title: Conditional inactivation of Has2 reveals a crucial role for hyaluronan in skeletal growth, patterning, chondrocyte maturation and joint formation in the developing limb.
abstract: The glycosaminoglycan hyaluronan (HA) is a structural component of extracellular matrices and also interacts with cell surface receptors to directly influence cell behavior. To explore functions of HA in limb skeletal development, we conditionally inactivated the gene for HA synthase 2, Has2, in limb bud mesoderm using mice that harbor a floxed allele of Has2 and mice carrying a limb mesoderm-specific Prx1-Cre transgene. The skeletal elements of Has2-deficient limbs are severely shortened, indicating that HA is essential for normal longitudinal growth of all limb skeletal elements. Proximal phalanges are duplicated in Has2 mutant limbs indicating an involvement of HA in patterning specific portions of the digits. The growth plates of Has2-deficient skeletal elements are severely abnormal and disorganized, with a decrease in the deposition of aggrecan in the matrix and a disruption in normal columnar cellular relationships. Furthermore, there is a striking reduction in the number of hypertrophic chondrocytes and in the expression domains of markers of hypertrophic differentiation in the mutant growth plates, indicating that HA is necessary for the normal progression of chondrocyte maturation. In addition, secondary ossification centers do not form in the central regions of Has2 mutant growth plates owing to a failure of hypertrophic differentiation. In addition to skeletal defects, the formation of synovial joint cavities is defective in Has2-deficient limbs. Taken together, our results demonstrate that HA has a crucial role in skeletal growth, patterning, chondrocyte maturation and synovial joint formation in the developing limb.
authors.affiliation: Sanford Children's Health Research Center, Burnham Institute for Medical Research, La Jolla, CA 92037, USA.
authors.forename: Kazu
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Yingcui
authors.initials: Y
authors.lastname: Li
authors.forename: Caroline
authors.initials: C
authors.lastname: Jakuba
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Sugiyama
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sayo
authors.forename: Misako
authors.initials: M
authors.lastname: Okuno
authors.forename: Caroline N
authors.initials: CN
authors.lastname: Dealy
authors.forename: Bryan P
authors.initials: BP
authors.lastname: Toole
authors.forename: Junji
authors.initials: J
authors.lastname: Takeda
authors.forename: Yu
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Robert A
authors.initials: RA
authors.lastname: Kosher
mesh_terms: D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D019521:Body Patterning / Q000502:physiology; D001846:Bone Development / Q000502:physiology*; D049109:Cell Proliferation; D019902:Chondrocytes / Q000166:cytology / Q000502:physiology*; D024121:Collagen Type X / Q000235:genetics / Q000378:metabolism; D005109:Extracellular Matrix / Q000737:chemistry / Q000378:metabolism; D005121:Extremities / Q000196:embryology / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000235:genetics / Q000378:metabolism*; D007596:Joints / Q000002:abnormalities / Q000196:embryology / Q000254:growth & development; D017880:Limb Deformities, Congenital / Q000235:genetics; D008648:Mesoderm / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout
chemical_list: D053674:Aggrecans; D024121:Collagen Type X; D053823:Hedgehog Proteins; C514061:ihh protein, mouse; D006820:Hyaluronic Acid; D014453:Glucuronosyltransferase; C491099:Has2 protein, mouse; D000076002:Hyaluronan Synthases