Osteogenesis imperfecta, Marfan S. and Ehlers-Danlos Syndromes are a highly heterogeneous group of heritable systemic disorders of the connective tissue. Recent evidence indicates that many variants are caused by mutations in the genes for the proAlpha1(I) and proAlpha2(I) chains of type I procollagen. However, because of the large size of each proAlpha chain (1,500 amino acids), the large size of each gene (about 35 Kb) and the 11 or 12 enzymic post-translational modification steps, it is difficult to define the precise nature of the mutations at either the protein or gene level. We propose here to approach this problem with the use of Restriction Fragment Length Polymorphisms (RFLP). We have already identified three RFLP's associated with the human proAlpha2(I) gene. We will identify additional RFLP's for both the proAlpha1(I) and proAlpha2(I) genes. We will use these RFLP's as markers to study genetic disorders of type I procollagen. The approach will be to study affected and non-affected members of families with either OI or Marfan S. for the presence of RFLP's associated with either proAlpha gene segregating in the family. We will try to correlate the segregation of the phenotype with that of a marker and establish linkage between them. This approach will allow us to identify asymptomatic carriers and offer prenatal diagnosis in informative families. Furthermore, we will search for the presence of a non-random association of the RFLP's in haplotypes-like those recently identified for the Beta-globin cluster. The haplotypes may be not only of diagnostic but also of etiologic significance, as it has been shown in the Beta-thalassemias. We will also try to establish genetic linkage between the syntenic loci of proAlpha1(I) and human growth hormone, which will further increase the number of families whom we can study by genetic linkage. We will use Southern blotting for these experiments. Total genomic DNA will be estracted from leukocytes and/or cultured fibroblasts, restricted with a variety of restriction endonucleaes, electrophoresed on an agarose gel and transferred on a nitrocellulose filter. The filters will be hybridized with P32 nick-translated human genomic DNA probes coding for either the proAlpha1(I) or the proAlpha2(I) genes.
| Hortop, J; Tsipouras, P; Hanley, J A et al. (1986) Cardiovascular involvement in osteogenesis imperfecta. Circulation 73:54-61 |
| Tsipouras, P; Barabas, G; Matthews, W S (1986) Neurologic correlates of osteogenesis imperfecta. Arch Neurol 43:150-2 |
