Child and Family Research Institute, British Columbia Children's Hospital and Sunny Hill Health Centre, Vancouver, British Columbia, Canada.
PLoS One. 2012;7(12):e51501. doi: 10.1371/journal.pone.0051501. Epub 2012 Dec 7.
AIMS/HYPOTHESIS: We previously identified the transcription factor Myt3 as specifically expressed in pancreatic islets. Here, we sought to determine the expression and regulation of Myt3 in islets and to determine its significance in regulating islet function and survival.
Myt3 expression was determined in embryonic pancreas and adult islets by qPCR and immunohistochemistry. ChIP-seq, ChIP-qPCR and luciferase assays were used to evaluate regulation of Myt3 expression. Suppression of Myt3 was used to evaluate gene expression, insulin secretion and apoptosis in islets.
We show that Myt3 is the most abundant MYT family member in adult islets and that it is expressed in all the major endocrine cell types in the pancreas after E18.5. We demonstrate that Myt3 expression is directly regulated by Foxa2, Pdx1, and Neurod1, which are critical to normal β-cell development and function, and that Ngn3 induces Myt3 expression through alterations in the Myt3 promoter chromatin state. Further, we show that Myt3 expression is sensitive to both glucose and cytokine exposure. Of specific interest, suppressing Myt3 expression reduces insulin content and increases β-cell apoptosis, at least in part, due to reduced Pdx1, Mafa, Il-6, Bcl-xl, c-Iap2 and Igfr1 levels, while over-expression of Myt3 protects islets from cytokine induced apoptosis.
CONCLUSION/INTERPRETATION: We have identified Myt3 as a novel transcriptional regulator with a critical role in β-cell survival. These data are an important step in clarifying the regulatory networks responsible for β-cell survival, and point to Myt3 as a potential therapeutic target for improving functional β-cell mass.
目的/假设：我们之前发现转录因子 Myt3 特异性表达于胰岛。在此，我们试图确定 Myt3 在胰岛中的表达和调控情况，并确定其在调节胰岛功能和存活方面的意义。
通过 qPCR 和免疫组织化学法检测胚胎胰腺和成年胰岛中 Myt3 的表达。采用 ChIP-seq、ChIP-qPCR 和荧光素酶报告基因实验评估 Myt3 表达的调控情况。利用 Myt3 抑制来评估胰岛中的基因表达、胰岛素分泌和细胞凋亡情况。
我们表明，Myt3 是成年胰岛中最丰富的 MYT 家族成员，在 E18.5 之后表达于胰腺中的所有主要内分泌细胞类型。我们证明 Myt3 的表达受到 Foxa2、Pdx1 和 Neurod1 的直接调控，这些转录因子对于正常β细胞的发育和功能至关重要，而 Ngn3 通过改变 Myt3 启动子染色质状态诱导 Myt3 表达。此外，我们发现 Myt3 的表达对葡萄糖和细胞因子暴露均敏感。值得注意的是，抑制 Myt3 的表达会降低胰岛素含量并增加β细胞凋亡，至少部分原因是 Pdx1、Mafa、Il-6、Bcl-xl、c-Iap2 和 Igfr1 水平降低，而过表达 Myt3 可保护胰岛免受细胞因子诱导的凋亡。
结论/解释：我们将 Myt3 鉴定为一种新的转录调节因子，在β细胞存活中具有关键作用。这些数据是阐明负责β细胞存活的调控网络的重要一步，并表明 Myt3 可能是改善功能性β细胞质量的潜在治疗靶点。
