Modulation of LMNA splicing as a strategy to treat prelamin A diseases

• Text
• PDF

Abstract

The alternatively spliced products of LMNA, lamin C and prelamin A (the precursor to lamin A), are produced in similar amounts in most tissues and have largely redundant functions. This redundancy suggests that diseases, such as Hutchinson-Gilford progeria syndrome (HGPS), that are caused by prelamin A–specific mutations could be treated by shifting the output of LMNA more toward lamin C. Here, we investigated mechanisms that regulate LMNA mRNA alternative splicing and assessed the feasibility of reducing prelamin A expression in vivo. We identified an exon 11 antisense oligonucleotide (ASO) that increased lamin C production at the expense of prelamin A when transfected into mouse and human fibroblasts. The same ASO also reduced the expression of progerin, the mutant prelamin A protein in HGPS, in fibroblasts derived from patients with HGPS. Mechanistic studies revealed that the exon 11 sequences contain binding sites for serine/arginine-rich splicing factor 2 (SRSF2), and SRSF2 knockdown lowered lamin A production in cells and in murine tissues. Moreover, administration of the exon 11 ASO reduced lamin A expression in wild-type mice and progerin expression in an HGPS mouse model. Together, these studies identify ASO-mediated reduction of prelamin A as a potential strategy to treat prelamin A–specific diseases.

Authors

John M. Lee, Chika Nobumori, Yiping Tu, Catherine Choi, Shao H. Yang, Hea-Jin Jung, Timothy A. Vickers, Frank Rigo, C. Frank Bennett, Stephen G. Young, Loren G. Fong

Estrogen-mediated downregulation of AIRE influences sexual dimorphism in autoimmune diseases

• Text
• PDF

Abstract

Autoimmune diseases affect 5% to 8% of the population, and females are more susceptible to these diseases than males. Here, we analyzed human thymic transcriptome and revealed sex-associated differences in the expression of tissue-specific antigens that are controlled by the autoimmune regulator (AIRE), a key factor in central tolerance. We hypothesized that the level of AIRE is linked to sexual dimorphism susceptibility to autoimmune diseases. In human and mouse thymus, females expressed less AIRE (mRNA and protein) than males after puberty. These results were confirmed in purified murine thymic epithelial cells (TECs). We also demonstrated that AIRE expression is related to sexual hormones, as male castration decreased AIRE thymic expression and estrogen receptor α–deficient mice did not show a sex disparity for AIRE expression. Moreover, estrogen treatment resulted in downregulation of AIRE expression in cultured human TECs, human thymic tissue grafted to immunodeficient mice, and murine fetal thymus organ cultures. AIRE levels in human thymus grafted in immunodeficient mice depended upon the sex of the recipient. Estrogen also upregulated the number of methylated CpG sites in the AIRE promoter. Together, our results indicate that in females, estrogen induces epigenetic changes in the AIRE gene, leading to reduced AIRE expression under a threshold that increases female susceptibility to autoimmune diseases.

Authors

Nadine Dragin, Jacky Bismuth, Géraldine Cizeron-Clairac, Maria Grazia Biferi, Claire Berthault, Alain Serraf, Rémi Nottin, David Klatzmann, Ana Cumano, Martine Barkats, Rozen Le Panse, Sonia Berrih-Aknin

Schwann cells induce cancer cell dispersion and invasion

• Text
• PDF

Abstract

Nerves enable cancer progression, as cancers have been shown to extend along nerves through the process of perineural invasion, which carries a poor prognosis. Furthermore, the innervation of some cancers promotes growth and metastases. It remains unclear, however, how nerves mechanistically contribute to cancer progression. Here, we demonstrated that Schwann cells promote cancer invasion through direct cancer cell contact. Histological evaluation of murine and human cancer specimens with perineural invasion uncovered a subpopulation of Schwann cells that associates with cancer cells. Coculture of cancer cells with dorsal root ganglion extracts revealed that Schwann cells direct cancer cells to migrate toward nerves and promote invasion in a contact-dependent manner. Upon contact, Schwann cells induced the formation of cancer cell protrusions in their direction and intercalated between the cancer cells, leading to cancer cell dispersion. The formation of these processes was dependent on Schwann cell expression of neural cell adhesion molecule 1 (NCAM1) and ultimately promoted perineural invasion. Moreover, NCAM1-deficient mice showed decreased neural invasion and less paralysis. Such Schwann cell behavior reflects normal Schwann cell programs that are typically activated in nerve repair but are instead exploited by cancer cells to promote perineural invasion and cancer progression.

Authors

Sylvie Deborde, Tatiana Omelchenko, Anna Lyubchik, Yi Zhou, Shizhi He, William F. McNamara, Natalya Chernichenko, Sei-Young Lee, Fernando Barajas, Chun-Hao Chen, Richard L. Bakst, Efsevia Vakiani, Shuangba He, Alan Hall, Richard J. Wong

CCR7 and IRF4-dependent dendritic cells regulate lymphatic collecting vessel permeability

• Text
• PDF

Abstract

Lymphatic collecting vessels direct lymph into and from lymph nodes (LNs) and can become hyperpermeable as the result of a previous infection. Enhanced permeability has been implicated in compromised immunity due to reduced flow of lymph and immune cells to LNs, which are the primary site of antigen presentation to T cells. Presently, very little is known about the molecular signals that affect lymphatic collecting vessel permeability. Here, we have shown that lymphatic collecting vessel permeability is controlled by CCR7 and that the chronic hyperpermeability of collecting vessels observed in Ccr7^–/– mice is followed by vessel fibrosis. Reexpression of CCR7 in DCs, however, was sufficient to reverse the development of such fibrosis. IFN regulatory factor 4–positive (IRF4⁺) DCs constitutively interacted with collecting lymphatics, and selective ablation of this DC subset in Cd11c-Cre Irf4^fl/fl mice also rendered lymphatic collecting vessels hyperpermeable and fibrotic. Together, our data reveal that CCR7 plays multifaceted roles in regulating collecting vessel permeability and fibrosis, with one of the key players being IRF4-dependent DCs.

Authors

Stoyan Ivanov, Joshua P. Scallan, Ki-Wook Kim, Kathrin Werth, Michael W. Johnson, Brian T. Saunders, Peter L. Wang, Emma L. Kuan, Adam C. Straub, Melissa Ouhachi, Erica G. Weinstein, Jesse W. Williams, Carlos Briseño, Marco Colonna, Brant E. Isakson, Emmanuel L. Gautier, Reinhold Förster, Michael J. Davis, Bernd H. Zinselmeyer, Gwendalyn J. Randolph

RNA-binding protein IGF2BP3 targeting of oncogenic transcripts promotes hematopoietic progenitor proliferation

• Text
• PDF

Abstract

Posttranscriptional control of gene expression is important for defining both normal and pathological cellular phenotypes. In vitro, RNA-binding proteins (RBPs) have recently been shown to play important roles in posttranscriptional regulation; however, the contribution of RBPs to cell specification is not well understood. Here, we determined that the RBP insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) is specifically overexpressed in mixed lineage leukemia–rearranged (MLL-rearranged) B-acute lymphoblastic leukemia (B-ALL), which constitutes a subtype of this malignancy associated with poor prognosis and high risk of relapse. IGF2BP3 was required for the survival of B-ALL cell lines, as knockdown led to decreased proliferation and increased apoptosis. Enforced expression of IGF2BP3 provided murine BM cells with a strong survival advantage, led to proliferation of hematopoietic stem and progenitor cells, and skewed hematopoietic development to the B cell/myeloid lineage. Cross-link immunoprecipitation and high throughput sequencing uncovered the IGF2BP3-regulated transcriptome, which includes oncogenes MYC and CDK6 as direct targets. IGF2BP3 regulated transcripts via targeting elements within 3′ untranslated regions (3′UTR), and enforced IGF2BP3 expression in mice resulted in enhanced expression of Myc and Cdk6 in BM. Together, our data suggest that IGF2BP3-mediated targeting of oncogenic transcripts may represent a critical pathogenetic mechanism in MLL-rearranged B-ALL and support IGF2BP3 and its cognate RNA-binding partners as potential therapeutic targets in this disease.

Authors

Jayanth Kumar Palanichamy, Tiffany M. Tran, Jonathan M. Howard, Jorge R. Contreras, Thilini R. Fernando, Timothy Sterne-Weiler, Sol Katzman, Masoud Toloue, Weihong Yan, Giuseppe Basso, Martina Pigazzi, Jeremy R. Sanford, Dinesh S. Rao

LNK/SH2B3 regulates IL-7 receptor signaling in normal and malignant B-progenitors

• Text
• PDF

Abstract

Philadelphia chromosome–like acute lymphoblastic leukemia (Ph-like ALL) is a high-risk ALL commonly associated with alterations that affect the tyrosine kinase pathway, tumor suppressors, and lymphoid transcription factors. Loss-of-function mutations in the gene-encoding adaptor protein LNK (also known as SH2B3) are found in Ph-like ALLs; however, it is not clear how LNK regulates normal B cell development or promotes leukemogenesis. Here, we have shown that combined loss of Lnk and tumor suppressors Tp53 or Ink4a/Arf in mice triggers a highly aggressive and transplantable precursor B-ALL. Tp53^–/–Lnk^–/– B-ALLs displayed similar gene expression profiles to human Ph-like B-ALLs, supporting use of this model for preclinical and molecular studies. Preleukemic Tp53^–/–Lnk^–/– pro-B progenitors were hypersensitive to IL-7, exhibited marked self-renewal in vitro and in vivo, and were able to initiate B-ALL in transplant recipients. Mechanistically, we demonstrated that LNK regulates pro-B progenitor homeostasis by attenuating IL-7–stimuated JAK/STAT5 signaling via a direct interaction with phosphorylated JAK3. Moreover, JAK inhibitors were effective in prolonging survival of mice transplanted with Lnk^–/–Tp53^–/– leukemia. Additionally, synergistic administration of PI3K/mTOR and JAK inhibitors further abrogated leukemia development. Hence, our results suggest that LNK suppresses IL-7R/JAK/STAT signaling to restrict pro-/pre-B progenitor expansion and leukemia development, providing a pathogenic mechanism and a potential therapeutic approach for B-ALLs with LNK mutations.

Authors

Ying Cheng, Kudakwashe Chikwava, Chao Wu, Haibing Zhang, Anchit Bhagat, Dehua Pei, John K. Choi, Wei Tong

Involvement of activation-induced cytidine deaminase in skin cancer development

• Text
• PDF

Abstract

Most skin cancers develop as the result of UV light–induced DNA damage; however, a substantial number of cases appear to occur independently of UV damage. A causal link between UV-independent skin cancers and chronic inflammation has been suspected, although the precise mechanism underlying this association is unclear. Here, we have proposed that activation-induced cytidine deaminase (AID, encoded by AICDA) links chronic inflammation and skin cancer. We demonstrated that Tg mice expressing AID in the skin spontaneously developed skin squamous cell carcinoma with Hras and Trp53 mutations. Furthermore, genetic deletion of Aicda reduced tumor incidence in a murine model of chemical-induced skin carcinogenesis. AID was expressed in human primary keratinocytes in an inflammatory stimulus–dependent manner and was detectable in human skin cancers. Together, the results of this study indicate that inflammation-induced AID expression promotes skin cancer development independently of UV damage and suggest AID as a potential target for skin cancer therapeutics.

Authors

Taichiro Nonaka, Yoshinobu Toda, Hiroshi Hiai, Munehiro Uemura, Motonobu Nakamura, Norio Yamamoto, Ryo Asato, Yukari Hattori, Kazuhisa Bessho, Nagahiro Minato, Kazuo Kinoshita

Astrocytes are central in the pathomechanisms of vanishing white matter

• Text
• PDF

Abstract

Vanishing white matter (VWM) is a fatal leukodystrophy that is caused by mutations in genes encoding subunits of eukaryotic translation initiation factor 2B (eIF2B). Disease onset and severity are codetermined by genotype. White matter astrocytes and oligodendrocytes are almost exclusively affected; however, the mechanisms of VWM development remain unclear. Here, we used VWM mouse models, patients’ tissue, and cell cultures to investigate whether astrocytes or oligodendrocytes are the primary affected cell type. We generated 2 mouse models with mutations (Eif2b5^{Arg191His/Arg191His} and Eif2b4^{Arg484Trp/Arg484Trp}) that cause severe VWM in humans and then crossed these strains to develop mice with various mutation combinations. Phenotypic severity was highly variable and dependent on genotype, reproducing the clinical spectrum of human VWM. In all mutant strains, impaired maturation of white matter astrocytes preceded onset and paralleled disease severity and progression. Bergmann glia and retinal Müller cells, nonforebrain astrocytes that have not been associated with VWM, were also affected, and involvement of these cells was confirmed in VWM patients. In coculture, VWM astrocytes secreted factors that inhibited oligodendrocyte maturation, whereas WT astrocytes allowed normal maturation of VWM oligodendrocytes. These studies demonstrate that astrocytes are central in VWM pathomechanisms and constitute potential therapeutic targets. Importantly, astrocytes should also be considered in the pathophysiology of other white matter disorders.

Authors

Stephanie Dooves, Marianna Bugiani, Nienke L. Postma, Emiel Polder, Niels Land, Stephen T. Horan, Anne-Lieke F. van Deijk, Aleid van de Kreeke, Gerbren Jacobs, Caroline Vuong, Jan Klooster, Maarten Kamermans, Joke Wortel, Maarten Loos, Lisanne E. Wisse, Gert C. Scheper, Truus E.M. Abbink, Vivi M. Heine, Marjo S. van der Knaap

Matricellular protein CCN3 mitigates abdominal aortic aneurysm

• Text
• PDF

Abstract

Abdominal aortic aneurysm (AAA) is a major cause of morbidity and mortality; however, the mechanisms that are involved in disease initiation and progression are incompletely understood. Extracellular matrix proteins play an integral role in modulating vascular homeostasis in health and disease. Here, we determined that the expression of the matricellular protein CCN3 is strongly reduced in rodent AAA models, including angiotensin II–induced AAA and elastase perfusion–stimulated AAA. CCN3 levels were also reduced in human AAA biopsies compared with those in controls. In murine models of induced AAA, germline deletion of Ccn3 resulted in severe phenotypes characterized by elastin fragmentation, vessel dilation, vascular inflammation, dissection, heightened ROS generation, and smooth muscle cell loss. Conversely, overexpression of CCN3 mitigated both elastase- and angiotensin II–induced AAA formation in mice. BM transplantation experiments suggested that the AAA phenotype of CCN3-deficient mice is intrinsic to the vasculature, as AAA was not exacerbated in WT animals that received CCN3-deficient BM and WT BM did not reduce AAA severity in CCN3-deficient mice. Genetic and pharmacological approaches implicated the ERK1/2 pathway as a critical regulator of CCN3-dependent AAA development. Together, these results demonstrate that CCN3 is a nodal regulator in AAA biology and identify CCN3 as a potential therapeutic target for vascular disease.

Authors

Chao Zhang, Dustin van der Voort, Hong Shi, Rongli Zhang, Yulan Qing, Shuichi Hiraoka, Minoru Takemoto, Koutaro Yokote, Joseph V. Moxon, Paul Norman, Laure Rittié, Helena Kuivaniemi, G. Brandon Atkins, Stanton L. Gerson, Guo-Ping Shi, Jonathan Golledge, Nianguo Dong, Bernard Perbal, Domenick A. Prosdocimo, Zhiyong Lin

PI3-kinase mutation linked to insulin and growth factor resistance in vivo

• Text
• PDF

Abstract

The phosphatidylinositol 3-kinase (PI3K) signaling pathway is central to the action of insulin and many growth factors. Heterozygous mutations in the gene encoding the p85α regulatory subunit of PI3K (PIK3R1) have been identified in patients with SHORT syndrome — a disorder characterized by short stature, partial lipodystrophy, and insulin resistance. Here, we evaluated whether SHORT syndrome–associated PIK3R1 mutations account for the pathophysiology that underlies the abnormalities by generating knockin mice that are heterozygous for the Pik3r1^Arg649Trp mutation, which is homologous to the mutation found in the majority of affected individuals. Similar to the patients, mutant mice exhibited a reduction in body weight and length, partial lipodystrophy, and systemic insulin resistance. These derangements were associated with a reduced capacity of insulin and other growth factors to activate PI3K in liver, muscle, and fat; marked insulin resistance in liver and fat of mutation-harboring animals; and insulin resistance in vitro in cells derived from these mice. In addition, mutant mice displayed defective insulin secretion and GLP-1 action on islets in vivo and in vitro. These data demonstrate the ability of this heterozygous mutation to alter PI3K activity in vivo and the central role of PI3K in insulin/growth factor action, adipocyte function, and glucose metabolism.

Authors

Jonathon N. Winnay, Marie H. Solheim, Ercument Dirice, Masaji Sakaguchi, Hye-Lim Noh, Hee Joon Kang, Hirokazu Takahashi, Kishan K. Chudasama, Jason K. Kim, Anders Molven, C. Ronald Kahn, Pål R. Njølstad