Abstract：
Lunatic Fringe (LFNG) is required for spinal development. Biallelic pathogenic variants cause spondylocostal dysostosis type-III (SCD3), a rare disease generally characterized by malformed, asymmetrical, and attenuated development of the vertebral column and ribs. However, a variety of SCD3 cases reported have presented with additional features such as auditory alterations and digit abnormalities. There has yet to be a single, comprehensive, functional evaluation of causative LFNG variants and such analyses could unveil molecular mechanisms for phenotypic variability in SCD3. Therefore, nine LFNG missense variants associated with SCD3, c.564C>A, c.583T>C, c.842C>A, c.467T>G, c.856C>T, c.601G>A, c.446C>T, c.521G>A, and c.766G>A, were assessed in vitro for subcellular localization and protein processing. Glycosyltransferase activity was quantified for the first time in the c.583T>C, c.842C>A, and c.446C>T variants. Primarily, our results are the first to satisfy American College of Medical Genetics and Genomics PS3 criteria (functional evidence via well-established assay) for the pathogenicity of c.583T>C, c.842C>A, and c.446C>T, and replicate this evidence for the remaining six variants. Secondly, this work indicates that all variants that prevent Golgi localization also lead to impaired protein processing. It appears that the FRINGE domain is responsible for this phenomenon. Thirdly, our data suggests that variant proximity to the catalytic residue may influence whether LFNG is improperly trafficked and/or enzymatically dysfunctional. Finally, the phenotype of the axial skeleton, but not elsewhere, may be modulated in a variant-specific fashion. More reports are needed to continue testing this hypothesis. We anticipate our data will be used as a basis for discussion of genotype-phenotype correlations in SCD3.
摘要：
疯狂边缘（LFNG）是脊柱发育所必需的。双等位基因致病变异导致脊椎肋骨发育不良III型（SCD3），一种罕见的疾病，通常以畸形为特征，不对称,和衰减的脊柱和肋骨的发展。然而,报告的各种SCD3病例具有其他特征,如听觉改变和手指异常.还没有一个人，全面,对致病LFNG变异体的功能评估和此类分析可以揭示SCD3表型变异的分子机制。因此,与SCD3相关的九个LFNG错义变体，c.564C>A，c.583T>C，c.842C>A，c.467T>G，c.856C>T，c.601G>A，c.446C>T，c.521G>A，c.766G>A，在体外评估亚细胞定位和蛋白质加工。糖基转移酶活性在c.583T>C中首次定量，c.842C>A，和c.446C>T变体。首先,我们的结果是第一个满足美国医学遗传学和基因组学学院PS3标准（通过完善的测定功能证据）的致病性c.583T>C，c.842C>A，c.446C>T，并复制其余六个变体的证据。其次,这项工作表明，所有阻止高尔基定位的变体也会导致蛋白质加工受损。似乎FRINGE域是造成这种现象的原因。第三，我们的数据表明，与催化残基的变体接近可能会影响LFNG是否被不当贩运和/或酶功能失调。最后,轴向骨骼的表型，但不是在其他地方，可以以变体特异性方式调节。需要更多的报告来继续检验这一假设。我们预计我们的数据将用作讨论SCD3中基因型-表型相关性的基础。
