ZFP750 affects the cutaneous barrier through regulating lipid metabolism

Potential activity of chicken amniotic fluid in epidermal development by promoting keratinocyte differentiation

Epidermal barrier formation during fetal development, a fundamental biological process in mammals and birds, occurs in the amniotic cavity filled with amniotic fluid (AF). In keratinocytes, indispensable proteins for barrier formation are produced during differentiation, including transglutaminase 1 (TG1) and structural proteins encoded by a gene cluster, epidermal differentiation complex. In general, the chicken fetus rapidly forms a robust epidermal barrier during a relatively short embryonic day (ED); however, little is known about how chicken AF (cAF) contributes to the controls of gene expression of the factors involved in epidermal development. Here, we first demonstrated that the cross-linking activity of TG1 gradually increased, followed by the development of barrier function until ED18 in the chicken fetal epidermis. Then, we revealed that cAF harvested at specific fetal stages had the ability to enhance the expression and activity of TG1, and to facilitate the expression of genes for the other epidermal transglutaminases, structural proteins, and differentiation-related transcription factors in human cultured keratinocytes. Furthermore, the thermal denaturation of cAF components reduced cAF efficacy in promoting the expression of those factors. The fractionated proteinaceous solution of cAF possessed the activity to induce the protein expression of barrier formation-related factors, such as the transcription factor zinc finger protein 750. These results indicated that proteinaceous molecules in cAF have the potential to activate the gene expression networks involved in epidermal barrier formation. This finding will provide novel insights into the physiological role of AF in fetal epidermal development.

A graph theoretical approach to experimental prioritization in genome-scale investigations

The goal of systems biology is to gain a network level understanding of how gene interactions influence biological states, and ultimately inform upon human disease. Given the scale and scope of systems biology studies, resource constraints often limit researchers when validating genome-wide phenomena and potentially lead to an incomplete understanding of the underlying mechanisms. Further, prioritization strategies are often biased towards known entities (e.g. previously studied genes/proteins with commercially available reagents), and other technical issues that limit experimental breadth. Here, heterogeneous biological information is modeled as an association graph to which a high-performance minimum dominating set solver is applied to maximize coverage across the graph, and thus increase the breadth of experimentation. First, we tested our model on retrieval of existing gene functional annotations and demonstrated that minimum dominating set returns more diverse terms when compared to other computational methods. Next, we utilized our heterogenous network and minimum dominating set solver to assist in the process of identifying understudied genes to be interrogated by the International Mouse Phenotyping Consortium. Using an unbiased algorithmic strategy, poorly studied genes are prioritized from the remaining thousands of genes yet to be characterized. This method is tunable and extensible with the potential to incorporate additional user-defined prioritizing information. The minimum dominating set approach can be applied to any biological network in order to identify a tractable subset of features to test experimentally or to assist in prioritizing candidate genes associated with human disease.

Superficial ice and deep blaze: A defense strategy of the skin

It's crucial for skin to establish efficient defense strategies. Liu et al. reveal that the transcription factor ZNF750 recruits the histone demethylase KDM1A to silence pattern recognition receptors in the outer epidermis, making their expression limited to deeper, undifferentiated keratinocytes to address threats penetrating the skin.

The transcription regulators ZNF750 and LSD1/KDM1A dampen inflammation on the skin's surface by silencing pattern recognition receptors

The surface of the skin is continually exposed to pro-inflammatory stimuli; however, it is unclear why it is not constantly inflamed due to this exposure. Here, we showed undifferentiated keratinocytes residing in the deep epidermis could trigger a strong inflammatory response due to their high expression of pattern recognition receptors (PRRs) that detect damage or pathogens. As keratinocytes differentiated, they migrated outward toward the surface of the skin and decreased their PRR expression, which led to dampened immune responses. ZNF750, a transcription factor expressed only in differentiated keratinocytes, recruited the histone demethylase KDM1A/LSD1 to silence genes coding for PRRs (TLR3, IFIH1/MDA5, and DDX58/RIG1). Loss of ZNF750 or KDM1A in human keratinocytes or mice resulted in sustained and excessive inflammation resembling psoriatic skin, which could be restored to homeostatic conditions upon silencing of TLR3. Our findings explain how the skin's surface prevents excessive inflammation through ZNF750- and KDM1A-mediated suppression of PRRs.

Dietary lipid is largely deposited in skin and rapidly affects insulating properties

Skin has been shown to be a regulatory hub for energy expenditure and metabolism: mutations of skin lipid metabolism enzymes can change the rate of thermogenesis and susceptibility to diet-induced obesity. However, little is known about the physiological basis for this function. Here we show that the thermal properties of skin are highly reactive to diet: within three days, a high fat diet reduces heat transfer through skin. In contrast, a dietary manipulation that prevents obesity accelerates energy loss through skins. We found that skin was the largest target in a mouse body for dietary fat delivery, and that dietary triglyceride was assimilated both by epidermis and by dermal white adipose tissue. Skin from mice calorie-restricted for 3 weeks did not take up circulating lipids and showed a highly depleted stratum corneum. Dietary triglyceride acyl groups persist in skin for weeks after feeding. Using multi-modal lipid profiling, we have implicated both keratinocytes and sebocytes in the altered lipids which correlate with thermal function. In response to high fat feeding, wax diesters and ceramides accumulate, and triglycerides become more saturated. In contrast, in response to the dramatic loss of adipose tissue that accompanies restriction of the branched chain amino acid isoleucine, skin becomes more heat-permeable, resisting changes induced by Western diet feeding, with a signature of depleted signaling lipids. We propose that skin should be routinely included in physiological studies of lipid metabolism, given the size of the skin lipid reservoir and its adaptable functionality.

Epidermal RORα Maintains Barrier Integrity and Prevents Allergic Inflammation by Regulating Late Differentiation and Lipid Metabolism

The skin epidermis provides a barrier that is imperative for preventing transepidermal water loss (TEWL) and protecting against environmental stimuli. The underlying molecular mechanisms for regulating barrier functions and sustaining its integrity remain unclear. RORα is a nuclear receptor highly expressed in the epidermis of normal skin. Clinical studies showed that the epidermal RORα expression is significantly reduced in the lesions of multiple inflammatory skin diseases. In this study, we investigate the central roles of RORα in stabilizing skin barrier function using mice with an epidermis-specific Rora gene deletion (RoraEKO). While lacking spontaneous skin lesions or dermatitis, RoraEKO mice exhibited an elevated TEWL rate and skin characteristics of barrier dysfunction. Immunostaining and Western blot analysis revealed low levels of cornified envelope proteins in the RoraEKO epidermis, suggesting disturbed late epidermal differentiation. In addition, an RNA-seq analysis showed the altered expression of genes related to "keratinization" and "lipid metabolism" in RORα deficient epidermis. A lipidomic analysis further uncovered an aberrant ceramide composition in the RoraEKO epidermis. Importantly, epidermal Rora ablation greatly exaggerated percutaneous allergic inflammatory responses to oxazolone in an allergic contact dermatitis (ACD) mouse model. Our results substantiate the essence of epidermal RORα in maintaining late keratinocyte differentiation and normal barrier function while suppressing cutaneous inflammation.

Myostatin regulates energy homeostasis through autocrine- and paracrine-mediated microenvironment communication

Myostatin (MSTN) has long been recognized as a critical regulator of muscle mass. Recently, there has been increasing interest in its role in metabolism. In our study, we specifically knocked out MSTN in brown adipose tissue (BAT) from mice (MSTNΔUCP1) and found that the mice gained more weight than did controls when fed a high-fat diet, with progressive hepatosteatosis and impaired skeletal muscle activity. RNA-Seq analysis indicated signatures of mitochondrial dysfunction and inflammation in the MSTN-ablated BAT. Further studies demonstrated that Kruppel-like factor 4 (KLF4) was responsible for the metabolic phenotypes observed, whereas fibroblast growth factor 21 (FGF21) contributed to the microenvironment communication between adipocytes and macrophages induced by the loss of MSTN. Moreover, the MSTN/SMAD2/3-p38 signaling pathway mediated the expression of KLF4 and FGF21 in adipocytes. In summary, our findings suggest that brown adipocyte-derived MSTN regulated BAT thermogenesis via autocrine and paracrine effects on adipocytes or macrophages, ultimately regulating systemic energy homeostasis.

Advance in Multi-omics Research Strategies on Cholesterol Metabolism in Psoriasis

The skin is a complex and dynamic organ where homeostasis is maintained through the intricate interplay between the immune system and metabolism, particularly cholesterol metabolism. Various factors such as cytokines, inflammatory mediators, cholesterol metabolites, and metabolic enzymes play crucial roles in facilitating these interactions. Dysregulation of this delicate balance contributes to the pathogenic pathways of inflammatory skin conditions, notably psoriasis. In this article, we provide an overview of omics biomarkers associated with psoriasis in relation to cholesterol metabolism. We explore multi-omics approaches that reveal the communication between immunometabolism and psoriatic inflammation. Additionally, we summarize the use of multi-omics strategies to uncover the complexities of multifactorial and heterogeneous inflammatory diseases. Finally, we highlight potential future perspectives related to targeted drug therapies and research areas that can advance precise medicine. This review aims to serve as a valuable resource for those investigating the role of cholesterol metabolism in psoriasis.

Skin Barrier in Atopic Dermatitis

A compromised permeability barrier is a hallmark of atopic dermatitis (AD). Localized to the outermost skin layer, the stratum corneum (SC) is critically dependent on terminal differentiation of epidermal keratinocytes, which transform into protein-rich corneocytes surrounded by extracellular lamellae of unique epidermal lipids, conferring permeability barrier function. These structures are disrupted in AD. A leaky barrier is prone to environmental insult, which in AD elicits type 2-dominant inflammation, in turn resulting in a vicious cycle further impairing the SC structure. Therapies directed at enforcing SC structure and anti-inflammatory strategies administered by topical and systemic route as well as UV therapy have differential effects on the permeability barrier. The expanding armamentarium of therapeutic modalities for AD treatment warrants optimization of their effects on permeability barrier function.

12th Tuscany Retreat on Cancer Research and Apoptosis: Genetic profiling, resistance mechanisms and novel treatment concepts in cancer and neurodegeneration

The 12th Tuscany Retreat on Cancer Research and Apoptosis was held on August 19-26, 2023. The biennial retreat aims to bring together scientists who advance research in cancer, cell death, and neurodegenerative diseases. Topics covered ranged from drug resistance in cancer to insights into novel molecular cell signaling mechanisms and targets, all related to the pathways and molecules that regulate programmed cell death and the diseases that result from the dysregulation of programmed cell death. In this meeting review, we summarize the content of the most recent retreat.

ZNF750 Regulates Skin Barrier Function by Driving Cornified Envelope and Lipid Processing Pathways

The epidermis is a constantly renewing stratified epithelial tissue that provides essential protective barrier functions. The major barrier is located at the outermost layers of the epidermis, formed by terminally differentiated keratinocytes reinforced by proteins of their cornified envelope and sequestered intercellular lipids. Disruptions to epidermal differentiation characterize various skin disorders. ZNF750 is an epithelial transcription factor essential for in vitro keratinocyte differentiation, whose truncating mutation in humans causes autosomal dominant psoriasis-like skin disease. In this study, we utilized an epidermal-specific Znf750 conditional knockout mouse model to uncover the role ZNF750 plays in epidermal development. We show that deletion of Znf750 in the developing skin does not block epidermal differentiation completely, suggesting in vivo compensatory feedback mechanisms, although it does result in impaired barrier function and perinatal lethality. Molecular dissection revealed ultrastructural defects in the differentiated layers of the epidermis, accompanied by alterations in the expression of ZNF750-dependent genes encoding key cornified envelope precursor proteins and lipid-processing enzymes, including gene subsets known to be mutated in human skin diseases involving impaired barrier function. Together, our findings provide molecular insights into the pathogenesis of human skin disease by linking ZNF750 to a subset of epidermal differentiation genes involved in barrier formation pathways.

Epigenetic priming of an epithelial enhancer by p63 and CTCF controls expression of a skin-restricted gene XP33

The transcription factor p63 is a renowned master regulator of gene expression of stratified epithelia. While multiple proteins have been identified as p63 bona fide targets, little is known about non-coding RNAs (ncRNAs) whose transcription is controlled by p63. Here, we describe a skin-specific non-coding RNA XP33 as a novel target of p63. XP33 levels are increased during keratinocyte differentiation in vitro, while its depletion results in decreased expression of late cornified gene LCE2D. By using publicly available multi-omics data, we show that CTCF and p63 establish an epithelial enhancer to prime XP33 transcription in a tissue-restricted manner. XP33 promoter and enhancer form a chromatin loop exclusively in keratinocytes but not in other cell types. Moreover, the XP33 enhancer is occupied by differentiation-specific factors that control XP33 transcription. Altogether, we identify a tissue-specific non-coding RNA whose expression is epigenetically regulated by p63 and CTCF.