Data that underlies this paper.

Germline variants in the CTNNB1 gene, encoding β-catenin protein, cause severe neurodevelopmental alterations manifested early in the infancy, and define the CTNNB1 syndrome. Patients with CTNNB1 syndrome display heterogeneous clinical manifestations, and most of them carry CTNNB1 pathogenic nonsense or frameshift variants that generate premature termination codons (PTC). We have previously described the neuropsychological manifestations of a group of CTNNB1 syndrome patients harboring novel β-catenin variants. Here, we have analysed the molecular and functional characterization of these β-catenin variants, performed genotype-phenotype analyses, and tested for β-catenin functional reconstitution. We describe a complex variety of N-terminal and C-terminal truncated β-catenin proteoforms generated by PTC. Protein stability of truncated proteoforms was variable, as indicated by their expression levels and biophysical analysis, and high protein stability correlated with better patient performance in visuospatial tests. Transcriptional activity was abrogated in most of the β-catenin variants, although some specific truncations, as well as a three-residues in-frame deletion variant, retained partial transcriptional activity. Reconstitution of full-length β-catenin expression and function was achieved in specific β-catenin PTC variants by induction of translational readthrough with aminoglycosides and protein synthesis stimulators. Inhibition of β-catenin degradation by MG-132 proteasome inhibitor also resulted in partial rescue of β-catenin transcriptional activity. Our results suggest the existence of intricate patterns of truncated β-catenin proteoforms in CTNNB1 syndrome patients, which may correlate with clinical manifestations, and provide insights to increase the function of β-catenin in patients carrying CTNNB1 pathogenic variants.编码β-连环蛋白（β-catenin）的CTNNB1基因（CTNNB1）的生殖系变异，可导致婴儿早期即出现严重神经发育异常，并定义了CTNNB1综合征（CTNNB1 syndrome）。CTNNB1综合征患者的临床表现具有异质性，多数患者携带CTNNB1致病性无义变异或移码变异，此类变异可产生提前终止密码子（PTC）。我们此前曾报道了一组携带新型β-连环蛋白变异的CTNNB1综合征患者的神经心理学表现。 本研究对这些β-连环蛋白变异的分子与功能特征进行了分析，开展了基因型-表型关联分析，并检测了β-连环蛋白的功能重建情况。我们发现，由PTC介导产生了多种复杂的N端及C端截短β-连环蛋白蛋白质变体（proteoforms）。通过蛋白表达水平检测与生物物理分析可知，截短蛋白质变体的稳定性存在差异，且较高的蛋白稳定性与患者在视觉空间测试中的更佳表现呈正相关。 多数β-连环蛋白变异的转录活性被完全消除，但部分特定截短变异以及一种三残基框内缺失变异仍保留了部分转录活性。通过氨基糖苷类与蛋白质合成刺激剂诱导翻译通读，可在携带特定CTNNB1提前终止密码子变异的患者中实现全长β-连环蛋白的表达与功能重建。使用蛋白酶体抑制剂MG-132抑制β-连环蛋白降解，也可部分挽救其转录活性。 本研究结果表明，CTNNB1综合征患者体内存在复杂多样的截短β-连环蛋白蛋白质变体谱，该变体谱或与临床表型相关；本研究同时为提升携带CTNNB1致病性变异患者的β-连环蛋白功能提供了新的研究思路。