IN-VITRO DETECTION OF CALRETININ IMMUNOREACTIVITY IN CHICKEN-EMBRYO DORSAL-ROOT GANGLION NEURONS - A POSSIBLE DEVELOPMENTAL MARKER

Calretinin, a cytosolic calcium-binding protein, is widely expressed i n mammalian and chicken neurons, including subpopulations of dorsal ro ot ganglion neurons. In chicken embryo spinal ganglion cells, calretin in first appears on the 9th day of incubation. To determine whether th e expression of this protein is maintained in vitro and depends on the developmental stage, dissociated dorsal root ganglion cultures from c hick embryos at E6 and E10 (before or after establishing connections) were processed for calretinin immunohistochemistry. Cultured neurons f rom E6 embryos never showed calretinin immunoreactivity at any culture duration, whereas neurons from E10 embryos displayed strong immunosta ining immediately after attaching to the culture dish. Quantitative ev aluation revealed that the percentage of calretinin-positive neurons i ncreased until day 3 in culture and afterwards declined in parallel th e total cell number. These results indicate that primary sensory neuro ns express calretinin in vitro similarly as in vivo and the gene expre ssion depends from the establishment of connections with peripheral ta rgets.