SEQUENCE, MOLECULAR-PROPERTIES, AND CHROMOSOMAL MAPPING OF MOUSE LUMICAN

Purpose. Lumican is a major proteoglycan of vertebrate cornea. This st udy characterizes mouse lumican, its molecular form, cDNA sequence, an d chromosomal localization. Methods. Lumican sequence was determined f rom cDNA clones selected from a mouse corneal cDNA expression library using a bovine lumican cDNA probe. Tissue expression and size of lumic an mRNA were determined using Northern hybridization. Glycosidase dige stion followed by Western blot analysis provided characterization of m olecular properties of purified mouse corneal lumican. Chromosomal map ping of the lumican gene (Lcn) used Southern hybridization of a panel of genomic DNAs from an interspecific murine backcross. Results. Mouse lumican is a 338-amino acid protein with high-sequence identity to bo vine and chicken lumican proteins. The N-terminus of the lumican prote in contains consensus sequences for tyrosine sulfation. A 1.9-kb lumic an mRNA is present in cornea and several other tissues. Antibody again st bovine lumican reacted with recombinant mouse lumican expressed in Escherichia coli and also detected high molecular weight proteoglycans in extracts of mouse cornea. Keratanase digestion of corneal proteogl ycans released lumican protein, demonstrating the presence of sulfated keratan sulfate chains on mouse corneal lumican in vivo. The lumican gene (Lcn) was mapped to the distal region of mouse chromosome 10. The Lcn map site is in the region of a previously identified developmenta l mutant, eye blebs, affecting corneal morphology. Conclusions. This s tudy demonstrates sulfated keratan sulfate proteoglycan in mouse corne a and describes the tools (antibodies and cDNA) necessary to investiga te the functional role of this important corneal molecule using natura lly occurring and induced mutants of the murine lumican gene.