title: The role of hyaluronan produced by Has2 gene expression in development of the spine.
abstract: METHODS
  Histologic analysis of spine development in cartilage-specific knockout mice.
  
  
  OBJECTIVE
  To evaluate the role hyaluronan produced by hyaluronan synthase-2 (Has2) in spine development.
  
  
  BACKGROUND
  The Has2 gene is responsible for most hyaluronan production throughout the body, including the skeleton. However, it is not possible to study the involvement of hyaluronan in skeletal development using constitutive Has2 knockout mice, as the embryonic mice die early before skeletal development has occurred. This problem can be overcome by the use of cartilage-specific knockout mice.
  
  
  METHODS
  Mice possessing floxed Has2 genes were crossed with mice expressing Cre recombinase under control of the type II collagen promoter to generate cartilage-specific Has2 knockout mice. Spine development was studied by histology.
  
  
  RESULTS
  Knockout mice died near birth and displayed severe abnormality in skeletal development. The spine showed defects in vertebral body size and the formation of the intervertebral discs. There was no evidence for the formation of an organized primary center of ossification within the vertebrae, and the appearance and organization of the hypertrophic chondrocytes was abnormal. Although no organized endochondral ossification appeared to be taking place, there was excessive bone formation at the center of the vertebrae. There was also a generalized increased cellularity of the vertebral cartilage and a corresponding decrease in the abundance of extracellular matrix. The nucleus pulposus of the intervertebral discs were less flattened than in the control mice and possessed an increased amount of large vacuolated cells. Remnants of the notochord could also be seen between adjacent discs.
  
  
  CONCLUSIONS
  Hyaluronan production by Has2 is essential for normal vertebral and intervertebral disc development within the spine, and the absence of this synthase impairs the organization of both soft and hard tissue elements.
authors.affiliation: Genetics Unit, Shriners Hospital for Children, McGill University, Montreal, Quebec, Canada. proughley@shriners.mcgill.ca
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Roughley
authors.forename: Lisa
authors.initials: L
authors.lastname: Lamplugh
authors.forename: Eunice R
authors.initials: ER
authors.lastname: Lee
authors.forename: Kazu
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Yu
authors.initials: Y
authors.lastname: Yamaguchi
mesh_terms: D053674:Aggrecans / Q000096:biosynthesis; D000818:Animals; D001842:Bone and Bones / Q000002:abnormalities / Q000378:metabolism; D002356:Cartilage / Q000378:metabolism; D024043:Collagen Type II / Q000235:genetics; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D014453:Glucuronosyltransferase / Q000235:genetics* / Q000378:metabolism; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000096:biosynthesis / Q000502:physiology*; D007150:Immunohistochemistry; D019426:Integrases / Q000235:genetics / Q000378:metabolism; D007403:Intervertebral Disc / Q000196:embryology / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic / Q000235:genetics; D013131:Spine / Q000196:embryology / Q000378:metabolism*; D013997:Time Factors
chemical_list: D053674:Aggrecans; D024043:Collagen Type II; D006820:Hyaluronic Acid; D014453:Glucuronosyltransferase; C491099:Has2 protein, mouse; D000076002:Hyaluronan Synthases; C045073:Cre recombinase; D019426:Integrases