title: Modulated expression of type X collagen in Meckel's cartilage with different developmental fates.
abstract: Mammalian Meckel's cartilage undergoes regionally diverse histodifferentiation: the caudal end of Meckel's cartilage extends to the developing ear and gives rise to malleus and incus through endochondral ossification while its major distal region differentiates into sphenomandibular ligament and the anterior ligament of the malleus tympanic plate through fibrous transformation. Since the entire Meckel's cartilage develops up to chondrocyte hypertrophy, the regional extracellular matrix components in the hypertrophic Meckel's cartilage may differ in association with the diverse developmental fates. In this project, the expressions of cartilage collagens were investigated in developing rat Meckel's cartilage and particular interest was given to type X collagen. A cDNA, HP114, encoding the NC1 domain of rat alpha 1(X) collagen was cloned, and a synthetic peptide based on the sequence deduced from HP114 was used to generate a monospecific antibody. In situ hybridization of newborn rat condylar and angular cartilages undergoing endochondral ossification showed restricted labeling with the alpha 1(X) collagen probe in the hypertrophic chondrocyte layer. In contrast, the alpha 1(X) collagen probe totally failed to label the major distal portion of Meckel's cartilage even in the hypertrophic cartilage zone. Immunohistochemistry using the anti-type X collagen monospecific antibody consistently failed to recognize the epitope in the corresponding portion of Meckel's cartilage throughout the experimental periods of gestational Day 17, newborn, and Postnatal Day 7, while the strictly localized positive staining was found in the posterior part of Meckel's cartilage which gave rise to malleus and incus. Since major cartilage collagens type II and type IX were found to be present throughout Meckel's cartilage, we postulate that the regulatory molecular mechanism of type X collagen expression may be closely associated with the developmental fates of fibrous transformation and endochondral ossification in mammalian Meckel's cartilage.
authors.affiliation: Department of Orthodontics, Harvard School of Dental Medicine, Boston, Massachusetts 02115, USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Chung
authors.forename: H H
authors.initials: HH
authors.lastname: Park
authors.forename: K
authors.initials: K
authors.lastname: Ting
authors.forename: H
authors.initials: H
authors.lastname: Takita
authors.forename: S S
authors.initials: SS
authors.lastname: Apte
authors.forename: Y
authors.initials: Y
authors.lastname: Kuboki
authors.forename: I
authors.initials: I
authors.lastname: Nishimura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D002358:Cartilage, Articular / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism*; D003001:Cloning, Molecular; D003094:Collagen / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D015342:DNA Probes; D018076:DNA, Complementary / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D008334:Mandible / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000911:Antibodies, Monoclonal; D017931:DNA Primers; D015342:DNA Probes; D018076:DNA, Complementary; D010446:Peptide Fragments; D003094:Collagen