The retinoblastoma gene product (pRb) is a chromatin-associated protein that can either suppress or promote activity of key regulators of tissue-specific differentiation. We found that twelve weeks after transfection of the exogenous active (ΔB/X and Δр34) or inactive (ΔS/N) forms of RB into the 10T1/2 mesenchymal stem cells and clonal selection not a single cell line did contain exogenous RB, despite being G-418 resistant. However, the consequences of the transient production of exogenous RB had different effects on the cell fate. The ΔB/X and Δр34 cells transfected with active form of RB showed elevated levels of inducible adipocyte differentiation (AD). On the contrary, the ΔS/N cells transfected with inactive RB mutant were insensitive to induction of AD associated with abolishing of expression of the PPARγ2. Additionally, the PPARγ2 promoter in undifferentiated ΔS/N cells was hypermethylated, but all except −60 position CpG became mostly demethylated after cells exposure to AD. We conclude that while transient expression of inactive exogenous RB induces long term epigenetic alterations that prevent adipogenesis, production of active exogenous RBs results in an AD-promoting epigenetic state. These results indicate that pRb is involved in the establishment of hereditary epigenetic memory at least by creating a methylation pattern of PPARγ2.

视网膜母细胞瘤基因产物 (pRb) 是一种染色质相关蛋白，可以抑制或促进组织特异性分化的关键调节因子的活性。我们发现，在将外源活性（ΔB/X 和 Δр34）或无活性（ΔS/N）形式的 RB 转染到 10T1/2 间充质干细胞和克隆选择后十二周，没有一个细胞系确实含有外源性 RB，尽管抗 G-418。然而，瞬时产生外源RB的后果对细胞命运有不同的影响。用活性形式的 RB 转染的 ΔB/X 和 Δр34 细胞显示可诱导的脂肪细胞分化 (AD) 水平升高。相反，转染无活性RB突变体的ΔS/N细胞对与消除PPARγ2表达相关的AD的诱导不敏感。此外，未分化的 ΔS/N 细胞中的 PPARγ2 启动子是高甲基化的，但除了 -60 位 CpG 之外的所有启动子在细胞暴露于 AD 后大部分都去甲基化。我们得出结论，虽然无活性外源性RB的瞬时表达会诱导长期的表观遗传改变，从而阻止脂肪生成，但活性外源性RB的产生会导致促进AD的表观遗传状态。这些结果表明，pRb 至少通过产生 PPARγ2 的甲基化模式参与了遗传表观遗传记忆的建立。活性外源性RB的产生导致促进AD的表观遗传状态。这些结果表明，pRb 至少通过产生 PPARγ2 的甲基化模式参与了遗传表观遗传记忆的建立。活性外源性RB的产生导致促进AD的表观遗传状态。这些结果表明，pRb 至少通过产生 PPARγ2 的甲基化模式参与了遗传表观遗传记忆的建立。