Jacqueline Ho - US grants

DESCRIPTION (provided by applicant): MicroRNAs (miRNAs) are a group of novel small RNAs that regulate gene expression via the post- transcriptional repression of specific target mRNAs. As a group, miRNAs play a key role in diverse developmental processes, and are required for the differentiation of embryonic stem cells;however the function of miRNAs during kidney development remains largely undefined. Our preliminary work indicates that the loss of miRNAs within the nephron progenitor compartment of the developing kidney results in a premature depletion of this population, and as a consequence, a marked decrease in nephron number. Furthermore, this is accompanied by elevated expression of the pro-apoptotic protein Bim (also known as Bcl-2L11) specifically in nephron progenitors, and an increase in apoptosis in this cell population. We propose that specific miRNAs promote the survival of nephron progenitors by regulating the expression of Bim, and that this mechanism represents a means of determining congenital nephron endowment during normal kidney development. Specific aim 1: To characterize the role of Bim (Bcl-2L11) in the survival of nephron progenitors during kidney development. Specific aim 2: To define the function of the miRNA clusters, mmu-miR-106b~25 and mmu- miR-17~92, in regulating Bim expression and nephron progenitors. Specific aim 3: To determine the functional role of mmu-miR-10a during kidney development. The work proposed in this grant will serve as the foundation for the PI's transition into an independent career as a physician-scientist in an academic pediatric renal division over the next two years. The mentored phase (K99) will occur at Children's Hospital Boston and Harvard Medical School under the guidance of Dr. Jordan Kreidberg. PUBLIC HEALTH RELEVANCE: Together, these studies will further our understanding of the molecular and cellular processes that regulate nephron progenitors in establishing the full complement of nephrons during kidney development. This will ultimately inform the pathophysiology underlying congenital renal anomalies, the leading cause of renal failure in young children, and the mechanisms that determine congenital nephron number, which has important implications for long-term kidney health.

DESCRIPTION (provided by applicant): Chronic insufficient sleep and over nutrition are both associated with the incidence of cardiovascular and metabolic diseases. Substantial evidence supports a contribution of low-grade inflammation in the hypothalamus and peripheral metabolic tissues to the emergence of cardio metabolic pathologies in diet- induced obesity. However, the mechanisms underlying the development of metabolic deficits elicited by poor sleep are less understood. Epidemiological and empirical studies provide correlative evidence supporting a role for peripheral inflammation in the development of metabolic deficits induced by poor sleep, but a causal relationship has yet to be established. Moreover, it is unknown whether insufficient sleep elicits neuroinflammation in brain regions that regulate energy homeostasis, as is observed in over nutrition. To elucidate mechanisms of metabolic dysfunction resulting from poor sleep and over nutrition, the proposed project will test the hypothesis that inflammation contributes to metabolic deficits observed in these conditions by addressing two specific aims. Specific Aim 1 will determine the extent to which sleep disruption and over nutrition elicit inflammatory responses in the brain and periphery. To this end, sleep will be moderately disrupted and over nutrition will be induced with a high-fat diet in mice. Site-specific analyses o inflammatory mediators in metabolically relevant tissues, including brain regions that regulate energy balance, will be conducted following these manipulations. Specific Aim 2 will determine the extent to which anti-inflammatory actions preserve metabolic function in individuals subjected to sleep disruption and over nutrition. To address this aim, insulin sensitivity will be assessed following sleep disruption or high-fat diet exposure in genetic knockout mice that lack specific pro-inflammatory cytokine signaling. Pharmacological intervention will be employed as a complementary approach; insulin sensitivity will be assessed in genetically intact mice treated with anti-inflammatory agents throughout the period of exposure to sleep disruption or high-fat diet. Together, these aims will establish neural and peripheral targets of inflammation following sleep disruption and over nutrition, and will directly test the hypothesis that inflammation induced by these factors leads to metabolic dysfunction. The findings from the proposed aims will greatly contribute to our understanding of the pathogenesis of cardio metabolic diseases associated with poor sleep and over nutrition, and will help inform practices and policies that address these prevalent public health concerns.

DESCRIPTION (provided by applicant): Renal dysplasia/hypoplasia is a leading cause of renal failure in children, leading to significant morbidity and mortality associated with transplan and dialysis. The risk of chronic kidney disease is linked to decreased renal reserve as a result of the formation of fewer and/or abnormal nephrons during kidney development. While much is known about the genetic control of nephron development, very little is known about the role of microRNAs (miRNAs), small, non-coding RNA molecules that negatively regulate gene expression. Our laboratory has data demonstrating that the miR-17~92 miRNA cluster is crucial to regulating nephron number and formation. Conditional loss of miR-17~92 in nephron progenitors results in renal hypodysplasia, glomerular injury and renal dysfunction in adult mice. Moreover, we observe an intermediate phenotype in animals with heterozygous loss of miR-17~92 in nephron progenitors, suggesting that the gene dosage of miR- 17~92 is key. Heterozygous mutations in the orthologous human gene (MIR17HG) results in the first known developmental defects associated with a miRNA mutation in humans, including renal anomalies. We hypothesize that loss of the miR-17~92 cluster in nephron progenitors results in an intrinsic nephron progenitor defect, and therefore abnormal nephron number and pattern during kidney development. Aim 1. Define the role of miR-17~92 gene dosage in establishing nephron number and pattern. Aim 2. Characterize the intrinsic defect in miR-17~92 null nephron progenitors. Aim 3. Validate downstream miR-17~92 targets to elucidate mechanism(s) by which the miR-17~92 cluster regulates nephron number and patterning.

ABSTRACT Approximately 20% of all hospitalized patients and nearly 50% of critically ill inpatients are estimated to suffer from acute kidney injury (AKI), which is associated with high rates of morbidity and mortality. While the kidney may recover, the patients are at a higher risk for subsequently developing chronic kidney disease (CKD); other times, the acute injury is so severe that there is no kidney recovery. One of the hallmarks of AKI is damage to the renal microvasculature. This damage alters endothelial function, contributing to hypoxic and inflammatory injury to the renal parenchyma. Although an angiogenic response (vascular sprouting from existing vessels) is key to endothelial cell repair (and therefore AKI recovery), the renal microvasculature is thought to have a limited reparative capacity. There are currently no specific therapies for AKI, nor are there available interventions to decrease the risk of progression to CKD after AKI. Much of the current interventions are focused on the tubular epithelium. There are several knowledge gaps that need to be addressed to develop therapies targeted at the renal microvasculature, including: (1) what are the molecular mechanisms that drive endothelial repair after AKI; and (2) is it possible to modulate the capacity of the renal microvasculature for repair after AKI? Our laboratory has previously shown that the miR-17~92 cluster (including the microRNAs (miRNAs): miR-17, miR-18a, miR-19a/b, miR-20a and miR-92a) is required for normal kidney development and function. This cluster is known to regulate angiogenesis in other cellular contexts such as tumorigenesis. There is limited information regarding miRNAs in the renal vasculature in AKI, and the role of miR-17~92 in this context is unknown. Our team has generated preliminary data following renal ischemia-reperfusion injury (IRI) showing that transgenic mice lacking miR-17~92 in endothelial cells are more susceptible to renal IRI. Our central hypothesis is that miR- 17~92 promotes endothelial cell repair after injury and protects against AKI; thus making it an exciting therapeutic target. To test this hypothesis, the following specific aims are proposed: Aim 1- To define the requirement for endothelial miR-17~92 during renal injury and repair; and Aim 2- To determine whether miR-17~92 is sufficient to protect against renal injury.