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Despite the growing number of genome-wide association studies (GWASs), it remains unclear to what extent gene-by-gene and gene-by-environment interactions influence complex traits in humans. The magnitude of genetic interactions in complex traits has been difficult to quantify because GWASs are generally underpowered to detect individual interactions of small effect. Here, we develop a method to test for genetic interactions that aggregates information across all trait-associated loci. Specifically, we test whether SNPs in regions of European ancestry shared between European American and admixed African American individuals have the same causal effect sizes. We hypothesize that in African Americans, the presence of genetic interactions will drive the causal effect sizes of SNPs in regions of European ancestry to be more similar to those of SNPs in regions of African ancestry. We apply our method to two traits: gene expression in 296 African Americans and 482 European Americans in the Multi-Ethnic Study of Atherosclerosis (MESA) and low-density lipoprotein cholesterol (LDL-C) in 74K African Americans and 296K European Americans in the Million Veteran Program (MVP). We find significant evidence for genetic interactions in our analysis of gene expression; for LDL-C, we observe a similar point estimate, although this is not significant, most likely due to lower statistical power. These results suggest that gene-by-gene or gene-by-environment interactions modify the effect sizes of causal variants in human complex traits.

Genome-wide association studies have revealed that the genetic architectures of complex traits vary widely, including in terms of the numbers, effect sizes, and allele frequencies of significant hits. However, at present we lack a principled way of understanding the similarities and differences among traits. Here, we describe a probabilistic model that combines mutation, drift, and stabilizing selection at individual sites with a genome-scale model of phenotypic variation. In this model, the architecture of a trait arises from the distribution of selection coefficients of mutations and from two scaling parameters. We fit this model for 95 diverse, highly polygenic quantitative traits from the UK Biobank. Notably, we infer similar distributions of selection coefficients across all these traits. This shared distribution implies that differences in architectures of highly polygenic traits arise mainly from the two scaling parameters: the mutational target size and heritability per site, which vary by orders of magnitude across traits. When these two scale factors are accounted for, the architectures of all 95 traits are nearly identical.

The orphan nuclear hormone receptor Nr4a1 plays a critical role in maintaining and expanding functional beta cell mass. Overexpression of Nr4a1 is sufficient to induce beta cell proliferation in primary beta cells by upregulating cell cycle progression, while maintaining glucose-stimulated insulin secretion. Full body deletion of Nr4a1 results in decreased beta cell mass, while resulting in modified fuel utilization in liver and muscle. Knock down of Nr4a1 decreases glycolytic and TCA cycle gene expression, impairs mitochondrial respiration, decreases cellular ATP levels, and ultimately decreases glucose-stimulated insulin secretion. While Nr4a1 is currently considered an orphaned nuclear hormone receptor, recent findings suggest that unsaturated fatty acids may function as a ligand, and that exposure to these fatty acid’s changes Nr4a1 affinity for promoters of genes involved in fuel utilization. To determine the effect of Nr4a1 presence of absence in the beta cell, and the effect of fatty acid exposure, we developed a beta cell specific, inducible, Nr4a1 knock out mouse. Male and female mice, deficient for Nr4a1 beginning at 3 months of age, were fed a normal chow or high fat diet for an additional four months. Here we present data demonstrating a sex specific difference in phenotype. Male mice demonstrated improved glucose tolerance at four months of feeding, while female mice demonstrated impaired glucose tolerance as early as one month of feeding. Here we present data regarding differences in beta cell mass, glucose stimulated insulin secretion, as well as Nr4a1 DNA binding from in islets from male and female mice exposed to unsaturated and saturated fatty acids. These data begin to demonstrate the role of Nr4a1 in controlling gene expression as a function of nutrient exposure, as well as sex-based differences in Nr4a1 activity. Disclosure J.S. Tessem: None. J. Herring: None. C.J. Smith: None. M.C. Austin: None. A.G. Wynn: None. Funding American Diabetes Association (1-17-IBS-101 to J.S.T.)

Novel trisubstituted ethylenes, ring-disubstituted propyl 2-cyano-3-phenyl-2-propenoates, RPhCH˭C(CN)CO2C3H7 (where R is 2-fluoro-5-methoxy, 2-fluoro-6-methoxy, 3-fluoro-4-methoxy, 4-fluoro-3-methoxy, 5-fluoro-2-methoxy, 2-fluoro-6-methyl, 3-fluoro-2-methyl, 4-fluoro-2-methyl, 4-fluoro-3-methyl, 5-fluoro-2-methyl) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and propyl cyanoacetate and characterized by CHN elemental analysis, IR, 1H- and 13C-NMR. All the ethylenes were copolymerized with styrene (M1) in solution with radical initiation (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR, GPC, DSC, and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (1.4–3.0% wt.), which then decomposed in the 500–800°C range.

We have shown that the orphan nuclear receptors Nr4a1 and Nr4a3 are critical for beta cell mitochondrial respiration and fuel utilization, and that loss of either factor impedes fuel utilization and insulin secretion. We have also demonstrated that prolonged culture of INS-1 832/13 beta cells with progressively increasing concentrations of palmitic acid results in decreased Nr4a1 and Nr4a3 expression, impaired mitochondrial respiration, and reduced insulin secretion. Here we explore the effect of 20-week high fat diet on wild type mice and mice deficient for either Nr4a1 or Nr4a3. Nr4a1 and Nr4a3 knock out mice have greater body weight than wild type animals when on a high fat diet. Mice deficient for Nr4a1 or Nr4a3 have no significant change in non-fasting blood glucose measurements as compared to wild type under normal chow conditions. Non-fasting blood glucose was elevated in both Nr4a1 and Nr4a3 knock out mice under high fat feeding conditions. Fasting glucose tolerance tests also demonstrate that Nr4a1 and Nr4a3 knock out mice have impaired glucose tolerance as compared to wild type animals under high fat feeding. Mitochondrial respiration of muscle, liver, adipose and islets are impaired as compared to wild type controls under high fat feeding. Glucose stimulated insulin secretion is impaired in islets from Nr4a1 or Nr4a3 knock out mice fed a high fat diet. These data demonstrate changes in various metabolic tissues as a result of high fat feeding and deletion of the Nr4a orphan nuclear receptors, demonstrating that they play a critical role in systemic fuel utilization. Disclosure C.J. Smith: None. K.B. Kener: None. J.S. Tessem: None.

The homeobox transcription factor Nkx6.1 is sufficient to increase functional β-cell mass, where functional β-cell mass refers to the combination of β-cell proliferation, glucose-stimulated insulin secretion (GSIS) and β-cell survival. Here, we demonstrate that the histone deacetylase 1 (HDAC1), which is an early target of Nkx6.1, is sufficient to increase functional β-cell mass. We show that HDAC activity is necessary for Nkx6.1-mediated proliferation, and that HDAC1 is sufficient to increase β-cell proliferation in primary rat islets and the INS-1 832/13 β-cell line. The increase in HDAC1-mediated proliferation occurs while maintaining GSIS and increasing β-cell survival in response to apoptotic stimuli. We demonstrate that HDAC1 overexpression results in decreased expression of the cell cycle inhibitor Cdkn1b/p27 which is essential for inhibiting the G1 to S phase transition of the cell cycle. This corresponds with increased expression of key cell cycle activators, such as Cyclin A2, Cyclin B1 and E2F1, which are activated by activation of the Cdk4/Cdk6/Cyclin D holoenzymes due to down-regulation of Cdkn1b/p27. Finally, we demonstrate that overexpression of Cdkn1b/p27 inhibits HDAC1-mediated β-cell proliferation. Our data suggest that HDAC1 is critical for the Nkx6.1-mediated pathway that enhances functional β-cell mass.

This report describes the results obtained by application of three methods (i.e., visual iodate, potentiometric bromate, and colorimetric molybdenum blue) to the determination of hydrazine and its methyl derivatives. In addition, the validity of continuous sampling techniques for vapor concentrations in air was determined by estimating the stability of acidified aqueous solutions of the hydrazines toward prolonged aeration.