Enhancer-independent promoter activity of the mouse alphaB-crystallin/small heat shock protein gene in the lens and cornea of transgenic mice.
The alphaB-crystallin/small heat shock protein gene is expressed very highly in the mouse eye lens and to a lesser extent in many other nonocular tissues, including the heart, skeletal muscle and brain. Previously we showed in transgenic mice that lens-specific alphaB-crystallin promoter activity is directed by a proximal promoter fragment (-164/+44) and that non-lens promoter activity depends on an upstream enhancer (-427/-259) composed of at least 5 cis-control elements. Here we have used truncated alphaB-crystallin promoter-CAT transgenes to test by biphasic CAT assays and/or histochemistry for specific expression in the cornea and lens. Deletion either of 87 bp (-427/-340) from the 5' end of the alphaB-crystallin enhancer or of the whole enhancer (-427/-258) abolished alphaB-crystallin promoter activity in all tissues except the lens and corneal epithelium when examined by the biphasic CAT assay in 4-5-week-old transgenic mice. These truncations also lowered promoter strength in the lens. The -426/+44-CAT, -339/+44-CAT and -164/+44-CAT (previously thought to be lens-specific in transgenic mice) transgenes were all expressed in the 4-6-week-old corneal epithelium when examined histochemically. Immunohistochemical staining confirmed the presence of endogenous alphaB-crystallin in the mature corneal epithelial cells. CAT gene expression driven by the alphaB-crystallin promoter with or without the enhancer was evident in the embryonic and 4-6-week-old lens. By contrast, activity of the alphaB-crystallin promoter/enhancer-CAT transgene was not detectable in the corneal epithelium before birth. Taken together, these results indicate that the intact enhancer of the alphaB-crystallin/small heat shock protein gene is required for promoter activity in all tissues tested except the lens and cornea.
Gopal-Srivastava
R
R
Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892-2730, USA.
Kays
W T
WT
Piatigorsky
J
J
D000818:Animals; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D003315:Cornea / Q000502:physiology*; D003459:Crystallins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D019573:Epithelium, Corneal / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D007908:Lens, Crystalline / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic; D019076:Transgenes
D003459:Crystallins; D006360:Heat-Shock Proteins; D015500:Chloramphenicol O-Acetyltransferase