A new mutation in exon 7 of NEMO gene: late skewed X-chromosome inactivation in an incontinentia pigmenti female patient with immunodeficiency

Partial Loss of NEMO Function in a Female Carrier with No Incontinentia Pigmenti

Background/Objectives: The nuclear factor (NF)-kB essential modulator (NEMO) has a crucial role in the NFκB pathway. Hypomorphic IKBKG pathogenic variants cause ectodermal dysplasia with immunodeficiency (EDA-ID) in affected males. However, heterozygous amorphic IKBKG variants could be responsible for Incontinentia Pigmenti (IP) in female carriers. Typically, IP patients do not exhibit immunodeficiency, although hypomorphic variants might lead to immunodeficiency in female IP patients. Here, we report the case of an IKBKG female carrier, with no IP but an unexpected picture of immunodeficiency. She had a positive family history for the same genetic condition. Methods: We performed immunological, molecular, and functional analysis to evaluate NEMO contribution. Results: The patient was healthy until the age of 25 when severe asthma and Hashimoto thyroiditis occurred. She had HLAB27-positive ankylosing spondylitis, non-tubercular mycobacteriosis, and pulmonary aspergillosis infections. We found CD19+ B cell lymphopenia and T cell subset alterations. Sanger sequencing revealed a heterozygous IKBKG variant at position +1 of the 5' UTR of the gene which disrupted the normal pre-mRNA splicing. We observed a decreased NEMO protein expression, a reduced level of mRNA, and a defective NF-κB pathway. Conclusions: These findings suggest a possible correlation between the partial loss of NEMO function and the immunodeficiency observed in this patient. This case could expand our understanding of NEMO deficiency in female carriers.

Prevalence and clinical characteristics of incontinentia pigmenti: a nationwide population-based study

BACKGROUND

Incontinentia pigmenti (IP) is an X-linked dominant multisystemic disorder caused by pathogenic variants in the IKBKG gene. Population-based research into the epidemiology of IP is lacking.

METHODS

This nationwide cross-sectional study from Jan 1st, 1995 to August 25th, 2021, searched the Danish National Patient Registry (DNPR), the Danish National Database of Rare Genetic Diseases (RareDis) and the Danish Genodermatosis Database to identify patients recorded with a diagnosis of IP. This search was followed by diagnosis validation and collection of clinical data from patient medical records. We investigated the clinical characteristics and genetics of the final cohort of validated IP cases. We estimated the point prevalence in the Danish population, based on non-deceased IP patients currently living in Denmark. Furthermore, we estimated the birth prevalence from 1995 to 2020, assuming a diagnostic delay of up to six months.

RESULTS

We identified a validated cohort of 75 IP patients, including 71 (94.7%) females and 4 (5.3%) males. We estimated a birth prevalence of 2.37 (95% CI: 1.74-3.25) per 100,000 or 1 in 42,194. A total of 54 (72%) patients had a genetic diagnosis, including 39 (72.2%) with the recurrent exon 4-10 deletion and 10 (18.5%) with point mutations in IKBKG. A positive family history was reported in 53.3%. Besides the recognizable blaschkolinear skin lesions reported in 70 (93.3%) of the patients, commonly reported manifestations included the involvement of the teeth (58.7%), the central nervous system (30.7%), hair (26.7%), and eyes (22.6%), as well as nail dystrophy (16.0%).

CONCLUSIONS

We identified and characterized a nationwide population-based cohort of IP patients and report a birth prevalence of 2.37 per 100,000 live births, which is twice as high as previous estimates.

Non-Skewed X-inactivation Results in NF-κB Essential Modulator (NEMO) Δ-exon 5-autoinflammatory Syndrome (NEMO-NDAS) in a Female with Incontinentia Pigmenti

PURPOSE

Genetic hypomorphic defects in X chromosomal IKBKG coding for the NF-κB essential modulator (NEMO) lead to ectodermal dysplasia and immunodeficiency in males and the skin disorder incontinentia pigmenti (IP) in females, respectively. NF-κB essential modulator (NEMO) Δ-exon 5-autoinflammatory syndrome (NEMO-NDAS) is a systemic autoinflammatory disease caused by alternative splicing and increased proportion of NEMO-Δex5. We investigated a female carrier presenting with IP and NEMO-NDAS due to non-skewed X-inactivation.

METHODS

IKBKG transcripts were quantified in peripheral blood mononuclear cells isolated from the patient, her mother, and healthy controls using RT-PCR and nanopore sequencing. Corresponding proteins were analyzed by western blotting and flow cytometry. Besides toll-like receptor (TLR) and tumor necrosis factor (TNF) signaling, the interferon signature, cytokine production and X-inactivation status were investigated.

RESULTS

IP and autoinflammation with recurrent fever, oral ulcers, hepatitis, and neutropenia, but no immunodeficiency was observed in a female patient. Besides moderately reduced NEMO signaling function, type I interferonopathy, and elevated IL-18 and CXCL10 were found. She and her mother both carried the heterozygous variant c.613 C > T p.(Gln205*) in exon 5 of IKBKG previously reported in NEMO-deficient patients. However, X-inactivation was skewed in the mother, but not in the patient. Alternative splicing led to increased ratios of NEMO-Dex5 over full-length protein in peripheral blood cell subsets causing autoinflammation. Clinical symptoms partially resolved under treatment with TNF inhibitors.

CONCLUSION

Non-skewed X-inactivation can lead to NEMO-NDAS in females with IP carrying hypomorphic IKBKG variants due to alternative splicing and increased proportions of NEMO-∆ex5.

An Atypical Incontinentia Pigmenti Female with Persistent Mucocutaneous Hyperinflammation and Immunodeficiency Caused by a Novel Germline IKBKG Missense Mutation

While most missense mutations of the IKBKG gene typically result in Ectodermal Dysplasia with Immunodeficiency, there have been rare reported instances of missense mutations of the IKBKG gene causing both Incontinentia Pigmenti (IP) and immunodeficiency in female patients. In this study, we described an atypical IP case in a 19-year-old girl, characterized by hyperpigmented and verrucous skin areas over the entire body. Remarkably, she experienced recurrent red papules whenever she had a feverish upper respiratory tract infection. Immunohistochemical staining unveiled a substantial accumulation of CD68+ macrophages alongside the TNF-α positive cells in the dermis tissue of new pustules, with increased apoptotic basal keratinocytes in the epidermis tissue of these lesions. Starting from the age of 8 years old, the patient suffered from severe and sustained chronic respiratory mucous membrane scar hyperplasia and occluded subglottic lumen. In addition to elevated erythrocyte sedimentation rate values, inflammatory cells were observed in the pathologic lesions of endobronchial biopsies and Bronchoalveolar Lavage Fluid (BALF) smear. Further histological analysis revealed a destructive bronchus epithelium integrity with extensive necrosis. Simultaneously, the patient experienced recurrent incomplete intestinal obstructions and lips contracture. The patient's BALF sample displayed an augmented profile of proinflammatory cytokines and chemokines, suggesting a potential link to systemic hyperinflammation, possibly underlying the pathogenic injuries affecting the subglottic, respiratory, and digestive systems. Furthermore, the patient presented with recurrent pneumonias and multiple warts accompanied by a T+BlowNKlow immunophenotype. Next generation sequencing showed that the patient carried a novel de novo germline heterozygous missense mutation in the IKBKG gene (c. 821T>C, p. L274P), located in the highly conserved CC2 domain. TA-cloning sequencing of patient's cDNA yielded 30 mutant transcripts out of 44 clones. In silico analysis indicated that the hydrogen bond present between Ala270 and Leu274 in the wild-type NEMO was disrupted by the Leu274Pro mutation. However, this mutation did not affect NEMO expression in peripheral blood mononuclear cells (PBMCs). Moreover, patient PBMCs exhibited significantly impaired TNF-α production following Lipopolysaccharide (LPS) stimulation. X-chromosome inactivation in T cells and neutrophils were not severely skewed. Reduced levels of IκBα phosphorylation and degradation in patient's PBMCs were observed. The NF-κB luciferase reporter assay conducted using IKBKG-deficient HEK293T cells revealed a significant reduction in NF-kB activity upon LPS stimulation. These findings adds to the ever-growing knowledge on female IP that might contribute to the better understanding of this challenging disorder.

The Impact of the IKBKG Gene on the Appearance of the Corpus Callosum Abnormalities in Incontinentia Pigmenti

Incontinentia pigmenti (IP) is a rare skin disease combined with anomalies of the teeth, eyes, and central nervous system (CNS). Mutations of the IKBKG gene are responsible for IP. Among the most frequent CNS abnormalities found in IP using magnetic resonance imaging (MRI) are corpus callosum (CC) abnormalities. The aim of the study was to determine the presence of CC abnormalities, their relationship with the IKBKG mutations, and the possible presence of mutations of other genes. A group of seven IP patients was examined. Analyses of the IKBKG gene and the X-chromosome inactivation pattern were performed, as well as MRI and whole exome sequencing (WES) with the focus on the genes relevant for neurodegeneration. WES analysis showed IKBKG mutation in all examined patients. A patient who had a mutation of a gene other than IKBKG was excluded from further study. Four of the seven patients had clinically diagnosed CNS anomalies; two out of four had MRI-diagnosed CC anomalies. The simultaneous presence of IKBKG mutation and CC abnormalities and the absence of other mutations indicate that IKBKG may be the cause of CC abnormalities and should be included in the list of genes responsible for CC abnormalities.

Cutaneous mosaicism: Special considerations for women

Genetic mosaicism results from postzygotic mutations during embryogenesis. Cells harboring pathogenic mutations distribute throughout the developing embryo and can cause clinical disease in the tissues they populate. Cutaneous mosaicism is readily visualized since affected tissue often follows predetermined patterns, such as lines of Blaschko. Due to its clinical accessibility, cutaneous mosaicism is well suited for genetic analysis. An individual's unaffected tissue can be used as an intrapatient genetic control, a technique that has yielded insight into the genetic etiologies of many disorders, several of which bear mutations in genes that would otherwise be embryonic-lethal. Particular mosaic diseases can also disproportionally impact women. Two such diseases, incontinentia pigmenti (IP) and congenital hemidysplasia with ichthyosiform erythroderma and limb defects (CHILD) syndrome, arise from mutations on the X chromosome. Both diseases result in fetal demise in males in most cases, thus making the two diseases largely specific to women. Women with McCune–Albright Syndrome, caused by somatic mutations in GNAS, often experience precocious puberty and infertility as a result of uncontrolled cAMP regulation in affected tissue. Women with cutaneous mosaicism carry a risk of transmission to offspring when gonosomal mosaicism is present, yet cutaneous disease burden does not correlate with germline transmission risk. Cutaneous mosaic disease represents a biologically unique set of disorders that can warrant special clinical attention in women.

Skin manifestations of inborn errors of NF-κB

More than 400 single gene defects have been identified as inborn errors of immunity, including many arising from genes encoding proteins that affect NF-κB activity. We summarise the skin phenotypes in this subset of disorders and provide an overview of pathogenic mechanisms. NF-κB acts cell-intrinsically in basal epithelial cells during differentiation of skin appendages, influences keratinocyte proliferation and survival, and both responses to and amplification of inflammation, particularly TNF. Skin phenotypes include ectodermal dysplasia, reduction and hyperproliferation of keratinocytes, and aberrant recruitment of inflammatory cells, which often occur in combination. Phenotypes conferred by these rare monogenic syndromes often resemble those observed with more common defects. This includes oral and perineal ulceration and pustular skin disease as occurs with Behcet's disease, hyperkeratosis with microabscess formation similar to psoriasis, and atopic dermatitis. Thus, these genotype-phenotype relations provide diagnostic clues for this subset of IEIs, and also provide insights into mechanisms of more common forms of skin disease.

Immunity and Genetics at the Revolving Doors of Diagnostics in Primary Immunodeficiencies

Primary immunodeficiencies (PIDs) are a large and growing group of disorders commonly associated with recurrent infections. However, nowadays, we know that PIDs often carry with them consequences related to organ or hematologic autoimmunity, autoinflammation, and lymphoproliferation in addition to simple susceptibility to pathogens. Alongside this conceptual development, there has been technical advancement, given by the new but already established diagnostic possibilities offered by new genetic testing (e.g., next-generation sequencing). Nevertheless, there is also the need to understand the large number of gene variants detected with these powerful methods. That means advancing beyond genetic results and resorting to the clinical phenotype and to immunological or alternative molecular tests that allow us to prove the causative role of a genetic variant of uncertain significance and/or better define the underlying pathophysiological mechanism. Furthermore, because of the rapid availability of results, laboratory immunoassays are still critical to diagnosing many PIDs, even in screening settings. Fundamental is the integration between different specialties and the development of multidisciplinary and flexible diagnostic workflows. This paper aims to tell these evolving aspects of immunodeficiencies, which are summarized in five key messages, through introducing and exemplifying five clinical cases, focusing on diseases that could benefit targeted therapy.

What's Sex Got to Do With COVID-19? Gender-Based Differences in the Host Immune Response to Coronaviruses

The novel severe acute respiratory syndrome coronavirus 2, the cause of the coronavirus disease 2019 (COVID-19) pandemic, has ravaged the world, with over 22 million total cases and over 770,000 deaths worldwide as of August 18, 2020. While the elderly are most severely affected, implicating an age bias, a striking factor in the demographics of this deadly disease is the gender bias, with higher numbers of cases, greater disease severity, and higher death rates among men than women across the lifespan. While pre-existing comorbidities and social, behavioral, and lifestyle factors contribute to this bias, biological factors underlying the host immune response may be crucial contributors. Women mount stronger immune responses to infections and vaccinations and outlive men. Sex-based biological factors underlying the immune response are therefore important determinants of susceptibility to infections, disease outcomes, and mortality. Despite this, gender is a profoundly understudied and often overlooked variable in research related to the immune response and infectious diseases, and it is largely ignored in drug and vaccine clinical trials. Understanding these factors will not only help better understand the pathogenesis of COVID-19, but it will also guide the design of effective therapies and vaccine strategies for gender-based personalized medicine. This review focuses on sex-based differences in genes, sex hormones, and the microbiome underlying the host immune response and their relevance to infections with a focus on coronaviruses.

T Cell Impairment Is Predictive for a Severe Clinical Course in NEMO Deficiency

PURPOSE

NEMO-deficient patients present with variable degrees of immunodeficiency. Accordingly, treatment ranges from antibiotic prophylaxis and/or IgG-substitution to allogenic hematopoietic stem cell transplantation (HSCT). The correct estimation of the immunodeficiency is essential to avoid over- as well as under-treatment. We compare the immunological phenotype of a NEMO-deficient patient with a newly-described splice site mutation that causes truncation of the NEMO zinc-finger (ZF) domain and a severe clinical course with the immunological phenotype of three NEMO-deficient patients with missense mutations and milder clinical courses and all previously published patients.

METHODS

Lymphocyte subsets, proliferation, and intracellular NEMO-expression were assessed by FACS. NF-κB signal transduction was determined by measuring IκBα-degradation and the production of cytokines upon stimulation with TNF-α, IL-1β, and TLR-agonists in immortalized fibroblasts and whole blood, respectively.

RESULTS

The patient with truncated ZF-domain of NEMO showed low levels of IgM and IgG, reduced class-switched memory B cells, almost complete skewing towards naïve CD45RA+ T cells, impaired T cell proliferation as well as cytokine production upon stimulation with TNF-α, IL-1β, and TLR-agonists. He suffered from severe infections (sepsis, pneumonia, osteomyelitis) during infancy. In contrast, three patients with missense mutations in IKBKG presented neither skewing of T cells towards naïvety nor impaired T cell proliferation. They are stable on prophylactic IgG-substitution or even off any prophylactic treatment.

CONCLUSION

The loss of the ZF-domain and the impaired T cell proliferation accompanied by almost complete persistence of naïve T cells despite severe infections are suggestive for a profound immunodeficiency. Allogenic HSCT should be considered early for these patients before chronic sequelae occur.

Absence of an osteopetrosis phenotype in IKBKG (NEMO) mutation-positive women: A case-control study

BACKGROUND

NF-κB essential modulator (NEMO), encoded by IKBKG, is necessary for activation of the ubiquitous transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Animal studies suggest NEMO is required for NF-κB mediated bone homeostasis, but this has not been thoroughly studied in humans. IKBKG loss-of-function mutation causes incontinentia pigmenti (IP), a rare X-linked disease featuring linear hypopigmentation, alopecia, hypodontia, and immunodeficiency. Single case reports describe osteopetrosis (OPT) in boys carrying hypomorphic IKBKG mutations.

METHOD

We studied the bone phenotype in women with IP with evaluation of radiographs of the spine and non-dominant arm and leg; lumbar spine and femoral neck aBMD using DXA; μ-CT and histomorphometry of trans-iliac crest biopsy specimens; bone turnover markers; and cellular phenotype in bone marrow skeletal (stromal) stem cells (BM-MSCs) in a cross-sectional, age-, sex-, and BMI-matched case-control study. X-chromosome inactivation was measured in blood leucocytes and BM-MSCs using a PCR method with methylation of HpaII sites. NF-κB activity was quantitated in BM-MSCs using a luciferase NF-κB reporter assay.

RESULTS

Seven Caucasian women with IP (age: 24-67 years and BMI: 20.0-35.2 kg/m²) and IKBKG mutation (del exon 4-10 (n = 4); c.460C>T (n = 3)) were compared to matched controls. The IKBKG mutation carriers had extremely skewed X-inactivation (>90:10%) in blood, but not in BM-MSCs. NF-κB activity was lower in BM-MSCs from IKBKG mutation carriers (n = 5) compared to controls (3094 ± 679 vs. 5422 ± 1038/μg protein, p < 0.01). However, no differences were identified on skeletal radiographics, aBMD, μ-architecture of the iliac crest, or bone turnover markers. The IKBKG mutation carriers had a 1.7-fold greater extent of eroded surfaces relative to osteoid surfaces (p < 0.01), and a 2.0-fold greater proportion of arrested reversal surface relative to active reversal surface (p < 0.01).

CONCLUSION

Unlike mutation-positive males, the IKBKG mutation-positive women did not manifest OPT.

Primary immunodeficiencies associated with eosinophilia

Background

Eosinophilia is not an uncommon clinical finding. However, diagnosis of its cause can be a dilemma once common culprits, namely infection, allergy and reactive causes are excluded. Primary immunodeficiency disorders (PID) are among known differentials of eosinophilia. However, the list of PIDs typically reported with eosinophilia is small and the literature lacks an inclusive list of PIDs which have been reported with eosinophilia. This motivated us to review the literature for all PIDs which have been described to have elevated eosinophils as this may contribute to an earlier diagnosis of PID and further the understanding of eosinophilia.

Methods

A retrospective PubMed, and Google Scholar search using the terms “eosinophilia” and “every individual PID” as classified by Expert Committee of the International Union of Immunological Societies with the limit of the English language was performed. Results were assessed to capture case(s) which reported eosinophilia in the context of PID conditions. Absolute eosinophil counts (AEC) were retrieved from manuscripts whenever reported.

Results

In addition to the typical PID conditions described with eosinophilia, we document that MHC class II deficiency, CD3γ deficiency, STAT1 deficiency (AD form), Kostmann disease, cyclic neutropenia, TCRα deficiency, Papillon-Lefevre syndrome, CD40 deficiency, CD40L deficiency, anhidrotic ectodermal dysplasia with immune deficiency, ataxia-telangiectasia, common variable immunodeficiency disorders (CVID), Blau syndrome, CARD9 deficiency, neonatal onset multisystem inflammatory disease or chronic infantile neurologic cutaneous and articular syndrome (NOMID/CINCA), chronic granulomatous disease, MALT1 deficiency and Roifman syndrome have been noted to have elevated eosinophils. Severe eosinophilia (>5.0 × 10⁹/L) was reported in Omenn syndrome, Wiskott Aldrich syndrome, ADA deficiency, autoimmune lymphoproliferative syndrome, immunodysregulation polyendocrinopathy enteropathy X-linked, STAT3 deficiency, DOCK8 deficiency, CD40 deficiency, MHC II deficiency, Kostmann disease, Papillon-Lefevre syndrome, and CVID.

Conclusions

This literature review shows that there is an extensive list of PIDs which have been reported with eosinophilia. This list helps clinicians to consider an extended differential diagnoses when tasked with exclusion of PID as a cause for eosinophilia.

Electronic supplementary material

The online version of this article (doi:10.1186/s13223-016-0130-4) contains supplementary material, which is available to authorized users.

Transplantation from a symptomatic carrier sister restores host defenses but does not prevent colitis in NEMO deficiency

NF-κB essential modulator (NEMO) deficiency causes ectodermal dysplasia with immunodeficiency in males, while manifesting as incontinentia pigmenti in heterozygous females. We report a family with NEMO deficiency, in which a female carrier displayed skewed X-inactivation favoring the mutant NEMO allele associated with symptoms of Behçet's disease. Hematopoietic stem cell transplantation of an affected boy from this donor reconstituted an immune system with retained skewed X-inactivation. After transplantation no more severe infections occurred, indicating that an active wild-type NEMO allele in only 10% of immune cells restores host defense. Yet he developed inflammatory bowel disease (IBD). While gut infiltrating immune cells stained strongly for nuclear p65 indicating restored NEMO function, this was not the case in intestinal epithelial cells - in contrast to cells from conventional IBD patients. These results extend murine observations that epithelial NEMO-deficiency suffices to cause IBD. High anti-TNF doses controlled the intestinal inflammation and symptoms of Behçet's disease.

[Incontinentia pigmenti with defect in cellular immunity]

BACKGROUND

Incontinentia pigmenti is a rare, X-linked genetic disease and affects all ectoderm-derived tissues such as skin, appendages, eyes, teeth and central nervous system as well as disorders of varying degree of cellular immunity characterized by decreasing melanin in the epidermis and increase in the dermis. When the condition occurs in males, it is lethal.

CASE REPORT

We present the case of a 2-month-old infant with severe incontinentia pigmenti confirmed by histological examination of skin biopsy. The condition evolved with severe neurological disorders and seizures along with severe cellular immune deficiency, which affected the development of severe infections and caused the death of the patient.

CONCLUSIONS

The importance of early clinical diagnosis is highlighted along with the importance of multidisciplinary management of neurological disorders and infectious complications.

VARIABLE EXPRESSION OF RETINOPATHY IN A PEDIGREE OF PATIENTS WITH INCONTINENTIA PIGMENTI

PURPOSE

To characterize the varied ocular manifestations of incontinentia pigmenti (IP) in a large pedigree.

METHODS

All available members of the kindred who were affected with IP were examined with ophthalmoscopy, wide-field color photos, and fluorescein angiography.

RESULTS

Individual family members demonstrated variable expression of retinopathy characteristic of IP. There was severe retinopathy in two eyes: one associated with concurrent persistent fetal vasculature and another with rhegmatogenous retinal detachment. Another individual with biopsy-confirmed IP demonstrated no retinopathy in either eye. When present, retinopathy manifested asymmetrically between eyes of the same individual.

CONCLUSION

Cutaneous manifestations of IP are irregular and nonuniform due to lyonization of the X chromosome. In this report, we identify asymmetric retinal disease between eyes in the same individual and variable retinal findings within the kindred. These differences may be explained by random inactivation of the X chromosome or other epigenetic modifications.

Importance of long-time simulations for rare event sampling in zinc finger proteins

Molecular dynamics (MD) simulation methods have seen significant improvement since their inception in the late 1950s. Constraints of simulation size and duration that once impeded the field have lessened with the advent of better algorithms, faster processors, and parallel computing. With newer techniques and hardware available, MD simulations of more biologically relevant timescales can now sample a broader range of conformational and dynamical changes including rare events. One concern in the literature has been under which circumstances it is sufficient to perform many shorter timescale simulations and under which circumstances fewer longer simulations are necessary. Herein, our simulations of the zinc finger NEMO (2JVX) using multiple simulations of length 15, 30, 1000, and 3000 ns are analyzed to provide clarity on this point.

Understanding the Complex Circuitry of lncRNAs at the X-inactivation Center and Its Implications in Disease Conditions

Balanced gene expression is a high priority in order to maintain optimal functioning since alterations and variations could result in acute consequences. X chromosome inactivation (X-inactivation) is one such strategy utilized by mammalian species to silence the extra X chromosome in females to uphold a similar level of expression between the two sexes. A functionally versatile class of molecules called long noncoding RNA (lncRNA) has emerged as key regulators of gene expression and plays important roles during development. An lncRNA that is indispensable for X-inactivation is X-inactive specific transcript (Xist), which induces a repressive epigenetic landscape and creates the inactive X chromosome (Xi). With recent advents in the field of X-inactivation, novel positive and negative lncRNA regulators of Xist such as Jpx and Tsix, respectively, have broadened the regulatory network of X-inactivation. Xist expression failure or dysregulation has been implicated in producing developmental anomalies and disease states. Subsequently, reactivation of the Xi at a later stage of development has also been associated with certain tumors. With the recent influx of information about lncRNA biology and advancements in methods to probe lncRNA, we can now attempt to understand this complex network of Xist regulation in development and disease. It has become clear that the presence of an extra set of genes could be fatal for the organism. Only by understanding the precise ways in which lncRNAs function can treatments be developed to bring aberrations under control. This chapter summarizes our current understanding and knowledge with regard to how lncRNAs are orchestrated at the X-inactivation center (Xic), with a special focus on how genetic diseases come about as a consequence of lncRNA dysregulation.

Systematic review of central nervous system anomalies in incontinentia pigmenti

The objective of this study was to present a systematic review of the central nervous system (CNS) types of anomalies and to consider the possibility to include CNS anomalies in Incontinentia pigmenti (IP) criteria. The analyzed literature data from 1,393 IP cases were from the period 1993–2012. CNS anomalies were diagnosed for 30.44% of the investigated IP patients. The total number of CNS types of anomalies per patient was 1.62. In the present study there was no significantly higher number of anomalies per patient in females than males. The most frequent CNS types of anomalies were seizures, motor impairment, mental retardation, and microcephaly. The most frequently registered CNS lesions found using brain imaging methods were brain infarcts or necrosis, brain atrophies, and corpus callosum lesions. IKBKG exon 4–10 deletion was present in 86.00% of genetically confirmed IP patients. The frequency of CNS anomalies, similar to the frequency of retinal anomalies in IP patients, concurrent with their severity, supports their recognition in the list of IP minor criteria.

Ectodermal dysplasias: a clinical and molecular review

The ectodermal dysplasias are a large group of hereditary disorders characterized by alterations of structures of ectodermal origin. Although some syndromes can have specific features, many of them share common clinical characteristics. Two main groups of ectodermal dysplasias can be distinguished. One group is characterized by aplasia or hypoplasia of ectodermal tissues, which fail to develop and differentiate because of a lack of reciprocal signaling between ectoderm and mesoderm, the other has palmoplantar keratoderma as its most striking feature, with additional manifestations when other highly specialized epithelia are also involved. In recent decades, the genes responsible for at least 30 different types of ectodermal dysplasia have been identified, throwing light on the pathogenic mechanisms involved and their correlation with clinical findings.

Serial cytokine expressions in infants with incontinentia pigmenti

NF-κB dysfunction resulting from NEMO (NF-kappaB essential modulator) mutation can lead to significant alterations in cytokine production. However, little is known about changes in the expression of downstream molecules in patients with incontinentia pigmenti (IP). We aim to investigate serial cytokine expressions during the first 2 years of life in young infants with IP, the period in which skin inflammation and morphological changes are most significant. Gene analysis and X-inactivation test were performed for the two neonates with IP. Peripheral mononuclear cells were obtained after birth and successively at 6-month interval up to the age of two years. Levels of TNF-α and IL-6 were analyzed with ELISA before and after stimulating with Toll-like receptor ligands. The result showed the male IP patient had normal NEMO allele. His cytokine level, although initially lower, had returned to a level comparable with those of controls at 12 months of age. The female infant had mutated NEMO gene. Her baseline TNF-α level was significantly higher than those of the control subjects at birth and remained high by 6 months of age. All cytokine responses had decreased significantly by 2 years of age, the time in which all vesicular skin lesions had resolved. Both infants had normal serum immunoglobulin level and remained infection free during the follow up period. To our knowledge, this is the first report that demonstrates serial changes of cytokine profiles in humans with IP. This study showed that in the presence of NEMO mutation, alteration of cytokine production was remarkable during the first year of life, which may account for the prominent inflammatory changes in skin morphology.

Infectious diseases in patients with IRAK-4, MyD88, NEMO, or IκBα deficiency

Autosomal recessive IRAK-4 and MyD88 deficiencies predispose affected patients to recurrent invasive pyogenic bacterial infection. Both defects result in the selective impairment of cellular responses to Toll-like receptors (TLRs) other than TLR3 and of cellular responses to most interleukin-1 receptors (IL-1Rs), including IL-1R, IL-18R, and IL-33R. Hypomorphic mutations in the X-linked NEMO gene and hypermorphic mutations in the autosomal IKBA gene cause X-linked recessive and autosomal dominant anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) syndromes. Both of these defects impair NF-κB-mediated cellular responses to multiple receptors, including TLRs, IL-1Rs, and tumor necrosis factor receptors (TNF-Rs). They therefore confer a much broader predisposition to infections than that for IRAK-4 and MyD88 deficiencies. These disorders were initially thought to be rare but have now been diagnosed in over 170 patients worldwide. We review here the infectious diseases affecting patients with inborn errors of NF-κB-dependent TLR and IL-1R immunity.

NEMO is a key component of NF-κB- and IRF-3-dependent TLR3-mediated immunity to herpes simplex virus

BACKGROUND

Children with germline mutations in Toll-like receptor 3 (TLR3), UNC93B1, TNF receptor-associated factor 3, and signal transducer and activator of transcription 1 are prone to herpes simplex virus-1 encephalitis, owing to impaired TLR3-triggered, UNC-93B-dependent, IFN-α/β, and/or IFN-λ-mediated signal transducer and activator of transcription 1-dependent immunity.

OBJECTIVE

We explore here the molecular basis of the pathogenesis of herpes simplex encephalitis in a child with a hypomorphic mutation in nuclear factor-κB (NF-κB) essential modulator, which encodes the regulatory subunit of the inhibitor of the Iκβ kinase complex.

METHODS

The TLR3 signaling pathway was investigated in the patient's fibroblasts by analyses of IFN-β, IFN-λ, and IL-6 mRNA and protein levels, by quantitative PCR and ELISA, respectively, upon TLR3 stimulation (TLR3 agonists or TLR3-dependent viruses). NF-κB activation was assessed by electrophoretic mobility shift assay and interferon regulatory factor 3 dimerization on native gels after stimulation with a TLR3 agonist.

RESULTS

The patient's fibroblasts displayed impaired responses to TLR3 stimulation in terms of IFN-β, IFN-λ, and IL-6 production, owing to impaired activation of both NF-κB and IRF-3. Moreover, vesicular stomatitis virus, a potent IFN-inducer in human fibroblasts, and herpes simplex virus-1, induced only low levels of IFN-β and IFN-λ in the patient's fibroblasts, resulting in enhanced viral replication and cell death, as reported for UNC-93B-deficient fibroblasts.

CONCLUSION

Herpes simplex encephalitis may occur in patients carrying NF-κB essential modulator mutations, due to the impairment of NF-κB- and interferon regulatory factor 3-dependent-TLR3-mediated antiviral IFN production.

The common NF-κB essential modulator (NEMO) gene rearrangement in Korean patients with incontinentia pigmenti

Incontinentia pigmenti (IP) is a rare X-linked dominant disorder characterized by highly variable abnormalities of the skin, eyes and central nervous system. A mutation of the nuclear factor-κB essential modulator (NEMO) located at Xq28 is believed to play a role in pathogenesis and the mutation occurs mostly in female patients due to fatal consequence of the mutation in males in utero. This study was designed to identify the common NEMO rearrangement in four Korean patients with IP. Deletion of exons 4 to 10 in the NEMO, the most common mutation in IP patients, was detected in all of the patients by the use of long-range PCR analysis. This method enabled us to discriminate between NEMO and pseudogene rearrangements. Furthermore, all of the patients showed skewed XCI patterns, indicating pathogenicity of IP was due to cells carrying the mutant X chromosome. This is the first report of genetically confirmed cases of IP in Korea.

NEMO gene mutations in Chinese patients with incontinentia pigmenti

BACKGROUND/PURPOSE

Incontinentia pigmenti is a rare, X-linked, dominant genodermatosis affecting skin, teeth, eyes, and central nervous system. Symptoms are associated with mutations in the nuclear factor-kappa B essential modulator (NEMO) gene on chromosome Xq28. Here, a subpopulation of Chinese patients with incontinentia pigmenti were examined to investigate the frequency and pattern of NEMO mutations, and to analyze their clinical features.

METHODS

From January 1996 to August 2006, 52 participants (21 probands and 31 family members) were screened for symptoms of incontinentia pigmenti and NEMO gene mutations. We designed a NEMO-specific PCR primer, referred to as In2S, to detect a deletion of exon 4-10 of the NEMO gene, which represents the mutation most frequently associated with incontinentia pigmenti. For participants without this deletion, all exons were sequenced to screen for other NEMO mutations. In addition, the clinical manifestations and family histories of the participants were analyzed.

RESULTS

Exon 4-10 was deleted in 13 probands, and one proband had a novel point mutation (G549C) in exon 5 that converted a glutamine to a histidine. Seven probands (33%) had no mutation in any of the exons of the NEMO gene. One of four participants who presented with hyperpigmentation also had the exon 4-10 deletion. One patient had a positive family history before the study took place, but no NEMO mutation was identified in any of the family members. Remarkably, the mothers of three of the probands exhibited the exon 4-10 deletion; however, their clinical manifestations were subtle and unrecognizable.

CONCLUSION

Mutational analysis of the NEMO gene was helpful in diagnosing incontinentia pigmenti among participants with a nearly normal phenotype or an incomplete form of the disease that only caused hyperpigmentation symptoms.

Two male patients with incontinentia pigmenti

BACKGROUND

Incontinentia pigmenti (IP) is a rare, complex, X-linked genodermatosis in which skin changes are combined with defects of other organs. It appears almost exclusively in females and is usually lethal in men. It is estimated that according to the available reported cases, there have been approximately 900-1,200 affected individuals, out of which 60 males. The aim of the study was to report two additional individual male cases with IP.

CASE REPORTS

We discovered two male patients with IP according to standard IP diagnostic criteria. The diagnosis was made by a dermatologist and confirmed by cutaneous histopathology and ultrastructural analysis. The pedigrees, karyotype analyses and routine laboratory findings were made. Two male probands were the only ones with IP in their families, with no history of miscarriages. Both probands had normal karyotype. In one proband, acrocentric chromosomes of the group D had tendency of forming associations. Histopathological and ultrastructural skin analyses revealed findings typical for IP.

CONCLUSION

The detection of each male case is very valuable because of their rarity. Application of the standard diagnostic criteria is necessary for comparison and epidemiological analysis. Monitoring such probands allows a better determination of how genetic transmission occurs, and is important because of the different degrees of severity of IP.

Ocular anomalies in incontinentia pigmenti: Literature review and meta-analysis

Introduction. Incontinentia pigmenti (IP) is an X-linked genodermatosis in which skin changes are combined with dental, eye and central nervous system anomalies. Objective. The goal of the study was to analyze ocular findings, IP minor criteria in available literature concerning IP cases published until now. Methods. We have done meta-analysis of 1931 IP patients found in 302 references published until 2010. Comparison of data published for the 1906-1976 and 1976-2010 periods was made. The collected data were mainly frequencies of ocular anomalies. Chi-square test was used to compare observed frequencies with their expectations. Results. Of total number of IP patients, 1,227 were ophthalmologically investigated. In 449 such patients 972 eye anomalies were registered, 2.16 anomalies per patient. Proportion of ophthalmologically investigated IP patients in the period 1906-1975 (70%) was higher than corresponding proportion (60%) for the period 1976-2010. For 1906-2010 period 36.5% IP patients with eye anomalies were diagnosed. The number of amaurotic eyes per patient did not significantly differ for the two periods (p=0.50; >0.05). The total number of eye anomalies per patient significantly differed for the same periods (p=0.00005; <0.05). Retinal anomalies were most frequent in both periods. Conclusion. This study suggests that IP is far more frequent than anyone could estimate. We believe that this study, covering 1906-2010 period, gives more reliable information about ophthalmological findings in IP; considering them as severe anomalies. Early detection and treatment of ophthalmological, neurological etc. findings may prevent severe consequences that IP may cause.

Genetic deficiencies of innate immune signalling in human infectious disease

The type-1 cytokine (interleukin 12, interleukin 23, interferon gamma, interleukin 17) signalling pathway is triggered during infection by activation of phagocyte-expressed pattern-recognition receptors that recognise specific pathogen-associated molecular patterns. Triggering of this pathway results, among other things, in activation of microbicidal mechanisms in phagocytic cells. Individuals with a deficiency in one of the proteins in the pathway are unusually susceptible to otherwise poorly pathogenic, mostly environmental, mycobacteria and salmonellae. Individuals with deficiencies in other innate immune signalling proteins show unusual susceptibility to pathogens other than mycobacteria or salmonellae. We discuss recent insights into key molecules involved in type-1 cytokine signalling pathways and provide an update on the molecular genetic defects underlying mendelian susceptibility to mycobacterial disease. We also discuss deficiencies in the innate immune signalling proteins that lead to susceptibility to other pathogens. Knowledge of innate immune signalling has allowed the identification of defects in such patients. However, some patients have enhanced susceptibility to pathogens even though no mutations have been found in the candidate genes identified thus far. Whereas a few patients might have autoantibodies against type-1 cytokines, others might harbour mutations in new genes and pathways that still need to be identified.

Genetic syndromic immunodeficiencies with antibody defects

This article reviews the major syndromic immunodeficiencies with significant antibody defects, many of which may require intravenous immunogammaglobulin therapy. The authors define syndromic immunodeficiency as an illness associated with a characteristic group of phenotypic abnormalities or laboratory features that comprise a recognizable syndrome. Many are familial with a defined inheritance pattern. Immunodeficiency may not be a major part of the illness and may not be present in all patients; thus, these conditions differ from primary immunodeficiency syndromes, in which immune abnormalities are a consistent and prominent feature of their disease.

Hypomorphic nuclear factor-kappaB essential modulator mutation database and reconstitution system identifies phenotypic and immunologic diversity

BACKGROUND

Human hypomorphic nuclear factor-kappaB essential modulator (NEMO) mutations cause diverse clinical and immunologic phenotypes, but understanding of their scope and mechanistic links to immune function and genotype is incomplete.

OBJECTIVE

We created and analyzed a database of hypomorphic NEMO mutations to determine the spectrum of phenotypes and their associated genotypes and sought to establish a standardized NEMO reconstitution system to obtain mechanistic insights.

METHODS

Phenotypes of 72 individuals with NEMO mutations were compiled. NEMO L153R and C417R were investigated further in a reconstitution system. TNF-alpha or Toll-like receptor (TLR)-5 signals were evaluated for nuclear factor-kappaB activation, programmed cell death, and A20 gene expression.

RESULTS

Thirty-two different mutations were identified; 53% affect the zinc finger domain. Seventy-seven percent were associated with ectodermal dysplasia, 86% with serious pyogenic infection, 39% with mycobacterial infection, 19% with serious viral infection, and 23% with inflammatory diseases. Thirty-six percent of individuals died at a mean age of 6.4 years. CD40, IL-1, TNF-alpha, TLR, and T-cell receptor signals were impaired in 15 of 16 (94%), 6 of 7 (86%), 9 of 11 (82%), 9 of 14 (64%), and 7 of 18 (39%), respectively. Hypomorphism-reconstituted NEMO-deficient cells demonstrated partial restoration of NEMO functions. Although both L153R and C417R impaired TLR and TNF-alpha-induced NF-kappaB activation, L153R also increased TNF-alpha-induced programmed cell death with decreased A20 expression.

CONCLUSION

Distinct NEMO hypomorphs define specific disease and genetic characteristics. A reconstitution system can identify attributes of hypomorphisms independent of an individual's genetic background. Apoptosis susceptibility in L153R reconstituted cells defines a specific phenotype of this mutation that likely contributes to the excessive inflammation with which it is clinically associated.

X-chromosome inactivation and skin disease

X-chromosome inactivation (XCI) is the process in which females transcriptionally silence one of their two X chromosomes in early embryonic development, equalizing X chromosome gene expression between males and females. XCI depends on a gene called XIST, a functional RNA molecule that does not code for a protein. Recent studies indicate abundant intergenic transcription and nonprotein coding RNAs in the human genome, which are suspected to function in modulating gene expression. XCI may therefore serve as a useful model to learn and understand the potential function of these elements, as well as their effects on human disease. Here, we review the genetic and molecular basis of XCI and describe how the mechanistics of this process lead to the phenotypes of X-linked skin diseases, most notably in the pattern of lines, swirls, and whorls first noted by the dermatologist Alfred Blaschko. We suggest that XCI, and other epigenetic phenomena, will continue to impact our understanding of the genetic mechanisms of disease.Journal of Investigative Dermatology (2008) 128, 2753-2759; doi:10.1038/jid.2008.145; published online 29 May 2008.

Alterations of the IKBKG locus and diseases: an update and a report of 13 novel mutations

Mutations in the inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase gamma (IKBKG), also called nuclear factor-kappaB (NF-kB) essential modulator (NEMO), gene are the most common single cause of incontinentia pigmenti (IP) in females and anhydrotic ectodermal dysplasia with immunodeficiency (EDA-ID) in males. The IKBKG gene, located in the Xq28 chromosomal region, encodes for the regulatory subunit of the inhibitor of kappaB (IkB) kinase (IKK) complex required for the activation of the NF-kB pathway. Therefore, the remarkably heterogeneous and often severe clinical presentation reported in IP is due to the pleiotropic role of this signaling transcription pathway. A recurrent exon 4_10 genomic rearrangement in the IKBKG gene accounts for 60 to 80% of IP-causing mutations. Besides the IKBKG rearrangement found in IP females (which is lethal in males), a total of 69 different small mutations (missense, frameshift, nonsense, and splice-site mutations) have been reported, including 13 novel ones in this work. The updated distribution of all the IP- and EDA-ID-causing mutations along the IKBKG gene highlights a secondary hotspot mutation in exon 10, which contains only 11% of the protein. Furthermore, familial inheritance analysis revealed an unexpectedly high incidence of sporadic cases (>65%). The sum of the observations can aid both in determining the molecular basis of IP and EDA-ID allelic diseases, and in genetic counseling in affected families.

Mutations in the zinc finger domain of IKK gamma block the activation of NF-kappa B and the induction of IL-2 in stimulated T lymphocytes

Mutations in the zinc finger of I kappa B kinase gamma (IKK gamma) are associated with hypohidrotic ectodermal dysplasia-immune deficiency (HED-ID) in which the major immune deficit is the inability to switch Ab heavy chain class. However, the pathophysiologic role of the mutations has not been fully delineated. Since help from activated Th cells is essential in Ab class switching, we sought to examine how these mutations affect T cell activation. Using a human T cell line that was null for IKK gamma, we generated cells stably expressing two of the reported mutations, namely, D406V and C417R. Cells expressing either mutation failed to induce IL-2 following stimulation with PMA/ionomycin while the induction of IL-2 was restored in cells reconstituted with the wild type IKK gamma. The lack of IL-2 upregulation correlated with the lack of NF-kappaB activation as evidenced by the inability to induce I kappa B alpha degradation, NF-kappaB binding to DNA and the expression of a reporter gene. However, both mutations did not prevent the incorporation of IKK gamma into the IKK complex and, interestingly, the induced phosphorylation of I kappa B alpha at S32 and S36 and its subsequent ubiquitination were not affected. The suppression of IL-2 induction was solely due to the inhibition of NF-kappaB activation as the mutations did not impair the activation of AP-1 and NFAT. Our data indicated that the failure of T cells to undergo activation in response to TCR stimuli may play a role in the pathophysiology of HED-ID and also showed that IKK gamma has a role in the post-ubiquitination processing of I kappa B alpha.

NF-kappaB and inflammation in genetic disease

By responding to pro-inflammatory cytokines, such as IL-1beta and TNF-alpha, and controlling itself the expression of numerous mediators of inflammation, NF-kappaB plays a pivotal role in controlling the proper sequence of events characterizing the inflammation process. Although excessive NF-kappaB activation is often associated with inflammatory signs in many different tissues, impaired NF-kappaB activation can also generate inflammation. This is the case in humans suffering from the genetic disease incontinentia pigmenti that exhibit severe skin inflammation. Identifying the molecular basis of this pathology, mutations affecting the gene coding for NEMO, has allowed production of mouse models for investigating the disease. Their characterization supports the view that a very tight positive and negative regulation of the NF-kappaB signaling pathway is required in vivo to ensure not only a fine-tuned response to injury or infection but also to maintain tissue homeostasis.

NF-κB-related genetic diseases

The recent identification of genetic diseases (incontinentia pigmenti, anhidrotic ectodermal dysplasia with immunodeficiency and cylindromatosis) resulting from mutations affecting components of the nuclear factor-kappaB (NF-kappaB) signaling pathway provides a unique opportunity to understand the function of NF-kappaB in vivo. Besides confirming the importance of NF-kappaB in innate and acquired immunity or bone mass control, analysis of these diseases has uncovered new critical roles played by this transcription factor in the development and homeostasis of the epidermis and the proper function of lymphatic vessels. In addition, the identified mutations will help understanding at the molecular level how NF-kappaB is activated in response to cell stimulation.