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.