Lysyl-Protocollagen Hydroxylase Deficiency in Fibroblasts from Siblings with Hydroxylysine-Deficient Collagen

Abstract

Cell culture studies were performed on members of a family in which two sisters, ages 9 and 12, have a similar disorder characterized clinically by severe scoliosis, joint laxity and recurrent dislocations, hyperextensible skin, and thin scars. The skin collagen from the sisters was markedly deficient in hydroxylysine, but other amino acids were present in normal amounts. Hydroxylysine in collagen from fascia and bone was reduced to a lesser extent. Since the most likely explanation for the hydroxylysihie deficiency was a reduction in enzymatic hydroxylation of lysine residues in protocollagen, we measured the activity of lysyl-protocollagen hydroxylase in crude lysates of cultured skin fibroblasts. Enzyme activities in the two affected children were 14 and 10% of controls, whereas the activity was about 60% of normal in the mother, a pattern most consistent with autosomal recessive inheritance. The mutant enzyme demonstrated the same cofactor requirements as that from normal cells. Deficiency of lysyl-protocollagen hydroxylase is the first inborn error of human collagen metabolism to be defined at the biochemical level.Heritable disorders of connective tissue include both dominantly and recessively inherited syndromes (1). Abnormalities in the structural protein, collagen, have been suggested in autosomal, dominantly inherited osteogenesis imperfecta, and in the Marfan and Ehlers-Danlos syndromes (2), but none of the putative biochemical defects has been established as specific for any of these disorders. Autosomal, recessively inherited homocystinuria due to deficiency of cystathionine synthetase shares many of the clinical features of the Marfan syndrome and produces a secondary defect in connective tissue (3). A distinctive mendelian inheritance pattern provides powerful evidence of genetic heterogeneity. We have recently studied a family in which two sisters had some clinical features of the Ehlers-Danlos and Marfan syndromes but in which both parents and an older sister were unaffected, suggesting recessive inheritance (4). The affected 9-and 12-year old sisters had severe progressive scoliosis present since infancy, hyperextensible skin, marked joint laxity and recurrent joint dislocations, and mild arachnodactyly. Ectopia lentis was absent, intelligence was normal, and urinary amino acids were not increased. Amino-acid analysis of dermal collagen from the affected sisters disclosed a marked reduction in hydroxylysine to about 5% of normal, but normal amounts of hydroxyproline and other amino acids. The hydroxylysine content was also reduced in samples of lumbodorsal fascia and variably reduced in bone, but was about normal in a single sample of costal cartilage. The amino-acid compositions of skin from the parents and from the clinically unaffected older sister were normal. The hydroxylysine content of dermis was also normal in three patients, each with the Marfan and EhlersDanlos syndromes. Collagen from the skin of the affected children was more soluble in denaturing solvents than that derived ...

Abnormal properties of collagen lysyl hydroxylase from skin fibroblasts of siblings with hydroxylysine-deficient collagen.

“…The hydroxylations are catalyzed by two separate enzymes, prolyl hydroxylase, (prolyl-protocollagen hydroxylase The Journal of Clinical Investigation Volume 57 January 1976 -83-93 or collagen prolyl hydroxylase EC 1.14.11.2), and lysyl hydroxylase (lysyl-protocollagen hydroxylase or collagen lysyl hydroxylase). Lysates of cultured skin fibroblasts from the affected siblings contained normal levels of prolyl hydroxylase activity but reduced lysyl hydroxylase activity (less than 15% of that present in fibroblasts from normal subjects) (3). In vitro assays of prolyl and lysyl hydroxylase activity in crude lysates of normal and mutant cells require the presence of oxygen, ca-ketoglutarate, ascorbic acid, and ferrous ion for the hydroxylation reactions to occur at optimal rates.…”

Ehlers-Danlos syndrome type VI with cystic malformations of the meninges in a 7-year-old girl

“…In the majority of cases, the symptoms have been biochemically attributed to a deficiency of collagen lysylhydroxylase 1 [9,11,15,17]. This form, commonly called EDS VIA (MIM 225400), results from different mutations in the lysylhydroxylase I gene [15,18].…”

A patient with Ehlers-Danlos syndrome type VI is a compound heterozygote for mutations in the lysyl hydroxylase gene.

“…The potential lethality ofthe disease is a reported tendency for spontaneous arterial rupture (10). Clinical diagnosis of EDS VI is confirmed by an assay of LH activity in cultured skin fibroblasts (11).…”