Prenatal Diagnosis of Collagen Disorders by Direct Biochemical Analysis of Chorionic Villus Biopsies

Abstract

We have developed a method for early prenatal diagnosis of molecular disorders of collagens I and 111. The method takes advantage of the fact that isolated chorionic villi contain significant amounts of collagens in their extracellular matrix (stroma) and that they synthesize collagens in vitro. After metabolic labeling of chorion villus biopsies in toto with radioactive amino acids, collagens are extracted and analyzed by SDS-PAGE. Direct staining of the gel shows collagens synthesized in vivo, whereas autoradiofluorography identifies collagens synthesized during incubation in vitro. Unlike collagens synthesized by cultured amniotic fluid cells, collagens extracted from chorionic villi are not overmodified and thus allow better identification of molecular defects. Results are available within 3 to 5 d after biopsy. Using this method, we have correctly excluded Ehlers-Danlos syndrome type IV in two pregnancies, Ehlers-Danlos syndrome type VII in one pregnancy, and lethal osteogenesis imperfecta in four pregnancies. In addition, we correctly predicted a healthy fetus and an embryo 0 1 and EDS types VII and IV are heritable connective tissue disorders associated with molecular defects of collagen I (01 and EDS VII) and collagen 111 (EDS IV) (1,2). Collagen I is a heterotrimer composed of two proal(1)-chains and one proa2(I)-chain that form a triple helix.The genes coding for these proa-chains, COLlAl and COLlA2, are located on chromosomes 17 and 7, respectively (3). In contrast, collagen I11 is a homotrimer composed of three proal(II1)-chains coded for by COL3Al on chromosome 2 (3). affected with lethal osteogenesis imperfecta in consecutive pregnancies from a couple in which the asymptomatic mother was a somatic mosaic for a COLlAl G-to-A transition (Gly355Asp). Direct collagen analysis of chorion villus biopsies labeled in toto is rapid and reliable and may become the method of choice for the prenatal diagnosis of selected collagen disorders. Biochemical analysis of collagens synthesized by cultured skin fibroblasts is currently the standard method for diagnostic confirmation of 01, EDS IV, and EDS VII. Cultured fibroblasts synthesize and secrete both collagens I and 111, and alterations in the structure and/or the quantity of these collagens can be demonstrated in most (although not all) patients affected with 01, EDS IV, and EDS VII.EDS IV, EDS VII, and severe forms of 0 1 are crippling or even life-threatening conditions. For prospective parents affected by these conditions, the risk of having an affected child is 50%, whereas for parents of a sporadic patient with lethal 01, the recurrence risk is 5 to 8% (4,5). Because prenatal diagnosis is often requested by couples at risk, efforts have been made to develop methods for the early identification of affected fetuses by means of ultrasonography, biochemistry, and DNA analyses. Transabdominal ultrasound examination is effective in identifying fetuses with perinatally lethal 0 1 (01 type 11)

Collagen matrix deposition is dramatically enhanced in vitro when crowded with charged macromolecules: The biological relevance of the excluded volume effect

“…PAGE) Protein samples were separated under non-reducing conditions either using pre-cast gradient NuPage 3-8% Tris-acetate polyacrylamide gels (Invitrogen, Singapore) or 5% resolving/3% stacking polyacrylamide gels as outlined in [10]. Protein standards used were the Precision Plus Dual Color and Prestained Broad Range (Bio-Rad, Singapore), and collagen type I (Koken Co., Tokyo, Japan).…”

Prenatal diagnosis of a novelCOL1A1 mutation in osteogenesis imperfecta type I carried through full term pregnancy

“…Indeed, the indication for CVS was not OI diagnosis, but rather fetal karyotyping because of a previous fetus with trisomy 18. In previously reported cases of prenatally diagnosed OI that applied DNA based techniques, the indication was either a severe form of the disease (type II or III) (Valli et al, 1993;DiMaio et al, 1993;Raghunath et al, 1994;Gomez-Lira et al, 1994), or an ultrasonographic abnormality compatible with OI in the appropriate familial context (Ghosh et al, 1984;Robinson et al, 1987;Constantine et al, 1991;Thompson, 1993;Bulas et al, 1994;Berge et al, 1995). Evaluation of the accuracy of ultrasonography in assigning speci®c diagnoses in lethal skeletal dysplasias, including OI, yielded a rate of about 50%, and in 8/14 cases, the erroneous diagnosis impacted the accuracy of genetic counselling (Tretter et al, 1998).…”

“…Molecular analyses of fetal DNA is an option reserved for the few cases where the mutation in the affected family member is known. Few studies have used molecular analyses for prenatal OI diagnosis (Tsipouras et al, 1987;Bateman et al, 1991;Valli et al, 1993;DiMaio et al, 1993;Raghunath et al, 1994;Gomez-Lira et al, 1994;Lund et al, 1996a, b;Pepin et al, 1997). Here we report the use of prenatal molecular analysis from CVS for mild (type I) OI in a Jewish Israeli family with a novel COL1A1 mutation.…”

Technique to accurately quantify collagen content in hyperconfluent cell culture

“…After the incubation step, the samples were neutralized with 0.1N NaOH. The samples were analyzed by SDS-PAGE under non-reducing conditions described in (Lareu et al 2007;Raghunath et al 1994). Briefly, a 10% homemade SDS gel made up of 3% stacking and 5% resolving components is used.…”