Meeting Abstract

P1.34  Monday, Jan. 4  Investigation of Cadherin Expression During Secondary Neurulation in the Chick Tail Bud OLSON, K.E.**; WIENS, D.J.; Univ. of Northern Iowa, Cedar Falls; Univ. of Northern Iowa, Cedar Falls wiens@uni.edu

Cadherins are a group of cell adhesion molecules that help mediate cell interactions involved in cell migration and organogenesis during development. Cadherin expression has been studied in the development of the primary neural tube (NT) and migrating neural crest cells in chicken, mouse, and rat, but not during secondary neurulation in the chick. Following formation of the primary NT during embryonic development, secondary neurulation occurs at three days by cavitation in the mesenchyme of the tail bud, a process that is expected to require dynamic changes in cell adhesion. We investigated the expression patterns of N-cadherin (N-cad), E-cadherin (E-cad), cadherin-6B (cad-6B), cadherin-7 (cad-7), and cadherin-11 (cad-11) in the tail bud during Hamburger and Hamilton stages 15, 17, and 19-21 using immunolocalization. At stage 15, only E-cad staining was found. At stage 17, low to medium staining of only N-cad and cad-11 was documented in the secondary NT. By stage 19 (17 hours later) N-cad was highly expressed in the secondary NT, notochord, and tail bud somites. Positive staining for E-cad was still observed in the epithelium of the skin, as expected. Cad-6B was positively stained in the dorsal secondary NT and in the floor plate at the distal end of the tail bud. Cad-7 was expressed with low to medium intensity in the dorsal-most region of the secondary NT. Cad-11 expression was observed in the tail bud somites, the secondary NT, and the mesenchyme of the tail bud. Our findings show that expression of cadherins becomes more abundant in the secondary NT as development progresses suggesting an involvement in cell organization. We are investigating the intervening stages to further define the dynamic pattern of cadherin expression during secondary neurulation.