A lacZ and neo cassette replaced exon 1 and part of intron 1 of the locus. LoxP sites flanked the neo. Mutant embryos expressed lacZ in the dorsal spinal cord, in the lung bud and in the developing choroids plexus. In the newborn, high expression was observed in osteocytes, but surprisingly not in tissues shown to express Pdpn, such as lung and kidney.