hopkins综合征的突变谱和表型特征，强化了基因型-表型相关性，加强了对表型变异性的认识，有助于进一步研究发病机制和改进遗传咨询。分子动力学模拟用于探索错义突变如何损害 TCF4 功能的原子级机制。发现突变 T606A、K607E 和 R578C 直接或间接影响 DNA 结合，而 V617I 仅诱导细微的构象变化，这与相应患者的较温和临床表型一致。该研究扩展了Pitt-Hopkins综合征的突变谱和表型特征，强化了基因型-表型相关性，加强了对表型变异性的认识，有助于进一步研究发病机制和改进遗传咨询。分子动力学模拟用于探索错义突变如何损害 TCF4 功能的原子级机制。发现突变 T606A、K607E 和 R578C 直接或间接影响 DNA 结合，而 V617I 仅诱导细微的构象变化，这与相应患者的较温和临床表型一致。该研究扩展了Pitt-Hopkins综合征的突变谱和表型特征，强化了基因型-表型相关性，加强了对表型变异性的认识，有助于进一步研究发病机制和改进遗传咨询。这与相应患者较轻的临床表型一致。该研究扩展了Pitt-Hopkins综合征的突变谱和表型特征，强化了基因型-表型相关性，加强了对表型变异性的认识，有助于进一步研究发病机制和改进遗传咨询。这与相应患者较轻的临床表型一致。该研究扩展了Pitt-Hopkins综合征的突变谱和表型特征，强化了基因型-表型相关性，加强了对表型变异性的认识，有助于进一步研究发病机制和改进遗传咨询。