The mouse beta B1-crystallin promoter: strict regulation of lens fiber cell specificity.
Previous studies have shown that the chicken beta B1-crystallin promoter (-434/+30) contains all of the signals necessary to specifically direct high level expression of heterologous genes to the lens fiber cells of mice. In the present study, the mouse beta B1-crystallin gene was cloned, and its regulation was investigated to further elucidate the mechanisms controlling lens fiber cell-specific gene expression. Phylogenetic footprinting analysis of the 5' flanking sequence from the mouse, rat, human and chicken beta B1-crystallin genes identified several known and putative functional cis elements including the PL2 element which is required for lens-specific expression of the chicken beta B1 promoter. Surprisingly, however, all six mouse beta B1-crystallin/CAT constructs tested (-1493/+44, -1493/+30, -870/+30, -250/+30, -135/+30 and -98/+30) were inactive in three different mammalian lens-derived cell lines while only the -870/+30 and -98/+30 constructs were active in chicken primary patched lens epithelial cells. In contrast, the chicken beta B1-crystallin promoter (-434/+30) was transcriptionally active in all lens-derived cells tested. Transgenic mice harboring a mouse beta B1-crystallin -1493/+44 CAT construct did express the transgene specifically in lens fiber cells, however, at lower levels than that previously reported for a chicken -434/+30 CAT construct. These data suggest that, as in other crystallin genes, the regulatory signals controlling lens fiber cell-specific expression are conserved between chicken and mouse. However, the inability of the mouse beta B1-crystallin promoter to function in mammalian lens-derived cultured cells implies that this gene has acquired additional cis-regulatory elements to ensure lens fiber cell specificity.
Chen
W V
WV
Department of Biological Sciences, University of Delaware, Newark, 19716, USA.
Fielding Hejtmancik
J
J
Piatigorsky
J
J
Duncan
M K
MK
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002645:Chickens; D003001:Cloning, Molecular; D003459:Crystallins / Q000235:genetics*; D018983:DNA Footprinting; D018076:DNA, Complementary / Q000096:biosynthesis / Q000737:chemistry; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics*; D007150:Immunohistochemistry; D007908:Lens, Crystalline / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D014162:Transfection; D038206:beta-Crystallin B Chain
C491363:Crybb1 protein, mouse; D003459:Crystallins; D018076:DNA, Complementary; D038206:beta-Crystallin B Chain