Expression of Evc and Lbn Responsible for Ellis-van Creveld Syndrome in Tibial Growth Plate

Ellis-van Creveld (Evc) syndrome is an autosomal recessive chondrodysplasia characterized by disproportionate dwarfism, postaxial polydactyly, natal teeth and dysplatic nails. Ellis-van Creveld (EVC) gene, which is mutated in patients with Evc syndrome, has recently been identified by positional cloning. LIMBIN(LBN), responsible for bovine chondrodysplastic dwarfism, is also mutated in patients with Evc syndrome. However, the physiological role of EVC and LBN have not been elucidated. To assess the role of Evc and Lbn in the rat tibia were most abundant at embryonic day 1, 28 and 56. The analysis by in situ hybridization revealed that the Evc was expressed mainly in prehypertrophic and hypertrophic chondrocytes in the rat tibial growth plate at postnatal stage. Lbn was detected strongly in proliferative chodnrocyte and moderately in prehypertrophic chondrocytes. These profiles of Evc and Lbn expression reflected the abnormalities in chondrocytes of patients with Evc syndrome. Our results suggest that Evc and Lbn may affect chondrocyte differentiation and proliferation in endochondral ossification, respectively

Characterization of the chromosomal inversion associated with the Koa mutation in the mouse revealed the cause of skeletal abnormalities

<p>Abstract</p> <p>Background</p> <p>Koala (<it>Koa</it>) is a dominant mutation in mice causing bushy muzzle and pinna, and is associated with a chromosomal inversion on the distal half of chromosome 15. To identify the gene responsible for the <it>Koa </it>phenotypes, we investigated phenotypes of <it>Koa </it>homozygous mice and determined the breakpoints of the inversion with a genetic method using recombination between two different chromosomal inversions.</p> <p>Results</p> <p>Skeletal preparation of <it>Koa </it>homozygotes showed marked deformity of the ribs and a wider skull with extended zygomatic arches, in addition to a general reduction in the lengths of long bones. They also had open eyelids at birth caused by a defect in the extension of eyelid anlagen during the embryonic stages. The proximal and distal breakpoints of the <it>Koa </it>inversion were determined to be 0.8-Mb distal to the <it>Trsps1 </it>gene and to 0.1-Mb distal to the <it>Hoxc4 </it>gene, respectively, as previously reported. The phenotypes of mice with the recombinant inverted chromosomes revealed the localization of the gene responsible the <it>Koa </it>phenotype in the vicinity of the proximal recombinant breakpoint. Expression of the <it>Trsps1 </it>gene in this region was significantly reduced in the <it>Koa </it>homozygous and heterozygous embryos.</p> <p>Conclusion</p> <p>While no gene was disrupted by the chromosomal inversion, an association between the <it>Koa </it>phenotype and the proximal recombinant breakpoint, phenotypic similarities with <it>Trps1</it>-deficient mice or human patients with <it>TRSP1 </it>mutations, and the reduced expression of the <it>Trsps1 </it>gene in <it>Koa </it>mice, indicated that the phenotypes of the <it>Koa </it>mice are caused by the altered expression of the <it>Trps1 </it>gene.</p

Elevated fibroblast growth factor signaling is critical for the pathogenesis of the dwarfism in Evc2/Limbin mutant mice

Ellis-van Creveld (EvC) syndrome is a skeletal dysplasia, characterized by short limbs, postaxial polydactyly, and dental abnormalities. EvC syndrome is also categorized as a ciliopathy because of ciliary localization of proteins encoded by the two causative genes, EVC and EVC2 (aka LIMBIN). While recent studies demonstrated important roles for EVC/EVC2 in Hedgehog signaling, there is still little known about the pathophysiological mechanisms underlying the skeletal dysplasia features of EvC patients, and in particular why limb development is affected, but not other aspects of organogenesis that also require Hedgehog signaling. In this report, we comprehensively analyze limb skeletogenesis in Evc2 mutant mice and in cell and tissue cultures derived from these mice. Both in vivo and in vitro data demonstrate elevated Fibroblast Growth Factor (FGF) signaling in Evc2 mutant growth plates, in addition to compromised but not abrogated Hedgehog-PTHrP feedback loop. Elevation of FGF signaling, mainly due to increased Fgf18 expression upon inactivation of Evc2 in the perichondrium, critically contributes to the pathogenesis of limb dwarfism. The limb dwarfism phenotype is partially rescued by inactivation of one allele of Fgf18 in the Evc2 mutant mice. Taken together, our data uncover a novel pathogenic mechanism to understand limb dwarfism in patients with Ellis-van Creveld syndrome

Positional cloning of the gene LIMBIN responsible for bovine chondrodysplastic dwarfism

Chondrodysplastic dwarfism in Japanese brown cattle is an autosomal recessive disorder characterized by short limbs. Previously, we mapped the locus responsible for the disease on the distal end of bovine chromosome 6. Here, we narrowed the critical region to ≈2 cM by using linkage analysis, constructed a BAC and YAC contig covering this region, and identified a gene, LIMBIN (LBN), that possessed disease-specific mutations in the affected calves. One mutation was a single nucleotide substitution leading to an activation of a cryptic splicing donor site and the other was a one-base deletion resulting in a frameshift mutation. Strong expression of the Lbn gene was observed in limb buds of developing mouse embryos and in proliferating chondrocytes and bone-forming osteoblasts in long bones. These findings indicate that LBN is responsible for bovine chondrodysplastic dwarfism and has a critical role in a skeletal development

A nonsense mutation in mouse Adamtsl2 causes uterine hypoplasia and an irregular estrous cycle

The spontaneous mutation stubby (stb) in mice causes chondrodysplasia and male infertility due to impotence through autosomal recessive inheritance. In this study, we conducted linkage analysis to localize the stb locus within a 1.6 Mb region on mouse chromosome 2 and identified a nonsense mutation in Adamtsl2 of stb/stb mice. Histological analysis revealed disturbed endochondral ossification with a reduced hypertrophic chondrocyte layer and stiff skin with a thickened dermal layer. These phenotypes are similar to those observed in humans and mice with ADAMTSL2/Adamtsl2 mutations. Moreover, stb/stb female mice exhibited severe uterine hypoplasia at 5 weeks of age and irregular estrous cycles at 10 weeks of age. In normal mice, Adamtsl2 was more highly expressed in the ovary and pituitary gland than in the uterus, and this expression was decreased in stb/stb mice. These findings suggest that Adamtsl2 may function in these organs rather than in the uterus. Thus, we analyzed Gh expression in the pituitary gland and plasma estradiol and IGF1 levels, which are required for the development of the female reproductive tract. There was no significant difference in Gh expression and estradiol levels, whereas IGF1 levels in stb/stb mice were significantly reduced to 54–59% of those in +/+ mice. We conclude that Adamtsl2 is required for the development of the uterus and regulation of the estrous cycle in female mice, and decreased IGF1 may be related to these abnormalities

Development of Durability Test Device for Magnetorheological Fluids with Two Types of Rotors and Their Long-Term Torque Characteristics

Magnetorheological fluids (MRFs) are composites of micron-sized and/or nano-sized Fe particles and nonmagnetic oils, and their rheological properties change with changes in the magnetic field. To distinguish between material and mechanical deterioration, we developed a durability test system without the influence of mechanical sealing and bearing on the MRFs. We used a set of rotors and stators to create a V-shaped MRF layer. However, the test device produces a constant magnetic field with a permanent magnet instead of an electromagnetic coil to make a compact design and cannot be tested under various dynamic magnetic inputs. Therefore, we developed a durability test system with an electric magnet to create a variable magnetic input and two sets of rotors, and compared their magnetic properties and the results of the durability tests. From the findings, the measured torque for the parallel plate case was lower than the predicted value. In contrast, the V-shaped disk exhibits a higher torque than the estimated values. Durability tests for the two types of MRFs were conducted. The torque variation for the nano MRF is significantly smaller for both the parallel and V-shaped plates. In addition, the duration of both MRFs for the V-shaped plate was much shorter than that for the parallel plate

Skeletal analysis of the long bone abnormality (lbab/lbab) mouse, a novel chondrodysplastic C-type natriuretic peptide mutant.

Long bone abnormality (lbab/lbab) is a strain of dwarf mice. Recent studies revealed that the phenotype is caused by a spontaneous mutation in the Nppc gene, which encodes mouse C-type natriuretic peptide (CNP). In this study, we analyzed the chondrodysplastic skeletal phenotype of lbab/lbab mice. At birth, lbab/lbab mice are only slightly shorter than their wild-type littermates. Nevertheless, lbab/lbab mice do not undergo a growth spurt, and their final body and bone lengths are only ~60% of those of wild-type mice. Histological analysis revealed that the growth plate in lbab/lbab mice, especially the hypertrophic chondrocyte layer, was significantly thinner than in wild-type mice. Overexpression of CNP in the cartilage of lbab/lbab mice restored their thinned growth plate, followed by the complete rescue of their impaired endochondral bone growth. Furthermore, the bone volume in lbab/lbab mouse was severely decreased and was recovered by CNP overexpression. On the other hand, the thickness of the growth plate of lbab/+ mice was not different from that of wild-type mice; accordingly, impaired endochondral bone growth was not observed in lbab/+ mice. In organ culture experiments, tibial explants from fetal lbab/lbab mice were significantly shorter than those from lbab/+ mice and elongated by addition of 10(-7) M CNP to the same extent as lbab/+ tibiae treated with the same dose of CNP. These results demonstrate that lbab/lbab is a novel mouse model of chondrodysplasia caused by insufficient CNP action on endochondral ossification