Browsing by Author "Field, Loren"

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    A remarkable adaptive paradigm of heart performance and protection emerges in response to marked cardiac-specific overexpression of ADCY8
    (eLife Sciences, 2022-12-14) Tarasov, Kirill V.; Chakir, Khalid; Riordon, Daniel R.; Lyashkov, Alexey E.; Ahmet, Ismayil; Perino, Maria Grazia; Silvester, Allwin Jennifa; Zhang, Jing; Wang, Mingyi; Lukyanenko, Yevgeniya O.; Qu, Jia-Hua; Barrera, Miguel Calvo-Rubio; Juhaszova, Magdalena; Tarasova, Yelena S.; Ziman, Bruce; Telljohann, Richard; Kumar, Vikas; Ranek, Mark; Lammons, John; Bychkov, Rostislav; de Cabo, Rafael; Jun, Seungho; Keceli, Gizem; Gupta, Ashish; Yang, Dongmei; Aon, Miguel A.; Adamo, Luigi; Morrell, Christopher H.; Otu, Walter; Carroll, Cameron; Chambers, Shane; Paolocci, Nazareno; Huynh, Thanh; Pacak, Karel; Weiss, Robert; Field, Loren; Sollott, Steven J.; Lakatta, Edward G.; Medicine, School of Medicine
    Adult (3 month) mice with cardiac-specific overexpression of adenylyl cyclase (AC) type VIII (TGAC8) adapt to an increased cAMP-induced cardiac workload (~30% increases in heart rate, ejection fraction and cardiac output) for up to a year without signs of heart failure or excessive mortality. Here, we show classical cardiac hypertrophy markers were absent in TGAC8, and that total left ventricular (LV) mass was not increased: a reduced LV cavity volume in TGAC8 was encased by thicker LV walls harboring an increased number of small cardiac myocytes, and a network of small interstitial proliferative non-cardiac myocytes compared to wild type (WT) littermates; Protein synthesis, proteosome activity, and autophagy were enhanced in TGAC8 vs WT, and Nrf-2, Hsp90α, and ACC2 protein levels were increased. Despite increased energy demands in vivo LV ATP and phosphocreatine levels in TGAC8 did not differ from WT. Unbiased omics analyses identified more than 2,000 transcripts and proteins, comprising a broad array of biological processes across multiple cellular compartments, which differed by genotype; compared to WT, in TGAC8 there was a shift from fatty acid oxidation to aerobic glycolysis in the context of increased utilization of the pentose phosphate shunt and nucleotide synthesis. Thus, marked overexpression of AC8 engages complex, coordinate adaptation "circuity" that has evolved in mammalian cells to defend against stress that threatens health or life (elements of which have already been shown to be central to cardiac ischemic pre-conditioning and exercise endurance cardiac conditioning) that may be of biological significance to allow for proper healing in disease states such as infarction or failure of the heart.
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    Cyclin D2 is sufficient to drive β cell self-renewal and regeneration
    (Taylor & Francis, 2017-11-03) Tschen, Shuen-ing; Zeng, Chun; Field, Loren; Dhawan, Sangeeta; Bhushan, Anil; Georgia, Senta; Medicine, School of Medicine
    Diabetes results from an inadequate mass of functional β cells, due to either β cell loss caused by autoimmune destruction (type I diabetes) or β cell failure in response to insulin resistance (type II diabetes). Elucidating the mechanisms that regulate β cell mass may be key to developing new techniques that foster β cell regeneration as a cellular therapy to treat diabetes. While previous studies concluded that cyclin D2 is required for postnatal β cell self-renewal in mice, it is not clear if cyclin D2 is sufficient to drive β cell self-renewal. Using transgenic mice that overexpress cyclin D2 specifically in β cells, we show that cyclin D2 overexpression increases β cell self-renewal post-weaning and results in increased β cell mass. β cells that overexpress cyclin D2 are responsive to glucose stimulation, suggesting they are functionally mature. β cells that overexpress cyclin D2 demonstrate an enhanced regenerative capacity after injury induced by streptozotocin toxicity. To understand if cyclin D2 overexpression is sufficient to drive β cell self-renewal, we generated a novel mouse model where cyclin D2 is only expressed in β cells of cyclin D2−/− mice. Transgenic overexpression of cyclin D2 in cyclin D2−/− β cells was sufficient to restore β cell mass, maintain normoglycaemia, and improve regenerative capacity when compared with cyclin D2−/− littermates. Taken together, our results indicate that cyclin D2 is sufficient to regulate β cell self-renewal and that manipulation of its expression could be used to enhance β cell regeneration.
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    Whole-Genome Sequencing to Identify the Genetic Etiology of a Spontaneous Thymoma Mouse Model
    (JPGN Reports, 2021) Conces, Madison L.; Hancock, Bradley A.; Atale, Rutuja; Solzak, Jeffrey P.; Bunting, Karen; Corvelo, Andre; Field, Loren; Badve, Sunil; Liu, Jianyun; Brutkiewicz, Randy R.; Loehrer, Patrick J.; Radovich, Milan; Pediatrics, School of Medicine
    Background: A mouse model for thymoma was previously created serendipitously by the random introduction of a transgene consisting of a mouse α-cardiac promoter, a constitutively active human transforming growth factor-β, and a simian virus 40 integration sequence into C3HeB/FeJ mice. Previous data demonstrated that the likely cause of thymomas in the thymoma mouse model was due to insertional mutagenesis by the transgene. At the time, fluorescence in situ hybridization was used to localize the transgene to the short arm of chromosome 2 (Chr2qF2-G region). In this exploratory study, we aimed to identify the exact insertion site of the transgene as this could provide clues to the genetic causation of thymomas in humans. Materials and Methods: To identify the insertion site of the transgene, germline DNA from the thymoma mouse model was sequenced using low-pass, fragment-library, whole genome sequencing. Long-insert mate pair whole genome sequencing was employed to traverse the repetitive regions of the mouse’s genome and identify the integration site. Results: The transgene was found to be integrated into a repetitive area of the mouse genome, specifically on Chr2qF1 within the intron of the FAM227B gene. Tandem integration of the transgene was observed with enumeration of an estimated 30 copies. Initial results suggested that a nearby gene, fibroblast growth factor 7 (Fgf7), could be affected by the gene insertion. Conclusions: Whole genome sequencing of this thymoma mouse model identified the region of tandem integration of a transgene on Chr2qF1 that may have potential translational implications in helping to understand the genomic etiology of thymoma in humans.