Meeting Abstract

P3.26  Saturday, Jan. 5  locating abaxial cells of the sternal rib in stage x+ somites WINSLOW, B. B.*; SHEARMAN, R. M.; BURKE, A. C.; Wesleyan University; Wesleyan University; Wesleyan University bwinslow@wesleyan.edu

The chick rib is a structure that differentiates in two embryonic environments. The vertebral portion of the rib consists of somitic chondroblasts that differentiate in somitic derived connective tissue and is therefore defined as primaxial. Our previous work demonstrates that the sternal component of the rib is abaxial, meaning though the rib chondroblasts are somite derived, they are enveloped by lateral plate connective tissue that will form the periosteum. Data suggest that abaxial cells are not committed to a specific fate prior to migration, but are patterned once in the abaxial domain. Consistent with this, transplants of thoracic level segmental plate to the cervical region result in ectopic vertebral ribs, but an absence of the abaxial sternal ribs. Our goal is to develop a strategy for selective labeling of abaxial cells in thoracic somities. Our working hypothesis states that abaxial cells are not committed to a specific fate prior to migration. We will test this by examining the fate of sternal rib cells when transplanted to the cervical region. We are selectively labeling specific areas of stage X+ somites in ovo by confined micro-electroporation of plasmid vectors encoding alkaline phosphatase or green fluorescent protein. Preliminary data suggest that middle portions of HH stage 17-19 thoracic somites contain both primaxial and abaxial cells, and anteriolateral corners may contain only abaxial cells.