Prolyl 3-hydroxylation is a rare collagen type I post translational modification in fibrillar collagens. The primary 3Hyp substrate sites in type I collagen are targeted by an endoplasmic reticulum (ER) complex composed by cartilage associated protein (CRTAP), prolyl 3-hydroxylase 1 (P3H1) and prolyl cis/trans isomerase B, whose mutations cause recessive forms of osteogenesis imperfecta with impaired levels of α1(I)3Hyp986. The absence of collagen type I 3Hyp in wild type zebrafish provides the unique opportunity to clarify the role of the complex in vertebrate. Zebrafish knock outs for crtap and p3h1 were generated by CRISPR/Cas9. Mutant fish have the typical OI patients’ reduced size, body disproportion and altered mineralization. Vertebral body fusions, deformities and fractures are accompanied to reduced size, thickness and bone volume. Intracellularly, collagen type I is overmodified, and partially retained causing enlarged ER cisternae. In the extracellular matrix the abnormal collagen type I assembles in disorganized fibers characterized by altered diameter. The data support the defective chaperone role of the 3-hydroxylation complex as the primary cause of the skeletal phenotype.

Prolyl 3-hydroxylation 是纤维状胶原蛋白中罕见的 I 型胶原蛋白翻译后修饰。I 型胶原蛋白中的主要 3Hyp 底物位点被内质网 (ER) 复合物靶向，该复合物由软骨相关蛋白 (CRTAP)、脯氨酰 3-羟化酶 1 (P3H1) 和脯氨酰顺式/反式异构酶 B 组成，其突变导致隐性形式的α1(I)3Hyp986 水平受损的成骨不全。野生型斑马鱼中 I 型胶原蛋白 3Hyp 的缺失为阐明复合物在脊椎动物中的作用提供了独特的机会。斑马鱼淘汰crtap和p3h1由 CRISPR/Cas9 生成。突变鱼具有典型的 OI 患者的体型减小、身体不成比例和矿化改变。椎体融合、畸形和骨折伴随着尺寸、厚度和骨量的减少。在细胞内，I 型胶原蛋白过度修饰，部分保留导致 ER 池扩大。在细胞外基质中，异常的 I 型胶原蛋白聚集在以直径改变为特征的无序纤维中。数据支持 3-羟基化复合物的缺陷伴侣作用是骨骼表型的主要原因。