SM37, a skeletogenic gene of the sea urchin embryo linked to the SM50 gene

The genomic DNA region that contains the SM50 gene also included a second gene that appeared to encode another skeletogenic matrix protein. The two genes were linked at a distance of about 12 kb. Based on the molecular weight of the implied protein the gene was termed SM37. The SM37 protein included a long tandem sequence of short glycine-rich repeats that was similar to the glycine-rich repeats included in the SM50 protein and several other skeletal matrix proteins, although the sequence of SM37 repeat was distinct. The overall structure of the SM37 protein was similar to SM50 as well. However, SM37 was only about 30% identical in amino acid sequence to SM50, and coding region probes behaved as a single copy sequence under standard conditions. The SM37 gene included the same cis-regulatory elements as the SM50 gene, although in a different order with respect to transcription. This gene was regulated coordinately with SM50 during development, and like SM50 was expressed exclusively in skeletogenic mesenchyme lineages