Spatial and temporal distribution of lamprin mRNA 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 hybridization during chondrogenesis of trabecular cartilage in day 17-33 post-fertilization prolarval lampreys. Lamprin mRNA transcripts were first detected during day 19, concomitant with the end of the condensation phase of chondrogenesis and the initiation of matrix synthesis as indicated by light microscopic examination. In the stages which followed, the hybridization signal increased with progressive intensity, paralleling matrix synthesis, suggesting transcriptional control of lamprin gene expression. Spatially, lamprin expression patterns mirrored the rostrocaudal development 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 matrix proteins such as elastin and collagen of higher vertebrates. It is concluded that certain aspects of chondrogenesis are critical to the normal development of a functional cartilaginous matrix and are conserved throughout the vertebrate taxa.