SPATIAL AND TEMPORAL EXPRESSION OF SYNDECAN – 2 IN CHICK HEART DEVELOPMENT

Abstract

Syndecan – 2 (syn2) is a member of the syndecan family of cell surface heparan sulfate (HS) proteoglycans. While various heparan sulfate proteoglycans mediate events such as cell adhesion, growth factor binding, syn2 has been shown to participate in organizing fibrillar matrices and in axis determination during development. To examine the distribution of syn2 during cardiogenesis, embryonic chick hearts were subjected to immunohistochemical analysis using a syn2-specific polyclonal antibody (R1891). Upon examination of paraffin-embedded thick sections, syn2 exhibited a developmental and a tissue-type specific pattern of expression. Although syn2 was previously reported in the condensing mesenchyme of murine limb tissue, syn2 was not detected in the chick mesenchymal tissue, in either the atrioventricular or outflow tract regions. Interestingly, cardiac muscle throughout the heart expressed syn2 in a developmentally regulated pattern. Syndecan-2 was noticeably absent in early hearts (Hamburger-Hamilton stages 12–14); however, by stages 15–17, cardiac muscle began to exhibit detectable syn2 staining. During later stages of cardiogenesis (stages 19 – 24), syn2 became widely expressed throughout all cardiac muscle. These results demonstrate the presence and the developmental pattern of syn2 during cardiogenesis. From previous studies on the role of syn2 during other developmental processes, it is possible that this proteoglycan is also functioning as a matrix organizer or as an axis-determining molecule during critical stages of cardiac morphogenesis.