Early in the pathogenesis of type 2 diabetes mellitus (T2DM), dysregulated glucagon secretion from pancreatic α cells occurs prior to impaired glucose-stimulated insulin secretion (GSIS) from β ...cells. However, whether hyperglucagonemia is causally linked to β cell dysfunction remains unclear. Here we show that glucagon stimulates via cAMP-PKA-CREB signaling hepatic production of the neuropeptide kisspeptin1, which acts on β cells to suppress GSIS. Synthetic kisspeptin suppresses GSIS in vivo in mice and from isolated islets in a kisspeptin1 receptor-dependent manner. Kisspeptin1 is increased in livers and in serum from humans with T2DM and from mouse models of diabetes mellitus. Importantly, liver Kiss1 knockdown in hyperglucagonemic, glucose-intolerant, high-fat-diet fed, and Leprdb/db mice augments GSIS and improves glucose tolerance. These observations indicate a hormonal circuit between the liver and the endocrine pancreas in glycemia regulation and suggest in T2DM a sequential link between hyperglucagonemia via hepatic kisspeptin1 to impaired insulin secretion.
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•Glucagon stimulates both hepatic kisspeptin1 production and gluconeogenesis•Kisspeptin1 suppresses glucose-stimulated insulin secretion (GSIS) from β cells•Hyperglucagonemia in diabetes impairs insulin secretion via hepatic kisspeptin1•In diabetic mice, liver Kiss1 knockdown improves GSIS and glycemia
Both glucagon and insulin, hormones of the pancreatic islets of Langerhans, tightly control blood glucose levels. This article uncovers a trihormonal glucoregulatory circuit in which glucagon stimulates liver kisspeptin1 production, which in turn suppresses insulin secretion. The findings also suggest in diabetes mellitus a causal link between hyperglucagonemia and defective insulin secretion via liver-derived kisspeptin1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Genome-wide association studies (GWASs) for osteoporotic traits have identified over 1000 associations; however, their impact has been limited by the difficulties of causal gene ...identification and a strict focus on bone mineral density (BMD). Here, we use Diversity Outbred (DO) mice to directly address these limitations by performing a systems genetics analysis of 55 complex skeletal phenotypes. We apply a network approach to cortical bone RNA-seq data to discover 66 genes likely to be causal for human BMD GWAS associations, including the genes
SERTAD4
and
GLT8D2
. We also perform GWAS in the DO for a wide-range of bone traits and identify
Qsox1
as a gene influencing cortical bone accrual and bone strength. In this work, we advance our understanding of the genetics of osteoporosis and highlight the ability of the mouse to inform human genetics.
The retrotrapezoid nucleus (RTN) consists, by definition, of Phox2b-expressing, glutamatergic, non-catecholaminergic, noncholinergic neurons located in the parafacial region of the medulla oblongata. ...An unknown proportion of RTN neurons are central respiratory chemoreceptors and there is mounting evidence for biochemical diversity among these cells. Here, we used multiplexed
hybridization and single-cell RNA-Seq in male and female mice to provide a more comprehensive view of the phenotypic diversity of RTN neurons. We now demonstrate that the RTN of mice can be identified with a single and specific marker,
mRNA (
). Most (∼75%) RTN neurons express low-to-moderate levels of
and display chemoreceptor properties. Namely they are activated by hypercapnia, but not by hypoxia, and express proton sensors, TASK-2 and Gpr4. These
-low RTN neurons also express varying levels of transcripts for
,
, and
, and receptors for substance P, orexin, serotonin, and ATP. A subset of RTN neurons (∼20-25%), typically larger than average, express very high levels of
mRNA. These
-high RTN neurons do not express
after hypercapnia and have low-to-undetectable levels of
or
transcripts; they also express
, but are essentially devoid of
and
transcripts. In male rats,
is also a marker of the RTN but, unlike in mice, this gene is expressed by other types of nearby neurons located within the ventromedial medulla. In sum,
is a selective marker of the RTN in rodents;
-low neurons, the vast majority, are central respiratory chemoreceptors, whereas
-high neurons likely have other functions.
Central respiratory chemoreceptors regulate arterial PCO
by adjusting lung ventilation. Such cells have recently been identified within the retrotrapezoid nucleus (RTN), a brainstem nucleus defined by genetic lineage and a cumbersome combination of markers. Using single-cell RNA-Seq and multiplexed
hybridization, we show here that a single marker,
mRNA (
), identifies RTN neurons in rodents. We also suggest that >75% of these
neurons are chemoreceptors because they are strongly activated by hypercapnia and express high levels of proton sensors (
and
). The other RTN neurons express very high levels of
, but low levels of
, and do not respond to hypercapnia. Their function is unknown.
Mesenchymal stem cells (MSCs) participate in the repair/remodelling of many tissues, where MSCs commit to different lineages dependent on the cues in the local microenvironment. Here we show that ...TGFβ-activated RhoA/ROCK signalling functions as a molecular switch regarding the fate of MSCs in arterial repair/remodelling after injury. MSCs differentiate into myofibroblasts when RhoA/ROCK is turned on, endothelial cells when turned off. The former is pathophysiologic resulting in intimal hyperplasia, whereas the latter is physiological leading to endothelial repair. Further analysis revealed that MSC RhoA activation promotes formation of an extracellular matrix (ECM) complex consisting of connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF). Inactivation of RhoA/ROCK in MSCs induces matrix metalloproteinase-3-mediated CTGF cleavage, resulting in VEGF release and MSC endothelial differentiation. Our findings uncover a novel mechanism by which cell-ECM interactions determine stem cell lineage specificity and offer additional molecular targets to manipulate MSC-involved tissue repair/regeneration.
Nuclear lamins are components of the nuclear lamina, a structural scaffolding for the cell nucleus. Defects in lamins A and C cause an array of human diseases, including muscular dystrophy, ...lipodystrophy, and progeria, but no diseases have been linked to the loss of lamins B1 or B2. To explore the functional relevance of lamin B2, we generated lamin B2-deficient mice and found that they have severe brain abnormalities resembling lissencephaly, with abnormal layering of neurons in the cerebral cortex and cerebellum. This neuronal layering abnormality is due to defective neuronal migration, a process that is dependent on the organized movement of the nucleus within the cell. These studies establish an essential function for lamin B2 in neuronal migration and brain development.
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Chronic natural killer large granular lymphocyte (NK-LGL) leukemia, also referred to as chronic lymphoproliferative disorder of NK cells, is a rare disorder defined by prolonged expansion of clonal ...NK cells. Similar prevalence of STAT3 mutations in chronic T-LGL and NK-LGL leukemia is suggestive of common pathogenesis. We undertook whole-genome sequencing to identify mutations unique to NK-LGL leukemia. The results were analyzed to develop a resequencing panel that was applied to 58 patients. Phosphatidylinositol 3-kinase pathway gene mutations (PIK3CD/PIK3AP1) and TNFAIP3 mutations were seen in 5% and 10% of patients, respectively. TET2 was exceptional in that mutations were present in 16 (28%) of 58 patient samples, with evidence that TET2 mutations can be dominant and exclusive to the NK compartment. Reduced-representation bisulfite sequencing revealed that methylation patterns were significantly altered in TET2 mutant samples. The promoter of TET2 and that of PTPRD, a negative regulator of STAT3, were found to be methylated in additional cohort samples, largely confined to the TET2 mutant group. Mutations in STAT3 were observed in 19 (33%) of 58 patient samples, 7 of which had concurrent TET2 mutations. Thrombocytopenia and resistance to immunosuppressive agents were uniquely observed in those patients with only TET2 mutation (Games-Howell post hoc test, P = .0074; Fisher's exact test, P = .00466). Patients with STAT3 mutation, inclusive of those with TET2 comutation, had lower hematocrit, hemoglobin, and absolute neutrophil count compared with STAT3 wild-type patients (Welch's t test, P ≤ .015). We present the discovery of TET2 mutations in chronic NK-LGL leukemia and evidence that it identifies a unique molecular subtype.
•TET2 mutations are present in 28% of chronic NK-LGL leukemia, and TET2 promoter methylation is also detected.•TET2 and STAT3 mutated singly or comutated are associated with distinct patterns of cytopenias, as well as response to immunosuppressives.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Genetic risk scores (GRS) have been developed that differentiate individuals with type 1 diabetes from those with other forms of diabetes and are starting to be used for population screening; ...however, most studies were conducted in European-ancestry populations. This study identifies novel genetic variants associated with type 1 diabetes risk in African-ancestry participants and develops an African-specific GRS.
We generated single nucleotide polymorphism (SNP) data with the ImmunoChip on 1,021 African-ancestry participants with type 1 diabetes and 2,928 control participants. HLA class I and class II alleles were imputed using SNP2HLA. Logistic regression models were used to identify genome-wide significant (
< 5.0 × 10
) SNPs associated with type 1 diabetes in the African-ancestry samples and validate SNPs associated with risk in known European-ancestry loci (
< 2.79 × 10
).
African-specific (HLA-
*03:01-HLA-
*02:01) and known European-ancestry HLA haplotypes (HLA-
*03:01-HLA-
*05:01-HLA-
*02:01, HLA-
*04:01-HLA-
*03:01-HLA-
*03:02) were significantly associated with type 1 diabetes risk. Among European-ancestry defined non-HLA risk loci, six risk loci were significantly associated with type 1 diabetes in subjects of African ancestry. An African-specific GRS provided strong prediction of type 1 diabetes risk (area under the curve 0.871), performing significantly better than a European-based GRS and two polygenic risk scores in independent discovery and validation cohorts.
Genetic risk of type 1 diabetes includes ancestry-specific, disease-associated variants. The GRS developed here provides improved prediction of type 1 diabetes in African-ancestry subjects and a means to identify groups of individuals who would benefit from immune monitoring for early detection of islet autoimmunity.
HIV protease inhibitors (HIV-PIs) target the HIV aspartyl protease, which cleaves the HIV gag-pol polyprotein into shorter proteins required for the production of new virions. HIV-PIs are a ...cornerstone of treatment for HIV but have been associated with lipodystrophy and other side effects. In both human and mouse fibroblasts, we show that HIV-PIs caused an accumulation of prelamin A. The prelamin A in HIV-PI-treated fibroblasts migrated more rapidly than nonfarnesylated prelamin A, comigrating with the farnesylated form of prelamin A that accumulates in ZMPSTE24-deficient fibroblasts. The accumulation of farnesyl-prelamin A in response to HIV-PI treatment was exaggerated in fibroblasts heterozygous for Zmpste24 deficiency. HIV-PIs inhibited the endoproteolytic processing of a GFP-prelamin A fusion protein. The HIV-PIs did not affect the farnesylation of HDJ-2, nor did they inhibit protein farnesyltransferase in vitro. HIV-PIs also did not inhibit the activities of the isoprenyl-cysteine carboxyl methyltransferase ICMT or the prenylprotein endoprotease RCE1 in vitro, but they did inhibit ZMPSTE24 (IC₅₀: lopinavir, 18.4 ± 4.6 μM; tipranavir, 1.2 ± 0.4 μM). We conclude that the HIV-PIs inhibit ZMPSTE24, leading to an accumulation of farnesyl-prelamin A. The inhibition of ZMPSTE24 by HIV-PIs could play a role in the side effects of these drugs.
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