Wang Wei, Oh Seon, Koester Mark, Abramowicz Sandra, Wang Nan, Tall Alan R, Welch Carrie L
From the Department of Medicine, Division of Molecular Medicine, Columbia University, New York, NY.
Circ Cardiovasc Genet. 2016 Jun;9(3):213-22. doi: 10.1161/CIRCGENETICS.115.001294. Epub 2016 Apr 20.
Genome-wide association studies for coronary artery disease/myocardial infarction revealed a 58 kb risk locus on 9p21.3. Refined genetic analyses revealed unique haplotype blocks conferring susceptibility to atherosclerosis per se versus risk for acute complications in the presence of underlying coronary artery disease. The cell proliferation inhibitor locus, CDKN2A, maps just upstream of the myocardial infarction risk block, is at least partly regulated by the noncoding RNA, ANRIL, overlapping the risk block, and has been associated with platelet counts in humans. Thus, we tested the hypothesis that CDKN2A deficiency predisposes to increased platelet production, leading to increased platelet activation in the setting of hypercholesterolemia.
Platelet production and activation were measured in B6-Ldlr(-/-)Cdkn2a(+/-) mice and a congenic strain carrying the region of homology with the human 9p21.3/CDKN2A locus. The strains exhibit decreased expression of CDKN2A (both p16(INK4a) and p19(ARF)) but not CDKN2B (p15(INK4b)). Compared with B6-Ldlr(-/-) controls, both Cdkn2a-deficient strains exhibited increased platelet counts and bone marrow megakaryopoiesis. The platelet overproduction phenotype was reversed by treatment with cyclin-dependent kinase 4/6 inhibitor, PD0332991/palbociclib, that mimics the endogenous effect of p16(INK4a). Western diet feeding resulted in increased platelet activation, increased thrombin/antithrombin complex, and decreased bleeding times in Cdkn2a-deficient mice compared with controls.
Together, the data suggest that one or more Cdkn2a transcripts modulate platelet production and activity in the setting of hypercholesterolemia, amenable to pharmaceutical intervention. Enhanced platelet production and activation may predispose to arterial thrombosis, suggesting an explanation, at least in part, for the association of 9p21.3 and myocardial infarction.
冠状动脉疾病/心肌梗死的全基因组关联研究揭示了9p21.3上一个58 kb的风险位点。精细的基因分析显示，独特的单倍型块赋予了动脉粥样硬化本身的易感性，而不是存在潜在冠状动脉疾病时急性并发症的风险。细胞增殖抑制剂基因座CDKN2A位于心肌梗死风险块的上游，至少部分受非编码RNA ANRIL调控，与风险块重叠，并且与人类血小板计数有关。因此，我们检验了以下假设：CDKN2A缺乏易导致血小板生成增加，从而在高胆固醇血症情况下导致血小板活化增加。
在B6-Ldlr(-/-)Cdkn2a(+/-)小鼠和携带与人9p21.3/CDKN2A基因座同源区域的同基因品系中测量血小板生成和活化。这些品系表现出CDKN2A（p16(INK4a)和p19(ARF)）表达降低，但CDKN2B（p15(INK4b)）表达未降低。与B6-Ldlr(-/-)对照相比，两个Cdkn2a缺陷品系均表现出血小板计数增加和骨髓巨核细胞生成增加。用细胞周期蛋白依赖性激酶4/6抑制剂PD0332991/帕博西尼治疗可逆转血小板过度生成表型，该抑制剂模拟了p16(INK4a)的内源性作用。与对照相比，西方饮食喂养导致Cdkn2a缺陷小鼠的血小板活化增加、凝血酶/抗凝血酶复合物增加以及出血时间缩短。
总之，数据表明一个或多个Cdkn2a转录本在高胆固醇血症情况下调节血小板生成和活性，这适合进行药物干预。血小板生成和活化增强可能易导致动脉血栓形成，这至少部分解释了9p21.3与心肌梗死之间的关联。
