Loss-of-function variants in CHST14 cause a dermatan 4-O-sulfotransferase deficiency named musculocontractural Ehlers–Danlos syndrome-CHST14 (mcEDS-CHST14), resulting in complete depletion of the dermatan sulfate moiety of decorin glycosaminoglycan (GAG) chains, which is replaced by chondroitin sulfate. Recently, we uncovered structural alteration of GAG chains in the skin of patients with mcEDS-CHST14. Here, we conducted the first systematic investigation of Chst14 gene-deleted homozygote (Chst14^−/−) mice. We used skin samples of wild-type (Chst14^+/+) and Chst14^−/− mice. Mechanical fragility of the skin was measured with a tensile test. Pathology was observed using light microscopy, decorin immunohistochemistry and electron microscopy (EM) including cupromeronic blue (CB) staining. Quantification of chondroitin sulfate and dermatan sulfate was performed using enzymatic digestion followed by anion-exchange HPLC. In Chst14^−/− mice, skin tensile strength was significantly decreased compared with that in Chst14^+/+ mice. EM showed that collagen fibrils were oriented in various directions to form disorganized collagen fibers in the reticular layer. Through EM-based CB staining, rod-shaped linear GAG chains were found to be attached at one end to collagen fibrils and protruded outside of the fibrils, in contrast to them being round and wrapping the collagen fibrils in Chst14^+/+ mice. A very low level of dermatan sulfate disaccharides was detected in the skin of Chst14^−/− mice by anion-exchange chromatography. Chst14^−/− mice, exhibiting similar abnormalities in the GAG structure of decorin and collagen networks in the skin, could be a reasonable model for skin fragility of patients with mcEDS-CHST14, shedding light on the role of dermatan sulfate in maintaining skin strength.

中文翻译：

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Chst14-/- 小鼠皮肤的系统研究：由 CHST14 变体 (mcEDS-CHST14) 引起的肌肉挛缩性 Ehlers-Danlos 综合征皮肤脆性模型

CHST14中的功能丧失变异导致皮肤素 4 - O-磺基转移酶缺乏，称为肌肉收缩性 Ehlers-Danlos 综合征-CHST14 (mcEDS - CHST14 )，导致核心蛋白聚糖 (GAG) 链的硫酸皮肤素部分完全耗尽，这是被硫酸软骨素取代。最近，我们发现了 mcEDS -CHST14患者皮肤中 GAG 链的结构改变。在这里，我们对Chst14基因缺失的纯合子 ( Chst14 ^-/- ) 小鼠进行了首次系统研究。我们使用了野生型 ( Chst14 ^+/+ ) 和Chst14 ^{-/-的皮肤样本}老鼠。用拉伸试验测量皮肤的机械脆性。使用光学显微镜、核心蛋白聚糖免疫组织化学和电子显微镜 (EM) 观察病理学，包括铜苯蓝 (CB) 染色。硫酸软骨素和硫酸皮肤素的定量使用酶消化然后阴离子交换 HPLC 进行。在Chst14 ^-/-小鼠中，与Chst14 ^+/+相比，皮肤拉伸强度显着降低老鼠。EM 显示胶原原纤维在不同方向上定向，在网状层中形成杂乱无章的胶原纤维。通过基于 EM 的 CB 染色，发现棒状线性 GAG 链的一端附着在胶原原纤维上并突出到原纤维外，而在Chst14 ^+/+小鼠中它们是圆形的并包裹着胶原原纤维。通过阴离子交换色谱法在Chst14 ^-/-小鼠的皮肤中检测到非常低水平的硫酸皮肤素二糖。Chst14 ^-/-小鼠在皮肤中的核心蛋白聚糖和胶原网络的 GAG 结构中表现出相似的异常，可能是 mcEDS -CHST14患者皮肤脆弱性的合理模型，揭示硫酸皮肤素在维持皮肤强度方面的作用。