Concise Communication

Abstract

Hematopoietic stem cells (HSCs) are highly susceptible to ionizing radiation–mediated death via induction of ROS, DNA double-strand breaks, and apoptotic pathways. The development of therapeutics capable of mitigating ionizing radiation–induced hematopoietic toxicity could benefit both victims of acute radiation sickness and patients undergoing hematopoietic cell transplantation. Unfortunately, therapies capable of accelerating hematopoietic reconstitution following lethal radiation exposure have remained elusive. Here, we found that systemic administration of pleiotrophin (PTN), a protein that is secreted by BM-derived endothelial cells, substantially increased the survival of mice following radiation exposure and after myeloablative BM transplantation. In both models, PTN increased survival by accelerating the recovery of BM hematopoietic stem and progenitor cells in vivo. PTN treatment promoted HSC regeneration via activation of the RAS pathway in mice that expressed protein tyrosine phosphatase receptor-zeta (PTPRZ), whereas PTN treatment did not induce RAS signaling in PTPRZ-deficient mice, suggesting that PTN-mediated activation of RAS was dependent upon signaling through PTPRZ. PTN strongly inhibited HSC cycling following irradiation, whereas RAS inhibition abrogated PTN-mediated induction of HSC quiescence, blocked PTN-mediated recovery of hematopoietic stem and progenitor cells, and abolished PTN-mediated survival of irradiated mice. These studies demonstrate the therapeutic potential of PTN to improve survival after myeloablation and suggest that PTN-mediated hematopoietic regeneration occurs in a RAS-dependent manner.

Authors

Heather A. Himburg, Xiao Yan, Phuong L. Doan, Mamle Quarmyne, Eva Micewicz, William McBride, Nelson J. Chao, Dennis J. Slamon, John P. Chute

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Abstract

Transport of oxygen by red blood cells (rbc) is critical for life and embryogenesis. Here, we determined that provision of the lipid mediator sphingosine 1-phosphate (S1P) to the systemic circulation is an essential function of rbc in embryogenesis. Mice with rbc-specific deletion of sphingosine kinases 1 and 2 (Sphk1 and Sphk2) showed embryonic lethality between E11.5 and E12.5 due to defects in vascular development. Administration of an S1P1 receptor agonist to pregnant dams rescued early embryonic lethality. Even though rbc-specific Sphk1 Sphk2–KO embryos were anemic, the erythropoietic capacity of hematopoietic stem cells (HSCs) was not impaired, suggesting that rbc can develop in the absence of sphingosine kinase activity. Indeed, transplantation of HSCs deficient for Sphk1 and Sphk2 into adult mice produced rbc that lacked S1P and attenuated plasma S1P levels in recipients. However, in adult animals, both rbc and endothelium contributed to plasma S1P. Together, these findings demonstrate that rbc are essential for embryogenesis by supplying the lysophospholipid S1P, which regulates embryonic vascular development via its receptors.

Authors

Yuquan Xiong, Peiying Yang, Richard L. Proia, Timothy Hla

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Abstract

Glaucoma is a leading cause of blindness, afflicting more than 60 million people worldwide. Increased intraocular pressure (IOP) due to impaired aqueous humor drainage is a major risk factor for the development of glaucoma. Here, we demonstrated that genetic disruption of the angiopoietin/TIE2 (ANGPT/TIE2) signaling pathway results in high IOP, buphthalmos, and classic features of glaucoma, including retinal ganglion degeneration and vision loss. Eyes from mice with induced deletion of Angpt1 and Angpt2 (A1A2FloxWB mice) lacked drainage pathways in the corneal limbus, including Schlemm’s canal and lymphatic capillaries, which share expression of the PROX1, VEGFR3, and FOXC family of transcription factors. VEGFR3 and FOXCs have been linked to lymphatic disorders in patients, and FOXC1 has been linked to glaucoma. In contrast to blood endothelium, in which ANGPT2 is an antagonist of ANGPT1, we have shown that both ligands cooperate to regulate TIE2 in the lymphatic network of the eye. While A1A2FloxWB mice developed high IOP and glaucoma, expression of ANGPT1 or ANGPT2 alone was sufficient for ocular drainage. Furthermore, we demonstrated that loss of FOXC2 from lymphatics results in TIE2 downregulation, suggesting a mechanism for ocular defects in patients with FOXC mutations. These data reveal a pathogenetic and molecular basis for glaucoma and demonstrate the importance of angiopoietin ligand cooperation in the lymphatic endothelium.

Authors

Benjamin R. Thomson, Stefan Heinen, Marie Jeansson, Asish K. Ghosh, Anees Fatima, Hoon-Ki Sung, Tuncer Onay, Hui Chen, Shinji Yamaguchi, Aris N. Economides, Ann Flenniken, Nicholas W. Gale, Young-Kwon Hong, Amani Fawzi, Xiaorong Liu, Tsutomu Kume, Susan E. Quaggin

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Abstract

Recently, patient mutations that activate PI3K signaling have been linked to a primary antibody deficiency. Here, we used whole-exome sequencing and characterized the molecular defects in 4 patients from 3 unrelated families diagnosed with hypogammaglobulinemia and recurrent infections. We identified 2 different heterozygous splice site mutations that affect the same splice site in PIK3R1, which encodes the p85α subunit of PI3K. The resulting deletion of exon 10 produced a shortened p85α protein that lacks part of the PI3K p110-binding domain. The hypothetical loss of p85α-mediated inhibition of p110 activity was supported by elevated phosphorylation of the known downstream signaling kinase AKT in patient T cell blasts. Analysis of patient blood revealed that naive T and memory B cell counts were low, and T cell blasts displayed enhanced activation-induced cell death, which was corrected by addition of the PI3Kδ inhibitor IC87114. Furthermore, B lymphocytes proliferated weakly in response to activation via the B cell receptor and TLR9, indicating a B cell defect. The phenotype exhibited by patients carrying the PIK3R1 splice site mutation is similar to that of patients carrying gain-of-function mutations in PIK3CD. Our results suggest that PI3K activity is tightly regulated in T and B lymphocytes and that various defects in the PI3K-triggered pathway can cause primary immunodeficiencies.

Authors

Marie-Céline Deau, Lucie Heurtier, Pierre Frange, Felipe Suarez, Christine Bole-Feysot, Patrick Nitschke, Marina Cavazzana, Capucine Picard, Anne Durandy, Alain Fischer, Sven Kracker

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Abstract

Cancer has long been viewed as a genetic disease; however, epigenetic silencing as the result of aberrant promoter DNA methylation is frequently associated with cancer development, suggesting an epigenetic component to the disease. Nonetheless, it has remained unclear whether an epimutation (an aberrant change in epigenetic regulation) can induce tumorigenesis. Here, we exploited a functionally validated cis-acting regulatory element and devised a strategy to induce developmentally regulated genomic targeting of DNA methylation. We used this system to target DNA methylation within the p16Ink4a promoter in mice in vivo. Engineered p16Ink4a promoter hypermethylation led to transcriptional suppression in somatic tissues during aging and increased the incidence of spontaneous cancers in these mice. Further, mice carrying a germline p16Ink4a mutation in one allele and a somatic epimutation in the other had accelerated tumor onset and substantially shortened tumor-free survival. Taken together, these results provide direct functional evidence that p16Ink4a epimutation drives tumor formation and malignant progression and validate a targeted methylation approach to epigenetic engineering.

Authors

Da-Hai Yu, Robert A. Waterland, Pumin Zhang, Deborah Schady, Miao-Hsueh Chen, Yongtao Guan, Manasi Gadkari, Lanlan Shen

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Abstract

The transmission of pruritoceptive (itch) messages involves specific neural circuits within the spinal cord that are distinct from those that transmit pain messages. These itch-specific circuits are tonically regulated by inhibitory interneurons in the dorsal horn. Consistent with these findings, it has previously been reported that loss of GABAergic interneurons in mice harboring a deletion of the transcription factor Bhlhb5 generates a severe, nonremitting condition of chronic itch. Here, we tested the hypothesis that the neuropathic itch in BHLHB5-deficient animals can be treated by restoring inhibitory controls through spinal cord transplantation and integration of precursors of cortical inhibitory interneurons derived from the embryonic medial ganglionic eminence. We specifically targeted the transplants to segments of the spinal cord innervated by areas of the body that were most severely affected. BHLHB5-deficient mice that received transplants demonstrated a substantial reduction of excessive scratching and dramatic resolution of skin lesions. In contrast, the scratching persisted and skin lesions worsened over time in sham-treated mice. Together, these results indicate that cell-mediated restoration of inhibitory controls has potential as a powerful, cell-based therapy for neuropathic itch that not only ameliorates symptoms of chronic itch, but also may modify disease.

Authors

Joao M. Braz, Dina Juarez-Salinas, Sarah E. Ross, Allan I. Basbaum

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Abstract

The neuropeptide kisspeptin regulates reproduction by stimulating gonadotropin-releasing hormone (GnRH) neurons via the kisspeptin receptor KISS1R. In addition to GnRH neurons, KISS1R is expressed in other brain areas and peripheral tissues, which suggests that kisspeptin has additional functions beyond reproduction. Here, we studied the energetic and metabolic phenotype in mice lacking kisspeptin signaling (Kiss1r KO mice). Compared with WT littermates, adult Kiss1r KO females displayed dramatically higher BW, leptin levels, and adiposity, along with strikingly impaired glucose tolerance. Conversely, male Kiss1r KO mice had normal BW and glucose regulation. Surprisingly, despite their obesity, Kiss1r KO females ate less than WT females; however, Kiss1r KO females displayed markedly reduced locomotor activity, respiratory rate, and energy expenditure, which were not due to impaired thyroid hormone secretion. The BW and metabolic phenotype in Kiss1r KO females was not solely reflective of absent gonadal estrogen, as chronically ovariectomized Kiss1r KO females developed obesity, hyperleptinemia, reduced metabolism, and glucose intolerance compared with ovariectomized WT females. Our findings demonstrate that in addition to reproduction, kisspeptin signaling influences BW, energy expenditure, and glucose homeostasis in a sexually dimorphic and partially sex steroid–independent manner; therefore, alterations in kisspeptin signaling might contribute, directly or indirectly, to some facets of human obesity, diabetes, or metabolic dysfunction.

Authors

Kristen P. Tolson, Christian Garcia, Stephanie Yen, Stephanie Simonds, Aneta Stefanidis, Alison Lawrence, Jeremy T. Smith, Alexander S. Kauffman

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Abstract

Damage to the intestinal mucosa results in the translocation of microbes from the intestinal lumen into the circulation. Microbial translocation has been proposed to trigger immune activation, inflammation, and coagulopathy, all of which are key factors that drive HIV disease progression and non-HIV comorbidities; however, direct proof of a causal link is still lacking. Here, we have demonstrated that treatment of acutely SIV-infected pigtailed macaques with the drug sevelamer, which binds microbial lipopolysaccharide in the gut, dramatically reduces immune activation and inflammation and slightly reduces viral replication. Furthermore, sevelamer administration reduced coagulation biomarkers, confirming the contribution of microbial translocation in the development of cardiovascular comorbidities in SIV-infected nonhuman primates. Together, our data suggest that early control of microbial translocation may improve the outcome of HIV infection and limit noninfectious comorbidities associated with AIDS.

Authors

Jan Kristoff, George Haret-Richter, Dongzhu Ma, Ruy M. Ribeiro, Cuiling Xu, Elaine Cornell, Jennifer L. Stock, Tianyu He, Adam D. Mobley, Samantha Ross, Anita Trichel, Cara Wilson, Russell Tracy, Alan Landay, Cristian Apetrei, Ivona Pandrea

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Abstract

In a wide array of kidney diseases, type 1 angiotensin (AT1) receptors are present on the immune cells that infiltrate the renal interstitium. Here, we examined the actions of AT1 receptors on macrophages in progressive renal fibrosis and found that macrophage-specific AT1 receptor deficiency exacerbates kidney fibrosis induced by unilateral ureteral obstruction (UUO). Macrophages isolated from obstructed kidneys of mice lacking AT1 receptors solely on macrophages had heightened expression of proinflammatory M1 cytokines, including IL-1. Evaluation of isolated AT1 receptor–deficient macrophages confirmed the propensity of these cells to produce exaggerated levels of M1 cytokines, which led to more severe renal epithelial cell damage via IL-1 receptor activation in coculture compared with WT macrophages. A murine kidney crosstransplantation concomitant with UUO model revealed that augmentation of renal fibrosis instigated by AT1 receptor–deficient macrophages is mediated by IL-1 receptor stimulation in the kidney. This study indicates that a key role of AT1 receptors on macrophages is to protect the kidney from fibrosis by limiting activation of IL-1 receptors in the kidney.

Authors

Jian-dong Zhang, Mehul B. Patel, Robert Griffiths, Paul C. Dolber, Phillip Ruiz, Matthew A. Sparks, Johannes Stegbauer, Huixia Jin, Jose A. Gomez, Anne F. Buckley, William S. Lefler, Daian Chen, Steven D. Crowley

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Abstract

The transcription factor steroidogenic factor 1 (SF-1; also known as NR5A1) is a crucial mediator of both steroidogenic and nonsteroidogenic tissue differentiation. Mutations within SF1 underlie different disorders of sexual development (DSD), including sex reversal, spermatogenic failure, ovarian insufficiency, and adrenocortical deficiency. Here, we identified a recessive mutation within SF1 that resulted in a substitution of arginine to glutamine at codon 103 (R103Q) in a child with both severe 46,XY-DSD and asplenia. The R103Q mutation decreased SF-1 transactivation of TLX1, a transcription factor that has been shown to be essential for murine spleen development. Additionally, the SF1 R103Q mutation impaired activation of steroidogenic genes, without affecting synergistic SF-1 and sex-determining region Y (SRY) coactivation of the testis development gene SOX9. Together, our data provide evidence that SF-1 is required for spleen development in humans via transactivation of TLX1 and that mutations that only impair steroidogenesis, without altering the SF1/SRY transactivation of SOX9, can lead to 46,XY-DSD.

Authors

David Zangen, Yotam Kaufman, Ehud Banne, Ariella Weinberg-Shukron, Abdulsalam Abulibdeh, Benjamin P. Garfinkel, Dima Dweik, Moein Kanaan, Núria Camats, Christa Flück, Paul Renbaum, Ephrat Levy-Lahad

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