Characterization of tetracycline-inducible bitransgenic Krt12rtTA/+/tet-O-LacZ mice.
OBJECTIVE
To prepare binary transgenic mouse lines that overexpress reporter genes in a corneal-epithelium-specific manner when induced by doxycycline.


METHODS
A gene-targeting construct containing an internal ribosomal entry site-reverse tetracycline transcription activator (IRES-rtTA) cassette was inserted into the Krt12 allele (keratin 12 gene) to produce a knock-in Krt12(rtTA/+) mouse line through gene-targeting techniques. The Krt12(rtTA/+) knock-in mice were bred with tet-O-LacZ reporter mice to obtain Krt12(rtTA/+)/tet-O-LacZ bitransgenic mice. The expression of the LacZ gene was induced in bitransgenic mice by administration of doxycycline in the drinking water and chow.


RESULTS
Administration of doxycycline induced a 15-fold increase of beta-galactosidase activity in the cornea of adult bitransgenic mice (Krt12(rtTA/+)/tet-O-lacZ). Administration of doxycycline either to single transgenic Krt12(rtTA/+) or tet-O-LacZ mice as a control did not induce overexpression of LacZ as it did in the bitransgenic mice. The induction of beta-galactosidase enzyme activity by doxycycline in bitransgenic mice took place in 24 hours and reached a plateau by 2 days. Histochemical analysis also showed that beta-galactosidase induction was limited to the corneal epithelium of bitransgenic mice fed doxycycline. The increased beta-galactosidase activity in corneal epithelium caused by doxycycline returned to basal levels in 4 weeks after the antibiotics were omitted from the diet.


CONCLUSIONS
A binary mouse model has been successfully established that conditionally overexpresses reporter genes in corneal epithelium. This mouse model will be useful in elucidating signaling pathways of various growth factors and cytokines and gene functions in the maintenance of homeostasis and pathogenesis in the adult mouse cornea.
Chikama
Tai-Ichiro
T
Department of Ophthahlmology, University of Cincinnati, Ohio 45267, USA.
Hayashi
Yasuhito
Y
Liu
Chia-Yang
CY
Terai
Noriko
N
Terai
Kazuto
K
Kao
Candace W-C
CW
Wang
Li
L
Hayashi
Miyuki
M
Nishida
Teruo
T
Sanford
Philip
P
Doestchman
Tom
T
Kao
Winston W-Y
WW
D000818:Animals; D019677:Artificial Gene Fusion; D015153:Blotting, Western; D004318:Doxycycline / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology*; D018390:Gene Targeting; D017930:Genes, Reporter / Q000502:physiology*; D005822:Genetic Vectors; D005838:Genotype; D053551:Keratin-12; D007633:Keratins / Q000235:genetics*; D007763:Lac Operon / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D012333:RNA, Messenger / Q000378:metabolism; D013752:Tetracycline; D015533:Transcriptional Activation; D019076:Transgenes; D001616:beta-Galactosidase / Q000096:biosynthesis
C507495:KRT12 protein, mouse; D053551:Keratin-12; D012333:RNA, Messenger; D007633:Keratins; D001616:beta-Galactosidase; D013752:Tetracycline; D004318:Doxycycline