Selective ablation of Ctip2/Bcl11b in epidermal keratinocytes triggers atopic dermatitis-like skin inflammatory responses in adult mice

The epidermal lipid-microbiome loop and immunity: Important players in atopic dermatitis

BACKGROUND

The promotion of epidermal barrier dysfunction is attributed to abnormalities in the lipid-microbiome positive feedback loop which significantly influences the imbalance of the epithelial immune microenvironment (EIME) in atopic dermatitis (AD). This imbalance encompasses impaired lamellar membrane integrity, heightened exposure to epidermal pathogens, and the regulation of innate and adaptive immunity. The lipid-microbiome loop is substantially influenced by intense adaptive immunity which is triggered by abnormal loop activity and affects the loop's integrity through the induction of atypical lipid composition and responses to dysregulated epidermal microbes. Immune responses participate in lipid abnormalities within the EIME by downregulating barrier gene expression and are further cascade-amplified by microbial dysregulation which is instigated by barrier impairment.

AIM OF REVIEW

This review examines the relationship between abnormal lipid composition, microbiome disturbances, and immune responses in AD while progressively substantiating the crosstalk mechanism among these factors. Based on this analysis, the "lipid-microbiome" positive feedback loop, regulated by immune responses, is proposed.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The review delves into the impact of adaptive immune responses that regulate the EIME, driving AD, and investigates potential mechanisms by which lipid supplementation and probiotics may alleviate AD through the up-regulation of the epidermal barrier and modulation of immune signaling. This exploration offers support for targeting the EIME to attenuate AD.

Developmental regulation of dermal adipose tissue by BCL11b

The distinct anatomic environment in which adipose tissues arise during organogenesis is a principle determinant of their adult expansion capacity. Metabolic disease results from a deficiency in hyperplastic adipose expansion within the dermal/subcutaneous depot; thus, understanding the embryonic origins of dermal adipose is imperative. Using single-cell transcriptomics throughout murine embryogenesis, we characterized cell populations, including Bcl11b + cells, that regulate the development of dermal white adipose tissue (dWAT). We discovered that BCL11b expression modulates the Wnt signaling microenvironment to enable adipogenic differentiation in the dermal compartment. Subcutaneous and visceral adipose arises from a distinct population of Nefl + cells during embryonic organogenesis, whereas Pi16 + /Dpp4 + fibroadipogenic progenitors support obesity-stimulated hypertrophic expansion in the adult. Together, these results highlight the unique regulatory pathways used by anatomically distinct adipose depots, with important implications for human metabolic disease.

The Role of Bcl11 Transcription Factors in Neurodevelopmental Disorders

Neurodevelopmental disorders (NDDs) comprise a diverse group of diseases, including developmental delay, autism spectrum disorder (ASD), intellectual disability (ID), and attention-deficit/hyperactivity disorder (ADHD). NDDs are caused by aberrant brain development due to genetic and environmental factors. To establish specific and curative therapeutic approaches, it is indispensable to gain precise mechanistic insight into the cellular and molecular pathogenesis of NDDs. Mutations of BCL11A and BCL11B, two closely related, ultra-conserved zinc-finger transcription factors, were recently reported to be associated with NDDs, including developmental delay, ASD, and ID, as well as morphogenic defects such as cerebellar hypoplasia. In mice, Bcl11 transcription factors are well known to orchestrate various cellular processes during brain development, for example, neural progenitor cell proliferation, neuronal migration, and the differentiation as well as integration of neurons into functional circuits. Developmental defects observed in both, mice and humans display striking similarities, suggesting Bcl11 knockout mice provide excellent models for analyzing human disease. This review offers a comprehensive overview of the cellular and molecular functions of Bcl11a and b and links experimental research to the corresponding NDDs observed in humans. Moreover, it outlines trajectories for future translational research that may help to better understand the molecular basis of Bcl11-dependent NDDs as well as to conceive disease-specific therapeutic approaches.

Inhibition of Anaplastic Lymphoma Kinase (Alk) as Therapeutic Target to Improve Brain Function in Neurofibromatosis Type 1 (Nf1)

Neurofibromatosis type 1 (Nf1) is a neurodevelopmental disorder and tumor syndrome caused by loss of function mutations in the neurofibromin gene (Nf1) and is estimated to affect 100,000 people in the US. Behavioral alterations and cognitive deficits have been found in 50-70% of children with Nf1 and include specific problems with attention, visual perception, language, learning, attention, and executive function. These behavioral alterations and cognitive deficits are observed in the absence of tumors or macroscopic structural abnormalities in the central nervous system. No effective treatments for the behavioral and cognitive disabilities of Nf1 exist. Inhibition of the anaplastic lymphoma kinase (Alk), a kinase which is negatively regulated by neurofibromin, allows for testing the hypothesis that this inhibition may be therapeutically beneficial in Nf1. In this review, we discuss this area of research and directions for the development of alternative therapeutic strategies to inhibit Alk. Even if the incidence of adverse reactions of currently available Alk inhibitors was reduced to half the dose, we anticipate that a long-term treatment would pose challenges for efficacy, safety, and tolerability. Therefore, future efforts are warranted to investigate alternative, potentially less toxic and more specific strategies to inhibit Alk function.

Biological treatment for bullous pemphigoid

Background

Bullous pemphigoid (BP) is the most common autoimmune subepidermal bullous disease. Topical or systemic corticosteroids are often used as the first-line treatment. However, long-term corticosteroid use may lead to significant side effects. Therefore, various adjuvant immunosuppressant therapies are used as steroid-sparing agents, with accumulating reports of biological treatments for severely recalcitrant BP.

Objective

To describe the clinical and immunological features of a series of patients with recalcitrant BP treated with immunobiological therapies. To assess the efficacy and safety of their therapies.

Methods

Patients receiving biological treatment for BP from two centers were assessed. Here, we described the clinical, immunopathological, and immunofluorescence findings of adult patients with BP and analyzed the clinical response and adverse events associated with various biological therapies.

Results

We identified nine eligible patients treated with rituximab (seven), omalizumab (three), or dupilumab (one). The mean age at diagnosis was 60.4 years, the average BP duration before biologic initiation was 1.9 years, and the average previous treatment failure was 2.11 therapies. The mean follow-up period from the first biological treatment to the last visit was 29.3 months. Satisfactory response, defined as clinical improvement, was achieved in 78% (7) of the patients, and total BP clearance was achieved in 55% (5) of the patients at the last follow-up visit. Additional rituximab courses improved the disease outcomes. No adverse events were reported.

Conclusions

Efficient and safe novel therapies can be considered in recalcitrant steroid-dependent BP non-responsive to conventional immunosuppressant therapies.

Selective Ablation of BCL11A in Epidermal Keratinocytes Alters Skin Homeostasis and Accelerates Excisional Wound Healing In Vivo

Transcriptional regulator BCL11A plays a crucial role in coordinating a suite of developmental processes including skin morphogenesis, barrier functions and lipid metabolism. There is little or no reports so far documenting the role of BCL11A in postnatal adult skin homeostasis and in the physiological process of tissue repair and regeneration. The current study establishes for the first time the In Vivo role of epidermal BCL11A in maintaining adult epidermal homeostasis and as a negative regulator of cutaneous wound healing. Conditional ablation of Bcl11a in skin epidermal keratinocytes (Bcl11a^ep−/−mice) enhances the keratinocyte proliferation and differentiation program, suggesting its critical role in epidermal homeostasis of adult murine skin. Further, loss of keratinocytic BCL11A promotes rapid closure of excisional wounds both in a cell autonomous manner likely via accelerating wound re-epithelialization and in a non-cell autonomous manner by enhancing angiogenesis. The epidermis specific Bcl11a knockout mouse serves as a prototype to gain mechanistic understanding of various downstream pathways converging towards the manifestation of an accelerated healing phenotype upon its deletion.

Bioengineered Efficacy Models of Skin Disease: Advances in the Last 10 Years

Models of skin diseases, such as psoriasis and scleroderma, must accurately recapitulate the complex microenvironment of human skin to provide an efficacious platform for investigation of skin diseases. Skin disease research has been shifting from less complex and less relevant 2D (two-dimensional) models to significantly more relevant 3D (three-dimensional) models. Three-dimensional modeling systems are better able to recapitulate the complex cell–cell and cell–matrix interactions that occur in vivo within skin. Three-dimensional human skin equivalents (HSEs) have emerged as an advantageous tool for the study of skin disease in vitro. These 3D HSEs can be highly complex, containing both epidermal and dermal compartments with integrated adnexal structures. The addition of adnexal structures to 3D HSEs has allowed researchers to gain more insight into the complex pathology of various hereditary and acquired skin diseases. One method of constructing 3D HSEs, 3D bioprinting, has emerged as a versatile and useful tool for generating highly complex HSEs. The development of commercially available 3D bioprinters has allowed researchers to create highly reproducible 3D HSEs with precise integration of multiple adnexal structures. While the field of bioengineered models for study of skin disease has made tremendous progress in the last decade, there are still significant efforts necessary to create truly biomimetic skin disease models. In future studies utilizing 3D HSEs, emphasis must be placed on integrating all adnexal structures relevant to the skin disease under investigation. Thorough investigation of the intricate pathology of skin diseases and the development of effective treatments requires use of highly efficacious models of skin diseases.

CTIP2 and lipid metabolism: regulation in skin development and associated diseases

INTRODUCTION

COUP-TF INTERACTING PROTEIN 2 (CTIP2) is a crucial transcription factor exhibiting its control through coupled modulation of epigenetic modification and transcriptional regulation of key genes related to skin, immune, and nervous system development. Previous studies have validated the essential role of CTIP2 in skin development and maintenance, propagating its effects in epidermal permeability barrier (EPB) homeostasis, wound healing, inflammatory diseases, and epithelial cancers. Lipid metabolism dysregulation, on the other hand, has also established its independent emerging role over the years in normal skin development and various skin-associated ailments. This review focuses on the relatively unexplored connections between CTIP2-mediated control of lipid metabolism and alteration of EPB homeostasis, delayed wound healing, inflammatory diseases exacerbation, and cancer promotion and progression.

AREAS COVERED

Here we have discussed the intricate interplay of various endogenous lipids and lipoproteins accompanying skin development and associated disease processes and the possible link to CTIP2-mediated regulation of lipid metabolism.

EXPERT OPINION

Establishing the link between CTIP2 and lipid metabolism alterations in the context of skin morphogenesis and diverse types of skin diseases including cancer can help us identify novel targets for effective therapeutic intervention.

Very Elevated IgE, Atopy, and Severe Infection: A Genomics-Based Diagnostic Approach to a Spectrum of Diseases

Elevated IgE has been long recognized as an important clinical marker of atopy but can be seen in a myriad of conditions. The discovery of autosomal dominant STAT3 deficiency marked the first recognition of hyper-IgE syndrome (HIES) and the first primary immunodeficiency linked to elevated IgE. Since then, genomic testing has increased the number of defects with associated mutations causing hyper-IgE syndrome and atopic diseases with FLG, DOCK8, SPINK5, and CARD11, among others. A spectrum of recurrent infections and atopy are hallmarks of elevated IgE with significant phenotypic overlap between each underlying condition. As treatment is predicated on early diagnosis, genomic testing is becoming a more commonly used diagnostic tool. We present a 6-year-old male patient with markedly elevated IgE and severe atopic dermatitis presenting with staphylococcal bacteremia found to have a heterozygous variant in FLG (p.S3247X) and multiple variants of unknown significance in BCL11B, ZAP70, LYST, and PTPRC. We review the genetic defects underpinning elevated IgE and highlight the spectrum of atopy and immunodeficiency seen in patients with underlying mutations. Although no one mutation is completely causative of the constellation of symptoms in this patient, we suggest the synergism of these variants is an impetus of disease.

Gardenia Jasminoides Ameliorates Antibiotic-Associated Aggravation of DNCB-Induced Atopic Dermatitis by Restoring the Intestinal Microbiome Profile

The intestinal microbiome is considered one of the key regulators of health. Accordingly, the severity of atopic dermatitis (AD) is mediated by the skin and intestinal microbiome environment. In this study, while evaluating the aggravation in AD symptoms by the antibiotics cocktail (ABX)-induced depletion of the intestinal microbiome, we sought to verify the effect of Gardenia jasminoides (GJ), a medicinal herb used for inflammatory diseases, on AD regarding its role on the intestinal microbiome. To verify the aggravation in AD symptoms induced by the depletion of the intestinal microbiome, we established a novel mouse model by administrating an ABX to create a microbiome-free environment in the intestine, and then applied 2,4-dinitrochlorobenzene (DNCB) to induce an AD-like skin inflammatory response. While ABX treatment aggravated AD-like symptoms, the 2-week administration of GJ improved these pathological changes. DNCB application upregulated immune cell count and serum cytokine expression, which were alleviated by GJ. Moreover, pathological alterations by antibiotics and DNCB, including histological damage of the intestine and the intestinal expression of IL-17, were recovered in GJ-treated mice. The beneficial effect of GJ was due to the restoration of the intestinal microbiome composition. Overall, we suggest GJ as a potential therapeutic agent for AD due to its regulation of the intestinal microbiome.

Bcl11b/Ctip2 in Skin, Tooth, and Craniofacial System

Ctip2/Bcl11b is a zinc finger transcription factor with dual action (repression/activation) that couples epigenetic regulation to gene transcription during the development of various tissues. It is involved in a variety of physiological responses under healthy and pathological conditions. Its role and mechanisms of action are best characterized in the immune and nervous systems. Furthermore, its implication in the development and homeostasis of other various tissues has also been reported. In the present review, we describe its role in skin development, adipogenesis, tooth formation and cranial suture ossification. Experimental data from several studies demonstrate the involvement of Bcl11b in the control of the balance between cell proliferation and differentiation during organ formation and repair, and more specifically in the context of stem cell self-renewal and fate determination. The impact of mutations in the coding sequences of Bcl11b on the development of diseases such as craniosynostosis is also presented. Finally, we discuss genome-wide association studies that suggest a potential influence of single nucleotide polymorphisms found in the 3’ regulatory region of Bcl11b on the homeostasis of the cardiovascular system.

The Role of Toll-Like Receptors in Skin Host Defense, Psoriasis, and Atopic Dermatitis

As the key defense molecules originally identified in Drosophila, Toll-like receptor (TLR) superfamily members play a fundamental role in detecting invading pathogens or damage and initiating the innate immune system of mammalian cells. The skin, the largest organ of the human body, protects the human body by providing a critical physical and immunological active multilayered barrier against invading pathogens and environmental factors. At the first line of defense, the skin is constantly exposed to pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), and TLRs, expressed in a cell type-specific manner by various skin cells, serve as key molecules to recognize PAMPs and DAMPs and to initiate downstream innate immune host responses. While TLR-initiated inflammatory responses are necessary for pathogen clearance and tissue repair, aberrant activation of TLRs will exaggerate T cell-mediated autoimmune activation, leading to unwanted inflammation, and the development of several skin diseases, including psoriasis, atopic dermatitis, systemic lupus erythematosus, diabetic foot ulcers, fibrotic skin diseases, and skin cancers. Together, TLRs are at the interface between innate immunity and adaptive immunity. In this review, we will describe current understanding of the role of TLRs in skin defense and in the pathogenesis of psoriasis and atopic dermatitis, and we will also discuss the development and therapeutic effect of TLR-targeted therapies.

BCL11B regulates MICA/B-mediated immune response by acting as a competitive endogenous RNA

Cancer immune surveillance is an important host protection process that inhibits carcinogenesis and maintains cellular homeostasis. The major histocompatibility complex class I-related molecules A and B (MICA and MICB) are NKG2D ligands that play important roles in tumor immune surveillance. In the present study, by a combined bioinformatics prediction and experimental approach, we identify BCL11B 3'-UTR as a putative MICA and MICB ceRNA. We demonstrate in several human cell lines of different origins that the knockdown of BCL11B downregulates surface expression of MICA and MICB. Furthermore, we demonstrate miRNA dependency of BCL11B-mediated MICA and MICB regulation in Dicer knockdown HCT116 cells. In addition, MICA/B-targeting miRNAs (miR-17, miR-93, miR-20a, miR-20b, miR-106a, and miR-106b) repressed the expression of BCL11B by targeting its 3'-UTR. Moreover, we showed that the BCL11B knockdown-mediated downregulation of MICA/B resulted in reduced NK cell elimination in vitro and in vivo through reduced recognition of NKG2D. Of particular significance, BCL11B displays tumor-suppressive properties. The expression of BCL11B is downregulated in colon cancer tissues and associated with a reduced median survival of colon cancer patients. Taken together, our study revealed a new mechanism of BCL11B that prevents immune evasion of cancerous cells by upregulation of the NKG2D ligands MICA and MICB in a ceRNA manner.

Thymic stromal lymphopoietin production induced by skin irritation results from concomitant activation of protease-activated receptor 2 and interleukin 1 pathways

BACKGROUND

Thymic stromal lymphopoietin (TSLP) mediates proallergic T helper 2-type responses by acting on leucocytes. Endogenous pathways regulating TSLP production are poorly defined.

OBJECTIVES

To uncover the mechanisms by which skin barrier disruption elicits TSLP production and to delineate the level at which individual mechanistic components may converge.

METHODS

A combination of primary keratinocytes, skin explants and in vivo strategies was employed. Murine skin was tape stripped in the presence of neutralizing antibodies or antagonists. Cells and explants were stimulated with interleukin (IL)-1 and protease-activated receptor 2 agonist (PAR-2-Ag). TSLP levels were quantified by enzyme-linked immunosorbent assay and real-time quantitative polymerase chain reaction. Chromatin immunoprecipitation and promoter reporter assays were used to examine recruitment and functional activity of nuclear factor kappa B (NF-κB) at the TSLP promoter.

RESULTS

TSLP induction in mouse skin occurred in a PAR-2- and IL-1-dependent manner. This scenario was duplicated by exogenous IL-1 plus PAR-2-Ag vs. each stimulus alone. Joint activity of PAR-2 and IL-1 was also observed in human keratinocytes. The TSLP promoter was identified as the target of PAR-2/IL-1, whereby PAR-2 activation augmented the recruitment of NF-κB and transcriptional activation over IL-1 alone. Combined treatment showed activity at concentrations of IL-1 unable to elicit NF-κB activity on their own.

CONCLUSIONS

Skin barrier disruption activates the IL-1 and the PAR-2 pathways, which act in concert to activate the TSLP promoter and possibly other inflammatory genes. Awareness of this combined activity may permit a more flexible clinical management by selective targeting of either pathway individually or collectively. What's already known about this topic? Thymic stromal lymphopoietin (TSLP) is rapidly induced upon skin perturbation and mediates proallergic T helper 2-type responses by acting on leucocytes. Endogenous control of TSLP expression is poorly understood, but interleukin (IL)-1 is one regulator in the cutaneous environment In addition to IL-1, protease-activated receptor 2 (PAR-2) organizes central inflammatory pathways in the skin. What does this study add? IL-1 and PAR-2 pathways cooperate in driving TSLP production in mice and humans. Pathway integration occurs at the level of the TSLP promoter through enhanced recruitment and transcriptional activation of nuclear factor kappa B. When PAR-2 is co-stimulated, very low IL-1 levels (inactive by themselves) can induce biologically meaningful responses in the skin environment. What is the translational message? Physical skin irritation results in robust TSLP production by simultaneous activation of PAR-2 and IL-1 pathways.

Type1 Interferons Potential Initiating Factors Linking Skin Wounds With Psoriasis Pathogenesis

Psoriasis is a chronic autoimmune skin disease that can often be triggered upon skin injury, known as Koebner phenomenon. Type 1 interferons (IFNα and IFNβ), key cytokines that activate autoimmunity during viral infection, have been suggested to play an indispensable role in initiating psoriasis during skin injury. Type 1 IFN-inducible gene signature has been identified as one of the major upregulated gene signatures in psoriatic skin. Type 1 IFNs treatments often directly induce or exacerbate psoriasis, whereas blocking type 1 IFNs signaling pathway in animal models effectively inhibits the development of T cell-mediated skin inflammation and psoriasis-like inflammatory diseases. Epidermal keratinocytes (KCs) occupy the outermost position in the skin and are the first responder to skin injury. Skin injury rapidly induces IFNβ from KCs and IFNα from dermal plasmacytoid dendritic cells (pDCs) through distinct mechanisms. Host antimicrobial peptide LL37 potentiates double-stranded RNA (dsRNA) immune pathways in keratinocytes and single-stranded RNA or DNA pathways in pDCs, leading to production of distinct type 1 IFN genes. IFNβ from KC promotes dendritic cell maturation and the subsequent T cell proliferation, contributing to autoimmune activation during skin injury and psoriasis pathogenesis. Accumulating evidences have indicated an important role of this dsRNA immune pathway in psoriasis pathogenesis. Together, this review describes how skin injury induces type 1 IFNs from skin cells and how this may initiate autoimmune cascades that trigger psoriasis. Targeting keratinocytes or type 1 IFNs in combination with T cell therapy may result in more sustainable effect to treat auto-inflammatory skin diseases such as psoriasis.

Bcl11b Regulates IL-17 Through the TGF-β/Smad Pathway in HDM-Induced Asthma

PURPOSE

T helper (Th) 17 cells play a critical role in the development of asthma, but the underlying mechanism of how interleukin (IL)-17 is regulated in allergic airway inflammation is poorly understood. In this study, we investigated the impact of Bcl11b on Th17 response in asthma.

METHODS

Blood samples from patients with mild asthma (MA) and severe asthma (SA) were collected. Expression of Bcl11b, IL-4, IL-5, IL-13, IL-17A and transforming growth factor (TGF)-β1 were determined in CD4⁺ T cells and plasma by polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). Relative mRNA and protein levels of Bcl11b, IL-17A and genes involved in the TGF/Smad signaling pathway were examined by PCR, ELISA and western blot analysis in house dust mite (HDM)-challenged mice. Ectopic expression of Bcl11b in HDM-stimulated primary mouse splenocytes was achieved by nucleofection of Bcl11b expression plasmid.

RESULTS

We found significantly decreased Bcl11b but increased IL-17A and TGF-β1 expression in patients with asthma and a strongly negative correlation between Bcl11b and these 2 cytokines in SA patients. Similar expression patterns of Bcl11b, IL-17A and TGF-β1 were also found in mice with HDM-induced allergic airway inflammation. We demonstrated further that Smad2/3 phosphorylation was increased in HDM-challenged mice and that ectopic expression of Bcl11b in HDM-stimulated primary mouse splenocytes reduced Smad2 phosphorylation and IL-17 expression.

CONCLUSIONS

Our findings demonstrate a potential effect of Bc111b in controlling IL-17-mediated inflammation in asthma and suggest that Bc111b may be a useful therapeutic target for asthma.

Functional characterization of common BCL11B gene desert variants suggests a lymphocyte-mediated association of BCL11B with aortic stiffness

The recent genome-wide analysis of carotid–femoral pulse wave velocity (PWV) identified a significant locus within the 14q32.2 gene desert. Gene regulatory elements for the transcriptional regulator B-cell CLL/lymphoma 11B (BCL11B) are within this locus and an attractive target for the gene association. We investigated the functional impact of these gene desert SNPs on BCL11B transcript in human aorta to characterize further its role in aortic stiffness. To do this, we used a large repository of aortic tissues (n = 185) from an organ transplant program and assessed ex vivo stiffness of the aortic rings. We tested association of three lead SNPs from the GWAS meta-analysis with ex vivo aortic stiffness and BCL11B aortic mRNA expression: rs1381289 and rs10782490 SNPs associated significantly with PWV and showed allele-specific differences in BCL11B mRNA. The risk alleles associated with lower BCL11B expression, suggesting a protective role for BCL11B. Despite strong association, we could not detect BCL11B protein in the human aorta. However, qPCR for CD markers showed that BCL11B transcript correlated strongly with markers for activated lymphocytes. Our data confirm the significance of the 14q32.2 region as a risk locus for aortic stiffness and an upstream regulator of BCL11B. The BCL11B transcript detected in the human aorta may reflect lymphocyte infiltration, suggesting that immune mechanisms contribute to the observed association of BCL11B with aortic stiffness.

BCL11B mutations in patients affected by a neurodevelopmental disorder with reduced type 2 innate lymphoid cells

The transcription factor BCL11B is essential for development of the nervous and the immune system, and Bcl11b deficiency results in structural brain defects, reduced learning capacity, and impaired immune cell development in mice. However, the precise role of BCL11B in humans is largely unexplored, except for a single patient with a BCL11B missense mutation, affected by multisystem anomalies and profound immune deficiency. Using massively parallel sequencing we identified 13 patients bearing heterozygous germline alterations in BCL11B. Notably, all of them are affected by global developmental delay with speech impairment and intellectual disability; however, none displayed overt clinical signs of immune deficiency. Six frameshift mutations, two nonsense mutations, one missense mutation, and two chromosomal rearrangements resulting in diminished BCL11B expression, arose de novo. A further frameshift mutation was transmitted from a similarly affected mother. Interestingly, the most severely affected patient harbours a missense mutation within a zinc-finger domain of BCL11B, probably affecting the DNA-binding structural interface, similar to the recently published patient. Furthermore, the most C-terminally located premature termination codon mutation fails to rescue the progenitor cell proliferation defect in hippocampal slice cultures from Bcl11b-deficient mice. Concerning the role of BCL11B in the immune system, extensive immune phenotyping of our patients revealed alterations in the T cell compartment and lack of peripheral type 2 innate lymphoid cells (ILC2s), consistent with the findings described in Bcl11b-deficient mice. Unsupervised analysis of 102 T lymphocyte subpopulations showed that the patients clearly cluster apart from healthy children, further supporting the common aetiology of the disorder. Taken together, we show here that mutations leading either to BCL11B haploinsufficiency or to a truncated BCL11B protein clinically cause a non-syndromic neurodevelopmental delay. In addition, we suggest that missense mutations affecting specific sites within zinc-finger domains might result in distinct and more severe clinical outcomes.

Transcription Factor CTIP1/ BCL11A Regulates Epidermal Differentiation and Lipid Metabolism During Skin Development

The epidermal permeability barrier (EPB) prevents organisms from dehydration and infection. The transcriptional regulation of EPB development is poorly understood. We demonstrate here that transcription factor COUP-TF-interacting protein 1 (CTIP1/BCL11A; hereafter CTIP1) is highly expressed in the developing murine epidermis. Germline deletion of Ctip1 (Ctip1^−/−) results in EPB defects accompanied by compromised epidermal differentiation, drastic reduction in profilaggrin processing, reduced lamellar bodies in granular layers and significantly altered lipid composition. Transcriptional profiling of Ctip1^−/− embryonic skin identified altered expression of genes encoding lipid-metabolism enzymes, skin barrier-associated transcription factors and junctional proteins. CTIP1 was observed to interact with genomic elements within the regulatory region of the gene encoding the differentiation-associated gene, Fos-related antigen2 (Fosl2) and lipid-metabolism-related gene, Fatty acid elongase 4 (Elvol4), and the expression of both was altered in Ctip1^−/− mice. CTIP1 appears to play a role in EPB establishment of via direct or indirect regulation of a subset of genes encoding proteins involved in epidermal differentiation and lipid metabolism. These results identify potential, CTIP1-regulated avenues for treatment of skin disorders involving EBP defects.

Essential role of microRNA-650 in the regulation of B-cell CLL/lymphoma 11B gene expression following transplantation: A novel mechanism behind the acute rejection of renal allografts

Kidney transplantation is an effective final therapeutic procedure for patients with end-stage kidney failure. Although advanced immunosuppressive therapy is administered following transplantation, certain patients still suffer from acute allograft rejection. MicroRNAs (miRs) have a potential diagnostic and therapeutic value for acute renal allograft rejection; however, their underlying mechanism of action is largely unknown. In the present study, an increased level of miR-650 was identified to be associated with the downregulation of B-cell CLL/lymphoma 11B (BCL11B) expression in acute renal allograft rejection. Furthermore, in vitro study using human renal glomerular endothelial cells (HRGECs) transfected with a miR-650 mimic revealed that key characteristics of acute renal allograft rejection were observed, including apoptosis, the release of cytokines and the chemotaxis of macrophages, while the effects were reduced in HRGECs transfected with a miR-650 inhibitor. The existence of a conserved miR-650 binding site on the 3'-untranslated region of BCL11B mRNA was predicted by computational algorithms and confirmed by a luciferase reporter assay. Knockdown of BCL11B with small interfering RNA (siRNA) significantly increased the apoptotic rate and significantly decreased the proliferation ability of HRGECs compared with the negative control group. HRGECs transfected with a combination of BCL11B siRNA and the miR-650 mimic demonstrated a significant increase in the rate of apoptosis compared with the control. These results suggest that the upregulation of miR-650 contributes to the development of acute renal allograft rejection by suppression of BCL11B, which leads to apoptosis and inflammatory responses. Thus, miR-650 and BCL11B may represent potential therapeutic targets for the prevention of acute renal allograft rejection.

Translational Animal Models of Atopic Dermatitis for Preclinical Studies

There is a medical need to develop new treatments for patients suffering from atopic dermatitis (AD). To improve the discovery and testing of novel treatments, relevant animal models for AD are needed. Generally, these animal models mimic different aspects of the pathophysiology of human AD, such as skin barrier defects and Th2 immune bias with additional Th1 and Th22, and in some populations Th17, activation. However, the pathomechanistic characterization and pharmacological validation of these animal models are generally incomplete. In this paper, we review animal models of AD in the context of preclinical use and their possible translation to the human disease. Most of these models use mice, but we will also critically evaluate dog models of AD, as increasing information on disease mechanism show their likely relevance for the human disease.

Etiology of epithelial barrier dysfunction in patients with type 2 inflammatory diseases

Epithelial barriers of the skin, gastrointestinal tract, and airway serve common critical functions, such as maintaining a physical barrier against environmental insults and allergens and providing a tissue interface balancing the communication between the internal and external environments. We now understand that in patients with allergic disease, regardless of tissue location, the homeostatic balance of the epithelial barrier is skewed toward loss of differentiation, reduced junctional integrity, and impaired innate defense. Importantly, epithelial dysfunction characterized by these traits appears to pre-date atopy and development of allergic disease. Despite our growing appreciation of the centrality of barrier dysfunction in initiation of allergic disease, many important questions remain to be answered regarding mechanisms disrupting normal barrier function. Although our external environment (proteases, allergens, and injury) is classically thought of as a principal contributor to barrier disruption associated with allergic sensitization, there is a need to better understand contributions of the internal environment (hormones, diet, and circadian clock). Systemic drivers of disease, such as alterations of the endocrine system, metabolism, and aberrant control of developmental signaling, are emerging as new players in driving epithelial dysfunction and allergic predisposition at various barrier sites. Identifying such central mediators of epithelial dysfunction using both systems biology tools and causality-driven laboratory experimentation will be essential in building new strategic interventions to prevent or reverse the process of barrier loss in allergic patients.

Bcl11b-A Critical Neurodevelopmental Transcription Factor-Roles in Health and Disease

B cell leukemia 11b (Bcl11b) is a zinc finger protein transcription factor with a multiplicity of functions. It works as both a genetic suppressor and activator, acting directly, attaching to promoter regions, as well as indirectly, attaching to promoter-bound transcription factors. Bcl11b is a fundamental transcription factor in fetal development, with important roles for the differentiation and development of various neuronal subtypes in the central nervous system (CNS). It has been used as a specific marker of layer V subcerebral projection neurons as well as striatal interneurons. Bcl11b also has critical developmental functions in the immune, integumentary and cardiac systems, to the extent that Bcl11b knockout mice are incompatible with extra-uterine life. Bcl11b has been implicated in a number of disease states including Huntington's disease, Alzheimer's disease, HIV and T-Cell malignancy, amongst others. Bcl11b is a fascinating protein whose critical roles in the CNS and other parts of the body are yet to be fully explicated. This review summarizes the current literature on Bcl11b and its functions in development, health, and disease as well as future directions for research.

Topical Tetracycline Improves MC903-induced Atopic Dermatitis in Mice through Inhibition of Inflammatory Cytokines and Thymic Stromal Lymphopoietin Expression

Background:

Tetracycline (TET) has been found to have both antibiotic and anti-inflammatory properties. The anti-inflammatory effect of topical TET on atopic dermatitis (AD) has not been reported. The purpose of this study was to explore the potential role of topical TET and its anti-inflammatory effects in a mouse model of AD.

Methods:

The 2% TET was applied topically to ears of MC903-induced AD-like BALB/c mice once a day. AD-like symptoms and severity were evaluated by assessing skin scoring of dermatitis, ear thickness, and frequency of scratching. Serum IgE and thymic stromal lymphopoietin (TSLP) levels were measured by enzyme-linked immunosorbent assay. Western blot was used for analyzing the expressions of TSLP, protease-activated receptor 2 (PAR2), and nuclear factor-kappa B (NF-κB) in skin lesions. Real-time polymerase chain reaction was performed to assess the mRNA levels of TSLP and inflammatory cytokines including interleukin (IL)-4, IL-13, tumor necrosis factor (TNF)-α, and IL-1β in skin lesions.

Results:

Scoring of dermatitis (9.00 ± 0.63 vs. 6.67 ± 1.03, P = 0.001), ear thickness (0.44 ± 0.02 mm vs. 0.40 ± 0.03 mm, P = 0.018), and serum IgE level (421.06 ± 212.13 pg/ml vs. 244.15 ± 121.39 pg/ml, P = 0.047) were all improved in the 2% TET treatment group compared with AD group. Topical TET significantly reduced the serum level of TSLP (119.04 ± 38.92 pg/ml vs. 65.95 ± 54.61 pg/ml, P = 0.011) and both mRNA and protein expressions of TSLP in skin lesions compared with AD group (P = 0.003 and 0.011, respectively), and NF-κB and PAR2 expression in skin lesions were also suppressed (P = 0.016 and 0.040, respectively). Furthermore, expressions of inflammatory cytokines IL-4, IL-13, and TNF-α in skin lesions were down-regulated in 2% TET group compared with AD group (P = 0.035, 0.008, and 0.044, respectively).

Conclusions:

Topical TET exerted anti-inflammatory effects through suppression of TSLP and inflammatory cytokines in AD mouse model, suggesting TET as a potential agent for the topical treatment of AD in the future.

Lipidomic analysis of epidermal lipids: a tool to predict progression of inflammatory skin disease in humans

INTRODUCTION

Lipidomics is the large-scale profiling and characterization of lipid species in a biological system using mass spectrometry. The skin barrier is mainly comprised of corneocytes and a lipid-enriched extracellular matrix. The major skin lipids are ceramides, cholesterol and free fatty acids (FFA). Lipid compositions are altered in inflammatory skin disorders with disrupted skin barrier such as atopic dermatitis (AD).

AREAS COVERED

Here we discuss some of the recent applications of lipidomics in human skin biology and in inflammatory skin diseases such as AD, psoriasis and Netherton syndrome. We also review applications of lipidomics in human skin equivalent and in pre-clinical animal models of skin diseases to gain insight into the pathogenesis of the skin disease. Expert commentary: Skin lipidomics analysis could be a fast, reliable and noninvasive tool to characterize the skin lipid profile and to monitor the progression of inflammatory skin diseases such as AD.

Lung-derived innate cytokines: new epigenetic targets of allergen-specific sublingual immunotherapy

OBJECTIVES

Sublingual allergen-specific immunotherapy is a safe and effective method for treatment of IgE-mediated respiratory allergies; however, the underlying mechanisms are not fully understood. This study was planned to test whether sublingual immunotherapy (SLIT) can exert epigenetic mechanisms through which the airway allergic responses can be extinguished.

MATERIALS AND METHODS

BALB/c mice were sensitized intraperitoneally and challenged intranasally. Then, they received sublingual treatment with recombinant Che a 2 (rChe a 2), a major allergen of Chenopodium album. After SLIT, allergen-specific antibodies in sera, cytokine profiles of spleen cell cultures, mRNA and protein expression of lung-derived IL-33, IL-25, and TSLP (thymic stromal lymphopoietin), and histone modifications of these three genes were assessed.

RESULTS

Following Immunotherapy, systemic immune responses shifted from Th2 to Th1 profile as demonstrated by significant decrease in IgE and IL-4 and substantial increase in IgG2a and IFN-γ. At local site, mRNA and protein levels of lung-derived pro-inflammatory cytokines IL-33 and TSLP were markedly down-regulated following SLIT that was associated with marked enrichment of trimethylated lysine 27 of histone H3 at promoter regions of these two cytokines.

CONCLUSION

In our study, sublingual immunotherapy with recombinant allergen effectively attenuated allergic immune responses, at least partly, by induction of distinct histone modifications at specific loci. Additionally, the lung-derived pro-allergic cytokines IL-33 and TSLP could be promising mucosal candidates for either monitoring allergic conditions or therapeutic approaches.

Transcription Factor CTIP2 Maintains Hair Follicle Stem Cell Pool and Contributes to Altered Expression of LHX2 and NFATC1

Transcription factor CTIP2 (COUP-TF-interacting protein 2), also known as BCL11B, is expressed in hair follicles of embryonic and adult skin. Ctip2-null mice exhibit reduced hair follicle density during embryonic development. In contrast, conditional inactivation of Ctip2 in epidermis (Ctip2^ep−/− mice) leads to a shorter telogen and premature entry into anagen during the second phase of hair cycling without a detectable change in the number of hair follicles. Keratinocytes of the bulge stem cells niche of Ctip2^ep−/− mice proliferate more and undergo reduced apoptosis than the corresponding cells of wild-type mice. However, premature activation of follicular stem cells in mice lacking CTIP2 leads to the exhaustion of this stem cell compartment in comparison to Ctip2^L2/L2 mice, which retained quiescent follicle stem cells. CTIP2 modulates expression of genes encoding EGFR and NOTCH1 during formation of hair follicles, and those encoding NFATC1 and LHX2 during normal hair cycling in adult skin. The expression of most of these genes is disrupted in mice lacking CTIP2 and these alterations may underlie the phenotype of Ctip2-null and Ctip2^ep−/− mice. CTIP2 appears to serve as a transcriptional organizer that integrates input from multiple signaling cues during hair follicle morphogenesis and hair cycling.

Thymic stromal lymphopoietin induction by skin irritation is independent of tumour necrosis factor-α, but supported by interleukin-1

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is an extensively studied cytokine linked to the pathogenesis of allergic diseases, but the inherent activities behind TSLP expression are not well defined.

OBJECTIVES

To explore the conditions favourable to TSLP induction outside of a typically allergic set-up and determine the associated mechanisms, and to assess whether TSLP is similarly controlled in murine and human skin.

METHODS

A combination of primary keratinocytes, skin explants/epidermal sheets and in vivo strategies was employed. The skin of wild-type and tumour necrosis factor knockout (TNF-/-) mice was subjected to acute irritation. Cells and specimens were stimulated with a range of TSLP inducers in the presence or absence of neutralizing antibodies. TSLP was quantitated by quantitative reverse-transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay and immunohistochemistry.

RESULTS

In addition to cytokines, skin irritation brought about by various causes (e.g. shaving, scratching and chemical perturbation) elicited uniformly high-level production of TSLP, which entered the circulatory system. Despite the potency of TNF-α as an in vitro TSLP inducer, the use of TNF-/- mice revealed that this mechanism was completely independent of endogenous TNF-α. Conversely, irritation-elicited TSLP depended on interleukin (IL)-1, which had a more pronounced influence in human skin than in murine skin. Murine and human skin differed considerably regarding TSLP regulation.

CONCLUSIONS

Thymic stromal lymphopoietin is a general responder to disrupted skin homeostasis and may have a role in triggering the alarm system of the skin. TSLP induction is rapid, transient and driven by a mechanism that does not involve TNF-α, but partially relies on the evolutionarily ancient IL-1 system. The irritated skin secretes TSLP into the circulatory system. TSLP regulation varies between species.

[CTIP2, a multifunctional protein: cellular physiopathology and therapeutic implications]

The transcription factor CTIP2 (BCL11B) is a multifunctional protein involved in numerous cell physiological processes. To date, many molecular mechanisms underlying this process have been discovered, which highlighted the importance of the epigenetic regulation of genes and the regulation of the elongation factor P-TEFb. Furthermore studies of the deregulation of CTIP2 showed the association of CTIP2 to numerous pathologies including cancer and cardiac hypertrophy. A better comprehension of the physiopathology of these diseases might lead to the design of therapeutical strategies intending to prevent CTIP2 deregulation. Moreover, CTIP2 and its associated proteins constitute potential targets in strategies aiming to reduce and/or purge HIV-1 cell reservoirs.

Retinoid-X-receptors (α/β) in melanocytes modulate innate immune responses and differentially regulate cell survival following UV irradiation

Understanding the molecular mechanisms of ultraviolet (UV) induced melanoma formation is becoming crucial with more reported cases each year. Expression of type II nuclear receptor Retinoid-X-Receptor α (RXRα) is lost during melanoma progression in humans. Here, we observed that in mice with melanocyte-specific ablation of RXRα and RXRβ, melanocytes attract fewer IFN-γ secreting immune cells than in wild-type mice following acute UVR exposure, via altered expression of several chemoattractive and chemorepulsive chemokines/cytokines. Reduced IFN-γ in the microenvironment alters UVR-induced apoptosis, and due to this, the survival of surrounding dermal fibroblasts is significantly decreased in mice lacking RXRα/β. Interestingly, post-UVR survival of the melanocytes themselves is enhanced in the absence of RXRα/β. Loss of RXRs α/β specifically in the melanocytes results in an endogenous shift in homeostasis of pro- and anti-apoptotic genes in these cells and enhances their survival compared to the wild type melanocytes. Therefore, RXRs modulate post-UVR survival of dermal fibroblasts in a "non-cell autonomous" manner, underscoring their role in immune surveillance, while independently mediating post-UVR melanocyte survival in a "cell autonomous" manner. Our results emphasize a novel immunomodulatory role of melanocytes in controlling survival of neighboring cell types besides controlling their own, and identifies RXRs as potential targets for therapy against UV induced melanoma.

The many lives of CTIP2: from AIDS to cancer and cardiac hypertrophy

CTIP2 is a key transcriptional regulator involved in numerous physiological functions. Initial works have shown the importance of CTIP2 in the establishment and persistence of HIV latency in microglial cells, the main latent/quiescent viral reservoir in the brain. Recent studies have highlighted the importance of CTIP2 in several other pathologies, such as cardiac hypertrophy and various types of human malignancies. Targeting CTIP2 may therefore constitute a new approach in the treatment of these pathologies.

The role of sphingolipid metabolism in cutaneous permeability barrier formation

The epidermal permeability barrier of mammalian skin is localized in the stratum corneum. Corneocytes are embedded in an extracellular, highly ordered lipid matrix of hydrophobic lipids consisting of about 50% ceramides, 25% cholesterol and 15% long and very long chain fatty acids. The most important lipids for the epidermal barrier are ceramides. The scaffold of the lipid matrix is built of acylceramides, containing ω-hydroxylated very long chain fatty acids, acylated at the ω-position with linoleic acid. After glucosylation of the acylceramides at Golgi membranes and secretion, the linoleic acid residues are replaced by glutamate residues originating from proteins exposed on the surface of corneocytes. Removal of their glucosyl residues generates a hydrophobic surface on the corneocytes used as a template for the formation of extracellular lipid layers of the water permeability barrier. Misregulation or defects in the formation of extracellular ceramide structures disturb barrier function. Important anabolic steps are the synthesis of ultra long chain fatty acids, their ω-hydroxylation, and formation of ultra long chain ceramides and glucosylceramides. The main probarrier precursor lipids, glucosylceramides and sphingomyelins, are packed in lamellar bodies together with hydrolytic enzymes such as glucosylceramide-β-glucosidase and acid sphingomyelinase and secreted into the intercelullar space between the stratum corneum and stratum granulosum. Inherited defects in the extracellular hydrolytic processing of the probarrier acylglucosylceramides impair epidermal barrier formation and cause fatal diseases: such as prosaposin deficiency resulting in lack of lysosomal lipid binding and transfer proteins, or the symptomatic clinical picture of the "collodion baby" in the absence of glucocerebrosidase. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.