Zinc and RING finger 3 (ZNRF3) is a negative-feedback regulator of Wnt/β-catenin signaling, which plays an important role in human brain development. Although somatically frequently mutated in cancer, germline variants in ZNRF3 have not been established as causative for neurodevelopmental disorders (NDDs). We identified 12 individuals with ZNRF3 variants and various phenotypes via GeneMatcher/Decipher and evaluated genotype-phenotype correlation. We performed structural modeling and representative deleterious and control variants were assessed using in vitro transcriptional reporter assays with and without Wnt-ligand Wnt3a and/or Wnt-potentiator R-spondin (RSPO). Eight individuals harbored de novo missense variants and presented with NDD. We found missense variants associated with macrocephalic NDD to cluster in the RING ligase domain. Structural modeling predicted disruption of the ubiquitin ligase function likely compromising Wnt receptor turnover. Accordingly, the functional assays showed enhanced Wnt/β-catenin signaling for these variants in a dominant negative manner. Contrarily, an individual with microcephalic NDD harbored a missense variant in the RSPO-binding domain predicted to disrupt binding affinity to RSPO and showed attenuated Wnt/β-catenin signaling in the same assays. Additionally, four individuals harbored de novo truncating or de novo or inherited large in-frame deletion variants with non-NDD phenotypes, including heart, adrenal, or nephrotic problems. In contrast to NDD-associated missense variants, the effects on Wnt/β-catenin signaling were comparable between the truncating variant and the empty vector and between benign variants and the wild type. In summary, we provide evidence for mirror brain size phenotypes caused by distinct pathomechanisms in Wnt/β-catenin signaling through protein domain-specific deleterious ZNRF3 germline missense variants.

中文翻译：

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有害的 ZNRF3 种系变异通过对 Wnt/β-catenin 信号转导的域特异性影响导致具有镜像脑表型的神经发育障碍


锌和无名指 3 （ZNRF3） 是 Wnt/β-catenin 信号传导的负反馈调节因子，在人脑发育中起重要作用。尽管在癌症中体细胞突变频繁，但 ZNRF3 中的种系变异尚未被确定为神经发育障碍 （NDD） 的病因。我们通过 GeneMatcher/Decipher 鉴定了 12 例具有 ZNRF3 变异和各种表型的个体，并评估了基因型-表型相关性。我们进行了结构建模，并使用 有和没有 Wnt 配体 Wnt 配体 Wnt3a 和/或 Wnt 增强剂 R-spondin （RSPO） 的体外转录报告基因测定评估了代表性的有害和对照变异。8 例个体携带新发错义变异并伴有 NDD。我们发现与大头 NDD 相关的错义变异聚集在 RING 连接酶结构域中。结构模型预测泛素连接酶功能的破坏可能会影响 Wnt 受体的周转。因此，功能测定显示这些变体的 Wnt/β-catenin 信号以显性阴性方式增强。相反，一个小头 NDD 个体在 RSPO 结合结构域中携带一个错义变异，预计会破坏与 RSPO 的结合亲和力，并在同一测定中显示 Wnt/β-catenin 信号减弱。此外，4 个个体携带具有非 NDD 表型（包括心脏、肾上腺或肾病问题）的新生截短或新发或遗传性大框内缺失变异。与 NDD 相关的错义变体相比，截断变体和空载体之间以及良性变体和野生型之间对 Wnt/β-catenin 信号传导的影响相当。 总之，我们提供了证据，证明 Wnt/β-catenin 信号传导中的不同病理机制通过蛋白质结构域特异性有害的 ZNRF3 种系错义变体引起的镜像脑大小表型。