CHARACTERIZATION AND EXPRESSION OF THE MOUSE LUMICAN GENE

Lumican is one of the major keratan sulfate proteoglycans (KSPG) in ve rtebrate corneas. We previously cloned the murine lumican cDNA. This s tudy determines the structure of murine lumican gene (Lum) and its exp ression during mouse embryonic developments. The mouse lumican gene wa s isolated from a bacterial artificial chromosome mouse genomic DNA li brary and characterized by polymerase chain reaction and Southern hybr idization. The lumican gene spans 6.9 kilobase pairs of mouse genome. The gene consists of three exons and two introns. Exon 1 constitutes 8 8 bases (b) of untranslated sequence. Exon 2 is 883 b and contains mos t of the coding sequence of lumican mRNA, and exon 3 has 152 b of codi ng sequence and 659 b of 3' noncoding sequence. The mouse lumican gene has a TATCA element, a presumptive TATA box, which locates 27 b 5'-up stream from the transcription initiation site, Northern hybridization and in situ hybridization indicate that ill early stages of embryonic development, day 7 post coitus the embryo expresses little or no lumic an, Thereafter, different levels of lumican mRNA can be detected in va rious organ systems, such as cornea stroma, dermis, cartilage, heart, lung, and kidney. The cornea and heart are the two tissues that have t he highest expression in adult. Immunoblotting studies found that KSPG core proteins became abundant in the cornea and sclera by postnatal d ay 10 but that sulfated KSPG could not be detected until after the eye s open. These results indicate that. lumican is widely distributed in most interstitial connective tissues, The modification of lumican with keratan sulfates in cornea is concurrent with eye opening and may con tribute to corneal transparency.