Knockout mice: Is it just genetics? Effect of enriched housing on fibulin-4+/- mice

Background. Fibulin-4 is an extracellular matrix protein expressed by vascular smooth muscle cells that is essential for maintaining arterial integrity. Fibulin-4-/- mice die just before birth due to arterial hemorrhage, but fibulin-4+/- mice appear to be outwardly normal. Experiments were therefore performed to determine whether fibulin-4+/- mice display arterial pathologies on a microscopic scale. After preliminary experiments were performed, a second purpose developed, which was to test the hypothesis that any observed pathologies would be ameliorated by housing the animals in enriched cages. Methodology. Fibulin-4+/- and wild-type mice were housed either four/cage in standard cages or two per cage in larger cages, each cage containing a tunnel and a wheel. After three weeks the mice were sacrificed, and the aortas perfusion-fixed and excised for light and electron microscopy. Principle Findings. When the mice were in standard cages, localized regions of disorganized extracellular matrix and collagen fibers consistently appeared between some of the medial smooth muscle cells in the fibulin-4+/- mice. In the wild-type mice, the smooth muscle cells were closely connected to each other and the media was more compact. The number of disorganized regions per square mm was significantly greater for fibulin-4+/- mice (172±43 (SEM)) than for wild-type mice (15±8) (p<0.01, n = 8). When the mice were in enriched cages, the fibulin-4+/- mice showed significantly fewer disorganized regions than those in standard cages (35±12) (p<0.05, n = 8). The wild type mice also showed fewer disorganized regions (3±2), but this difference was not significant. Conclusions. These results indicate that arterial pathologies manifested in fibulin-4+/- mice can be reduced by enriching the housing conditions, and imply that appropriate environments may counteract the effects of some genetic deficiencies

In frame fibrillin-1 gene deletion in autosomal dominant Weill-Marchesani syndrome

Weill-Marchesani syndrome (WMS) is a connective tissue disorder characterised by short stature, brachydactyly, joint stiffness, and characteristic eye anomalies including microspherophakia, ectopia of the lenses, severe myopia, and glaucoma. Both autosomal recessive (AR) and autosomal dominant (AD) modes of inheritance have been described and a gene for AR WMS has recently been mapped to chromosome 19p13.3-p13.2. Here, we report on the exclusion of chromosome 19p13.3-p13.2 in a large AD WMS family and show that, despite clinical homogeneity, AD and AR WMS are genetically heterogeneous entities. Because two AD WMS families were consistent with linkage to chromosome 15q21.1, the fibrillin-1 gene was sequenced and a 24 nt in frame deletion within a latent transforming growth factor-beta1 binding protein (LTBP) motif of the fibrillin-1 gene was found in a AD WMS family (exon 41, 5074_5097del). This in frame deletion cosegregated with the disease and was not found in 186 controls. This study strongly suggests that AD WMS and Marfan syndrome are allelic conditions at the fibrillin-1 locus and adds to the remarkable clinical heterogeneity of type I fibrillinopathies

Identification of the minimal combination of clinical features in probands for efficient mutation detection in the FBN1 gene.

International audienceMutations identified in the fibrillin-1 (FBN1) gene have been associated with Marfan syndrome (MFS). Molecular analysis of the gene is classically performed in probands with MFS to offer diagnosis for at-risk relatives and in children highly suspected of MFS. However, FBN1 gene mutations are found in an ill-defined group of diseases termed 'type I fibrillinopathies', which are associated with an increased risk of aortic dilatation and dissection. Thus, there is growing awareness of the need to identify these non-MFS probands, for which FBN1 gene screening should be performed. To answer this need we compiled the molecular data obtained from the screening of the FBN1 gene in 586 probands, which had been addressed to our laboratory for molecular diagnosis. In this group, the efficacy of FBN1 gene screening was high in classical MFS probands (72.5%,), low (58%) in those referred for incomplete MFS and only slight (14.3%) for patients referred as possible MFS. Using recursive partitioning, we found that the best predictor of the identification of a mutation in the FBN1 gene was the presence of features in at least three organ systems, combining one major, and various minor criteria. We also show that our original recommendation of two systems involved with at least one with major criterion represents the minimal criteria because in probands not meeting these criteria, the yield of mutation identification drastically falls. This recommendation should help clinicians and biologists in identifying probands with a high probability of carrying a FBN1 gene mutation, and thus optimize biological resources.European Journal of Human Genetics advance online publication, 18 March 2009; doi:10.1038/ejhg.2009.36

Marfan Database (third edition): new mutations and new routines for the software

The Marfan database is a software that contains routines for the analysis of mutations identified in the FBN1 gene that encodes fibrillin-1. Mutations in this gene are associated not only with Marfan syndrome but also with a spectrum of overlapping disorders. the third version of the Marfan database contains 137 entries. the software has been modified to accommodate four new routines and is now accessible on the World Wide Web at http://www.umd.necker.fr.Univ Paris 05, Hop Necker Enfants Malad, Clin Maurice Lamy, INSERM,U383, F-75743 Paris 15, FranceCHU Cochin Port Royal, Inst Cochin Genet Mol, F-75014 Paris, FranceHop Broussais, F-75014 Paris, FranceRoyal Alexandra Hosp Children New, Dept Med Genet, Sydney, NSW 2124, AustraliaRoyal Alexandra Hosp Children New, Dept Paediat & Child Hlth, Sydney, NSW 2124, AustraliaUniv Dundee, Ninewells Hosp & Med Sch, Dept Mol & Cellular Pathol, Mol Genet Lab, Dundee DD1 9SY, ScotlandInst Child Hlth, Unit Clin Genet & Fetal Med, N Thames E Clin Mol Genet Lab, London, EnglandUniv Edinburgh, Western Gen Hosp, Mol Med Ctr, Dept Med,Human Genet Unit, Edinburgh EH4 2XU, Midlothian, ScotlandSt George Hosp, Sch Med, London SW17 0RE, EnglandStanford Univ, Med Ctr, Howard Hughes Med Inst, Stanford, CA 94305 USAUniv Munich, Klinikm GroBhadern, Dept Cardiovasc Surg, D-81366 Munich, GermanyUniv Munich, Klinikm GroBhadern, Inst Clin Chem, D-81366 Munich, GermanyState Univ Ghent Hosp, Ctr Med Genet, B-9000 Ghent, BelgiumNatl Publ Hlth Inst, Dept Human Mol Genet, FIN-00300 Helsinki, FinlandUNIFESP, EPM, BR-04101000 São Paulo, BrazilHop Ambroise Pare, Lab Cent Biochim Hormonol & Genet Mol, F-92104 Boulogne, FranceStanford Univ, Med Ctr, Dept Genet, Stanford, CA 94305 USAUNIFESP, EPM, BR-04101000 São Paulo, BrazilWeb of Scienc

Heterozygous TGFBR2 mutations in Marfan syndrome.

These authors equally contributed to this work as the first authors (T.M. and G.C.-B.) or the last authors (C.B. and N.M.)Marfan syndrome is an extracellular matrix disorder with cardinal manifestations in the eye, skeleton and cardiovascular systems associated with defects in the gene encoding fibrillin (FBN1) at 15q21.1 (ref. 1). A second type of the disorder (Marfan syndrome type 2; OMIM 154705) is associated with a second locus, MFS2, at 3p25-p24.2 in a large French family (family MS1). Identification of a 3p24.1 chromosomal breakpoint disrupting the gene encoding TGF-beta receptor 2 (TGFBR2) in a Japanese individual with Marfan syndrome led us to consider TGFBR2 as the gene underlying association with Marfan syndrome at the MSF2 locus. The mutation 1524G-->A in TGFBR2 (causing the synonymous amino acid substitution Q508Q) resulted in abnormal splicing and segregated with MFS2 in family MS1. We identified three other missense mutations in four unrelated probands, which led to loss of function of TGF-beta signaling activity on extracellular matrix formation. These results show that heterozygous mutations in TGFBR2, a putative tumor-suppressor gene implicated in several malignancies, are also associated with inherited connective-tissue disorders