Role of nuclear protein Akirin in the modulation of female reproduction in Nilaparvata lugens (Hemiptera: Delphacidae)

Introduction: Akirin as a highly conserved transcription factor, exerts a profound influence on the growth, development, immune response, and reproductive processes in animals. The brown planthopper (BPH), Nilaparvata lugens, a major pest in rice production in Asia, possesses high reproductive capacity, a critical factor contributing to reduced rice yields. The aims of this study were to demonstrate the regulatory role of Akirin in the reproduction of BPH. Methods: In this study, quantitative PCR (qPCR) was used to detect the mRNA expression of genes. RNA interference (RNAi) was used to downregulate the expression of Akirin gene, and RNA sequencing (RNA-seq) was used to screen for differentially expressed genes caused by Akirin downregulation. Hormone contents were measured with the enzyme linked immunosorbent assay (ELISA), and protein content was evaluated with the bicinchoninic acid (BCA) method. Results: Using BPH genome data, we screened for an Akirin gene (NlAkirin). An analysis of tissue-specific expressions showed that NlAkirin was expressed in all tissues tested in female BPH, but its expression level was highest in the ovary. After inhibiting the mRNA expression of NlAkirin in BPH females, the number of eggs laid, hatching rate, and number of ovarioles decreased. Transcriptome sequencing was performed, following a NlAkirin double-stranded RNA treatment. Compared with the genes of the control, which was injected with GFP double-stranded RNA, there were 438 upregulated genes and 1012 downregulated genes; the expression of vitellogenin (Vg) and vitellogenin receptor (VgR) genes as well as the mRNA expression of genes related to the target of rapamycin (TOR), juvenile hormone (JH), and insulin pathways involved in Vg synthesis was significantly downregulated. As a result of NlAkirin knockdown, the titers of JH III and Ecdysone (Ecd) were downregulated in unmated females but returned to normal levels in mated females. The ovarian protein contents in both unmated and mated females were downregulated. Discussion and conclusion: Our results suggest that NlAkirin affects female BPH reproduction by regulating the mRNA expression of genes related to the Vg, VgR, TOR, JH, and insulin signaling pathways, in addition to the titers of JH III and Ecd. The findings of this research provide novel insights into the regulatory role of Akirin in insect reproductive capacity.

Akirin2 enhances antibacterial ability via interacting with 14-3-3ζ in V. splendidus-challenged Apostichopus japonicus

Akirin2 is pivotal for regulating host immunological responses in vertebrates, including antibacterial immunity and inflammation. However, the functional significance of Akirin2 in invertebrates remains largely unexplored. In this study, we cloned the complete cDNA sequence of Akirin2 from A. japonicus (AjAkirin2) and elucidated its immunological mechanism upon pathogen infection. The whole AjAkirin2 cDNA sequence spanned 1014 bp, which comprised a 630 bp open reading frame encoding 209 amino acids, a 230 bp 5'-untranslated region (UTR), and a 154 bp 3'-UTR. Spatial expression analysis displayed constitutive expression of AjAkirin2 in all examined tissues. Both mRNA and protein expression abundance of the AjAkirin2 showed considerably high in coelomocytes of sea cucumbers challenged with Vibrio splendidus or stimulated with lipopolysaccharide. In addition, we found that sea cucumbers with 107 CFU/mL V. splendidus infection had a lower survival rate upon AjAkirin2 knockdown. Mechanistically, the result of GST-pull down and co-IP assays indicated that AjAkirin2 directly interacted with Aj14-3-3ζ. Moreover, we also detected that AjAkirin2 positively regulated Aj14-3-3ζ expression in sea cucumber coelomocytes. Furthermore, the knockdown of AjAkirin2 or Aj14-3-3ζ resulted in increasing intracellular bacteria load and suppressed the expression of key genes of the NF-κB signaling pathway (p65 and p105) and inflammatory cytokines including IL-17, VEGF, and MMP-1. In summary, these results confirmed the critical role of AjAkirin2 in mediating innate immune responses against V. splendidus infection via interaction with Aj14-3-3ζ and thereby exerting antibacterial function.

Identification of AKIRIN2 as a potential biomarker and correlation with immunotherapy in gastric adenocarcinoma by integrated bioinformatics analysis

Gastric adenocarcinoma is major type of gastric cancer that endangers human health. AKIRIN2 has been shown to be associated with cholangiocarcinoma promoting invasion and angiogenesis. In this study, AKIRIN2 is highly expressed in Gastric adenocarcinoma through bioinformatics analysis based on Stomach adenocarcinoma samples data from The Cancer Genome Atlas. Correlation analysis showed that the high-expression of AKIRIN2 was associated with poor survival rate compared to the low-expression group. Univariate and multivariate Cox regression analyses determined the correlation between clinical characteristics and overall survival. Next, the correlation between AKIRIN2 and immune infiltration was evaluated. The distribution of 24 immune cells and their correlation with the expression of AKIRIN2 were explored using the immune cell database. In addition, three Immune cell methods were used to verify the positive correlation between immune cells and AKIRIN2. Also, Genomics of Drug Sensitivity in Cancer database was utilized to verify the correlation between AKIRIN2 expression level and the efficacy of chemotherapy and immunotherapy. The results showed that AKIRIN2 is an effective biomarker of Gastric adenocarcinoma prognosis, which can guide chemotherapy and immunotherapy and clarify the progress of Gastric adenocarcinoma promoted by immune microenvironment.

p53-mediated neurodegeneration in the absence of the nuclear protein Akirin2

Proper gene regulation is critical for both neuronal development and maintenance as the brain matures. We previously demonstrated that Akirin2, an essential nuclear protein that interacts with transcription factors and chromatin remodeling complexes, is required for the embryonic formation of the cerebral cortex. Here we show that Akirin2 plays a mechanistically distinct role in maintaining healthy neurons during cortical maturation. Restricting Akirin2 loss to excitatory cortical neurons resulted in progressive neurodegeneration via necroptosis and severe cortical atrophy with age. Comparing transcriptomes from Akirin2-null postnatal neurons and cortical progenitors revealed that targets of the tumor suppressor p53, a regulator of both proliferation and cell death encoded by Trp53, were consistently upregulated. Reduction of Trp53 rescued neurodegeneration in Akirin2-null neurons. These data: (1) implicate Akirin2 as a critical neuronal maintenance protein, (2) identify p53 pathways as mediators of Akirin2 functions, and (3) suggest Akirin2 dysfunction may be relevant to neurodegenerative diseases.

Molecular mechanism of enhancing the immune effect of the Newcastle disease virus vaccine in broilers fed with Bacillus cereus PAS38

The aim of this study was to explore the molecular mechanism of enhancing the immune effect of the Newcastle disease virus (NDV) vaccine in broilers fed with Bacillus cereus PAS38. The results showed that the NDV antibody titer of broilers in the treatment group supplemented with B. cereus PAS38 was higher than that of the control group, and the difference was significant at 28 days of age (P < 0.05). The spleen, thymus and bursa of fabricius of 42-day-old broilers were quickly collected to construct a differentially expressed gene library of suppression subtractive hybridization (SSH). A total of 31 immune-related differentially expressed genes were screened from three immune organs, of which 15 were up-regulated and 16 were down-regulated. After silencing the up-regulated genes MIF, CD74, DOCK2 and KLHL6, the expression levels of cytokines (Akirin2, NF-κB, IL-2, IL-4, IL-6, IFN-γ and TNF-α) in lymphocytes were reduced to varying degrees. B. cereus PAS38 might be involved in the proliferation, differentiation, activation, migration of B lymphocytes and vaccine antigen presentation by up-regulating the expression of MIF, CD74, DOCK2, KLHL6 and other genes. Moreover, it also stimulated plasma cells to produce immunoglobulins and specific antibodies, thereby improving the humoral immune function of broilers and enhancing the immune effect of the NDV vaccine.

Function of cofactor Akirin2 in the regulation of gene expression in model human Caucasian neutrophil-like HL60 cells

The Akirin family of transcription cofactors are involved throughout the metazoan in the regulation of different biological processes (BPs) such as immunity, interdigital regression, muscle and neural development. Akirin do not have catalytic or DNA-binding capability and exert its regulatory function primarily through interacting proteins such as transcription factors, chromatin remodelers, and RNA-associated proteins. In the present study, we focused on the human Akirin2 regulome and interactome in neutrophil-like model human Caucasian promyelocytic leukemia HL60 cells. Our hypothesis is that metazoan evolved to have Akirin2 functional complements and different Akirin2-mediated mechanisms for the regulation of gene expression. To address this hypothesis, experiments were conducted using transcriptomics, proteomics and systems biology approaches in akirin2 knockdown and wildtype (WT) HL60 cells to characterize Akirin2 gene/protein targets, functional complements and to provide evidence of different mechanisms that may be involved in Akirin2-mediated regulation of gene expression. The results revealed Akirin2 gene/protein targets in multiple BPs with higher representation of immunity and identified immune response genes as candidate Akirin2 functional complements. In addition to linking chromatin remodelers with transcriptional activation, Akirin2 also interacts with histone H3.1 for regulation of gene expression.

Innate immunity in C. elegans

In its natural habitat, C. elegans encounters a wide variety of microbes, including food, commensals and pathogens. To be able to survive long enough to reproduce, C. elegans has developed a complex array of responses to pathogens. These activities are coordinated on scales that range from individual organelles to the entire organism. Often, the response is triggered within cells, by detection of infection-induced damage, mainly in the intestine or epidermis. C. elegans has, however, a capacity for cell non-autonomous regulation of these responses. This frequently involves the nervous system, integrating pathogen recognition, altering host biology and governing avoidance behavior. Although there are significant differences with the immune system of mammals, some mechanisms used to limit pathogenesis show remarkable phylogenetic conservation. The past 20 years have witnessed an explosion of host-pathogen interaction studies using C. elegans as a model. This review will discuss the broad themes that have emerged and highlight areas that remain to be fully explored.

Transcription profile, NF-ĸB promoter activation, and antiviral activity of Amphiprion clarkii Akirin-2

Animal defense system constitutes a series of distinct mechanisms that specifically defend against microbial invasion. Understanding these complex biological mechanisms is of paramount importance for implementing disease prevention strategies. In this study, the transcription factor, Akirin-2 was identified from ornamental fish Amphiprion clarkii and its involvement in immune response was characterized. A. clarkii Akirin-2 (AcAkirin-2) was identified as a highly conserved protein with two nuclear localization signals. In-vitro localization analysis in fathead minnow cells revealed that AcAkirin-2 is strictly localized to the nucleus. With regard to tissue-specific expression without immune challenge, AcAkirin-2 expression was highest in the brain and lowest in the liver. Immune challenge experiments revealed that AcAkirin-2 expression was the strongest in response to poly I:C. Overexpression of AcAkirin-2 alone did not enhanced NF-ĸB activity significantly in HEK293T cells; however, it significantly enhanced NF-ĸB activity in the presence of poly I:C. AcAkirin-2-mediated expression of antiviral genes was analyzed using qPCR in mullet kidney cells and plaque assay was performed to decipher the involvement of AcAkirin-2 in antiviral immunity. AcAkirin-2 overexpression significantly enhanced the expression of Viperin but not of Mx. Plaque assays revealed the ability of AcAkirin-2 to enervate VHSV titers. Taken together, this study unveiled the involvement of AcAkirin-2 in NF-ĸB-mediated transcription of antiviral genes.

Akirin proteins in development and disease: critical roles and mechanisms of action

The Akirin genes, which encode small, nuclear proteins, were first characterized in 2008 in Drosophila and rodents. Early studies demonstrated important roles in immune responses and tumorigenesis, which subsequent work found to be highly conserved. More recently, a multiplicity of Akirin functions, and the associated molecular mechanisms involved, have been uncovered. Here, we comprehensively review what is known about invertebrate Akirin and its two vertebrate homologues Akirin1 and Akirin2, highlighting their role in regulating gene expression changes across a number of biological systems. We detail essential roles for Akirin family proteins in the development of the brain, limb, and muscle, in meiosis, and in tumorigenesis, emphasizing associated signaling pathways. We describe data supporting the hypothesis that Akirins act as a "bridge" between a variety of transcription factors and major chromatin remodeling complexes, and discuss several important questions remaining to be addressed. In little more than a decade, Akirin proteins have gone from being completely unknown to being increasingly recognized as evolutionarily conserved mediators of gene expression programs essential for the formation and function of animals.

Overlap of Genetic Risk between Interstitial Lung Abnormalities and Idiopathic Pulmonary Fibrosis

Rationale: Interstitial lung abnormalities (ILAs) are associated with the highest genetic risk locus for idiopathic pulmonary fibrosis (IPF); however, the extent to which there are unique associations among individuals with ILAs or additional overlap with IPF is not known.Objectives: To perform a genome-wide association study (GWAS) of ILAs.Methods: ILAs and a subpleural-predominant subtype were assessed on chest computed tomography (CT) scans in the AGES (Age Gene/Environment Susceptibility), COPDGene (Genetic Epidemiology of Chronic Obstructive Pulmonary Disease [COPD]), Framingham Heart, ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate End-points), MESA (Multi-Ethnic Study of Atherosclerosis), and SPIROMICS (Subpopulations and Intermediate Outcome Measures in COPD Study) studies. We performed a GWAS of ILAs in each cohort and combined the results using a meta-analysis. We assessed for overlapping associations in independent GWASs of IPF.Measurements and Main Results: Genome-wide genotyping data were available for 1,699 individuals with ILAs and 10,274 control subjects. The MUC5B (mucin 5B) promoter variant rs35705950 was significantly associated with both ILAs (P = 2.6 × 10^-27) and subpleural ILAs (P = 1.6 × 10^-29). We discovered novel genome-wide associations near IPO11 (rs6886640, P = 3.8 × 10^-8) and FCF1P3 (rs73199442, P = 4.8 × 10^-8) with ILAs, and near HTRE1 (rs7744971, P = 4.2 × 10^-8) with subpleural-predominant ILAs. These novel associations were not associated with IPF. Among 12 previously reported IPF GWAS loci, five (DPP9, DSP, FAM13A, IVD, and MUC5B) were significantly associated (P < 0.05/12) with ILAs.Conclusions: In a GWAS of ILAs in six studies, we confirmed the association with a MUC5B promoter variant and found strong evidence for an effect of previously described IPF loci; however, novel ILA associations were not associated with IPF. These findings highlight common genetically driven biologic pathways between ILAs and IPF, and also suggest distinct ones.

Akirin Is Required for Muscle Function and Acts Through the TGF-β Sma/Mab Signaling Pathway in Caenorhabditis elegans Development

Akirin, a conserved metazoan protein, functions in muscle development in flies and mice. However, this was only tested in the rodent and fly model systems. Akirin was shown to act with chromatin remodeling complexes in transcription and was established as a downstream target of the NFκB pathway. Here we show a role for Caenorhabditis elegans Akirin/AKIR-1 in the muscle and body length regulation through a different pathway. Akirin localizes to somatic tissues throughout the body of C. elegans, including muscle nuclei. In agreement with its role in other model systems, Akirin loss of function mutants exhibit defects in muscle development in the embryo, as well as defects in movement and maintenance of muscle integrity in the C. elegans adult. We also have determined that Akirin acts downstream of the TGF-β Sma/Mab signaling pathway in controlling body size. Moreover, we found that the loss of Akirin resulted in an increase in autophagy markers, similar to mutants in the TGF-β Sma/Mab signaling pathway. In contrast to what is known in rodent and fly models, C. elegans Akirin does not act with the SWI/SNF chromatin-remodeling complex, and is instead involved with the NuRD chromatin remodeling complex in both movement and regulation of body size. Our studies define a novel developmental role (body size) and a new pathway (TGF-β Sma/Mab) for Akirin function, and confirmed its evolutionarily conserved function in muscle development in a new organism.

A novel nuclear factor Akirin regulating the expression of antimicrobial peptides in Chinese mitten crab Eriocheir sinensis

Akirin, a recently discovered nuclear factor, participates in regulating various processes, including cell proliferation and differentiation, embryonic development, and immunity. In the present study, a novel Akirin was identified from Chinese mitten crab Eriocheir sinensis (designated as EsAkirin), and its primary functions in regulating antimicrobial peptides were explored. The open reading frame of EsAkirin was of 615 bp, encoding a polypeptide of 204 amino acid residues. The deduced amino acid sequence of EsAkirin shared high similarities ranging from 44.1% to 89.2% with other Akirins. In the phylogenetic tree, EsAkirin was firstly clustered with Akirins from shrimp and then assigned into the invertebrate branch. The mRNA transcripts of EsAkirin were constitutively expressed in all the tested tissues, with the highest expression level (5.07-fold compared to the stomach, p < 0.01) in hepatopancreas. The mRNA expression of EsAkirin in hemocytes was significantly increased at 6 h, and reached the maximum level at 24 h post stimulations with either lipopolysaccharide (LPS) (5.04-fold, p < 0.01) or Aeromonas hydrophila (3.10-fold, p < 0.01). After the injection of EsAkirin-dsRNA, the mRNA expressions of EsALF2, EsLYZ, EsCrus2 and EsDWD1 were significantly decreased (p < 0.01) upon LPS stimulation. EsAkirin protein was prominently distributed in the nucleus of E. sinensis hemocytes after LPS and A. hydrophila stimulations. The relative luciferase reporter system analysis revealed that the activity of nuclear factor-κB was significantly up-regulated (2.64-fold, p < 0.01) in human embryonic kidney (HEK293T) cells after the over-expression of EsAkirin. Collectively, these results suggested that EsAkirin might play an important role in the immune responses of E. sinensis by regulating the expression of antimicrobial peptides.

Molecular characterization and functional analysis of Akirin from black tiger shrimp (Penaeus monodon)

Akirin, which are members of the NF-κB signaling pathway, play critical roles in regulating the expression of antimicrobial peptides. In the present study, the Akirin gene from Penaeus monodon was identified from a transcriptome database and designated as PmAkirin. The complete sequence of the PmAkirin cDNA was 1508 bp, encoding a protein of 213 amino acids, and it showed 99% amino acid identity to the Litopenaeus vannamei Akirin. Two predicted nuclear localization signals (NLSs) were found, and the amino acid sequence alignments showed that PmAkirin was highly conserved at the N-terminus and C-terminus. PmAkirin expression was found to be the highest in the hemolymph, followed by the heart, gill, stomach, hepatopancreas, intestine, and muscle. When challenged with Vibrio parahaemolyticus infection, the PmAkirin mRNA and three antimicrobial peptides (AMPs: PmALF2, PmALF3, and PmCrus4) were upregulated. However, another five AMPs (PmALF6, PmCrus1, PmPEN3a, PmPEN3b, and PmPEN5) were downregulated by V. parahaemolyticus infection. Silencing PmAkirin by dsRNA significantly decreased the expression of the eight AMPs, which lead to an increase in the blood concentration of V. parahaemolyticus and higher mortality in the shrimp. In contrast, the overexpression of PmAkirin significantly increased the expression of the eight AMPs, which led to a reduction in the blood concentration of V. parahaemolyticus and promoted the survival of the shrimp. Taken together, we concluded that PmAkirin plays an important role in regulating the expression of AMPs in black tiger shrimp to defend against V. parahaemolyticus infection.

Coordinated signals from the DNA repair enzymes PARP-1 and PARP-2 promotes B-cell development and function

Poly (ADP-ribose) polymerase (PARP)-1 and PARP-2 regulate the function of various DNA-interacting proteins by transferring ADP-ribose emerging from catalytic cleavage of cellular β-NAD⁺. Hence, mice lacking PARP-1 or PARP-2 show DNA perturbations ranging from altered DNA integrity to impaired DNA repair. These effects stem from the central role that PARP-1 and PARP-2 have on the cellular response to DNA damage. Failure to mount a proper response culminates in cell death. Accordingly, PARP inhibitors are emerging as promising drugs in cancer therapy. However, the full impact of these inhibitors on immunity, including B-cell antibody production, remains elusive. Given that mice carrying dual PARP-1 and PARP-2 deficiency develop early embryonic lethality, we crossed PARP-1-deficient mice with mice carrying a B-cell-conditional PARP-2 gene deletion. We found that the resulting dually PARP-1 and PARP-2-deficient mice had perturbed bone-marrow B-cell development as well as profound peripheral depletion of transitional and follicular but not marginal zone B-cells. Of note, bone-marrow B-cell progenitors and peripheral mature B-cells were conserved in mice carrying either PARP-1 or PARP-2 deficiency. In dually PARP-1 and PARP-2-deficient mice, B-cell lymphopenia was associated with increased DNA damage and accentuated death in actively proliferating B-cells. Moreover, dual PARP-1 and PARP-2 deficiency impaired antibody responses to T-independent carbohydrate but not to T-dependent protein antigens. Notwithstanding the pivotal role of PARP-1 and PARP-2 in DNA repair, combined PARP-1 and PARP-2 deficiency did not perturb the DNA-editing processes required for the generation of a protective antibody repertoire, including Ig V(D)J gene recombination and IgM-to-IgG class switching. These findings provide key information as to the potential impact of PARP inhibitors on humoral immunity, which will facilitate the development of safer PARP-targeting regimens against cancer.

A critical role for the nuclear protein Akirin2 in the formation of mammalian muscle in vivo

Evolutionarily conserved Akirin nuclear proteins interact with chromatin remodeling complexes at gene enhancers and promoters, and have been reported to regulate cell proliferation and differentiation. Of the two mouse Akirin genes, Akirin2 is essential during embryonic development, with known in vivo roles in immune system function and the formation of the cerebral cortex. Here we demonstrate that Akirin2 is critical for mouse myogenesis, a tightly regulated developmental process through which myoblast precursors fuse to form mature skeletal muscle fibers. Loss of Akirin2 in somitic muscle precursor cells via Sim1-Cre-mediated excision of a conditional Akirin2 allele results in neonatal lethality. Mutant embryos exhibit a complete lack of forelimb, intercostal, and diaphragm muscles due to extensive apoptosis and loss of Pax3-positive myoblasts. Severe skeletal defects, including craniofacial abnormalities, disrupted ossification, and rib fusions are also observed, attributable to lack of skeletal muscles as well as patchy Sim1-Cre activity in the embryonic sclerotome. We further show that Akirin2 levels are tightly regulated during muscle cell differentiation in vitro, and that Akirin2 is required for the proper expression of muscle differentiation factors myogenin and myosin heavy chain. Our results implicate Akirin2 as a major regulator of mammalian muscle formation in vivo.

A Novel Role for α-Importins and Akirin in Establishment of Meiotic Sister Chromatid Cohesion in Caenorhabditis elegans

During meiotic prophase I, sister chromatid cohesion is established in a way that supports the assembly of the synaptonemal complex (SC). The SC connects homologous chromosomes, directing meiotic recombination to create crossovers. In this paper, we identify two proteins that cooperate to import and load meiotic cohesins, thus indirectly promoting SC assembly. AKIR-1 is a protein with a previously identified meiotic role in SC disassembly. akir-1 mutants have no obvious defects in sister chromatid cohesion. We identified ima-2, a gene encoding for an α-importin nuclear transport protein, as a gene interacting with akir-1 Analysis of akir-1;ima-2 double mutants reveals a decrease in the number of germline nuclei and the formation of polycomplexes (PCs) (an SC protein aggregate). These PCs contain proteins that are part of the two main substructures of the SC: the central region and the lateral element. Unlike typical PCs, they also contain sister chromatid cohesion proteins. In akir-1;ima-2 double mutants, PCs are located in both the nucleus and the cytoplasm. This suggests that the defects observed in the double mutants are both in nuclear import and in the assembly of sister chromatid cohesion. PC formation is also associated with recombination defects leading to reduced numbers of crossovers. Similarly to cohesion mutants, the pairing center protein HIM-8 is mislocalized in akir-1;ima-2 double mutants, forming multiple foci. We propose that AKIR-1 and IMA-2 operate in parallel pathways to import and load chromosomally associated cohesin complex proteins in meiotic nuclei, a novel finding for both of these conserved proteins.

Functional Evolution of Subolesin/Akirin

The Subolesin/Akirin constitutes a good model for the study of functional evolution because these proteins have been conserved throughout the metazoan and play a role in the regulation of different biological processes. Here, we investigated the evolutionary history of Subolesin/Akirin with recent results on their structure, protein-protein interactions and function in different species to provide insights into the functional evolution of these regulatory proteins, and their potential as vaccine antigens for the control of ectoparasite infestations and pathogen infection. The results suggest that Subolesin/Akirin evolved conserving not only its sequence and structure, but also its function and role in cell interactome and regulome in response to pathogen infection and other biological processes. This functional conservation provides a platform for further characterization of the function of these regulatory proteins, and how their evolution can meet species-specific demands. Furthermore, the conserved functional evolution of Subolesin/Akirin correlates with the protective capacity shown by these proteins in vaccine formulations for the control of different arthropod and pathogen species. These results encourage further research to characterize the structure and function of these proteins, and to develop new vaccine formulations by combining Subolesin/Akirin with interacting proteins for the control of multiple ectoparasite infestations and pathogen infection.

An essential role for the nuclear protein Akirin2 in mouse limb interdigital tissue regression

The regulation of interdigital tissue regression requires the interplay of multiple spatiotemporally-controlled morphogen gradients to ensure proper limb formation and release of individual digits. Disruption to this process can lead to a number of limb abnormalities, including syndactyly. Akirins are highly conserved nuclear proteins that are known to interact with chromatin remodelling machinery at gene enhancers. In mammals, the analogue Akirin2 is essential for embryonic development and critical for a wide variety of roles in immune function, meiosis, myogenesis and brain development. Here we report a critical role for Akirin2 in the regulation of interdigital tissue regression in the mouse limb. Knockout of Akirin2 in limb epithelium leads to a loss of interdigital cell death and an increase in cell proliferation, resulting in retention of the interdigital web and soft-tissue syndactyly. This is associated with perdurance of Fgf8 expression in the ectoderm overlying the interdigital space. Our study supports a mechanism whereby Akirin2 is required for the downregulation of Fgf8 from the apical ectodermal ridge (AER) during limb development, and implies its requirement in signalling between interdigital mesenchymal cells and the AER.

A comparative study of three akirin genes from big belly seahorse Hippocampus abdominalis: Molecular, transcriptional and functional characterization

Akirins, members of the NF-κB signaling pathway, are highly conserved nuclear proteins, which regulate gene expression in many physiological processes, including immunity, myogenesis, carcinogenesis, and embryogenesis. The akirin family in teleost fish consists of two to three genes. In the present study, three akirin genes from Hippocampus abdominalis were identified from a transcriptome database and designated as HaAkirin1, HaAkirin2(1), and HaAkirin2(2). The nuclear localization of HaAkirin1 and HaAkirin2(1) was confirmed by subcellular localization analysis. In contrast, diffused localization of HaAkirin2(2) was identified in the nucleus and cytoplasm that confirmed the aberrant nature of the nuclear localization signal. Phylogenetic analysis revealed a closer relationship of HaAkirins with other known teleost akirins. All three HaAkirin transcripts were ubiquitously expressed in all examined tissues with higher expression in ovary tissue. Immune challenge with LPS, poly I:C, and Streptococcus iniae exhibited a significant increase in the expression of all three HaAkirins in kidney and liver tissues. NF-κB luciferase assays revealed that relative luciferase activity was significantly higher for all three HaAkirin genes than mock controls. These results suggest that HaAkirin genes might play a role in regulating NF-κB dependent immune gene expression and their expression could be induced by bacterial and viral pathogen recognition molecular patterns.

Pathogen recognition and Toll-like receptor targeted therapeutics in innate immune cells

The innate immune system deploys a variety of pattern-recognition receptors (PRRs) which include Toll-like receptors (TLRs), RIG-I-like receptors, NOD-like receptors, and C-type lectin receptors to detect the invasion of pathogens and initiate protective responses. The intercellular and intracellular orchestration of signals from different PRRs, their endogenous or microbial ligands and accessory molecules determine the stimulatory or inhibitory responses. Progressing over the last two decades, considerable research on the molecular mechanisms underlying host-pathogen interactions has led to a paradigm shift of our understanding of TLR signaling in the innate immune system. Given that a significant amount of evidence implicates TLRs in the pathogenesis of immune diseases and cancer, and their activation occurs early in the inflammatory cascade, they are attractive targets for novel therapeutic agents. In this review, we discuss the recent advances in TLR signaling cross talks and the mechanism of pathogen recognition with special emphasis on the role of TLRs in tumor immunity and TLR-targeted therapeutics.

Akirin2 is essential for the formation of the cerebral cortex

Background

The proper spatial and temporal regulation of dorsal telencephalic progenitor behavior is a prerequisite for the formation of the highly-organized, six-layered cerebral cortex. Premature differentiation of cells, disruption of cell cycle timing, excessive apoptosis, and/or incorrect neuronal migration signals can have devastating effects, resulting in a number of neurodevelopmental disorders involving microcephaly and/or lissencephaly. Though genes encoding many key players in cortical development have been identified, our understanding remains incomplete. We show that the gene encoding Akirin2, a small nuclear protein, is expressed in the embryonic telencephalon. Converging evidence indicates that Akirin2 acts as a bridge between transcription factors (including Twist and NF-κB proteins) and the BAF (SWI/SNF) chromatin remodeling machinery to regulate patterns of gene expression. Constitutive knockout of Akirin2 is early embryonic lethal in mice, while restricted loss in B cells led to disrupted proliferation and cell survival.

Methods

We generated cortex-restricted Akirin2 knockouts by crossing mice harboring a floxed Akirin2 allele with the Emx1-Cre transgenic line and assessed the resulting embryos using in situ hybridization, EdU labeling, and immunohistochemistry.

Results

The vast majority of Akirin2 mutants do not survive past birth, and exhibit extreme microcephaly, with little dorsal telencephalic tissue and no recognizable cortex. This is primarily due to massive cell death of early cortical progenitors, which begins at embryonic day (E)10, shortly after Emx1-Cre is active. Immunostaining and cell cycle analysis using EdU labeling indicate that Akirin2-null progenitors fail to proliferate normally, produce fewer neurons, and undergo extensive apoptosis. All of the neurons that are generated in Akirin2 mutants also undergo apoptosis by E12. In situ hybridization for Wnt3a and Wnt-responsive genes suggest defective formation and/or function of the cortical hem in Akirin2 null mice. Furthermore, the apical ventricular surface becomes disrupted, and Sox2-positive progenitors are found to “spill” into the lateral ventricle.

Conclusions

Our data demonstrate a previously-unsuspected role for Akirin2 in early cortical development and, given its known nuclear roles, suggest that it may act to regulate gene expression patterns critical for early progenitor cell behavior and cortical neuron production.

Electronic supplementary material

The online version of this article (doi:10.1186/s13064-016-0076-8) contains supplementary material, which is available to authorized users.

Akirin interacts with Bap60 and 14-3-3 proteins to regulate the expression of antimicrobial peptides in the kuruma shrimp (Marsupenaeus japonicus)

Akirin is a recently discovered nuclear factor that plays important roles in innate immune responses. Akirin is a positive regulator of the NF-κB factor of the Drosophila immune deficiency (IMD) pathway, which shares extensive similarities with the mammalian tumor necrosis factor receptor (TNFR) signaling pathway. However, some studies found that the NF-κB transcriptional targets were also strongly repressed in akirin2 knockout mice following TLR, IL-1β and TNFα treatment. Therefore, the function of Akirin in the immune response requires further clarification. In this study, an Akirin homolog in the kuruma shrimp (Marsupenaeus japonicus) was identified. It was mainly expressed in hemocytes, heart and intestines. The expression of Akirin was upregulated by challenge with the Gram-negative bacterium Vibrio anguillarum, but was not significantly influenced by challenge with the Gram-positive bacterium Staphylococcus aureus. Knockdown of Akirin suppressed the expression of several IMD-Relish target effectors (antimicrobial peptides, AMPs). The limited regulating spectrum of Akirin might be associated with Bap60, a component of the Brahma (SWI/SNF) ATP-dependent chromatin-remodeling complex. In addition, Akirin also interacts with 14-3-3, which inhibited the expression of Akirin-target AMPs. The results suggested that Akirin is involved in the IMD-Relish pathway by interacting with Relish. The interaction of Akirin with Bap60 positively regulated the Akirin-Relish function, and its interaction with 14-3-3 negatively regulated the Akirin-Relish function.

Impact of host genetic polymorphisms on vaccine induced antibody response

Many host- and vaccine-specific factors modulate an antibody response. Host genetic polymorphisms, in particular, modulate the immune response in multiple ways on different scales. This review article describes how information on host genetic polymorphisms and corresponding immune cascades may be used to generate personalized vaccine strategies to optimize the antibody response.

Chromatin Remodeling and Transcriptional Control in Innate Immunity: Emergence of Akirin2 as a Novel Player

Transcriptional regulation of inflammatory gene expression has been at the forefront of studies of innate immunity and is coordinately regulated by transcription factors, including NF-κB, and chromatin modifiers. The growing evidence for involvement of chromatin in the regulation of gene expression in innate immune cells, has uncovered an evolutionarily conserved role of microbial sensing and chromatin remodeling. Toll-like receptors and RIG-I-like receptors trigger these signaling pathways leading to transcriptional expression of a set of genes involved in inflammation. Tightly regulated control of this gene expression is a paramount, and often foremost, goal of most biological endeavors. In this review, we will discuss the recent progress about the molecular mechanisms governing control of pro-inflammatory gene expression by an evolutionarily conserved novel nuclear protein Akirin2 in macrophages and its emergence as an essential link between NF-κB and chromatin remodelers for transcriptional regulation.