Promoter methylation is associated with the age-dependent loss of N-cadherin in the rat kidney.
The cadherins are cell adhesion molecules required for cellular homeostasis, and N-cadherin is the predominant cadherin expressed in proximal tubular epithelial cells in humans and rats. Our laboratory previously reported an age-dependent decrease in renal N-cadherin expression; the levels of N-cadherin mRNA and protein expression decreased in parallel, implicating a transcriptional mechanism in the age-dependent loss of expression (19). In this study, we examined the hypothesis that promoter hypermethylation underlies the loss of N-cadherin expression in aging rat kidney. We cloned the 5' flanking region of the rat N-cadherin gene and observed basic promoter activity in a 3,992-bp region localized immediately upstream of the ATG start site. Nucleotide analysis revealed 87% identity with the human N-cadherin minimal promoter region. Consistent with a role for regulation by DNA methylation, we found that a dense CpG island, which spans 1,104 bp (-1,158 to -55), flanks the rat N-cadherin gene; a similar CpG profile was found in the human N-cadherin 5' flanking region. Methylation-specific PCR analysis demonstrated that the promoter region of N-cadherin is heavily methylated in aged, but not young, rat kidney. Interestingly, the promoter is not methylated in age-matched, calorically restricted animals. In contrast, the promoter region is not methylated in either young or aged rat liver; this corresponds to the finding that aging is not associated with decreased N-cadherin expression in the liver. In addition, N-cadherin expression is markedly induced in NRK-52E cells treated with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine, further suggesting that methylation at CpG in the promoter region may underlie the age-dependent decrease in renal N-cadherin expression.
Akintola
Adebayo D
AD
Department of Systems Biology and Translational Medicine, College of Medicine, Texas A & M Health Science Center, College Station, TX 77843-1114, USA.
Crislip
Zachary L
ZL
Catania
Jeffrey M
JM
Chen
Gang
G
Zimmer
Warren E
WE
Burghardt
Robert C
RC
Parrish
Alan R
AR
D000375:Aging / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003596:Cytosine / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000235:genetics; D006147:Guanine / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D051381:Rats; D011916:Rats, Inbred F344
D015820:Cadherins; D004791:Enzyme Inhibitors; D006147:Guanine; D000077209:Decitabine; D003596:Cytosine; D004247:DNA; D001374:Azacitidine