Mutations in the interleukin receptor IL11RA cause autosomal recessive Crouzon-like craniosynostosis

Craniosynostosis-associated variants in the IL-11R complex: new insights and questions

Skull growth involves the expansion of both the flat calvarial bones of the skull and the fibrous marginal zones, termed sutures, between them. This process depends on co-ordinated proliferation of mesenchymal-derived progenitor cells within the sutures, and their differentiation to osteoblasts which produce the bone matrix required to expand the size of the bony plates. Defects lead to premature closure of these sutures, termed craniosynostosis, resulting in heterogeneous head shape differences due to restricted growth of one or more sutures. The impact on the individual depends on how many and which sutures are affected and the severity of the effect. Several genetic loci are responsible, including a wide range of variants in the gene for the interleukin 11 receptor (IL11RA, OMIM#600939). Recent work from Kespohl and colleagues provides new insights into how some of these variants influence IL-11R function; we discuss their influences on IL-11R structure and IL-11 function as a stimulus of osteoblast differentiation.

Molecular characterization of the craniosynostosis-associated interleukin-11 receptor variants p.T306_S308dup and p.E364_V368del

Interleukin-11 (IL-11) is a member of the IL-6 family of cytokines and is an important factor for bone homeostasis. IL-11 binds to and signals via the membrane-bound IL-11 receptor (IL-11R, classic signaling) or soluble forms of the IL-11R (sIL-11R, trans-signaling). Mutations in the IL11RA gene, which encodes the IL-11R, are associated with craniosynostosis, a human condition in which one or several of the sutures close prematurely, resulting in malformation of the skull. The biological mechanisms of how mutations within the IL-11R are linked to craniosynostosis are mostly unexplored. In this study, we analyze two variants of the IL-11R described in craniosynostosis patients: p.T306_S308dup, which results in a duplication of three amino-acid residues within the membrane-proximal fibronectin type III domain, and p.E364_V368del, which results in a deletion of five amino-acid residues in the so-called stalk region adjacent to the plasma membrane. The stalk region connects the three extracellular domains to the transmembrane and intracellular region of the IL-11R and contains cleavage sites for different proteases that generate sIL-11R variants. Using a combination of bioinformatics and different biochemical, molecular, and cell biology methods, we show that the IL-11R-T306_S308dup variant does not mature correctly, is intracellularly retained, and does not reach the cell surface. In contrast, the IL-11R-E364_V368del variant is fully biologically active and processed normally by proteases, thus allowing classic and trans-signaling of IL-11. Our results provide evidence that mutations within the IL11RA gene may not be causative for craniosynostosis and suggest that other regulatory mechanism(s) are involved but remain to be identified.

Understanding interleukin 11 as a disease gene and therapeutic target

Interleukin 11 (IL11) is an elusive member of the IL6 family of cytokines. While initially thought to be a haematopoietic and cytoprotective factor, more recent data show instead that IL11 is redundant for haematopoiesis and toxic. In this review, the reasons that led to the original misunderstandings of IL11 biology, which are now understandable, are explained with particular attention on the use of recombinant human IL11 in mice and humans. Following tissue injury, as part of an evolutionary ancient homeostatic response, IL11 is secreted from damaged mammalian cells to signal via JAK/STAT3, ERK/P90RSK, LKB1/mTOR and GSK3β/SNAI1 in autocrine and paracrine. This activates a program of mesenchymal transition of epithelial, stromal, and endothelial cells to cause inflammation, fibrosis, and stalled endogenous tissue repair, leading to organ failure. The role of IL11 signalling in cell- and organ-specific pathobiology is described, the large unknowns about IL11 biology are discussed and the promise of targeting IL11 signalling as a therapeutic approach is reviewed.

Interleukin-11 and its eminent role in tissue fibrosis: a possible therapeutic target

Interleukin-11 is a cytokine from the IL-6 family of cytokines that includes IL-6 and oncostatin-M. Initially described for its role in platelet generation, it is now appreciated that this cytokine has multiple functions. Recently it has been found that IL-11 is critical in fibrosis in multiple different organ systems and systemically as in the autoimmune disease systemic sclerosis. Animal models of fibrosis have determined that animals with IL-11 receptor deletions have retarded fibrosis and that in wild-type animals IL-11 is found at the organ of fibrosis. Recent evidence suggests that IL-11 may be a master regulator of fibrosis regardless of end target organ. With the development of neutralizing antibodies targeting the cytokine in pre-clinical models this could be a possible therapeutic, in a disease in which no specific therapies exist. This review appraises the evidence of the role of IL-11 in tissue fibrosis, its signalling properties, and therapeutic targeting. The review ends with an appraisal of indications for which IL-11 modulation is targeted.

The Emerging Role of Interleukin-(IL)-11/IL-11R in Bone Metabolism and Homeostasis: From Cytokine to Osteokine

Interleukin-(IL)-11 is a cytokine involved in hematopoiesis, cancer metastasis, and inflammation. IL-11 belongs to the IL-6 cytokine family, binding to the complex of receptors glycoprotein gp130 and the ligand-specific-receptor subunits (IL-11Rα or their soluble counterpart sIL-11R). IL-11/IL-11R signaling enhances osteoblast differentiation and bone formation and mitigates osteoclast-induced bone resorption and cancer bone metastasis. Recent studies have shown that systemic and osteoblast/osteocyte-specific IL-11 deficiency leads to reduced bone mass and formation, but also adiposity, glucose intolerance, and insulin resistance. In humans, mutations of IL-11 and the receptor IL-11RA genes are associated with height reduction, osteoarthritis, and craniosynostosis. In this review, we describe the emerging role of IL-11/IL-11R signaling in bone metabolism by targeting osteoblasts, osteoclasts, osteocytes, and bone mineralization. Furthermore, IL-11 promotes osteogenesis and suppresses adipogenesis, thereby influencing the fate of osteoblast/adipocyte differentiation derived from pluripotent mesenchymal stem cells. We have newly identified IL-11 as a bone-derived cytokine that regulates bone metabolism and the link between bone and other organs. Thus, IL-11 is vital in bone homeostasis and could be considered a potential therapeutic strategy.

Structures of the interleukin 11 signalling complex reveal gp130 dynamics and the inhibitory mechanism of a cytokine variant

Interleukin (IL-)11, an IL-6 family cytokine, has pivotal roles in autoimmune diseases, fibrotic complications, and solid cancers. Despite intense therapeutic targeting efforts, structural understanding of IL-11 signalling and mechanistic insights into current inhibitors are lacking. Here we present cryo-EM and crystal structures of the human IL-11 signalling complex, including the complex containing the complete extracellular domains of the shared IL-6 family β-receptor, gp130. We show that complex formation requires conformational reorganisation of IL-11 and that the membrane-proximal domains of gp130 are dynamic. We demonstrate that the cytokine mutant, IL-11 Mutein, competitively inhibits signalling in human cell lines. Structural shifts in IL-11 Mutein underlie inhibition by altering cytokine binding interactions at all three receptor-engaging sites and abrogating the final gp130 binding step. Our results reveal the structural basis of IL-11 signalling, define the molecular mechanisms of an inhibitor, and advance understanding of gp130-containing receptor complexes, with potential applications in therapeutic development.

The interleukin-11 receptor variant p.W307R results in craniosynostosis in humans

Craniosynostosis is characterized by the premature fusion and ossification of one or more of the sutures of the calvaria, often resulting in abnormal features of the face and the skull. In cases in which growth of the brain supersedes available space within the skull, developmental delay or cognitive impairment can occur. A complex interplay of different cell types and multiple signaling pathways are required for correct craniofacial development. In this study, we report on two siblings with craniosynostosis and a homozygous missense pathogenic variant within the IL11RA gene (c.919 T > C; p.W307R). The patients present with craniosynostosis, exophthalmos, delayed tooth eruption, mild platybasia, and a basilar invagination. The p.W307R variant is located within the arginine-tryptophan-zipper within the D3 domain of the IL-11R, a structural element known to be important for the stability of the cytokine receptor. Expression of IL-11R-W307R in cells shows impaired maturation of the IL-11R, no transport to the cell surface and intracellular retention. Accordingly, cells stably expressing IL-11R-W307R do not respond when stimulated with IL-11, arguing for a loss-of-function mutation. In summary, the IL-11R-W307R variant, reported here for the first time to our knowledge, is most likely the causative variant underlying craniosynostosis in these patients.

Inherited human ZNF341 deficiency

Typical hyper-IgE syndromes (HIES) are caused by autosomal-dominant-negative (DN) variants of STAT3 (Signal Transducer And Activator Of Transcription 3) or IL6ST (Interleukin 6 Cytokine Family Signal Transducer), biallelic partial loss-of-function (LOF) variants of IL6ST, or biallelic complete LOF variants of ZNF341 (Zinc Finger Protein 341). Including the two new cases described in this review, only 20 patients with autosomal-recessive (AR) ZNF341 deficiency have ever been reported. Patients with AR ZNF341 deficiency have clinical and immunological phenotypes resembling those of patients with autosomal-dominant STAT3 deficiency, but with a usually milder clinical presentation and lower NK (Natural Killer) cell counts. ZNF341-deficient cells have 50% the normal level of STAT3 in the resting state. However, as there is no clear evidence that STAT3 haploinsufficiency causes HIES, this decrease alone is probably insufficient to explain the HIES phenotype observed in the ZNF341-deficient patients. The combination of decreased basal expression level and impaired autoinduction of STAT3 observed in ZNF341-deficient lymphocytes is considered a more likely pathophysiological mechanism. We review here what is currently known about the ZNF341 gene and ZNF341 deficiency, and briefly discuss possible roles for this protein in addition to its control of STAT3 activity.

Atopic Dermatitis-like Genodermatosis: Disease Diagnosis and Management

Eczema is a classical characteristic not only in atopic dermatitis but also in various genodermatosis. Patients suffering from primary immunodeficiency diseases such as hyper-immunoglobulin E syndromes, Wiskott-Aldrich syndrome, immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome, STAT5B deficiency, Omenn syndrome, atypical complete DiGeorge syndrome; metabolic disorders such as acrodermatitis enteropathy, multiple carboxylase deficiency, prolidase deficiency; and other rare syndromes like severe dermatitis, multiple allergies and metabolic wasting syndrome, Netherton syndrome, and peeling skin syndrome frequently perform with eczema-like lesions. These genodermatosis may be misguided in the context of eczematous phenotype. Misdiagnosis of severe disorders unavoidably affects appropriate treatment and leads to irreversible outcomes for patients, which underlines the importance of molecular diagnosis and genetic analysis. Here we conclude clinical manifestations, molecular mechanism, diagnosis and management of several eczema-related genodermatosis and provide accessible advice to physicians.

An additional whole-exome sequencing study in 102 panel-undiagnosed patients: A retrospective study in a Chinese craniosynostosis cohort

Craniosynostosis (CRS) is a disease with prematurely fused cranial sutures. In the last decade, the whole-exome sequencing (WES) was widely used in Caucasian populations. The WES largely contributed in genetic diagnosis and exploration on new genetic mechanisms of CRS. In this study, we enrolled 264 CRS patients in China. After a 17-gene-panel sequencing designed in the previous study, 139 patients were identified with pathogenic/likely pathogenic (P/LP) variants according to the ACMG guideline as positive genetic diagnosis. WES was then performed on 102 patients with negative genetic diagnosis by panel. Ten P/LP variants were additionally identified in ten patients, increasing the genetic diagnostic yield by 3.8% (10/264). The novel variants in ANKH, H1-4, EIF5A, SOX6, and ARID1B expanded the mutation spectra of CRS. Then we designed a compatible research pipeline (RP) for further exploration. The RP could detect all seven P/LP SNVs and InDels identified above, in addition to 15 candidate variants found in 13 patients with worthy of further study. In sum, the 17-gene panel and WES identified positive genetic diagnosis for 56.4% patients (149/264) in 16 genes. At last, in our estimation, the genetic testing strategy of “Panel-first” saves 24.3% of the cost compared with “WES only”, suggesting the “Panel-first” is an economical strategy.

The outcome of targeted NGS screening in patients with syndromic forms of sagittal and pansynostosis - IL11RA is an emerging core-gene for pansynostosis

Here, we have studied the prevalence and spectrum of genetic alterations in syndromic forms of sagittal and pansynostosis. Eighteen patients with sagittal synostosis (isolated or combined with other synostoses, except coronal) or pansynostosis were phenotypically assessed by retrospective analysis of medical records, three-dimensional computed tomography skull reconstructions, and registered photos. Patient DNAs were analyzed using a targeted next-generation sequencing (NGS) panel including 63 craniosynostosis (CS) related genes. Pathogenic and likely pathogenic variants were found in 72% of the cases, mainly affecting FGFR2, TWIST1, IL11RA, and SKI. Two patients that were negative at NGS screening - one with a supernumerary marker chromosome with duplication of 15q25.2q26.3 and one with a pathogenic PHEX variant - were identified using microarray and single gene analysis, respectively. The overall diagnostic rate in the cohort was thus 83%. We identified two novel likely pathogenic variants in FGFR2 (NM_022970.3: c.811_812delGGinsCC, p.Gly271Pro) and TWIST1 (NM_000474.3: c.476T  >  A, p.Leu159His), and a novel variant of unclear phenotypic significance in RUNX2 (NM_001024630.3: c.340G > A, p.Val114Ile) which could suggest a modulatory effect. Notably, we also identified three new patients with pansynostosis and a Crouzon-like phenotype with IL11RA mutation. Targeted NGS using a broad panel of CS-related genes is a simple and powerful tool for detecting pathogenic mutations in patients with syndromic forms of CS and multiple suture involvement, in particular pansynostosis. Our results provide additional evidence of an association between pansynostosis and IL11RA, an emerging core gene for autosomal recessive CS.

IL-11 Is Elevated and Drives the Profibrotic Phenotype Transition of Orbital Fibroblasts in Thyroid-Associated Ophthalmopathy

Orbital fibrosis is a hallmark of tissue remodeling in thyroid-associated ophthalmopathy (TAO). Previous studies have shown that interleukin (IL)-11 plays a pivotal profibrotic role in various inflammatory and autoimmune diseases. However, the expression pattern of IL-11 in patients with TAO and whether IL-11 is mechanistically linked with pathological fibrosis remains unknown. In this study, we investigated IL-11 levels in the serum and orbital connective tissue of patients with TAO, and evaluated the correlation of these levels with the patient's clinical activity score. We also evaluated the expression pattern of IL-11Rα in orbital connective tissue. Furthermore, we elucidated the regulatory factors, profibrotic function, and downstream signaling pathways for IL-11 in TAO using in vitro studies. IL-11 levels in serum and orbital connective tissues were increased in patients with TAO, as compared with healthy controls. In addition, both levels were positively correlated with disease activity. Single-cell RNA sequencing of orbital connective tissue indicated that IL-11Rα was dominantly expressed in orbital fibroblasts (OFs). RNA sequencing of paired unstimulated and transforming growth factor (TGF)-β1-stimulated samples demonstrated that upregulation of IL-11 expression defined the dominant transcriptional response. IL-11 signaling was also confirmed to be downstream of TGF-β1 and IL-1β. Therefore, we deduced that IL-11 protein is secreted in an autocrine loop in TAO. We also indicated that IL-11 mediated the profibrotic phenotype switch by inducing the expression of myofibroblast differentiation markers, including α-smooth muscle actin and collagen type I α1, which could be abrogated by an anti-IL-11 neutralizing antibody. Furthermore, we revealed that extracellular regulated protein kinase may be a crucial factor in the pro-fibrotic, translationally specific signaling activity of IL-11. These data demonstrate that IL-11 plays a crucial role in orbital fibroblast phenotype switching and may be a potential therapeutic target candidate for the treatment of TAO.

New insights into IL-6 family cytokines in metabolism, hepatology and gastroenterology

IL-6 family cytokines are defined by the common use of the signal-transducing receptor chain glycoprotein 130 (gp130). Increasing evidence indicates that these cytokines are essential in the regulation of metabolic homeostasis as well as in the pathophysiology of multiple gastrointestinal and liver disorders, thus making them attractive therapeutic targets. Over the past few years, therapies modulating gp130 signalling have grown exponentially in several clinical settings including obesity, cancer and inflammatory bowel disease. A newly engineered gp130 cytokine, IC7Fc, has shown promising preclinical results for the treatment of type 2 diabetes, obesity and liver steatosis. Moreover, drugs that modulate gp130 signalling have shown promise in refractory inflammatory bowel disease in clinical trials. A deeper understanding of the main roles of the IL-6 family of cytokines during homeostatic and pathological conditions, their signalling pathways, sources of production and target cells will be crucial to the development of improved treatments. Here, we review the current state of the role of these cytokines in hepatology and gastroenterology and discuss the progress achieved in translating therapeutics targeting gp130 signalling into clinical practice.

Emerging roles for IL-11 in inflammatory diseases

Interleukin-11 (IL-11) is a cytokine that has been strongly implicated in the pathogenesis of fibrotic diseases and solid malignancies. Elevated IL-11 expression is also associated with several non-malignant inflammatory diseases where its function remains less well-characterized. Here, we summarize current literature surrounding the contribution of IL-11 to the pathogenesis of autoimmune inflammatory diseases, including rheumatoid arthritis, multiple sclerosis, diabetes and systemic sclerosis, as well as other chronic inflammatory conditions such as periodontitis, asthma, chronic obstructive pulmonary disease, psoriasis and colitis.

The IL6-like Cytokine Family: Role and Biomarker Potential in Breast Cancer

IL6-like cytokines are a family of regulators with a complex, pleiotropic role in both the healthy organism, where they regulate immunity and homeostasis, and in different diseases, including cancer. Here we summarise how these cytokines exert their effect through the shared signal transducer IL6ST (gp130) and we review the extensive evidence on the role that different members of this family play in breast cancer. Additionally, we discuss how the different cytokines, their related receptors and downstream effectors, as well as specific polymorphisms in these molecules, can serve as predictive or prognostic biomarkers with the potential for clinical application in breast cancer. Lastly, we also discuss how our increasing understanding of this complex signalling axis presents promising opportunities for the development or repurposing of therapeutic strategies against cancer and, specifically, breast neoplasms.

Influences of the IL-6 cytokine family on bone structure and function

The IL-6 family of cytokines comprises a large group of cytokines that all act via the formation of a signaling complex that includes the glycoprotein 130 (gp130) receptor. Despite this, many of these cytokines have unique roles that regulate the activity of bone forming osteoblasts, bone resorbing osteoclasts, bone-resident osteocytes, and cartilage cells (chondrocytes). These include specific functions in craniofacial development, longitudinal bone growth, and the maintenance of trabecular and cortical bone structure, and have been implicated in musculoskeletal pathologies such as craniosynostosis, osteoporosis, rheumatoid arthritis, osteoarthritis, and heterotopic ossifications. This review will work systematically through each member of this family and provide an overview and an update on the expression patterns and functions of each of these cytokines in the skeleton, as well as their negative feedback pathways, particularly suppressor of cytokine signaling 3 (SOCS3). The specific cytokines described are interleukin 6 (IL-6), interleukin 11 (IL-11), oncostatin M (OSM), leukemia inhibitory factor (LIF), cardiotrophin 1 (CT-1), ciliary neurotrophic factor (CNTF), cardiotrophin-like cytokine factor 1 (CLCF1), neuropoietin, humanin and interleukin 27 (IL-27).

Interleukin-11 (IL-11) receptor cleavage by the rhomboid protease RHBDL2 induces IL-11 trans-signaling

Interleukin-11 (IL-11) is a pleiotropic cytokine with both pro- and anti-inflammatory properties. It activates its target cells via binding to the membrane-bound IL-11 receptor (IL-11R), which then recruits a homodimer of the ubiquitously expressed, signal-transducing receptor gp130. Besides this classic signaling pathway, IL-11 can also bind to soluble forms of the IL-11R (sIL-11R), and IL-11/sIL-11R complexes activate cells via the induction of gp130 homodimerization (trans-signaling). We have previously reported that the metalloprotease ADAM10 cleaves the membrane-bound IL-11R and thereby generates sIL-11R. In this study, we identify the rhomboid intramembrane protease RHBDL2 as a so far unrecognized alternative sheddase that can efficiently trigger IL-11R secretion. We determine the cleavage site used by RHBDL2, which is located in the extracellular part of the receptor in close proximity to the plasma membrane, between Ala-370 and Ser-371. Furthermore, we identify critical amino acid residues within the transmembrane helix that are required for IL-11R proteolysis. We also show that ectopically expressed RHBDL2 is able to cleave the IL-11R within the early secretory pathway and not only at the plasma membrane, indicating that its subcellular localization plays a central role in controlling its activity. Moreover, RHBDL2-derived sIL-11R is biologically active and able to perform IL-11 trans-signaling. Finally, we show that the human mutation IL-11R-A370V does not impede IL-11 classic signaling, but prevents RHBDL2-mediated IL-11R cleavage.

Similarities and differences between IL11 and IL11RA1 knockout mice for lung fibro-inflammation, fertility and craniosynostosis

Loss of function (LOF) in IL11RA infers IL11 signaling as important for fertility, fibrosis, inflammation and incompletely penetrant craniosynostosis. The impact of LOF in IL11 has not been characterized. We generated IL11 knockout (Il11-/-) mice that are born in expected ratios and have normal hematological profiles. Lung fibroblasts from Il11-/- mice are resistant to pro-fibrotic stimulation with TGFβ1. Following bleomycin-induced lung injury, Il11-/- mice are protected from pulmonary fibrosis and exhibit lesser ERK, STAT3 and NF-kB activation, reduced Il1b, Timp1, Ccl2 and diminished IL6 expression, both at baseline and after injury: placing Il11 activity upstream of IL6 in this model. Il11-/- female mice are infertile. Unlike Il11ra1-/- mice, Il11-/- mice do not have craniosynostosis, have normal long bone mass and reduced body weights. These data further establish the role of IL11 signaling in lung fibrosis while suggesting that bone development abnormalities can be associated with mutation of IL11RA but not IL11, which may have implications for therapeutic targeting of IL11 signaling.

STAT3 Hyper-IgE Syndrome-an Update and Unanswered Questions

The hyper-IgE syndromes (HIES) are a heterogeneous group of inborn errors of immunity sharing manifestations including increased infection susceptibility, eczema, and raised serum IgE. Since the prototypical HIES description 55 years ago, areas of significant progress have included description of key disease-causing genes and differentiation into clinically distinct entities. The first two patients reported had what is now understood to be HIES from dominant-negative mutations in signal transduction and activator of transcription 3 (STAT3-HIES), conferring a broad immune defect across both innate and acquired arms, as well as defects in skeletal, connective tissue, and vascular function, causing a clinical phenotype including eczema, staphylococcal and fungal skin and pulmonary infection, scoliosis and minimal trauma fractures, and vascular tortuosity and aneurysm. Due to the constitutionally expressed nature of STAT3, initial reports at treatment with allogeneic stem cell transplantation were not positive and treatment has hinged on aggressive antimicrobial prophylaxis and treatment to prevent the development of end-organ disease such as pneumatocele. Research into the pathophysiology of STAT3-HIES has driven understanding of the interface of several signaling pathways, including the JAK-STAT pathways, interleukins 6 and 17, and the role of Th17 lymphocytes, and has been expanded by identification of phenocopies such as mutations in IL6ST and ZNF341. In this review we summarize the published literature on STAT3-HIES, present the diverse clinical manifestations of this syndrome with current management strategies, and update on the uncertain role of stem cell transplantation for this disease. We outline key unanswered questions for further study.

Human STAT3 variants underlie autosomal dominant hyper-IgE syndrome by negative dominance

Most patients with autosomal dominant hyper-IgE syndrome (AD-HIES) carry rare heterozygous STAT3 variants. Only six of the 135 in-frame variants reported have been experimentally shown to be dominant negative (DN), and it has been recently suggested that eight out-of-frame variants operate by haploinsufficiency. We experimentally tested these 143 variants, 7 novel out-of-frame variants found in HIES patients, and other STAT3 variants from the general population. Strikingly, all 15 out-of-frame variants were DN via their encoded (1) truncated proteins, (2) neoproteins generated from a translation reinitiation codon, and (3) isoforms from alternative transcripts or a combination thereof. Moreover, 128 of the 135 in-frame variants (95%) were also DN. The patients carrying the seven non-DN STAT3 in-frame variants have not been studied for other genetic etiologies. Finally, none of the variants from the general population tested, including an out-of-frame variant, were DN. Overall, our findings show that heterozygous STAT3 variants, whether in or out of frame, underlie AD-HIES through negative dominance rather than haploinsufficiency.

Interleukin 11 (IL-11): Role(s) in Breast Cancer Bone Metastases

Bone metastases represent the main problem related to the progression of breast cancer, as they are the main cause of death for these patients. Unfortunately, to date, bone metastases are incurable and represent the main challenge for the researcher. Chemokines and cytokines affect different stages of the metastatic process, and in bone metastases, interleukin (IL) -6, IL-8, IL-1β, and IL-11 participate in the interaction between cancer cells and bone cells. This review focuses on IL-11, a pleiotropic cytokine that, in addition to its well-known effects on several tissues, also mediates certain signals in cancer cells. In particular, as IL-11 works on bone remodeling, it plays a relevant role in the osteolytic vicious cycle of bone resorption and tumour growth, which characterizes bone metastasis. IL-11 appears as a candidate for anti-metastatic therapy. Even if different therapeutic approaches have considered IL-11 and the downstream-activated gp130 signaling pathways activated downstream of gp130, further studies are needed to decipher the contribution of the different cytokines and their mechanisms of action in breast cancer progression to define therapeutic strategies.

Endosomes as Signaling Platforms for IL-6 Family Cytokine Receptors

Interleukin-6 (IL-6) is the name-giving cytokine of a family of eleven members, including IL-6, CNTF, LIF, and IL-27. IL-6 was first recognized as a B-cell stimulating factor but we now know that the cytokine plays a pivotal role in the orchestration of inflammatory processes as well as in inflammation associated cancer. Moreover, IL-6 is involved in metabolic regulation and it has been shown to be involved in major neural activities such as neuroprotection, which can help to repair and to reduce brain damage. Receptor complexes of all members formed at the plasma membrane contain one or two molecules of the signaling receptor subunit GP130 and the mechanisms of signal transduction are well understood. IL-6 type cytokines can also signal from endomembranes, in particular the endosome, and situations have been reported in which endocytosis of receptor complexes are a prerequisite of intracellular signaling. Moreover, pathogenic GP130 variants were shown to interfere with spatial activation of downstream signals. We here summarize the molecular mechanisms underlying spatial regulation of IL-6 family cytokine signaling and discuss its relevance for pathogenic processes.

Ameliorative Effects of Osthole on Experimental Renal Fibrosis in vivo and in vitro by Inhibiting IL-11/ERK1/2 Signaling

Objectives: Natural product, osthole, has been proven to have a protective effect on organ fibrosis, including renal fibrosis. All of these studies are mainly focused on the regulation of TGF-β/Smad signaling pathway. However, due to the pleiotropic roles of TGF-β/Smad signaling, direct TGF-β-targeted treatments are unlikely to be therapeutically feasible in clinic. Recently, the downstream IL-11/ERK1/2 signaling of TGF-β has become an attractive therapeutic target without upstream disadvantages. Based on that, this study was designed to identify the potential effects of osthole on IL-11/ERK1/2 signaling pathway in renal fibrosis.

Methods: The renal fibrosis model was established in vivo and in vitro, we investigated the effects of osthole on unilateral ureteral obstruction (UUO)-induced renal fibrosis and TGF-β-induced HK-2 cells. After preliminarily confirming the antifibrogenic effects of osthole and the link between its antifibrogenic effects and the inhibition of IL-11/ERK1/2 signaling, we applied a direct IL-11-induced HK-2 cells fibrosis model to further explore the inhibitory effects of osthole on IL-11/ERK1/2 signaling pathway.

Results: Our results confirmed that osthole can decrease the secretion of fibrosis proteins, such as α-smooth muscle actin (α-SMA), collagen I, and fibronectin, ameliorate experimental renal fibrosis in vivo and in vitro, and the effect was associated with suppressing TGF-β1/Smad signaling. More importantly, we found that IL-11/ERK1/2 signaling in UUO-induced renal fibrosis and TGF-β-induced HK-2 cell model was obviously upregulated, and osthole treatment also significantly inhibited the abnormal IL-11/ERK1/2 signaling activation. Given the direct link between TGF-β/Smad signaling and IL-11/ERK1/2 signaling pathway, we have verified that osthole has a direct inhibitory effect on IL-11/ERK1/2 signaling independent of TGF-β signaling by using an IL-11-induced HK-2 cells fibrosis model. Osthole treatment decreased the protein expression of α-SMA, collagen I and fibronectin without changing their mRNA levels in IL-11-induced HK-2 cells. Moreover, it was observed that the IL-11/ERK1/2 inhibitor, U0126, partly blocked the antifibrogenic effects of osthole.

Conclusion: In this study, we found that osthole has a previously unrecognized role in inhibiting IL-11/ERK1/2 signaling pathway. Our work demonstrated that the antifibrogenic effect of osthole is not only mediated by TGF-β/Smad2/3 signaling, but also directly mediated by IL-11/ERK1/2 signaling pathway independent of TGF-β1 signaling.

The cytokine interleukin-11 crucially links bone formation, remodeling and resorption

Bone development is a complex process that requires the activity of several different signaling pathways and cell types. It involves the coordinated action of osteoclasts (cells that are capable of resorbing bone), osteoblasts (cells that are able to form bone), osteocytes (cells that form a syncytial network within the bone), skeletal muscle cells and the bone marrow. In recent years, the cytokine interleukin-11 (IL-11), a member of the IL-6 family of cytokines, has emerged as an important regulatory protein for bone formation, remodeling and resorption. Furthermore, coding missense mutations in the IL11RA gene, which encodes the IL-11 receptor (IL-11R), have recently been linked to craniosynostosis, a human disease in which the sutures that line the head bones close prematurely. This review summarizes current knowledge about IL-11 and highlights its role in bone development and homeostasis. It further discusses the specificity and redundancy provided by the other members of the IL-6 cytokine family and how they facilitate signaling and cross-talk between skeletal muscle cells, bone cells and the bone marrow. We describe their actions in physiological and in pathological states and discuss how this knowledge could be translated into therapy.

Single-suture craniosynostosis and the epigenome: current evidence and a review of epigenetic principles

Craniosynostosis (CS) is a congenital disease that arises due to premature ossification of single or multiple sutures, which results in skull deformities. The surgical management of single-suture CS continues to evolve and is driven by a robust body of clinical research; however, the molecular underpinnings of CS remain poorly understood. Despite long-standing hypotheses regarding the interaction of genetic predisposition and environmental factors, formal investigation of the epigenetic underpinnings of CS has been limited. In an effort to catalyze further investigation into the epigenetic basis of CS, the authors review the fundamentals of epigenetics, discuss recent studies that shed light on this emerging field, and offer hypotheses regarding the role of epigenetic mechanisms in the development of single-suture CS.

Functional and structural analysis of cytokine-selective IL6ST defects that cause recessive hyper-IgE syndrome

BACKGROUND

Biallelic variants in IL6ST, encoding GP130, cause a recessive form of hyper-IgE syndrome (HIES) characterized by high IgE level, eosinophilia, defective acute phase response, susceptibility to bacterial infections, and skeletal abnormalities due to cytokine-selective loss of function in GP130, with defective IL-6 and IL-11 and variable oncostatin M (OSM) and IL-27 levels but sparing leukemia inhibitory factor (LIF) signaling.

OBJECTIVE

Our aim was to understand the functional and structural impact of recessive HIES-associated IL6ST variants.

METHODS

We investigated a patient with HIES by using exome, genome, and RNA sequencing. Functional assays assessed IL-6, IL-11, IL-27, OSM, LIF, CT-1, CLC, and CNTF signaling. Molecular dynamics simulations and structural modeling of GP130 cytokine receptor complexes were performed.

RESULTS

We identified a patient with compound heterozygous novel missense variants in IL6ST (p.Ala517Pro and the exon-skipping null variant p.Gly484_Pro518delinsArg). The p.Ala517Pro variant resulted in a more profound IL-6- and IL-11-dominated signaling defect than did the previously identified recessive HIES IL6ST variants p.Asn404Tyr and p.Pro498Leu. Molecular dynamics simulations suggested that the p.Ala517Pro and p.Asn404Tyr variants result in increased flexibility of the extracellular membrane-proximal domains of GP130. We propose a structural model that explains the cytokine selectivity of pathogenic IL6ST variants that result in recessive HIES. The variants destabilized the conformation of the hexameric cytokine receptor complexes, whereas the trimeric LIF-GP130-LIFR complex remained stable through an additional membrane-proximal interaction. Deletion of this membrane-proximal interaction site in GP130 consequently caused additional defective LIF signaling and Stüve-Wiedemann syndrome.

CONCLUSION

Our data provide a structural basis to understand clinical phenotypes in patients with IL6ST variants.

Clinical Profile of Hyper-IgE Syndrome in India

Introduction: Hyper-IgE Syndrome (HIES) is a rare inborn error of immunity (IEI) characterized by a constellation of symptoms related to susceptibility to Staphylococcal skin and pulmonary infections, eczema, raised serum IgE (>2,000 IU/ml), craniofacial anomalies, and recurrent bone fractures. Data on HIES from the Indian subcontinent is scarce and restricted to small case series and case reports. This is the first compilation of national data on HIES. Materials and Methods: A total 103 cases clinically diagnosed and treated as HIES were analyzed from nine centers. Cases with clinical and/or molecular diagnosis of DOCK8 deficiency were not included. Patients were divided into two groups: group I for whom a heterozygous rare variant of STAT3 was identified, and group II, with clinical features similar to those of AD STAT3 deficiency, but without any genetic diagnosis. Results: Genetic diagnosis was available in 27 patients (26.2%) and all harbored rare variants in the STAT3 gene. Majority of these STAT3 HIES patients presented with recurrent skin abscesses (77.7%) or pneumonia (62.9%) or both (59.2%). Other features included eczema (37%), candidiasis (55.5%), facial dysmorphism (55.5%), recurrent fractures (11.1%), and retained primary teeth (7.4%). Mycobacterial infections were seen in a significant 18.5%. Mortality was seen in three subjects (11.1%). A similar trend in the clinical presentation was observed when all the 103 patients were analyzed together. Twenty percent of patients without a rare variant in the STAT3 gene had an NIH score of ≥40, whereas, 51.9% of STAT3 HIES subjects had scores below the cut off of ≥40. TH17 cell numbers were low in 10/11 (90.9%) STAT3 HIES tested. Rare variants observed were 8 in exon 21; 8 in exon 13; 3 in exon 10; 2 in exon 15, and one each in exon 6, 16, 17, 19, 22, and splice site downstream of exon 12. Seven variants were novel and included F174S, N567D, L404Sfs^*8, G419 =, M329K, T714I, R518X, and a splice site variant downstream of exon 12. Conclusions: The report includes seven novel STAT3 variants, including a rare linker domain nonsense variant and a CC domain variant. Mycobacterial diseases were more frequent, compared to western literature.

Historical overview of the interleukin-6 family cytokine

Interleukin-6 (IL-6) has been identified as a 26-kD secreted protein that stimulates B cells to produce antibodies. Later, IL-6 was revealed to have various functions that overlap with other IL-6 family cytokines and use the common IL-6 signal transducer gp130. IL-6 stimulates cells through multiple pathways, using both membrane and soluble IL-6 receptors. As indicated by the expanding market for IL-6 inhibitors, it has become a primary therapeutic target among IL-6 family cytokines. Here, we revisit the discovery of IL-6; discuss insights regarding the roles of this family of cytokines; and highlight recent advances in our understanding of regulation of IL-6 expression.

Interleukin-11 signaling underlies fibrosis, parenchymal dysfunction, and chronic inflammation of the airway

Interleukin (IL)-11 evolved as part of the innate immune response. In the human lung, IL-11 upregulation has been associated with viral infections and a range of fibroinflammatory diseases, including idiopathic pulmonary fibrosis. Transforming growth factor-beta (TGFβ) and other disease factors can initiate an autocrine loop of IL-11 signaling in pulmonary fibroblasts, which, in a largely ERK-dependent manner, triggers the translation of profibrotic proteins. Lung epithelial cells also express the IL-11 receptor and transition into a mesenchymal-like state in response to IL-11 exposure. In mice, therapeutic targeting of IL-11 with antibodies can arrest and reverse bleomycin-induced pulmonary fibrosis and inflammation. Intriguingly, fibroblast-specific blockade of IL-11 signaling has anti-inflammatory effects, which suggests that lung inflammation is sustained, in part, through IL-11 activity in the stroma. Proinflammatory fibroblasts and their interaction with the damaged epithelium may represent an important but overlooked driver of lung disease. Initially thought of as a protective cytokine, IL-11 is now increasingly recognized as an important determinant of lung fibrosis, inflammation, and epithelial dysfunction.

Hiding in Plain Sight: Interleukin-11 Emerges as a Master Regulator of Fibrosis, Tissue Integrity, and Stromal Inflammation

Interleukin (IL)-11 is upregulated in a wide variety of fibro-inflammatory diseases such as systemic sclerosis, rheumatoid arthritis, pulmonary fibrosis, inflammatory bowel disease, kidney disease, drug-induced liver injury, and nonalcoholic steatohepatitis. IL-11 is a member of the IL-6 cytokine family and has several distinct properties that define its unique and nonredundant roles in disease. The IL-11 receptor is highly expressed on stromal, epithelial and polarized cells, where noncanonical IL-11 signaling drives the three pathologies common to all fibro-inflammatory diseases-myofibroblast activation, parenchymal cell dysfunction, and inflammation-while also inhibiting tissue regeneration. This cytokine has been little studied, and publications on IL-11 peaked in the early 1990s, when it was largely misunderstood. Here we describe recent advances in our understanding of IL-11 biology, outline how misconceptions as to its function came about, and highlight the large potential of therapies targeting IL-11 signaling for treating human disease.

Absence of GP130 cytokine receptor signaling causes extended Stüve-Wiedemann syndrome

The gene IL6ST encodes GP130, the common signal transducer of the IL-6 cytokine family consisting of 10 cytokines. Previous studies have identified cytokine-selective IL6ST defects that preserve LIF signaling. We describe three unrelated families with at least five affected individuals who presented with lethal Stüve-Wiedemann–like syndrome characterized by skeletal dysplasia and neonatal lung dysfunction with additional features such as congenital thrombocytopenia, eczematoid dermatitis, renal abnormalities, and defective acute-phase response. We identified essential loss-of-function variants in IL6ST (a homozygous nonsense variant and a homozygous intronic splice variant with exon skipping). Functional tests showed absent cellular responses to GP130-dependent cytokines including IL-6, IL-11, IL-27, oncostatin M (OSM), and leukemia inhibitory factor (LIF). Genetic reconstitution of GP130 by lentiviral transduction in patient-derived cells reversed the signaling defect. This study identifies a new genetic syndrome caused by the complete lack of signaling of a whole family of GP130-dependent cytokines in humans and highlights the importance of the LIF signaling pathway in pre- and perinatal development.

Genomic variations and signatures of selection in Wuhua yellow chicken

Wuhua yellow chicken (WHYC) is an important traditional yellow-feathered chicken from China, which is characterized by its white tail feathers, white flight feathers, and strong disease resistance. However, the genomic basis of these unique traits associated with WHYC is poorly understood. In this study, whole-genome resequencing was performed with an average coverage of 20.77-fold to investigate heritable variation and identify selection signals in WHYC. Reads were mapped onto the chicken reference genome (Galgal5) with a coverage of 85.95%. After quality control, 11,953,471 single nucleotide polymorphisms and 1,069,574 insertion/deletions were obtained. In addition, 41,408 structural variants and 33,278 copy number variants were found. Comparative genomic analysis of WHYC and other yellow-feathered chicken breeds showed that selected regions were enriched in genes involved in transport and catabolism, immune system, infectious diseases, signal transduction, and signaling molecules and interactions. Several genes associated with disease resistance were also identified, including IFNA, IFNB, CD86, IL18, IL11RA, VEGFC, and ATG10. Furthermore, our results suggest that PMEL and TYRP1 may contribute to the white feather coloring in WHYC. These findings can improve our understanding of the genetic characteristics of WHYC and may contribute to future breed improvement.

Structural Understanding of Interleukin 6 Family Cytokine Signaling and Targeted Therapies: Focus on Interleukin 11

Cytokines are small signaling proteins that have central roles in inflammation and cell survival. In the half-century since the discovery of the first cytokines, the interferons, over fifty cytokines have been identified. Amongst these is interleukin (IL)-6, the first and prototypical member of the IL-6 family of cytokines, nearly all of which utilize the common signaling receptor, gp130. In the last decade, there have been numerous advances in our understanding of the structural mechanisms of IL-6 family signaling, particularly for IL-6 itself. However, our understanding of the detailed structural mechanisms underlying signaling by most IL-6 family members remains limited. With the emergence of new roles for IL-6 family cytokines in disease and, in particular, roles of IL-11 in cardiovascular disease, lung disease, and cancer, there is an emerging need to develop therapeutics that can progress to clinical use. Here we outline our current knowledge of the structural mechanism of signaling by the IL-6 family of cytokines. We discuss how this knowledge allows us to understand the mechanism of action of currently available inhibitors targeting IL-6 family cytokine signaling, and most importantly how it allows for improved opportunities to pharmacologically disrupt cytokine signaling. We focus specifically on the need to develop and understand inhibitors that disrupt IL-11 signaling.

A variant in IL6ST with a selective IL-11 signaling defect in human and mouse

The GP130 cytokine receptor subunit encoded by IL6ST is the shared receptor for ten cytokines of the IL-6 family. We describe a homozygous non-synonymous variant in IL6ST (p.R281Q) in a patient with craniosynostosis and retained deciduous teeth. We characterize the impact of the variant on cytokine signaling in vitro using transfected cell lines as well as primary patient-derived cells and support these findings using a mouse model with the corresponding genome-edited variant Il6st p.R279Q. We show that human GP130 p.R281Q is associated with selective loss of IL-11 signaling without affecting IL-6, IL-27, OSM, LIF, CT1, CLC, and CNTF signaling. In mice Il6st p.R279Q lowers litter size and causes facial synostosis and teeth abnormalities. The effect on IL-11 signaling caused by the GP130 variant shows incomplete penetrance but phenocopies aspects of IL11RA deficiency in humans and mice. Our data show that a genetic variant in a pleiotropic cytokine receptor can have remarkably selective defects.

The structure of the extracellular domains of human interleukin 11α receptor reveals mechanisms of cytokine engagement

Interleukin (IL) 11 activates multiple intracellular signaling pathways by forming a complex with its cell surface α-receptor, IL-11Rα, and the β-subunit receptor, gp130. Dysregulated IL-11 signaling has been implicated in several diseases, including some cancers and fibrosis. Mutations in IL-11Rα that reduce signaling are also associated with hereditary cranial malformations. Here we present the first crystal structure of the extracellular domains of human IL-11Rα and a structure of human IL-11 that reveals previously unresolved detail. Disease-associated mutations in IL-11Rα are generally distal to putative ligand-binding sites. Molecular dynamics simulations showed that specific mutations destabilize IL-11Rα and may have indirect effects on the cytokine-binding region. We show that IL-11 and IL-11Rα form a 1:1 complex with nanomolar affinity and present a model of the complex. Our results suggest that the thermodynamic and structural mechanisms of complex formation between IL-11 and IL-11Rα differ substantially from those previously reported for similar cytokines. This work reveals key determinants of the engagement of IL-11 by IL-11Rα that may be exploited in the development of strategies to modulate formation of the IL-11-IL-11Rα complex.

IL-11 in cardiac and renal fibrosis: Late to the party but a central player

Fibrosis is a pathophysiological hallmark of cardiorenal disease. In the heart, fibrosis leads to contractile dysfunction and arrhythmias; in the kidney, it is the final common pathway for many diseases and predicts end-stage renal failure. Despite this, there are currently no specific anti-fibrotic treatments available for cardiac or renal disease. Recently and unexpectedly, IL-11 was found to be of major importance for cardiorenal fibroblast activation and fibrosis. In mouse models, IL-11 overexpression caused fibrosis of the heart and kidney while genetic deletion of Il11ra1 protected against fibrosis and preserved organ function. Neutralizing antibodies against IL-11 or IL-11RA have been developed that have anti-fibrotic activity in human fibroblasts and protect against fibrosis in murine models of disease. While IL-11 biology has been little studied and, we suggest, largely misunderstood, its autocrine activity in myofibroblasts appears non-redundant for fibrosis, which offers new opportunities to better understand and potentially target cardiorenal fibrosis.

[The role of interleukin-11 in osteosarcoma]

Osteosarcoma is an often highly malignant mesenchymal tumor. By definition, osteosarcoma cells are able to form osteoid, which can mature into tumor bone. Osteosarcoma metastasizes preferentially to the lung. In Europe, the incidence is between 2 and 5 new diagnoses per 1,000,000 people per year. The underlying mechanisms for osteosarcoma formation are not well understood. However, previous radiotherapy or exposition to nuclear radiation increase the risk of osteosarcoma. Patients are usually treated with a neoadjuvant chemotherapy, followed by complete surgical resection of the tumor and post-surgical chemotherapy, which leads to a five-year survival rate of approximately 70% for all stages. Scientific publications in recent years have shown that expression of the cell surface protein interleukin-11 receptor (IL-11R) correlates with a worse prognosis for patients. The IL-11R is activated by its ligand, the cytokine IL-11. IL-11 activates several intracellular signaling cascades within its target cells and is known to be an important regulator of bone homeostasis. Patients with dysfunctional IL-11 signaling display different forms of craniosynostosis. IL-11 induces proliferation of osteosarcoma cell lines in vitro, and the IL-11 signaling cascade was further used to reduce tumor growth and lung metastasis in preclinical mouse models of primary intratibial osteosarcoma. This article gives a comprehensive overview of the frequency, classification, and etiology of osteosarcoma and describes the basic biology of the cytokine IL-11. Furthermore, it summarizes current knowledge about the functional role of IL-11 in osteosarcoma and lists possible therapeutic opportunities.

Jak-Stat Signaling Induced by Interleukin-6 Family Cytokines in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. It can be caused by chronic liver cell injury with resulting sustained inflammation, e.g., triggered by infections with hepatitis viruses B (HBV) and C (HCV). Death of hepatocytes leads to the activation of compensatory mechanisms, which can ultimately result in liver fibrosis and cirrhosis. Another common feature is the infiltration of the liver with inflammatory cells, which secrete cytokines and chemokines that act directly on the hepatocytes. Among several secreted proteins, members of the interleukin-6 (IL-6) family of cytokines have emerged as important regulatory proteins that might constitute an attractive target for therapeutic intervention. The IL-6-type cytokines activate multiple intracellular signaling pathways, and especially the Jak/STAT cascade has been shown to be crucial for HCC development. In this review, we give an overview about HCC pathogenesis with respect to IL-6-type cytokines and the Jak/STAT pathway. We highlight the role of mutations in genes encoding several proteins involved in the cytokine/Jak/STAT axis and summarize current knowledge about IL-6 family cytokines in this context. We further discuss possible anti-cytokine therapies for HCC patients in comparison to already established therapies.

Animal models of craniosynostosis

BACKGROUND

Various animal models mimicking craniosynostosis have been developed, using mutant zebrafish and mouse. The aim of this paper is to review the different animal models for syndromic craniosynostosis and analyze what insights they have provided in our understanding of the pathophysiology of these conditions.

MATERIAL AND METHODS

The relevant literature for animal models of craniosynostosis was reviewed.

RESULTS

Although few studies on craniosynostosis using zebrafish were published, this model appears useful in studying the suture formation mechanisms conserved across vertebrates. Conversely, several mouse models have been generated for the most common syndromic craniosynostoses, associated with mutations in FGFR1, FGFR2, FGFR3 and TWIST genes and also in MSX2, EFFNA, GLI3, FREM1, FGF3/4 genes. The mouse models have also been used to test pharmacological treatments to restore craniofacial growth.

CONCLUSIONS

Several zebrafish and mouse models have been developed in recent decades. These animal models have been helpful for our understanding of normal and pathological craniofacial growth. Mouse models mimicking craniosynostoses can be easily used for the screening of drugs as therapeutic candidates.

Current Approaches in the Development of Molecular and Pharmacological Therapies in Craniosynostosis Utilizing Animal Models

The development of the craniofacial skeleton is a spatial and temporal process where cranial sutures play a role in the regulation of morphogenesis and growth. Disruption of these cellular and molecular interactions may lead to craniosynostosis, the premature obliteration of one or more cranial sutures, yielding skull growth restriction and malformation perpendicular to the affected suture. Facial deformity and various functional CNS anomalies are other frequent complications. Cranial vault expansion and reconstructive surgery remain the mainstay of treatment but pose an elevated risk of morbidity for the infant. While the etiology of nonsyndromic craniosynostosis remains to be deciphered, gain-of-function mutations in FGFR1-3 and TWIST1 were found to be responsible for more than 3/4 of the most commonly encountered craniofacial syndromes. Animal models have been invaluable to further dissect the role of genes within the cranial sutures and for the development of alternative nonsurgical treatment strategies. In this review, we will present various molecular and pharmacological approaches for the treatment of craniosynostosis that have been tested using in vitro and in vivo assays as well as discuss their potential application in humans focusing on the case of tyrosine kinase inhibitors.

Evolution of the phenotype of craniosynostosis with dental anomalies syndrome and report of IL11RA variant population frequencies in a Crouzon-like autosomal recessive syndrome

In 2011, biallelic loss-of-function variants in the interleukin receptor 11 alpha gene IL11RA were found to be associated with a Crouzon-like craniosynostosis syndrome with associated dental anomalies (CRSDA). Since then, a total of 41 similar patients have been reported with IL11RA variants. We report two adult brothers diagnosed with Crouzon syndrome as children, in which the clinical diagnosis of CRSDA was made on reevaluation. Laboratory testing detected biallelic IL11RA variants, c.916_924dup (p.Thr306_Ser308dup) and c.781C > T (p.Arg261Cys), both of which have now been reported in other families. Protein modeling and conservation analysis show that these two mutation sites cluster together near a WSXWS motif that likely plays a significant role in regulating IL11RA protein function. Population analysis from gnomAD shows that Non-Finnish Europeans (similar to ethnicity of this family), have an allele frequency for p.Thr306_Ser308dup of 0.014% and p.Arg261Cys of 0.008%. We found other ethnicities have functional IL11RA missense variants at higher frequencies. With this report, we provide a summary of the clinical findings including details of middle ear anomalies associated with conductive hearing loss. We also provide data supporting the populations at risk for this condition to increase recognition and diagnosis of this rare autosomal recessive craniosynostosis syndrome.

An FDA-Approved Drug Screen for Compounds Influencing Craniofacial Skeletal Development and Craniosynostosis

Neural crest stem/progenitor cells (NCSCs) populate a variety of tissues, and their dysregulation is implicated in several human diseases including craniosynostosis and neuroblastoma. We hypothesised that small molecules that inhibit NCSC induction or differentiation may represent potential therapeutically relevant drugs in these disorders. We screened 640 FDA-approved compounds currently in clinical use for other conditions to identify those which disrupt development of NCSC-derived skeletal elements that form the zebrafish jaw. In the primary screen, we used heterozygous transgenic sox10:gfp zebrafish to directly visualise NCSC-derived jaw cartilage. We noted partial toxicity of this transgene in relation to jaw patterning, suggesting that our primary screen was sensitised for NCSC defects, and we confirmed 10 novel, 4 previously reported, and 2 functional analogue drug hits in wild-type embryos. Of these drugs, 9/14 and 7/14, respectively, are known to target pathways implicated in osteoarthritis pathogenesis or to cause reduced bone mineral density/increased fracture risk as side effects in patients treated for other conditions, suggesting that our screen enriched for pathways targeting skeletal tissue homeostasis. We selected one drug that inhibited NCSC induction and one drug that inhibits bone mineralisation for further detailed analyses which reflect our initial hypotheses. These drugs were leflunomide and cyclosporin A, respectively, and their functional analogues, teriflunomide and FK506 (tacrolimus). We identified their critical developmental windows of activity, showing that the severity of defects observed related to the timing, duration, and dose of treatment. While leflunomide has previously been shown to inhibit NCSC induction, we demonstrate additional later roles in cartilage remodelling. Both drugs altered expression of extracellular matrix metalloproteinases. As proof-of-concept, we also tested drug treatment of disease-relevant mammalian cells. While leflunomide treatment inhibited the viability of several human NCSC-derived neuroblastoma cell lines coincident with altered expression of genes involved in ribosome biogenesis and transcription, FK506 enhanced murine calvarial osteoblast differentiation and prevented fusion of the coronal suture in calvarial explants taken from Crouzon syndrome mice.

Activating mutations of the gp130/JAK/STAT pathway in human diseases

Cytokines of the interleukin-6 (IL-6) family are involved in numerous physiological and pathophysiological processes. Dysregulated and increased activities of its members can be found in practically all human inflammatory diseases including cancer. All cytokines activate several intracellular signaling cascades, including the Jak/STAT, MAPK, PI3K, and Src/YAP signaling pathways. Additionally, several mutations in proteins involved in these signaling cascades have been identified in human patients, which render these proteins constitutively active and result in a hyperactivation of the signaling pathway. Interestingly, some of these mutations are associated with or even causative for distinct human diseases, making them interesting targets for therapy. This chapter describes the basic biology of the gp130/Jak/STAT pathway, summarizes what is known about the molecular mechanisms of the activating mutations, and gives an outlook how this knowledge can be exploited for targeted therapy in human diseases.

Selective loss of function variants in IL6ST cause Hyper-IgE syndrome with distinct impairments of T-cell phenotype and function

Hyper-IgE syndromes comprise a group of inborn errors of immunity. STAT3-deficient hyper-IgE syndrome is characterized by elevated serum IgE levels, recurrent infections and eczema, and characteristic skeletal anomalies. A loss-of-function biallelic mutation in IL6ST encoding the GP130 receptor subunit (p.N404Y) has very recently been identified in a singleton patient (herein referred to as P^N404Y) as a novel etiology of hyper-IgE syndrome. Here, we studied a patient with hyper-IgE syndrome caused by a novel homozygous mutation in IL6ST (p.P498L; patient herein referred to as P^P498L) leading to abrogated GP130 signaling after stimulation with IL-6 and IL-27 in peripheral blood mononuclear cells as well as IL-6 and IL-11 in fibroblasts. Extending the initial identification of selective GP130 deficiency, we aimed to dissect the effects of aberrant cytokine signaling on T-helper cell differentiation in both patients. Our results reveal the importance of IL-6 signaling for the development of CCR6-expressing memory CD4⁺ T cells (including T-helper 17-enriched subsets) and non-conventional CD8⁺T cells which were reduced in both patients. Downstream functional analysis of the GP130 mutants (p.N404Y and p.P498L) have shown differences in response to IL-27, with the p.P498L mutation having a more severe effect that is reflected by reduced T-helper 1 cells in this patient (P^P498L) only. Collectively, our data suggest that characteristic features of GP130-deficient hyper-IgE syndrome phenotype are IL-6 and IL-11 dominated, and indicate selective roles of aberrant IL-6 and IL-27 signaling on the differentiation of T-cell subsets.

Human hyper-IgE syndrome: singular or plural?

Spectacular progress has been made in the characterization of human hyper-IgE syndrome (HIES) over the last 50 years. HIES is a primary immunodeficiency defined as an association of atopy in a context of very high serum IgE levels, characteristic bacterial and fungal diseases, low-level clinical and biological inflammation, and various non-hematopoietic developmental manifestations. Somewhat arbitrarily, three disorders were successively put forward as the underlying cause of HIES: autosomal dominant (AD) STAT3 deficiency, the only disorder corresponding to the original definition of HIES, and autosomal recessive (AR) DOCK8 and PGM3 deficiencies, in which atopy and high serum IgE levels occur in a context of manifestations not seen in patients with typical HIES. Indeed, these three disorders disrupt different molecular pathways, affect different cell types, and underlie different clinical phenotypes. Surprisingly, several other inherited inborn errors of immunity in which serum IgE levels are high, sometimes almost as high as those in HIES patients, are not considered to belong to the HIES group of diseases. Studies of HIES have been further complicated by the lack of a high serum IgE phenotype in all mouse models of the disease other than two Stat3 mutant strains. The study of infections in mutant mice has helped elucidate only some forms of HIES and infection. Mouse models of these conditions have also been used to study non-hematopoietic phenotypes for STAT3 deficiency, tissue-specific immunity for DOCK8 deficiency, and cell lineage maturation for PGM3 deficiency. We review here the history of the field of HIES since the first clinical description of this condition in 1966, together with the three disorders commonly referred to as HIES, focusing, in particular, on their mouse models. We propose the restriction of the term "HIES" to patients with an AD STAT3-deficiency phenotype, including the most recently described AR ZNF341 deficiency, thus excluding AR DOCK8 and PGM3 deficiencies from the definition of this disease.

Novel 1q22-q23.1 duplication in a patient with lambdoid and metopic craniosynostosis, muscular hypotonia, and psychomotor retardation

Craniosynostosis (CS) refers to the group of craniofacial malformations characterized by the premature closure of one or more cranial sutures. The disorder is clinically and genetically heterogeneous and occurs usually as an isolated trait, but can also be syndromic. In 30-60% of patients, CS is caused by known genetic factors; however, in the rest of the cases, causative molecular lesions remain unknown. In this paper, we report on a sporadic male patient affected by complex CS (metopic and unilateral lambdoid synostosis), muscular hypotonia, psychomotor retardation, and facial dysmorphism. Since a subset of CS results from submicroscopic chromosomal aberrations, we performed array comparative genomic hybridization (array CGH) in order to identify possibly causative copy-number variation. Array CGH followed by breakpoint sequencing revealed a previously unreported de novo 1.26 Mb duplication at chromosome 1q22-q23.1 that encompassed two genes involved in osteoblast differentiation: BGLAP, encoding osteocalcin (OCN), and LMNA, encoding lamin A/C. OCN is a major component of bone extracellular matrix and a marker of osteogenesis, whereas mutations in LMNA cause several genetic disorders called laminopathies, including mandibuloacral dysostosis (MAD) that manifests with low bone mass, severe bone deformities, and delayed closure of the cranial sutures. Since LMNA and BGLAP overexpression promote osteoblast differentiation and calcification, phenotype of our patient may result from misexpression of the genes. Based on our findings, we hypothesize that both LMNA and BGLAP may be implicated in the pathogenesis of CS in humans. However, further studies are needed to establish the exact pathomechanism underlying development of this defect.