Expression and regulation of type I collagen and other matrix components in opsteogenesis imperfecta ostebolasts

Expression and regulation of type I collagen and other matrix components in opsteogenesis imperfecta ostebolasts

178 Sixth International Conference on the Molecular Biology and Pathology of Matrix stability and secretion of mutant type I collagen in OI osteobla...

106KB Sizes 0 Downloads 58 Views

178

Sixth International Conference on the Molecular Biology and Pathology of Matrix

stability and secretion of mutant type I collagen in OI osteoblasts. Osteoblast expression of matrix components was detected by Northern Blot analysis of total RNA from a patient with an (zl (I) Gly 222 to Ala substitution, and some matrix constituents appeared to be differentially regulated in OI osteoblasts treated with TGF-~. Both c¢1 and 02. chains of type I collagen showed a 2.5 and 3.5 fold increase respectively, following a 48 hour incubation of OI osteoblasts with TGF-I3. The most significant changes were detected in both proteoglycans decorin and biglycan. Following a 48 hour stimulation with 5 ng/ml of TGF13,decorin showed a 5 to 10 fold decrease in transcript level, when compared to control osteoblasts. Stimulation of biglycan transcripts was detected in both normal and OI cells treated with 1 and 5 ng/ml of TGF-13. However the response of OI osteoblasts was not as high. We observed a 2 fold increase in OI osteoblasts, compared to a 6 fold in controls stimulated with 1 ng/ml of TGF-I3. Using 5ng/ml of TGF-~, OI osteoblasts showed a 6.5 fold decrease in biglycan stimulation. These studies will increase our understanding of the impact of collagenous and non-collagenous components of bone matrix on OI phenotype and pathology.

frequency <3%) a common founder for the mutation in these families is likely. A common ethnic thread uniting these three geographically dispersed kindreds is that of the Celtic tribes of the first millennium C.E. Belgic Celts were noted to inhabit Britain and Hibernia by Julius Caesar in his chronicles of the Gallic Wars. The settlement of Iceland occurred in the ninth and tenth century C.E. Icelandic sagas written in the first centuries after settlement suggest that a large percentage of the original population of Iceland were ethnic Celts taken to Iceland from Ireland by Norse Vikings as slaves. If the historical records regarding this ethnic group are valid, and assuming that the Belgian, Irish and Icelandic branches of this family were genetically isolated near the time suggested by the historical record, then at least one thousand years and as much as two thousand years have elapsed since the founder occurrence of the ArgSlg-Cys mutation in these three families. These studies were supported, in pad, by USPHS grants AR39740, AR42015 and HG00008.

The COL4A4 Gene is Mutated Benign Hematuria. ArgSt'-Cys-Associated Haplotype in Icelandic Family Suggests Early Origin of this Mutation. D. Holderbaum* J.F. Bleasel* H. J6nsson t, T. Saxne*, D.J. Prockop s, C.J. Williams{, and R.W. Moskowitz* *Case Westem Reserve University, Cleveland, Ohio; tLandspitalinn, Reykjavfk, Iceland; *Lund University, Lund, Sweden; ~Thomas Jefferson University, Philadelphia, Pennsylvania Five families have presently been described who have precocious osteoarthritis and mild spondyloepiphyseal dysplasia associated with Arg sl~Cys in COL2AI. Haplotype analysis was conducted using 5 RFLP's and the 3' UTR VNTR in COL2A1. Haplotype frequencies were determined by sampling of 69 unrelated indi-viduals of mixed European origin. Three of the five families have the mutation in association with a relatively rare COL2A1 haplotype. These families are currently living in the United States, New Zealand and Iceland, and are of Belgian, Irish and Icelandic heritage respectively. Because the mutation-associated haplotype shared by these three families is relatively rare (haplotype

in Familial

F.T.L. van der Loop* H.H. Lemminkt W.N. Nillesent, H.G. Brunnert, L.A.H. Monnenst, C.H. Schr6dert, H.J.M. Smeets* *Division of Genetics, University of Limburg, Maastricht, The Netherlands; tDepts of Human Genetics and Pediatrics, University Hospital Nijmegen, Nijmegen, The Netherlands. Autosomal dominant familial benign hematuria is characterized by persistent microhematuria and normal renal function. Histologically, thinning of the glomerular basement membrane is visible. This resembles early stages of the severe renal disorder Alport syndrome. The predominant form of Alport syndrome is caused by mutations in the X-linked COL4A5 gene. In 1994, we reported the first mutations in the COL4A3 and COL4A4 genes in autosomal recessive Alport syndrome. Linkage to the same COL4A3/COL4A4 locus at 2q35-37 has been demonstrated for the autosomal dominant form as well. With markers from the COL4A3/COL4A4 genes we were able to demonstrate linkage to familial benign hematuria in a large Dutch pedigree (Zmax = 3.58 at theta = 0.0). Subsequently, a glycine to glutamic acid substitution was identified in the collagenous region of the COL4A4 gene. Homozygosity for a similar COL4A4