van der Rest M, Hayes A, Marie P, Desbarats M, Kaplan P, Glorieux F H
Am J Med Genet. 1986 Jul;24(3):433-46. doi: 10.1002/ajmg.1320240306.
An infant was born with osteogenesis imperfecta (OI) and died after 7 days. In addition, there were amniotic constriction bands and amputations of several digits of the upper and lower limbs. The radiologic picture was suggestive of type III OI. Histomorphometric analysis of the bone showed a trabecular bone volume of 15.1% compared to 26.9% for age-matched controls. This was due to a decreased apposition of matrix by the osteoblasts. Because abnormal collagen synthesis has been suggested as the underlying defect in most forms of OI, collagen studies were undertaken using intact tissues. Bone and skin collagen solubilities were strikingly reduced. Shortened type I collagen molecules, representing 25% of the total type I collagen, were produced by pepsin digestion of the demineralized bone matrix. The molecular weight of the shortened collagen, was 10 kd lower than normal for both the alpha 1 and alpha 2 chains as determined by gel electrophoresis. The bone acetic acid-soluble collagen showed few shortened alpha-chains. Twenty-five percent of the acid-soluble bone collagen was cleaved into shortened molecules by a pepsin digestion. The shortened alpha 1 chain was purified by high-performance liquid chromatography (HPLC) and digested with CNBr. The analysis of the resulting fragments by HPLC and by gel electrophoresis unequivocally demonstrated that the shortened alpha 1 chain was derived from the alpha 1(I) chains and that the pepsin sensitivity extends from the amino terminal end of the chain to the alpha 1(I) CB5 peptide, approximately 120 residues inside the triple helix. These studies show a distinct structural abnormality of type I collagen in the bone matrix of this patient resulting in an increased sensitivity of the collagen to general enzymatic proteolysis. The importance of correlating clinical and biochemical information in OI is emphasized; classification and genetic counseling based only on clinical observations are inaccurate.
一名婴儿出生时患有成骨不全症（OI），7天后死亡。此外，还有羊膜束带以及上下肢多个手指和脚趾的截断。影像学表现提示为III型OI。对骨骼的组织形态计量学分析显示，小梁骨体积为15.1%，而年龄匹配的对照组为26.9%。这是由于成骨细胞对基质的附着减少所致。由于异常胶原蛋白合成被认为是大多数形式OI的潜在缺陷，因此使用完整组织进行了胶原蛋白研究。骨骼和皮肤胶原蛋白的溶解度显著降低。通过对脱矿骨基质进行胃蛋白酶消化，产生了占总I型胶原蛋白25%的缩短I型胶原蛋白分子。通过凝胶电泳测定，缩短胶原蛋白的α1和α2链的分子量均比正常低10kd。骨骼乙酸可溶性胶原蛋白显示出很少的缩短α链。25%的酸溶性骨胶原蛋白通过胃蛋白酶消化被切割成缩短分子。缩短的α1链通过高效液相色谱（HPLC）纯化并用溴化氰消化。通过HPLC和凝胶电泳对所得片段进行分析明确表明，缩短的α1链源自α1（I）链，并且胃蛋白酶敏感性从链的氨基末端延伸至α1（I）CB5肽，大约在三螺旋内部120个残基处。这些研究表明该患者骨基质中I型胶原蛋白存在明显的结构异常，导致胶原蛋白对一般酶促蛋白水解的敏感性增加。强调了在OI中关联临床和生化信息的重要性；仅基于临床观察进行分类和遗传咨询是不准确的。
