Prenatal diagnosis and prevention of inherited abnormalities of collagen

Perinatal differential diagnosis of cystic kidney disease and urinary tract obstruction: anatomic pathologic, ultrasonographic and genetic findings

According to the classification of Osathanondh and Potter of cystic kidney diseases an antenatal differential diagnosis is presented, which is based on the anatomic pathologic, ultrasonographic and genetic findings. Since the ultrasound evaluation influences the obstetric and neonatal management, each second and third trimester sonography should consider the most common malformations in pediatric autopsies. The autosomal recessive polycystic kidney disease (ARPK), autosomal dominant polycystic kidney disease (ADPK), multicystic renal dysplasia, obstructive multicystic kidneys and cystic renal malformations found in other syndromes with genetic linkage are discussed in this review.

Collagen biosynthesis in cell culture from chorionic villi

After chorionic villus biopsy of human placenta, cell cultures were propagated with Ham's F10 medium or Eagle's minimum essential medium (MEM). It was possible to study the morphology of the cells by transmission electron microscopy (TEM) after a special culture of the cells in a collagen gel. The cells embedded in a collagen gel were able to contract the gel and to organize collagen fibres, as fibroblast cultures do. TEM showed vacuolization and well-developed cisternae of the endoplasmic reticulum, especially in the case of MEM culture. The aim was to determine whether cells cultivated from early placenta were able to synthesize enough collagen for a metabolic study. A high level of collagen biosynthesis could be quantified. Types I and III collagen can be determined which is useful for studying the abnormalities of collagen synthesis in suspected cases of osteogenesis imperfecta or Ehlers-Danlos type IV syndrome. The hydroxylation of lysine can also be studied with respect to Ehlers-Danlos type VI syndrome. Moreover, these cells, in contrast to fibroblast cultures, made it possible to study the biosynthesis of type IV collagen.

Ehlers-Danlos syndrome type VII: phenotype and genotype

A patient suffering from a severe form of Ehlers-Danlos syndrome is presented (EDS type VII). The presence of bilateral congenital hip dislocation, generalized joint hypermobility and a soft hyperelastic skin with abnormal scarring suggested a specific collagen type I defect. SDS-PAGE analysis of collagens secreted into the medium of fibroblast cultures showed a retarded migration of more than half of the alpha 2(I) chains. CNBr peptide mapping of the HPLC-purified altered chain localized the mutant locus to the N-terminal region of the protein. cDNA analysis of the corresponding gene COL1A2 revealed, in addition to the expected collagen sequence, a transcript missing the entire exon 6. This exon encodes a major crosslinking site within collagen fibres as well as the N-propeptidase cleavage site. The skipping of exon 6 is caused by a splice site mutation substituting an A for a G at the first nucleotide of intron 6.

Length polymorphisms in new human collagen-like loci

Two new collagen-like loci have been identified in the human genome which have sequence similarity to the triple-helical coding region of the pro-alpha 2(I) gene. Both loci exhibit length polymorphism due to alleles that contain deletions. The deletion at one locus is 400 bp while the deletion at the second locus is 200 bp. The second locus is on chromosome 17 and its two alleles are not in Hardy-Weinberg equilibrium. These loci are candidates for involvement in connective tissue disorders.

Type III collagen mutations cause fragile cerebral arteries

Premature vascular aneurysms and fragility of cerebral arteries are commonly associated with type III collagen mutations and physical signs suggesting a generalized abnormality of connective tissue. Sometimes these traits are clearly genetically transmitted. Here we present seven examples of early cerebrovascular aneurysms or fragility including five examples of carotid cavernous sinus aneurysms. With one exception in which we suspect the mutation is too small to be detected, all of them had easily visible abnormalities of their type III collagen proteins. Further work in progress will eventually allow the characterization of their mutations at gene sequence level and will be followed by the ability to prevent transmission of the mutant genes in these families.