Pregnancy-Specific Mechanisms Regulating Beta-Cell Proliferation and Mass

妊娠期糖尿病(GDM)，或在怀孕期间首次表现出的高血糖，会恶化怀孕结果，并对母亲和她的后代造成长期的健康风险。与所有类型的糖尿病一样，功能相对不足的胰腺β细胞是导致妊娠期糖尿病的根本缺陷。正常情况下，β细胞通过扩大β细胞团来适应怀孕期间的代谢挑战。这种肿块在产后消退。因此，妊娠是一种独特的生理状态，发生在完全发育的成年人中，需要β细胞团的快速、动态变化。不幸的是，正常妊娠β细胞适应的机制和妊娠期糖尿病的潜在缺陷还知之甚少。我们的长期目标是了解妊娠期间β细胞增殖和质量的调节机制，以便利用这一知识在所有类型的糖尿病中治疗β细胞的扩增。在β细胞中催乳素受体信号缺失导致妊娠期糖尿病的工作基础上，我们最近发现了新的催乳素受体差异表达基因(PRLR-DEGS)和PRLR-DEG表达的关键转录调节因子。这笔赠款的目的是精确定义PRLR如何在怀孕期间和产后调节β细胞基因的表达。我们提出了一个中心假设，即PRLR信号协调了一个预期的转录程序，即妊娠期间β细胞团的扩张和产后退化期间足够的β细胞团的存活。我们将通过以下具体目标来检验这一假说：(1)阐明妊娠期间β细胞内调节PRLRDEGS的转录机制。为此，我们将使用CHIP-SEQ和ATAC-SEQ来研究PRLR-degs在怀孕期间或对催乳素刺激的反应中在小鼠和人类胰岛中是如何调节的。在AIM(2)中，我们将使用单细胞核糖核酸测序、谱系追踪和共定位研究来定义孕期PRLR信号依赖和独立的β细胞亚群。对于目的(3)，我们将通过脉冲追逐标记和对妊娠期间增殖的β细胞的谱系追踪来识别β细胞在产后早期的β细胞群消退过程中的存活机制，并研究产后特定时期可诱导的PRLR值的丢失如何影响β细胞群。总之，这些研究结果将揭示PRLR下游的转录机制，并阐明妊娠增殖的独特方面(目标1)，确定跨孕期β细胞亚群的时空分布(目标2)，并确立PRLR信号在产后调节β细胞中的新作用(目标3)。我们的研究意义重大，因为这些发现将澄清妊娠β细胞适应的机制，并扩大我们对PRLR激活如何调节转录的理解。在基础水平上，这些研究将扩大我们对调节β细胞质量动态变化的机制的理解，这可能确定促进β细胞出于治疗目的而扩增的新策略。

Gestational diabetes (GDM), or hyperglycemia that first manifests during pregnancy, worsens pregnancy outcomes and long-term health risks for both a mother and her offspring. As with all types of diabetes, a relative insufficiency of functional pancreatic β-cells is a fundamental defect contributing to GDM. Normally, β-cells adapt to the metabolic challenges of pregnancy by expanding β-cell mass. This expanded mass regresses in the postpartum period. Thus, pregnancy is a unique physiologic condition that occurs in a fully-developed adult and requires rapid, dynamic changes in β-cell mass. Unfortunately, the mechanisms of normal gestational β-cell adaptation and the defects underlying GDM are poorly understood. Our long-term goal is to understand the mechanisms regulating β-cell proliferation and mass during pregnancy, in order to leverage that knowledge for therapeutic expansion of β-cells in all types of diabetes. Building on our work establishing that loss of prolactin receptor (PRLR) signaling in β-cells results in GDM, we recently identified novel PRLR differentially expressed genes (PRLR-DEGs) and key transcriptional regulators of PRLR-DEG expression. The objective of this grant is to precisely define how PRLR regulates β-cell gene expression during pregnancy and the postpartum period. We propose the central hypothesis that PRLR signaling orchestrates an anticipatory transcriptional program of β-cell mass expansion during gestation and survival of adequate β-cell mass during postpartum regression. We will test this hypothesis with the following Specific Aims: (1) elucidate transcriptional mechanisms regulating PRLR-DEGs within β-cells during pregnancy. To do so, we will use ChIP-seq and ATAC-seq to examine how PRLR-DEGs are regulated in mouse and human islets during pregnancy or in response to prolactin stimulation. In Aim (2) we will define PRLR signaling-dependent and -independent β-cell subpopulations during pregnancy using single-cell RNA sequencing, lineage tracing and colocalization studies. For Aim (3) we will identify mechanisms of β-cell survival during β-cell mass regression in the early postpartum period through pulse-chase labeling and lineage tracing of β-cells that proliferated during pregnancy, as well as examine how inducible loss of PRLR specifically within the postpartum period affects β-cell mass. Together, results from these studies will reveal transcriptional mechanisms downstream of PRLR and illuminate unique aspects of gestational proliferation (Aim 1), define β-cell subpopulations spatially and temporally across pregnancy (Aim 2), and establish a new role for PRLR signaling in regulation of β-cells postpartum (Aim 3). Our research is significant because these findings would clarify mechanisms of gestational β-cell adaptation and expand our understanding of how PRLR activation regulates transcription. At a fundamental level, these studies will expand our understanding of the mechanisms regulating dynamic changes in β-cell mass, which may identify novel strategies to promote β-cell expansion for therapeutic purposes.