heparitin-sulfate and Bone-Diseases--Developmental

Topics: Amidohydrolases; Animals; Bone Diseases, Developmental; Cell Membrane; Gene Expression Regulation, Developmental; Gene Targeting; Heparan Sulfate Proteoglycans; Heparitin Sulfate; Mice; Mice, Knockout; Models, Animal; Models, Chemical; Mutation; N-Acetylglucosaminyltransferases; Polymers; Protein Binding; Proteoglycans; Sulfotransferases

The fibroblast growth factor receptor family consists of four receptor tyrosine kinases which bind with varying affinity and specificity to a family of at least fifteen polypeptide ligands. The receptors and ligands perform many essential functions during growth, development and repair. Recent discoveries show that a growing number of skeletal abnormalities result from mutations in the fibroblast growth factor receptors. These findings have led to a greater understanding of the role of fibroblast growth factor signaling during skeletogenesis and have focused research interests on the effects of fibroblast growth factors on endochondral and intramembranous bone development.

Topics: Alternative Splicing; Animals; Bone Development; Bone Diseases, Developmental; Cartilage; Extremities; Fibroblast Growth Factors; Heparin; Heparitin Sulfate; Humans; Ossification, Heterotopic; Osteogenesis; Protein Structure, Tertiary; Receptors, Fibroblast Growth Factor; Signal Transduction

We studied three patients with severe skeletal dysplasia, T cell immunodeficiency, and developmental delay. Whole-exome sequencing revealed homozygous missense mutations affecting exostosin-like 3 (EXTL3), a glycosyltransferase involved in heparan sulfate (HS) biosynthesis. Patient-derived fibroblasts showed abnormal HS composition and altered fibroblast growth factor 2 signaling, which was rescued by overexpression of wild-type

Topics: Animals; Bone Diseases, Developmental; Child, Preschool; Developmental Disabilities; Female; Heparitin Sulfate; Humans; Immunologic Deficiency Syndromes; Induced Pluripotent Stem Cells; Infant; Lymphocytes; Mutation; N-Acetylglucosaminyltransferases; Zebrafish

Mucopolysaccharidoses (MPS) are a group of lysosomal storage diseases caused by mutations in lysosomal enzymes involved in degradation of glycosaminoglycans (GAGs). Patients with MPS grow poorly and become physically disabled due to systemic bone disease. While many of the major skeletal effects in mouse models for MPS have been described, no detailed analysis that compares GAGs levels and characteristics of bone by micro-CT has been done. The aims of this study were to assess severity of bone dysplasia among four MPS mouse models (MPS I, IIIA, IVA and VII), to determine the relationship between severity of bone dysplasia and serum keratan sulfate (KS) and heparan sulfate (HS) levels in those models, and to explore the mechanism of KS elevation in MPS I, IIIA, and VII mouse models. Clinically, MPS VII mice had the most severe bone pathology; however, MPS I and IVA mice also showed skeletal pathology. MPS I and VII mice showed severe bone dysplasia, higher bone mineral density, narrowed spinal canal, and shorter sclerotic bones by micro-CT and radiographs. Serum KS and HS levels were elevated in MPS I, IIIA, and VII mice. Severity of skeletal disease displayed by micro-CT, radiographs and histopathology correlated with the level of KS elevation. We showed that elevated HS levels in MPS mouse models could inhibit N-acetylgalactosamine-6-sulfate sulfatase enzyme. These studies suggest that KS could be released from chondrocytes affected by accumulation of other GAGs and that KS could be useful as a biomarker for severity of bone dysplasia in MPS disorders.

Topics: Animals; Biomarkers; Bone and Bones; Bone Density; Bone Diseases, Developmental; Chondrocytes; Disease Models, Animal; Female; Glycosaminoglycans; Heparitin Sulfate; Humans; Keratan Sulfate; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mucopolysaccharidoses; Spinal Canal; X-Ray Microtomography

The extracellular glycoprotein fibrillin-1 forms microfibrils that act as the template for elastic fibers. Most mutations in fibrillin-1 cause Marfan syndrome with severe cardiovascular and ocular symptoms, and tall stature. This is in contrast to mutations within a heparin-binding TB domain (TB5), which is downstream of the arg-gly-asp cell adhesion domain, which can cause Weill-Marchesani syndrome (WMS) or Acromicric (AD) and Geleophysic Dysplasias (GD). WMS is characterized by short limbs, joint stiffness and ocular defects, whilst fibrillin-1 AD and GD have severe short stature, joint defects and thickened skin. We previously showed that TB5 binds heparin. Here, we show that the corresponding region of fibrillin-2 binds heparin very poorly, highlighting a novel functional difference between the two isoforms. This finding enabled us to map heparin/heparan sulfate binding to two sites on fibrillin-1 TB5 using a mutagenesis approach. Once these sites were mapped, we were able to investigate whether disease-causing mutations in this domain disrupt binding to HS. We show that a WMS deletion mutant, and five AD and GD point mutants all have disrupted heparin binding to TB5. These data provide insights into the biology of fibrillins and the pathologies of WMS, AD and GD.

Topics: Binding Sites; Bone Diseases, Developmental; Cell Line; Fibrillin-1; Fibrillin-2; Fibrillins; Fibroblasts; Gene Deletion; HEK293 Cells; Heparitin Sulfate; Humans; Limb Deformities, Congenital; Microfilament Proteins; Mutagenesis; Mutation; Oligosaccharides; Protein Isoforms; Protein Structure, Tertiary; Recombinant Proteins; Weill-Marchesani Syndrome