Pregnancy-Specific Mechanisms Regulating Beta-Cell Proliferation and Mass

妊娠糖尿病 (GDM) 或在怀孕期间首次出现的高血糖会恶化妊娠结局，并给母亲及其后代带来长期健康风险。与所有类型的糖尿病一样，功能性胰腺 β 细胞相对不足是导致 GDM 的一个基本缺陷。通常，β细胞通过扩大β细胞质量来适应妊娠的代谢挑战。这种扩大的肿块在产后会消退。因此，怀孕是一种独特的生理状况，发生在发育完全的成年人身上，需要β细胞量快速、动态的变化。不幸的是，人们对正常妊娠 β 细胞适应机制和 GDM 潜在缺陷知之甚少。我们的长期目标是了解妊娠期间调节 β 细胞增殖和质量的机制，以便利用这些知识对所有类型的糖尿病进行 β 细胞的治疗性扩增。基于我们确定 β 细胞中催乳素受体 (PRLR) 信号传导缺失会导致 GDM 的工作，我们最近发现了新的 PRLR 差异表达基因 (PRLR-DEG) 和 PRLR-DEG 表达的关键转录调节因子。这笔资助的目的是精确定义 PRLR 如何在怀孕期间和产后期调节 β 细胞基因表达。我们提出的中心假设是，PRLR 信号传导协调了妊娠期间 β 细胞质量扩张的预期转录程序以及产后回归期间足够 β 细胞质量的存活。我们将通过以下具体目标来检验这一假设：（1）阐明妊娠期间调节 β 细胞内 PRLR-DEG 的转录机制。为此，我们将使用 ChIP-seq 和 ATAC-seq 来检查小鼠和人类胰岛在怀孕期间或响应催乳素刺激时如何调节 PRLR-DEG。在目标 (2) 中，我们将使用单细胞 RNA 测序、谱系追踪和共定位研究来定义妊娠期间 PRLR 信号依赖和独立的 β 细胞亚群。对于目标 (3)，我们将通过对妊娠期间增殖的 β 细胞进行脉冲追踪标记和谱系追踪，确定产后早期 β 细胞质量回归过程中 β 细胞存活的机制，并检查产后期间 PRLR 的诱导性丢失如何影响 β 细胞质量。总之，这些研究的结果将揭示 PRLR 下游的转录机制，阐明妊娠增殖的独特方面（目标 1），定义整个妊娠期间空间和时间上的 β 细胞亚群（目标 2），并确立 PRLR 信号在产后 β 细胞调节中的新作用（目标 3）。我们的研究意义重大，因为这些发现将阐明妊娠 β 细胞适应机制，并扩大我们对 PRLR 激活如何调节转录的理解。从根本上讲，这些研究将扩大我们对调节 β 细胞群动态变化机制的理解，这可能会确定促进 β 细胞扩增用于治疗目的的新策略。

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.