SPATIAL AND TEMPORAL DISTRIBUTION OF LAMPRIN MESSENGER-RNA DURING CHONDROGENESIS OF TRABECULAR CARTILAGE IN THE SEA LAMPREY

The temporal and spatial expression patterns of lamprin, the principle structural protein in lamprey cartilages, were examined by in situ hy bridization during chondrogenesis in day 17-33 post-fertilization prol arval lampreys. Lamprin mRNA transcripts were first detected during da y 19, concomitant with the end of the condensation phase of chondrogen esis and the initiation of matrix synthesis as indicated by light micr oscopic examination. In the stages which followed, the hybridization s ignal increased with progressive intensity, paralleling matrix synthes is, suggesting transcriptional control of lamprin gene expression. Spa tially, lamprin expression patterns mirrored the rostrocaudal developm ent of the trabecular cartilage rudiment. No signal was detected over adjacent tissues or control sections. Some similarities exist between the temporal patterns of lamprin expression and the expression of matr ix proteins such as elastin and collagen of higher vertebrates. It is concluded that certain aspects of chondrogenesis are critical to the n ormal development of a functional cartilaginous matrix and are conserv ed throughout the vertebrate taxa.