Publications by authors named "Stephen M Eacker"

16 Publications

  • Page 1 of 1

Genome sequence of Monilinia vaccinii-corymbosi sheds light on mummy berry disease infection of blueberry and mating type.

G3 (Bethesda) 2021 Feb;11(2)

Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695, USA.

Mummy berry disease, caused by the fungal pathogen Monilinia vaccinii-corymbosi (Mvc), is one of the most economically important diseases of blueberries in North America. Mvc is capable of inducing two separate blighting stages during its life cycle. Infected fruits are rendered mummified and unmarketable. Genomic data for this pathogen is lacking, but could be useful in understanding the reproductive biology of Mvc and the mechanisms it deploys to facilitate host infection. In this study, PacBio sequencing and Hi-C interaction data were utilized to create a chromosome-scale reference genome for Mvc. The genome comprises nine chromosomes with a total length of 30 Mb, an N50 length of 4.06 Mb, and an average 413X sequence coverage. A total of 9399 gene models were predicted and annotated, and BUSCO analysis revealed that 98% of 1,438 searched conserved eukaryotic genes were present in the predicted gene set. Potential effectors were identified, and the mating-type (MAT) locus was characterized. Biotrophic effectors allow the pathogen to avoid recognition by the host plant and evade or mitigate host defense responses during the early stages of fruit infection. Following locule colonization, necrotizing effectors promote the mummification of host tissues. Potential biotrophic effectors utilized by Mvc include chorismate mutase for reducing host salicylate and necrotrophic effectors include necrosis-inducing proteins and hydrolytic enzymes for macerating host tissue. The MAT locus sequences indicate the potential for homothallism in the reference genome, but a deletion allele of the MAT locus, characterized in a second isolate, indicates heterothallism. Further research is needed to verify the roles of individual effectors in virulence and to determine the role of the MAT locus in outcrossing and population genotypic diversity.
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http://dx.doi.org/10.1093/g3journal/jkaa052DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8022979PMC
February 2021

High-Quality Assemblies for Three Invasive Social Wasps from the Genus.

G3 (Bethesda) 2020 10 5;10(10):3479-3488. Epub 2020 Oct 5.

Genomics Aotearoa and Department of Biochemistry, University of Otago, Dunedin 9054, Aotearoa, New Zealand

Social wasps of the genus have spread to nearly all landmasses worldwide and have become significant pests in their introduced ranges, affecting economies and biodiversity. Comprehensive genome assemblies and annotations for these species are required to develop the next generation of control strategies and monitor existing chemical control. We sequenced and annotated the genomes of the common wasp (), German wasp (), and the western yellowjacket (). Our chromosome-level assemblies each contain 176-179 Mb of total sequence assembled into 25 scaffolds, with 10-200 unanchored scaffolds, and 16,566-18,948 genes. We annotated gene sets relevant to the applied management of invasive wasp populations, including genes associated with spermatogenesis and development, pesticide resistance, olfactory receptors, immunity and venom. These genomes provide evidence for active DNA methylation in Vespidae and tandem duplications of venom genes. Our genomic resources will contribute to the development of next-generation control strategies, and monitoring potential resistance to chemical control.
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http://dx.doi.org/10.1534/g3.120.401579DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7534447PMC
October 2020

Defects in mRNA Translation in LRRK2-Mutant hiPSC-Derived Dopaminergic Neurons Lead to Dysregulated Calcium Homeostasis.

Cell Stem Cell 2020 10 25;27(4):633-645.e7. Epub 2020 Aug 25.

Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Adrienne Helis Malvin Medical Research Foundation, New Orleans, LA 70130, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Diana Helis Henry Medical Research Foundation, New Orleans, LA 70130, USA. Electronic address:

The G2019S mutation in leucine-rich repeat kinase 2 (LRRK2) is a common cause of familial Parkinson's disease (PD). This mutation results in dopaminergic neurodegeneration via dysregulated protein translation, although how alterations in protein synthesis contribute to neurodegeneration in human neurons is not known. Here we define the translational landscape in LRRK2-mutant dopaminergic neurons derived from human induced pluripotent stem cells (hiPSCs) via ribosome profiling. We found that mRNAs that have complex secondary structure in the 5' untranslated region (UTR) are translated more efficiently in G2019S LRRK2 neurons. This leads to the enhanced translation of multiple genes involved in Ca regulation and to increased Ca influx and elevated intracellular Ca levels, a major contributor to PD pathogenesis. This study reveals a link between dysregulated translation control and Ca homeostasis in G2019S LRRK2 human dopamine neurons, which potentially contributes to the progressive and selective dopaminergic neurotoxicity in PD.
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http://dx.doi.org/10.1016/j.stem.2020.08.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7542555PMC
October 2020

Discovery of noncanonical translation initiation sites through mass spectrometric analysis of protein N termini.

Genome Res 2018 01 21;28(1):25-36. Epub 2017 Nov 21.

McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

Translation initiation generally occurs at AUG codons in eukaryotes, although it has been shown that non-AUG or noncanonical translation initiation can also occur. However, the evidence for noncanonical translation initiation sites (TISs) is largely indirect and based on ribosome profiling (Ribo-seq) studies. Here, using a strategy specifically designed to enrich N termini of proteins, we demonstrate that many human proteins are translated at noncanonical TISs. The large majority of TISs that mapped to 5' untranslated regions were noncanonical and led to N-terminal extension of annotated proteins or translation of upstream small open reading frames (uORF). It has been controversial whether the amino acid corresponding to the start codon is incorporated at the TIS or methionine is still incorporated. We found that methionine was incorporated at almost all noncanonical TISs identified in this study. Comparison of the TISs determined through mass spectrometry with ribosome profiling data revealed that about two-thirds of the novel annotations were indeed supported by the available ribosome profiling data. Sequence conservation across species and a higher abundance of noncanonical TISs than canonical ones in some cases suggests that the noncanonical TISs can have biological functions. Overall, this study provides evidence of protein translation initiation at noncanonical TISs and argues that further studies are required for elucidation of functional implications of such noncanonical translation initiation.
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http://dx.doi.org/10.1101/gr.226050.117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5749180PMC
January 2018

A nuclease that mediates cell death induced by DNA damage and poly(ADP-ribose) polymerase-1.

Science 2016 10;354(6308)

Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.

Inhibition or genetic deletion of poly(ADP-ribose) (PAR) polymerase-1 (PARP-1) is protective against toxic insults in many organ systems. The molecular mechanisms underlying PARP-1-dependent cell death involve release of mitochondrial apoptosis-inducing factor (AIF) and its translocation to the nucleus, which results in chromatinolysis. We identified macrophage migration inhibitory factor (MIF) as a PARP-1-dependent AIF-associated nuclease (PAAN). AIF was required for recruitment of MIF to the nucleus, where MIF cleaves genomic DNA into large fragments. Depletion of MIF, disruption of the AIF-MIF interaction, or mutation of glutamic acid at position 22 in the catalytic nuclease domain blocked MIF nuclease activity and inhibited chromatinolysis, cell death induced by glutamate excitotoxicity, and focal stroke. Inhibition of MIF's nuclease activity is a potential therapeutic target for diseases caused by excessive PARP-1 activation.
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http://dx.doi.org/10.1126/science.aad6872DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134926PMC
October 2016

High-Content Genome-Wide RNAi Screen Reveals as a Key Mediator of Neuronal Cell Death.

eNeuro 2016 Sep-Oct;3(5). Epub 2016 Oct 24.

Neuroregeneration Program, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205; Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205; Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.

Neuronal loss caused by ischemic injury, trauma, or disease can lead to devastating consequences for the individual. With the goal of limiting neuronal loss, a number of cell death pathways have been studied, but there may be additional contributors to neuronal death that are yet unknown. To identify previously unknown cell death mediators, we performed a high-content genome-wide screening of short, interfering RNA (siRNA) with an siRNA library in murine neural stem cells after exposure to -methyl--nitroso-'-nitroguanidine (MNNG), which leads to DNA damage and cell death. Eighty genes were identified as key mediators for cell death. Among them, 14 are known cell death mediators and 66 have not previously been linked to cell death pathways. Using an integrated approach with functional and bioinformatics analysis, we provide possible molecular networks, interconnected pathways, and/or protein complexes that may participate in cell death. Of the 66 genes, we selected for further evaluation and found that CCR3 is a mediator of neuronal injury. CCR3 inhibition or deletion protects murine cortical cultures from oxygen-glucose deprivation-induced cell death, and deletion in mice provides protection from ischemia in vivo. Taken together, our findings suggest that CCR3 is a previously unknown mediator of cell death. Future identification of the neural cell death network in which CCR3 participates will enhance our understanding of the molecular mechanisms of neural cell death.
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http://dx.doi.org/10.1523/ENEURO.0185-16.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5075945PMC
October 2017

Cultured networks of excitatory projection neurons and inhibitory interneurons for studying human cortical neurotoxicity.

Sci Transl Med 2016 Apr;8(333):333ra48

Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.

Translating neuroprotective treatments from discovery in cell and animal models to the clinic has proven challenging. To reduce the gap between basic studies of neurotoxicity and neuroprotection and clinically relevant therapies, we developed a human cortical neuron culture system from human embryonic stem cells or human inducible pluripotent stem cells that generated both excitatory and inhibitory neuronal networks resembling the composition of the human cortex. This methodology used timed administration of retinoic acid to FOXG1(+) neural precursor cells leading to differentiation of neuronal populations representative of the six cortical layers with both excitatory and inhibitory neuronal networks that were functional and homeostatically stable. In human cortical neuronal cultures, excitotoxicity or ischemia due to oxygen and glucose deprivation led to cell death that was dependent on N-methyl-D-aspartate (NMDA) receptors, nitric oxide (NO), and poly(ADP-ribose) polymerase (PARP) (a cell death pathway called parthanatos that is distinct from apoptosis, necroptosis, and other forms of cell death). Neuronal cell death was attenuated by PARP inhibitors that are currently in clinical trials for cancer treatment. This culture system provides a new platform for the study of human cortical neurotoxicity and suggests that PARP inhibitors may be useful for ameliorating excitotoxic and ischemic cell death in human neurons.
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http://dx.doi.org/10.1126/scitranslmed.aad0623DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5595216PMC
April 2016

Androgen-dependent sertoli cell tight junction remodeling is mediated by multiple tight junction components.

Mol Endocrinol 2014 Jul 13;28(7):1055-72. Epub 2014 May 13.

The Jackson Laboratory (P.C., F.W.B., M.S., B.E.S., A.R.G., R.E.B.), Bar Harbor, Maine 04609; and Department of Neurology (S.M.E.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

Sertoli cell tight junctions (SCTJs) of the seminiferous epithelium create a specialized microenvironment in the testis to aid differentiation of spermatocytes and spermatids from spermatogonial stem cells. SCTJs must be chronically broken and rebuilt with high fidelity to allow the transmigration of preleptotene spermatocytes from the basal to adluminal epithelial compartment. Impairment of androgen signaling in Sertoli cells perturbs SCTJ remodeling. Claudin (CLDN) 3, a tight junction component under androgen regulation, localizes to newly forming SCTJs and is absent in Sertoli cell androgen receptor knockout (SCARKO) mice. We show here that Cldn3-null mice do not phenocopy SCARKO mice: Cldn3(-/-) mice are fertile, show uninterrupted spermatogenesis, and exhibit fully functional SCTJs based on imaging and small molecule tracer analyses, suggesting that other androgen-regulated genes must contribute to the SCARKO phenotype. To further investigate the SCTJ phenotype observed in SCARKO mutants, we generated a new SCARKO model and extensively analyzed the expression of other tight junction components. In addition to Cldn3, we identified altered expression of several other SCTJ molecules, including down-regulation of Cldn13 and a noncanonical tight junction protein 2 isoform (Tjp2iso3). Chromatin immunoprecipitation was used to demonstrate direct androgen receptor binding to regions of these target genes. Furthermore, we demonstrated that CLDN13 is a constituent of SCTJs and that TJP2iso3 colocalizes with tricellulin, a constituent of tricellular junctions, underscoring the importance of androgen signaling in the regulation of both bicellular and tricellular Sertoli cell tight junctions.
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http://dx.doi.org/10.1210/me.2013-1134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4075161PMC
July 2014

The interplay of microRNA and neuronal activity in health and disease.

Front Cell Neurosci 2013 27;7:136. Epub 2013 Aug 27.

Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine Baltimore, MD, USA ; Department of Neurology, Johns Hopkins University School of Medicine Baltimore, MD, USA.

MicroRNAs (miRNAs) are small 19-23 nucleotide regulatory RNAs that function by modulating mRNA translation and/or turnover in a sequence-specific fashion. In the nervous system, miRNAs regulate the production of numerous proteins involved in synaptic transmission. In turn, neuronal activity can regulate the production and turnover of miRNA through a variety of mechanisms. In this way, miRNAs and neuronal activity are in a reciprocal homeostatic relationship that balances neuronal function. The miRNA function is critical in pathological states related to overexcitation such as epilepsy and stroke, suggesting miRNA's potential as a therapeutic target. We review the current literature relating the interplay of miRNA and neuronal activity and provide future directions for defining miRNA's role in disease.
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http://dx.doi.org/10.3389/fncel.2013.00136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3753455PMC
August 2013

MicroRNA-223 is neuroprotective by targeting glutamate receptors.

Proc Natl Acad Sci U S A 2012 Nov 29;109(46):18962-7. Epub 2012 Oct 29.

Neuroregeneration Program, Institute for Cell Engineering, Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.

Stroke is a major cause of mortality and morbidity worldwide. Extracellular glutamate accumulation leading to overstimulation of the ionotropic glutamate receptors mediates neuronal injury in stroke and in neurodegenerative disorders. Here we show that miR-223 controls the response to neuronal injury by regulating the functional expression of the glutamate receptor subunits GluR2 and NR2B in brain. Overexpression of miR-223 lowers the levels of GluR2 and NR2B by targeting 3'-UTR target sites (TSs) in GluR2 and NR2B, inhibits NMDA-induced calcium influx in hippocampal neurons, and protects the brain from neuronal cell death following transient global ischemia and excitotoxic injury. MiR-223 deficiency results in higher levels of NR2B and GluR2, enhanced NMDA-induced calcium influx, and increased miniature excitatory postsynaptic currents in hippocampal neurons. In addition, the absence of MiR-223 leads to contextual, but not cued memory deficits and increased neuronal cell death following transient global ischemia and excitotoxicity. These data identify miR-223 as a major regulator of the expression of GluR2 and NR2B, and suggest a therapeutic role for miR-223 in stroke and other excitotoxic neuronal disorders.
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http://dx.doi.org/10.1073/pnas.1121288109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3503176PMC
November 2012

Neuronal activity regulates hippocampal miRNA expression.

PLoS One 2011 3;6(10):e25068. Epub 2011 Oct 3.

Neuroregeneration, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.

Neuronal activity regulates a broad range of processes in the hippocampus, including the precise regulation of translation. Disruptions in proper translational control in the nervous system are associated with a variety of disorders that fall in the autistic spectrum. MicroRNA (miRNA) represent a relatively recently discovered player in the regulation of translation in the nervous system. We have conducted an in depth analysis of how neuronal activity regulates miRNA expression in the hippocampus. Using deep sequencing we exhaustively identify all miRNAs, including 15 novel miRNAs, expressed in hippocampus of the adult mouse. We identified 119 miRNAs documented in miRBase but less than half of these miRNA were expressed at a level greater than 0.1% of total miRNA. Expression profiling following induction of neuronal activity by electroconvulsive shock demonstrates that most miRNA show a biphasic pattern of expression: rapid induction of specific mature miRNA expression followed by a decline in expression. These results have important implications into how miRNAs influence activity-dependent translational control.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0025068PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3184962PMC
January 2012

NMDA-induced neuronal survival is mediated through nuclear factor I-A in mice.

J Clin Invest 2010 Jul;120(7):2446-56

Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

Identification of the signaling pathways that mediate neuronal survival signaling could lead to new therapeutic targets for neurologic disorders and stroke. Sublethal doses of NMDA can induce robust endogenous protective mechanisms in neurons. Through differential analysis of primary library expression and microarray analyses, here we have shown that nuclear factor I, subtype A (NFI-A), a member of the NFI/CAAT-box transcription factor family, is induced in mouse neurons by NMDA receptor activation in a NOS- and ERK-dependent manner. Knockdown of NFI-A induction using siRNA substantially reduced the neuroprotective effects of sublethal doses of NMDA. Further analysis indicated that NFI-A transcriptional activity was required for the neuroprotective effects of NMDA receptor activation. Additional evidence of the neuroprotective effects of NFI-A was provided by the observations that Nfia(-/-) neurons were highly sensitive to NMDA-induced excitotoxicity and were more susceptible to developmental cell death than wild-type neurons and that Nfia(+/-) mice were more sensitive to NMDA-induced intrastriatal lesions than were wild-type animals. These results identify NFI-A as what we believe to be a novel neuroprotective transcription factor with implications in neuroprotection and neuronal plasticity following NMDA receptor activation.
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http://dx.doi.org/10.1172/JCI33144DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2898580PMC
July 2010

Understanding microRNAs in neurodegeneration.

Nat Rev Neurosci 2009 Dec 11;10(12):837-41. Epub 2009 Nov 11.

Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

Interest in the functions of microRNAs (miRNAs) in the nervous system has recently expanded to include their roles in neurodegeneration. Investigations have begun to reveal the influence of miRNAs on both neuronal survival and the accumulation of toxic proteins that are associated with neurodegeneration, and are providing clues as to how these toxic proteins can influence miRNA expression.
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http://dx.doi.org/10.1038/nrn2726DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120241PMC
December 2009

Hormonal regulation of testicular steroid and cholesterol homeostasis.

Mol Endocrinol 2008 Mar 21;22(3):623-35. Epub 2007 Nov 21.

Department of Genome Sciences, University of Washington, Seattle, Washington 98195, USA.

The male sex steroid, testosterone (T), is synthesized from cholesterol in the testicular Leydig cell under control of the pituitary gonadotropin LH. Unlike most cells that use cholesterol primarily for membrane synthesis, steroidogenic cells have additional requirements for cholesterol, because it is the essential precursor for all steroid hormones. Little is known about how Leydig cells satisfy their specialized cholesterol requirements for steroid synthesis. We show that in mice with a unique hypomorphic androgen mutation, which disrupts the feedback loop governing T synthesis, that genes involved in cholesterol biosynthesis/uptake and steroid biosynthesis are up-regulated. We identify LH as the central regulatory molecule that controls both steroidogenesis and Leydig cell cholesterol homeostasis in vivo. In addition to the primary defect caused by high levels of LH, absence of T signaling exacerbates the lipid homeostasis defect in Leydig cells by eliminating a short feedback loop. We show that T signaling can affect the synthesis of steroids and modulates the expression of genes involved in de novo cholesterol synthesis. Surprisingly, accumulation of active sterol response element-binding protein 2 is not required for up-regulation of genes involved in cholesterol biosynthesis and uptake in Leydig cells.
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http://dx.doi.org/10.1210/me.2006-0534DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2262169PMC
March 2008

Transcriptional profiling of androgen receptor (AR) mutants suggests instructive and permissive roles of AR signaling in germ cell development.

Mol Endocrinol 2007 Apr 23;21(4):895-907. Epub 2007 Jan 23.

Department of Genome Sciences, University of Washington School of Medicine, Box 355065, 1705 NE Pacific, Foege Building, Room 133C, Seattle, Washington 98195-5065, USA.

The androgen receptor (AR) is a transcription factor that plays a critical role in male sexual development, spermatogenesis, and maintenance of hormonal homeostasis. Despite the extensive knowledge of the phenotypic consequences of mutations in Ar, very little is known about the transcriptional targets of AR within the testis. To identify potential targets of androgen signaling in the testis, we have analyzed the transcriptional profile of adult testes from Ar hypomorphs alone or in combination with Sertoli cell-specific Ar ablation. Using Affymetrix MOE430A mouse genome arrays we interrogated more than 22,000 transcripts. We found the expression level of 62 transcripts in the Ar mutants differed by greater than 2-fold compared with wild type. We also found that more transcripts were up-regulated than down-regulated, highlighting AR's role as a transcriptional repressor in the testis. Twelve transcripts were uniquely affected, and 16 transcripts were more severely affected in Sertoli cell-specific Ar ablation compared with hypomorphic Ar mutants. Using a comparative genomic approach, we analyzed the 6 kb around the transcriptional start sites of affected transcripts for conserved AREs (androgen response elements). We identified at least one conserved ARE in 65% of the genes misregulated in our microarray analysis where clear mouse-human orthologs were available. We used a reporter assay in cell culture to functionally verify the AREs for the kallikrein 27 gene. This suggests that the majority of the misregulated transcripts have a high probability of being direct AR targets. The transcripts affected by these Ar mutations encode a diverse array of proteins whose molecular functions support the contention that AR supports spermatogenesis in both a permissive and instructive fashion.
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http://dx.doi.org/10.1210/me.2006-0113DOI Listing
April 2007

Differential regulation of KiSS-1 mRNA expression by sex steroids in the brain of the male mouse.

Endocrinology 2005 Jul 14;146(7):2976-84. Epub 2005 Apr 14.

Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195-7290, USA.

Kisspeptins are products of the Kiss1 gene, which bind to GPR54, a G protein-coupled receptor. Kisspeptins and GPR54 have been implicated in the neuroendocrine regulation of GnRH secretion. To test the hypothesis that testosterone regulates Kiss1 gene expression, we compared the expression of KiSS-1 mRNA among groups of intact, castrated, and castrated/testosterone (T)-treated male mice. In the arcuate nucleus (Arc), castration resulted in a significant increase in KiSS-1 mRNA, which was completely reversed with T replacement, whereas in the anteroventral periventricular nucleus, the results were the opposite, i.e. castration decreased and T increased KiSS-1 mRNA expression. In the Arc, the effects of T on KiSS-1 mRNA were completely mimicked by estrogen but only partially mimicked by dihydrotestosterone, a nonaromatizable androgen, suggesting that both estrogen receptor (ER) and androgen receptor (AR) play a role in T-mediated regulation of KiSS-1. Studies of the effects of T on KiSS-1 expression in mice with either a deletion of the ERalpha or a hypomorphic allele to the AR revealed that the effects of T are mediated by both ERalpha and AR pathways, which was confirmed by the presence of either ERalpha or AR coexpression in most KiSS-1 neurons in the Arc. These observations suggest that KiSS-1 neurons in the Arc, whose transcriptional activity is inhibited by T, are targets for the negative feedback regulation of GnRH secretion, whereas KiSS-1 neurons in the anteroventral periventricular nucleus, whose activity is stimulated by T, may mediate other T-dependent processes.
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http://dx.doi.org/10.1210/en.2005-0323DOI Listing
July 2005