Isolation and characterization of the mouse liver/bone/kidney-type alkaline phosphatase gene

The gene coding for the mouse alkaline phosphatase expressed in liver, bone, kidney and placenta (liver/bone/kidney-type alkaline phosphatase, L/B/K-ALP) was isolated and characterized. This gene consists of 12 exons and it is at least 49 kb long. The first two exons are separated by a long intron which is at least 32 kb in size, whereas the other exons span within the remaining 17 kb. Primer extension and S1-nuclease mapping analyses with placental mRNA demonstrate a single major transcription start site, which is preceded by a G + C-rich region containing a TATA-like sequence and three copies of the consensus binding site for the transcription factor Sp1. Transfection experiments using two different reporter genes show that the 5′-flanking region of the gene is active as a promoter in undifferentiated F9 teratocarcinoma cells, but not in 3T3 fibroblasts, consistent with the L/B/K-ALP mRNA level in the two cell lines. As expected from the sequence similarity at the cDNA level, the structural organization of the mouse gene is similar to that of the human and rat L/B/K-ALP genes, suggesting that they all derive from a single ancestral gene.