TRANSIENT CALRETININ EXPRESSION DURING INTERVERTEBRAL DISC FORMATION OF THE CHICK-EMBRYO

Calretinin immunoreactivity was localized during chick embryonic cervi cal spine development from day 4 until day 16. A transitory expression of calretinin could be seen from embryonic day 5 to embryonic day 15 in the mesenchymal cells forming the intervertebral disc. Calretinin w as most abundant at embryonic day 8 when a maximal proliferation of ce lls occurred. At embryonic day 12, calretinin positive fibroblasts wer e located along the fibers forming the annulus fibrosus. At embryonic day 16, calretinin immunoreactivity could no more be detected in the c ervical column. In conclusion, an intracellular calcium binding protei ns belonging to the calmodulin/troponin C superfamily, appeared to be a marker for the disc formation.