Project description:The serine/threonine kinase LKB1 is a tumor suppressor gene which also plays key roles in metabolic function in peripheral tissues through its direct phosphorylation and activation of the AMP-activated protein kinase (AMPK). The LKB1/AMPK pathway plays key roles in the liver in suppressing transcriptional programs of gluconeogenesis and lipogenesis, and hepatic LKB1 is required for the ability of the type 2 diabetes agent metformin to lower blood glucose levels in mice. To more broadly define how the LKB1/AMPK pathway controls hepatic metabolism, transcriptional profiling was employed using mice with an inducible liver-specific deletion of Lkb1. Unexpectedly, LKB1/AMPK signaling broadly controls the expression of many phase I xenobiotic metabolism genes, including several members of the cytochrome P450 family. In particular, expression of CYP2E1, an important mediator of drug detoxification, was markedly reduced upon LKB1 loss. LKB1 liver-specific knockout mice exposed to hepatocarcinogens, exhibited marked resistance to carcinogen-induced hepatocyte apoptosis, proliferation, senescence, and liver fibrosis and tumorigenesis.
Project description:RNA-Seq was performed on pancreatic islets from four transgenic mouse strains affecting LKB1 and AMPK. A conditional LKB1 knockout strain was generated. Double conditional knockouts for AMPK alpha1 and AMPK alpha2 were also generated. These conditional strains were crossed with RIP-Cre (driven by rat insulin promoter) or Ins1-Cre mice to generate LKB1 knockout and AMPK double knockout strains.
Project description:The 5' AMP-activated protein kinase (AMPK) is a master energy sensing kinase that is regulated by phosphorylation of Thr172 in its activation loop. Three kinases can phosphorylate AMPK at Thr172: the tumor suppressor LKB1, CAMKK2 and TAK1. While LKB1- and CAMKK2-mediated AMPK Thr172 phosphorylation have been well-characterized, much less is known about TAK1-dependent AMPK phosphorylation. An important target of TAK1 is IκB kinase (IKK) which controls NF-B transcription factor activation. Here, we tested the hypothesis that IKK acted downstream of TAK1 to activate AMPK by phosphorylating Thr172. IKK was required for phosphorylation of Thr172 in AMPK in response to treatment with IL-1 or TNF- treatment or by TAK1 overexpression. Additionally, IKK regulated basal AMPK Thr172 phosphorylation in several cancer cell types independently of TAK1, indicating that other modes of IKK activation could lead to AMPK activation. We found that IKK directly phosphorylated AMPK at Thr172 independently of LKB1 or energy stress. This finding indicated that while LKB1 activates AMPK as a sensor of energetic stress, IKK activated AMPK in response to extracellular inflammatory signals and through distinct pathways downstream of IKK activation. Accordingly, in LKB1-deficient cells, IKK inhibition caused a reduction in AMPK Thr172 phosphorylation in response to the mitochondrial inhibitor phenformin. This response led to enhanced apoptosis and suggests that IKK inhibition in combination with phenformin could be used clinically to treat patients with LKB1-deficient cancers.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:LKB1 encodes a Ser/Thr kinase and acts as an evolutionarily conserved sensor of cellular energy status in eukaryotic cells. LKB1 functions as the major upstream kinase to phosphorylate AMPK and 12 other AMPK-related kinases, which is required for their activation in many cellular contexts. Once activated, AMPK and AMPK-related kinases phosphorylate a diverse array of downstream effectors to switch on ATP-generating catabolic processes and switch off ATP-consuming anabolic processes, thus restoring energy balance during periods of energetic stress. To study the role and mechanisms of Lkb1 in the regulation of hematopoietic stem cell (HSC) biology, we performed transcriptome analysis of sorted LSK (Lin-, Sca-1+, c-Kit+) cells from Lkb1 WT and KO bone marrows at 1 day post-completing tamoxifen injection (DPI). To identify more proximal molecular effects, we chose 1 DPI due to the modest phenotypes in Lkb1 KO mice, yet documentation of efficient Lkb1 deletion in LSK cells at this very early time point. We treated Lkb1 L/L rosa26CreERT2 and Lkb1 L/L mice (C57BL/Ka-CD45.2:Thy-1.1 background) with Tamoxifen for 5 days to somatically delete Lkb1 in adult mice, and generated Lkb1 WT and KO mice. At 1 DPI, we prepared single-cell suspensions from bone marrow (from femoral and tibial bones), and stained and sorted LSK populations using FACSAria (Becton Dickinson, Mountain View, CA). The RNA was extracted from sorted LSK cells, amplified and subjected to gene profiling. The samples include 3 Lkb1 WT (Lkb1 WT 5-7) and 4 Lkb1 KO (Lkb1 KO 4-7) replicates.
Project description:Translational research is commonly performed in the C57B6/J mouse strain, chosen for its genetic homogeneity and phenotypic uniformity. Here, we evaluate the suitability of the white-footed deer mouse (Peromyscus leucopus) as a model organism for aging research, offering a comparative analysis against C57B6/J and diversity outbred (DO) Mus musculus strains. Our study includes comparisons of body composition, skeletal muscle function, and cardiovascular parameters, shedding light on potential applications and limitations of P. leucopus in aging studies. Notably, P. leucopus exhibits distinct body composition characteristics, emphasizing reduced muscle force exertion and a unique metabolism, particularly in fat mass. Cardiovascular assessments showed changes in arterial stiffness, challenging conventional assumptions and highlighting the need for a nuanced interpretation of aging-related phenotypes. Our study also highlights inherent challenges associated with maintaining and phenotyping P. leucopus cohorts. Behavioral considerations, including anxiety-induced responses during handling and phenotyping assessment, pose obstacles in acquiring meaningful data. Moreover, the unique anatomy of P. leucopus necessitates careful adaptation of protocols designed for Mus musculus. While showcasing potential benefits, further extensive analyses across broader age ranges and larger cohorts are necessary to establish the reliability of P. leucopus as a robust and translatable model for aging studies.
Project description:Metformin is the front-line treatment for type 2 diabetes worldwide. It acts via effects on glucose and lipid metabolism in metabolic tissues, leading to enhanced insulin sensitivity. Despite significant effort, the molecular basis for metformin response remains poorly understood, with a limited number of specific biochemical pathways studied to date. To broaden our understanding of hepatic metformin response, we combine phospho-protein enrichment in tissue from genetically engineered mice with a quantitative proteomics platform to enable the discovery and quantification of basophilic kinase substrates in-vivo. We define proteins that binding to 14-3-3 are acutely regulated by metformin treatment and/or loss of the serine/threonine kinase, LKB1. Inducible binding of 250 proteins following metformin treatment is observed, 44% LKB1-dependent. Beyond AMPK, metformin activates Protein Kinase D and MAPKAPK2 in an LKB1-independent manner, revealing additional kinases that may mediate aspects of metformin response. Deeper analysis uncovered substrates of AMPK in endocytosis and calcium homeostasis.