Expression of Chr9p21 genes CDKN2B (p15(INK4b)), CDKN2A (p16(INK4a), p14(ARF)) and MTAP in human atherosclerotic plaque.
OBJECTIVE
The pathophysiology underlying the chromosome (Chr) 9p21 locus of atherosclerosis susceptibility is presently unknown. Here, we sought to determine whether protein coding genes in the Chr9p21 region, i.e. cyclin-dependent kinase inhibitors CDKN2B (p15(INK4b)), CDKN2A (p16(INK4a), p14(ARF)) and methylthioadenosine phosphorylase (MTAP) were expressed in human atherosclerotic lesions and whether expression was correlated with lesion composition.


RESULTS
Protein expression of p15(INK4b), p16(INK4a), p14(ARF) and MTAP was demonstrated by immunostaining in normal and atherosclerotic coronary arteries and co-localized with CD68 and smooth muscle alpha-actin positive cells. Quantitative RT-PCR in human endarteryectomy specimens (n = 57) revealed increased p16(INK4a) and decreased MTAP expression in macrophage-rich lesions (P<0.001 and P = 0.007, respectively). Functional studies suggest that decreased MTAP expression in macrophage-rich lesions might be mediated through down-regulation by TNF-alpha. No clear association of p15(INK4b), p16(INK4a), p14(ARF), and MTAP expression in plaque tissue with Chr9p21 haplotypes was found. The latter finding was corroborated by the lack of correlation of RNA expression of 9p21-regulated transcripts EU741058 and NR_003529 of antisense non-coding RNA in the INK4 locus (ANRIL) with mRNA expression of these genes. In contrast, ANRIL DQ485454 which is not genetically determined by the 9p21 genotype was significantly correlated with MTAP expression (P = 0.01).


CONCLUSIONS
CDKN2B (p15(INK4b)), CDKN2A (p16(INK4a), p14(ARF)), and MTAP are abundantly expressed in atherosclerotic lesions. While expression levels showed no clear association with Chr9p21 genotype, association of high p16(INK4a) and low MTAP expression with a less stable plaque phenotype suggests a more general role of these proteins in atherogenesis.
Holdt
Lesca Miriam
LM
Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, University Leipzig, Leipzig, Germany.
Sass
Kristina
K
Gäbel
Gábor
G
Bergert
Hendrik
H
Thiery
Joachim
J
Teupser
Daniel
D
D000199:Actins / Q000032:analysis; D015703:Antigens, CD / Q000032:analysis; D015214:Antigens, Differentiation, Myelomonocytic / Q000032:analysis; D001344:Autopsy; D002899:Chromosomes, Human, Pair 9; D003324:Coronary Artery Disease / Q000201:enzymology / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D050762:Cyclin-Dependent Kinase Inhibitor p15 / Q000032:analysis / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis / Q000235:genetics*; D004691:Endarterectomy; D020022:Genetic Predisposition to Disease; D057809:HEK293 Cells; D006239:Haplotypes; D006801:Humans; D007150:Immunohistochemistry; D008264:Macrophages / Q000737:chemistry; D010641:Phenotype; D011683:Purine-Nucleoside Phosphorylase / Q000032:analysis / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis; D025803:Tumor Suppressor Protein p14ARF / Q000032:analysis / Q000235:genetics*; D000097382:CD68 Molecule
D000199:Actins; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D011683:Purine-Nucleoside Phosphorylase; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D025803:Tumor Suppressor Protein p14ARF; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C493966:CDKN2B protein, human; C021784:5'-methylthioadenosine phosphorylase