Lrig1-expressing epidermal progenitors require SCD1 to maintain the dermal papilla niche

Niche cells are widely known to regulate stem/progenitor cells in many mammalian tissues. In the hair, dermal papilla niche cells are well accepted to regulate hair stem/progenitor cells. However, how niche cells themselves are maintained is largely unknown. We present evidence implicating hair matrix progenitors and the lipid modifying enzyme, Stearoyl CoA Desaturase 1, in the regulation of the dermal papilla niche during the anagen-catagen transition of the mouse hair cycle. Our data suggest that this takes place via autocrine Wnt signalling and paracrine Hedgehog signalling. To our knowledge, this is the first report demonstrating a potential role for matrix progenitor cells in maintaining the dermal papilla niche.

Familial multiple discoid fibromas is linked to a locus on chromosome 5 including the FNIP1 gene

Previously, we reported a series of families presenting with trichodiscomas, inherited in an autosomal dominant pattern. The phenotype was named familial multiple discoid fibromas (FMDF). The genetic cause of FMDF remained unknown so far. Trichodiscomas are skin lesions previously reported to be part of the same spectrum as the fibrofolliculoma observed in Birt-Hogg-Dubé syndrome (BHD), an inherited disease caused by pathogenic variants in the FLCN gene. Given the clinical and histological differences with BHD and the exclusion of linkage with the FLCN locus, the phenotype was concluded to be distinct from BHD. We performed extensive clinical evaluations and genetic testing in ten families with FMDF. We identified a FNIP1 frameshift variant in nine families and genealogical studies showed common ancestry for eight families. Using whole exome sequencing, we identified six additional rare variants in the haplotype surrounding FNIP1, including a missense variant in the PDGFRB gene that was found to be present in all tested patients with FMDF. Genome-wide linkage analysis showed that the locus on chromosome 5 including FNIP1 was the only region reaching the maximal possible LOD score. We concluded that FMDF is linked to a haplotype on chromosome 5. Additional evaluations in families with FMDF are required to unravel the exact genetic cause underlying the phenotype. When evaluating patients with multiple trichodisomas without a pathogenic variant in the FLCN gene, further genetic testing is warranted and can include analysis of the haplotype on chromosome 5.

Germline intergenic duplications at Xq26.1 underlie Bazex-Dupré-Christol basal cell carcinoma susceptibility syndrome

BACKGROUND

Bazex-Dupré-Christol syndrome (BDCS; MIM301845) is a rare X-linked dominant genodermatosis characterized by follicular atrophoderma, congenital hypotrichosis and multiple basal cell carcinomas (BCCs). Previous studies have linked BDCS to an 11·4-Mb interval on chromosome Xq25-q27.1. However, the genetic mechanism of BDCS remains an open question.

OBJECTIVES

To investigate the genetic aetiology and molecular mechanisms underlying BDCS.

METHODS

We ascertained multiple individuals from eight unrelated families affected with BDCS (F1-F8). Whole-exome (F1 and F2) and genome sequencing (F3) were performed to identify putative disease-causing variants within the linkage region. Array comparative genomic hybridization and quantitative polymerase chain reaction (PCR) were used to explore copy number variations, followed by long-range gap PCR and Sanger sequencing to amplify the duplication junctions and to define the head-tail junctions. Hi-C was performed on dermal fibroblasts from two affected individuals with BDCS and one control. Public datasets and tools were used to identify regulatory elements and transcription factor binding sites within the minimal duplicated region. Immunofluorescence was performed in hair follicles, BCCs and trichoepitheliomas from patients with BDCS and sporadic BCCs. The ACTRT1 variant c.547dup (p.Met183Asnfs*17), previously proposed to cause BDCS, was evaluated with t allele frequency calculator.

RESULTS

In eight families with BDCS, we identified overlapping 18-135-kb duplications (six inherited and two de novo) at Xq26.1, flanked by ARHGAP36 and IGSF1. Hi-C showed that the duplications did not affect the topologically associated domain, but may alter the interactions between flanking genes and putative enhancers located in the minimal duplicated region. We detected ARHGAP36 expression near the control hair follicular stem cell compartment, and found increased ARHGAP36 levels in hair follicles in telogen, in BCCs and in trichoepitheliomas from patients with BDCS. ARHGAP36 was also detected in sporadic BCCs from individuals without BDCS. Our modelling showed the predicted maximum tolerated minor allele frequency of ACTRT1 variants in control populations to be orders of magnitude higher than expected for a high-penetrant ultra-rare disorder, suggesting loss of function of ACTRT1 variants to be an unlikely cause for BDCS.

CONCLUSIONS

Noncoding Xq26.1 duplications cause BDCS. The BDCS duplications most likely lead to dysregulation of ARHGAP36. ARHGAP36 is a potential therapeutic target for both inherited and sporadic BCCs. What is already known about this topic? Bazex-Dupré-Christol syndrome (BDCS) is a rare X-linked basal cell carcinoma susceptibility syndrome linked to an 11·4-Mb interval on chromosome Xq25-q27.1. Loss-of-function variants in ACTRT1 and its regulatory elements were suggested to cause BDCS. What does this study add? BDCS is caused by small tandem noncoding intergenic duplications at chromosome Xq26.1. The Xq26.1 BDCS duplications likely dysregulate ARHGAP36, the flanking centromeric gene. ACTRT1 loss-of-function variants are unlikely to cause BDCS. What is the translational message? This study provides the basis for accurate genetic testing for BDCS, which will aid precise diagnosis and appropriate surveillance and clinical management. ARHGAP36 may be a novel therapeutic target for all forms of sporadic basal cell carcinomas.

Combined germline pathogenic variants in FLCN and TP53 are associated with early onset renal cell carcinoma and brain tumors

BACKGROUND

We present a family consisting of a father and his two children with an exceptional phenotype of childhood renal cell carcinoma and brain tumors. Extensive genetic testing revealed two inherited tumor predisposition syndromes in all three family members: Birt-Hogg-Dubé syndrome and Li-Fraumeni syndrome. The corresponding genes (FLCN and TP53) are both located on the short arm of chromosome 17.

METHODS

We describe the phenotype and performed single nucleotide polymorphism (SNP)-based loss of heterozygosity (LOH) analysis of the tumors.

RESULTS

All examined tumors showed somatic loss of the wild-type alleles of both FLCN and TP53.

CONCLUSIONS

We hypothesize that a synergistic effect of both mutations caused the unusual phenotype of childhood renal cell carcinoma in this family. This family emphasizes the importance of further genetic testing if a tumor develops at an unexpected young age in an inherited cancer predisposition syndrome.

Comment on Balsamo et al.: Birt-Hogg-Dubé syndrome with simultaneous hyperplastic polyposis of the gastrointestinal tract: case report and review of the literature

The publication by Balsamo and colleagues describes a patient with Birt-Hogg-Dubé syndrome and hyperplastic polyposis throughout the gastro-intestinal tract. We question whether the diagnosis of BHD in this patient was justified. Using the previously proposed diagnostic criteria for establishing the diagnosis of BHD as a guideline, we systematically describe our concerns. In our opinion, the patient described by Balsamo and colleagues does not meet any of the proposed major and minor criteria for the diagnosis of Birt-Hogg-Dubé syndrome. Therefore, we believe that it is not justified to suggest a possible association between hyperplastic polyposis and Birt-Hogg-Dubé syndrome based on this patient, even though a higher risk for colorectal polyposis in Birt-Hogg-Dubé syndrome has not been excluded so far.

Huriez syndrome: Additional pathogenic variants supporting allelism to SMARCAD syndrome

Huriez syndrome (HRZ, OMIM181600) is a rare genodermatosis characterized by scleroatrophic hands and feet, hypoplastic nails, palmoplantar keratoderma, and predisposition to cutaneous squamous cell carcinoma (cSCC). We report herein three HRZ families from Croatia, the Netherlands, and Germany. Deep sequencing followed by Sanger validation, confirmed the presence of germline causative SMARCAD1 heterozygous pathogenic variants. All seven HRZ patients displayed hypohidrosis, adermatoglyphia, and one patient developed cSCC at 32 years of age. Two novel monoallelic germline mutations were identified which are predicted to disrupt the first exon-intron boundary of the skin-specific SMARCAD1 isoform. On the basis of phenotypic and genotypic convergence with Adermatoglyphia (OMIM136000) and Basan syndrome (OMIM129200), our results lend credence to the notion that these three Mendelian disorders are allelic. We propose adding Huriez syndrome to the previously suggested SMARCAD syndrome designation, which was originally invoked to describe the spectrum of monogenic disorders between Adermatoglyphia and Basan syndrome.

ABERRANT WNT SIGNALING INDUCES COMEDO-LIKE CHANGES IN THE MURINE UPPER HAIR FOLLICLE

Stem cell proliferation and differentiation must be carefully balanced to support tissue maintenance and growth. Defective stem cell regulation may underpin diseases in many organs, including the skin. Lrig1-expressing stem cells residing in the HF junction zone (JZ) support sebaceous gland (SG) homeostasis. An emerging hypothesis from observations in both mouse and human holds that imbalances in key stem cell regulatory pathways such as Wnt signaling may lead to abnormal fate determination of these Lrig1^+ve cells. They accumulate and form cystic structures in the JZ that are similar to the comedones found in human acne. To test the possible involvement of Wnt signals in this scenario, we used the Lrig1-CreERT2 mouse line to modulate Wnt signaling in JZ stem cells. We observed that persistent activation of Wnt signaling leads to JZ cyst formation with associated SG atrophy. The cysts strongly express stem cell markers and can be partially reduced by all-trans retinoic acid treatment as well as by Hedgehog signaling inhibition. Conversely, loss of Wnt signaling leads to enlargement of JZ, infundibulum and SGs. These data implicate abnormal Wnt signaling in the generation of mouse pathologies that resemble human acne and respond to acne treatments.

Teledermatology in Primary Care in Singapore: Experiences of Family Doctors and Specialists

Most teledermatology studies focus on patients’ satisfaction; fewer focus on the experiences of healthcare professionals. This qualitative study explored healthcare professionals’ perceptions of teledermatology used for linking public primary care clinics with the specialist dermatology centre in Singapore. Semistructured in-depth interviews were conducted with 25 family physicians and dermatologists. Six themes were identified: satisfaction with the service; perceived patient benefits; rationale for introducing teledermatology; educational impact; challenges of virtual consultations; and desirable service refinements for the future. Family physicians and dermatologists were positive about the service, but highlighted a need to streamline referral processes and improve the quality of transmitted images. Reduced need for referral to the specialist centre could be achieved by expanding the polyclinic’s pharmacopoeia and treatment modalities. This study highlights the benefits of telemedicine for patient, professionals, and healthcare organizations, and these are reassuring given the widespread and rapid introduction of telemedicine through necessity during the COVID-19 pandemic.

Cutibacterium acnes: Much ado about maybe nothing much

Cutibacterium acnes (also known as Propionibacterium acnes) has long been implicated in the pathogenesis of acne, inspiring both therapeutic and personal care approaches aiming to control the disease by controlling the bacterium. The purported association has made people with acne feel dirty and led to the-at times excessive-use of cleansers, antiseptics and antibiotics for the condition. However, recent evidence seems to weaken the case for C. acnes' involvement. New genetics and molecular biology findings strongly suggest that abnormal differentiation of sebaceous progenitor cells causes comedones, the primary lesions in acne. Comodegenesis is initiated by androgens and is unlikely to be triggered by C. acnes, which probably doesn't affect sebaceous differentiation. Is there still a place for it in this understanding of acne? It is necessary to critically address this question because it has consequences for treatment. Antibiotic use for acne noticeably contributes to microbial drug resistance, which we can ill afford. In this Viewpoint, we explore if and how C. acnes (still) fits into the developing view on acne. We also briefly discuss the implications for therapy in the light of antibiotic resistance and the need for more targeted therapies.

The novel zebrafish model pretzel demonstrates a central role for SH3PXD2B in defective collagen remodelling and fibrosis in Frank-Ter Haar syndrome

Frank-Ter Haar syndrome (FTHS, MIM #249420) is a rare skeletal dysplasia within the defective collagen remodelling spectrum (DECORS), which is characterised by craniofacial abnormalities, skeletal malformations and fibrotic soft tissues changes including dermal fibrosis and joint contractures. FTHS is caused by homozygous or compound heterozygous loss-of-function mutation or deletion of SH3PXD2B (Src homology 3 and Phox homology domain-containing protein 2B; MIM #613293). SH3PXD2B encodes an adaptor protein with the same name, which is required for full functionality of podosomes, specialised membrane structures involved in extracellular matrix (ECM) remodelling. The pathogenesis of DECORS is still incompletely understood and, as a result, therapeutic options are limited. We previously generated an mmp14a/b knockout zebrafish and demonstrated that it primarily mimics the DECORS-related bone abnormalities. Here, we present a novel sh3pxd2b mutant zebrafish, pretzel, which primarily reflects the DECORS-related dermal fibrosis and contractures. In addition to relatively mild skeletal abnormalities, pretzel mutants develop dermal and musculoskeletal fibrosis, contraction of which seems to underlie grotesque deformations that include kyphoscoliosis, abdominal constriction and lateral folding. The discrepancy in phenotypes between mmp14a/b and sh3pxd2b mutants suggests that in fish, as opposed to humans, there are differences in spatiotemporal dependence of ECM remodelling on either sh3pxd2b or mmp14a/b The pretzel model presented here can be used to further delineate the underlying mechanism of the fibrosis observed in DECORS, as well as screening and subsequent development of novel drugs targeting DECORS-related fibrosis.This paper has an associated First Person interview with the first author of the article.

Neuroendocrinology and neurobiology of sebaceous glands

The nervous system communicates with peripheral tissues through nerve fibres and the systemic release of hypothalamic and pituitary neurohormones. Communication between the nervous system and the largest human organ, skin, has traditionally received little attention. In particular, the neuro-regulation of sebaceous glands (SGs), a major skin appendage, is rarely considered. Yet, it is clear that the SG is under stringent pituitary control, and forms a fascinating, clinically relevant peripheral target organ in which to study the neuroendocrine and neural regulation of epithelia. Sebum, the major secretory product of the SG, is composed of a complex mixture of lipids resulting from the holocrine secretion of specialised epithelial cells (sebocytes). It is indicative of a role of the neuroendocrine system in SG function that excess circulating levels of growth hormone, thyroxine or prolactin result in increased sebum production (seborrhoea). Conversely, growth hormone deficiency, hypothyroidism, and adrenal insufficiency result in reduced sebum production and dry skin. Furthermore, the androgen sensitivity of SGs appears to be under neuroendocrine control, as hypophysectomy (removal of the pituitary) renders SGs largely insensitive to stimulation by testosterone, which is crucial for maintaining SG homeostasis. However, several neurohormones, such as adrenocorticotropic hormone and α-melanocyte-stimulating hormone, can stimulate sebum production independently of either the testes or the adrenal glands, further underscoring the importance of neuroendocrine control in SG biology. Moreover, sebocytes synthesise several neurohormones and express their receptors, suggestive of the presence of neuro-autocrine mechanisms of sebocyte modulation. Aside from the neuroendocrine system, it is conceivable that secretion of neuropeptides and neurotransmitters from cutaneous nerve endings may also act on sebocytes or their progenitors, given that the skin is richly innervated. However, to date, the neural controls of SG development and function remain poorly investigated and incompletely understood. Botulinum toxin-mediated or facial paresis-associated reduction of human sebum secretion suggests that cutaneous nerve-derived substances modulate lipid and inflammatory cytokine synthesis by sebocytes, possibly implicating the nervous system in acne pathogenesis. Additionally, evidence suggests that cutaneous denervation in mice alters the expression of key regulators of SG homeostasis. In this review, we examine the current evidence regarding neuroendocrine and neurobiological regulation of human SG function in physiology and pathology. We further call attention to this line of research as an instructive model for probing and therapeutically manipulating the mechanistic links between the nervous system and mammalian skin.

Multicentric osteolytic syndromes represent a phenotypic spectrum defined by defective collagen remodeling

Frank-Ter Haar syndrome (FTHS), Winchester syndrome (WS), and multicentric osteolysis, nodulosis, and arthropathy (MONA) are ultra-rare multisystem disorders characterized by craniofacial malformations, reduced bone density, skeletal and cardiac anomalies, and dermal fibrosis. These autosomal recessive syndromes are caused by homozygous mutation or deletion of respectively SH3PXD2B (SH3 and PX Domains 2B), MMP14 (matrix metalloproteinase 14), or MMP2. Here, we give an overview of the clinical features of 63 previously reported patients with an SH3PXD2B, MMP14, or MMP2 mutation, demonstrating considerable clinical overlap between FTHS, WS, and MONA. Interestingly, the protein products of SH3PXD2B, MMP14, and MMP2 directly cooperate in collagen remodeling. We review animal models for these three disorders that accurately reflect the major clinical features and likewise show significant phenotypical similarity with each other. Furthermore, they demonstrate that defective collagen remodeling is central in the underlying pathology. As such, we propose a nosological revision, placing these SH3PXD2B, MMP14, and MMP2 related syndromes in a novel "defective collagen-remodelling spectrum (DECORS)". In our opinion, this revised nosology better reflects the central role for impaired collagen remodeling, a potential target for pharmaceutical intervention.

Functional analysis of a hypomorphic allele shows that MMP14 catalytic activity is the prime determinant of the Winchester syndrome phenotype

Winchester syndrome (WS, MIM #277950) is an extremely rare autosomal recessive skeletal dysplasia characterized by progressive joint destruction and osteolysis. To date, only one missense mutation in MMP14, encoding the membrane-bound matrix metalloprotease 14, has been reported in WS patients. Here, we report a novel hypomorphic MMP14 p.Arg111His (R111H) allele, associated with a mitigated form of WS. Functional analysis demonstrated that this mutation, in contrast to previously reported human and murine MMP14 mutations, does not affect MMP14’s transport to the cell membrane. Instead, it partially impairs MMP14’s proteolytic activity. This residual activity likely accounts for the mitigated phenotype observed in our patients. Based on our observations as well as previously published data, we hypothesize that MMP14’s catalytic activity is the prime determinant of disease severity. Given the limitations of our in vitro assays in addressing the consequences of MMP14 dysfunction, we generated a novel mmp14a/b knockout zebrafish model. The fish accurately reflected key aspects of the WS phenotype including craniofacial malformations, kyphosis, short-stature and reduced bone density owing to defective collagen remodeling. Notably, the zebrafish model will be a valuable tool for developing novel therapeutic approaches to a devastating bone disorder.

Mendelian Disorders of Cornification Caused by Defects in Intracellular Calcium Pumps: Mutation Update and Database for Variants in ATP2A2 and ATP2C1 Associated with Darier Disease and Hailey-Hailey Disease

The two disorders of cornification associated with mutations in genes coding for intracellular calcium pumps are Darier disease (DD) and Hailey-Hailey disease (HHD). DD is caused by mutations in the ATP2A2 gene, whereas the ATP2C1 gene is associated with HHD. Both are inherited as autosomal-dominant traits. DD is mainly defined by warty papules in seborrheic and flexural areas, whereas the major symptoms of HHD are vesicles and erosions in flexural skin. Both phenotypes are highly variable. In 12%-40% of DD patients and 12%-55% of HHD patients, no mutations in ATP2A2 or ATP2C1 are found. We provide a comprehensive review of clinical variability in DD and HHD and a review of all reported mutations in ATP2A2 and ATP2C1. Having the entire spectrum of ATP2A2 and ATP2C1 variants allows us to address the question of a genotype-phenotype correlation, which has not been settled unequivocally in DD and HHD. We created a database for all mutations in ATP2A2 and ATP2C1 using the Leiden Open Variation Database (LOVD v3.0), for variants reported in the literature and future inclusions. This data may be of use as a reference tool in further research on treatment of DD and HHD.

Review of familial cerebral cavernous malformations and report of seven additional families

Cerebral cavernous malformations are vascular anomalies of the central nervous system characterized by clusters of enlarged, leaky capillaries. They are caused by loss-of-function mutations in KRIT1, CCM2, or PDCD10. The proteins encoded by these genes are involved in four partially interconnected signaling pathways that control angiogenesis and endothelial permeability. Cerebral cavernous malformations can occur sporadically, or as a familial autosomal dominant disorder (FCCM) with incomplete clinical and neuroradiological penetrance and great inter-individual variability. Although the clinical course is unpredictable, symptoms typically present during adult life and include headaches, focal neurological deficits, seizures, and potentially fatal stroke. In addition to neural lesions, extraneural cavernous malformations have been described in familial disease in several tissues, in particular the skin. We here present seven novel FCCM families with neurologic and cutaneous lesions. We review histopathological and clinical features and provide an update on the pathophysiology of cerebral cavernous malformations and associated cutaneous vascular lesions. © 2016 Wiley Periodicals, Inc.

Expression and knockdown of zebrafish folliculin suggests requirement for embryonic brain morphogenesis

Background

Birt-Hogg-Dubé syndrome (BHD) is a dominantly inherited familial cancer syndrome characterised by the development of benign skin fibrofolliculomas, multiple lung and kidney cysts, spontaneous pneumothorax and susceptibility to renal cell carcinoma. BHD is caused by mutations in the gene encoding Folliculin (FLCN). Little is known about what FLCN does in a healthy individual and how best to treat those with BHD. As a first approach to developing a vertebrate model for BHD we aimed to identify the temporal and spatial expression of flcn transcripts in the developing zebrafish embryo. To gain insights into the function of flcn in a whole organism system we generated a loss of function model of flcn by the use of morpholino knockdown in zebrafish.

Results

flcn is expressed broadly and upregulated in the fin bud, somites, eye and proliferative regions of the brain of the Long-pec stage zebrafish embryos. Together with knockdown phenotypes, expression analysis suggest involvement of flcn in zebrafish embryonic brain development. We have utilised the zFucci system, an in vivo, whole organism cell cycle assay to study the potential role of flcn in brain development. We found that at the 18 somite stage there was a significant drop in cells in the S-M phase of the cell cycle in flcn morpholino injected embryos with a corresponding increase of cells in the G1 phase. This was particularly evident in the brain, retina and somites of the embryo. Timelapse analysis of the head region of flcn morpholino injected and mismatch control embryos shows the temporal dynamics of cell cycle misregulation during development.

Conclusions

In conclusion we show that zebrafish flcn is expressed in a non-uniform manner and is likely required for the maintenance of correct cell cycle regulation during embryonic development. We demonstrate the utilisation of the zFucci system in testing the role of flcn in cell proliferation and suggest a function for flcn in regulating cell proliferation in vertebrate embryonic brain development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12861-016-0119-8) contains supplementary material, which is available to authorized users.

Neurocutaneous Manifestations of Genetic Mosaicism

Genetic mosaicism is defined as the presence of two or more genetically distinct cell populations in a single individual. Ever more disorders are found to be manifestations of mosaicism and together constitute a significant proportion of the morbidity confronting pediatric specialists. An emerging category is that of overgrowth syndromes with skin manifestations and neurological or developmental abnormalities, such as the well-known Proteus syndrome. In recent years, we have seen dramatic advances in our understanding of these disorders and we now know the genetic basis of many of them. This has profound consequences for diagnosis, counselling, and even treatment, with therapies targeted to specific pathways becoming available for clinical use. Recognizing such overgrowth syndromes, therefore, is more important than ever. Fortunately, their skin manifestations can provide important diagnostic clues when evaluated in the entire phenotypic context. In this review, I provide an overview of the most frequently seen mosaic neurocutaneous phenotypes and discuss their molecular basis.

Cerebral lipid accumulation in Chanarin-Dorfman Syndrome

Chanarin-Dorfman Syndrome (CDS) is caused by a defect in the CGI-58/ABHD5 gene resulting in a deficiency of CGI-58 and in intracellular accumulation of triacylglycerol in skin and liver. Patients are mainly characterized by congenital ichthyosis, but the clinical phenotype is very heterogeneous. Distinct brain involvement has never been described. We present a clinical description of two patients with congenital ichthyosis. On suspicion of Sjögren-Larsson syndrome (SLS) single-voxel 1H-MR spectroscopy of the brain was performed and biochemical testing of fatty aldehyde dehydrogenase (FALDH) to establish this diagnosis gave normal results. Vacuolisation in a peripheral blood smear has led to the CDS suspicion. In both patients the diagnosis CDS was confirmed by ABHD5 mutation analysis. Interestingly, a clear lipid accumulation in the cerebral white matter, cortex and basal ganglia was demonstrated in both CDS-patients. These results demonstrate, for the first time, cerebral involvement in CDS and give new insights in the complex phenotype. Since the clinical implications of this abnormal cerebral lipid accumulation are still unknown, further studies are warranted.

Immunohistochemical analysis of the mechanistic target of rapamycin and hypoxia signalling pathways in basal cell carcinoma and trichoepithelioma

BACKGROUND

Basal cell carcinoma (BCC) is the most common cancer in Caucasians. Trichoepithelioma (TE) is a benign neoplasm that strongly resembles BCC. Both are hair follicle (HF) tumours. HFs are hypoxic microenvironments, therefore we hypothesized that hypoxia-induced signalling pathways could be involved in BCC and TE as they are in other human malignancies. Hypoxia-inducible factor 1 (HIF1) and mechanistic/mammalian target of rapamycin (mTOR) are key players in these pathways.

OBJECTIVES

To determine whether HIF1/mTOR signalling is involved in BCC and TE.

METHODS

We used immunohistochemical staining of formalin-fixed paraffin-embedded BCC (n = 45) and TE (n = 35) samples to assess activity of HIF1, mTORC1 and their most important target genes. The percentage positive tumour cells was assessed manually in a semi-quantitative manner and categorized (0%, <30%, 30-80% and >80%).

RESULTS

Among 45 BCC and 35 TE examined, expression levels were respectively 81% and 57% (BNIP3), 73% and 75% (CAIX), 79% and 86% (GLUT1), 50% and 19% (HIF1α), 89% and 88% (pAKT), 55% and 61% (pS6), 15% and 25% (pMTOR), 44% and 63% (PHD2) and 44% and 49% (VEGF-A). CAIX, Glut1 and PHD2 expression levels were significantly higher in TE when only samples with at least 80% expression were included.

CONCLUSIONS

HIF and mTORC1 signalling seems active in both BCC and TE. There are no appreciable differences between the two with respect to pathway activity. At this moment immunohistochemical analyses of HIF, mTORC1 and their target genes does not provide a reliable diagnostic tool for the discrimination of BCC and TE.

Topical rapamycin as a treatment for fibrofolliculomas in Birt-Hogg-Dubé syndrome: a double-blind placebo-controlled randomized split-face trial

BACKGROUND

Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominant disorder characterised by the occurrence of benign, mostly facial, skin tumours called fibrofolliculomas, multiple lung cysts, spontaneous pneumothorax and an increased renal cancer risk. Current treatments for fibrofolliculomas have high rates of recurrence and carry a risk of complications. It would be desirable to have a treatment that could prevent fibrofolliculomas from growing. Animal models of BHD have previously shown deregulation of mammalian target of rapamycin (mTOR). Topical use of the mTOR inhibitor rapamycin is an effective treatment for the skin tumours (angiofibromas) in tuberous sclerosis complex, which is also characterised by mTOR deregulation. In this study we aimed to determine if topical rapamycin is also an effective treatment for fibrofolliculomas in BHD.

METHODS

We performed a double blinded, randomised, facial left-right controlled trial of topical rapamycin 0.1% versus placebo in 19 BHD patients. Trial duration was 6 months. The primary outcome was cosmetic improvement as measured by doctors and patients. Changes in fibrofolliculoma number and size were also measured, as was occurrence of side effects.

RESULTS

No change in cosmetic status of fibrofolliculomas was reported in the majority of cases for the rapamycin treated (79% by doctors, 53% by patients) as well as the placebo treated facial sides (both 74%). No significant differences between rapamycin and placebo treated facial halves were observed (p = 1.000 for doctors opinion, p = 0.344 for patients opinion). No significant difference in fibrofolliculoma number or change in size of the fibrofolliculomas was seen after 6 months. Side effects occurred more often after rapamycin treatment (68% of patients) than after placebo (58% of patients; p = 0.625). A burning sensation, erythema, itching and dryness were most frequently reported.

CONCLUSIONS

This study provides no evidence that treatment of fibrofolliculomas with topical rapamycin in BHD results in cosmetic improvement.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00928798.

A de novo FLCN mutation in a patient with spontaneous pneumothorax and renal cancer; a clinical and molecular evaluation

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant condition due to germline FLCN (folliculin) mutations, characterized by skin fibrofolliculomas, lung cysts, pneumothorax and renal cancer. We identified a de novo FLCN mutation, c.499C>T (p.Gln167X), in a patient who presented with spontaneous pneumothorax. Subsequently, typical skin features and asymptomatic renal cancer were diagnosed. Probably, de novo FLCN mutations are rare. However, they may be under-diagnosed if BHD is not considered in sporadic patients who present with one or more of the syndromic features. Genetic and immunohistochemical analysis of the renal tumour indicated features compatible with a tumour suppressor role of FLCN. The finding that mutant FLCN was expressed in the tumour might indicate residual functionality of mutant FLCN, a notion which will be explored in future studies.

The tumor suppressor folliculin regulates AMPK-dependent metabolic transformation

The Warburg effect is a tumorigenic metabolic adaptation process characterized by augmented aerobic glycolysis, which enhances cellular bioenergetics. In normal cells, energy homeostasis is controlled by AMPK; however, its role in cancer is not understood, as both AMPK-dependent tumor-promoting and -inhibiting functions were reported. Upon stress, energy levels are maintained by increased mitochondrial biogenesis and glycolysis, controlled by transcriptional coactivator PGC-1α and HIF, respectively. In normoxia, AMPK induces PGC-1α, but how HIF is activated is unclear. Germline mutations in the gene encoding the tumor suppressor folliculin (FLCN) lead to Birt-Hogg-Dubé (BHD) syndrome, which is associated with an increased cancer risk. FLCN was identified as an AMPK binding partner, and we evaluated its role with respect to AMPK-dependent energy functions. We revealed that loss of FLCN constitutively activates AMPK, resulting in PGC-1α-mediated mitochondrial biogenesis and increased ROS production. ROS induced HIF transcriptional activity and drove Warburg metabolic reprogramming, coupling AMPK-dependent mitochondrial biogenesis to HIF-dependent metabolic changes. This reprogramming stimulated cellular bioenergetics and conferred a HIF-dependent tumorigenic advantage in FLCN-negative cancer cells. Moreover, this pathway is conserved in a BHD-derived tumor. These results indicate that FLCN inhibits tumorigenesis by preventing AMPK-dependent HIF activation and the subsequent Warburg metabolic transformation.

Report of the 10th Annual International Pachyonychia Congenita Consortium Meeting

The International Pachyonychia Congenita Consortium (IPCC) was founded in 2004 in Park City, Utah, USA. Its goal is to find a cure for pachyonychia congenita, a rare keratinizing disorder. From February 14th–17th, 2013, the group convened in Park City for their tenth annual meeting. The 2013 meeting focused on how to best move forward with clinical trials and on learning from work in other scientific areas, with an emphasis on understanding mechanisms of pain and hyperkeratosis. Considerable time was spent on discussing the best way to move forward with development of new treatments and how to obtain or develop tools that can measure treatment outcomes in PC.

Birt-Hogg-Dube syndrome is a novel ciliopathy

Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant disorder where patients are predisposed to kidney cancer, lung and kidney cysts and benign skin tumors. BHD is caused by heterozygous mutations affecting folliculin (FLCN), a conserved protein that is considered a tumor suppressor. Previous research has uncovered multiple roles for FLCN in cellular physiology, yet it remains unclear how these translate to BHD lesions. Since BHD manifests hallmark characteristics of ciliopathies, we speculated that FLCN might also have a ciliary role. Our data indicate that FLCN localizes to motile and non-motile cilia, centrosomes and the mitotic spindle. Alteration of FLCN levels can cause changes to the onset of ciliogenesis, without abrogating it. In three-dimensional culture, abnormal expression of FLCN disrupts polarized growth of kidney cells and deregulates canonical Wnt signalling. Our findings further suggest that BHD-causing FLCN mutants may retain partial functionality. Thus, several BHD symptoms may be due to abnormal levels of FLCN rather than its complete loss and accordingly, we show expression of mutant FLCN in a BHD-associated renal carcinoma. We propose that BHD is a novel ciliopathy, its symptoms at least partly due to abnormal ciliogenesis and canonical Wnt signalling.

Epigenetic changes in Basal Cell Carcinoma affect SHH and WNT signaling components

Background

The genetic background of Basal Cell Carcinoma (BCC) has been studied extensively, while its epigenetic makeup has received comparatively little attention. Epigenetic alterations such as promoter hypermethylation silence tumor suppressor genes (TSG) in several malignancies.

Objective

We sought to analyze the promoter methylation status of ten putative (tumor suppressor) genes that are associated with Sonic Hedgehog (SHH), WNT signaling and (hair follicle) tumors in a large series of 112 BCC and 124 healthy control samples by methylation-specific PCR.

Results

Gene promoters of SHH (P = 0.016), adenomatous polyposis coli (APC) (P = 0.003), secreted frizzled-related protein 5 (SFRP5) (P = 0.004) and Ras association domain family 1A (RASSF1A) (P = 0.023) showed significantly more methylation in BCC versus normal skin. mRNA levels of these four genes were reduced for APC and SFRP5 in BCC (n = 6) vs normal skin (n = 6). Down regulation of SHH, APC and RASSF1A could be confirmed on protein level as well (P<0.001 for all genes) by immunohistochemical staining. Increased canonical WNT activity was visualized by β-catenin staining, showing nuclear β-catenin in only 28/101 (27.7%) of BCC. Absence of nuclear β-catenin in some samples may be due to high levels of membranous E-cadherin (in 94.1% of the samples).

Conclusions

We provide evidence that promoter hypermethylation of key players within the SHH and WNT pathways is frequent in BCC, consistent with their known constitutive activation in BCC. Epigenetic gene silencing putatively contributes to BCC tumorigenesis, indicating new venues for treatment.

Differential susceptibility of Cx26 mutations associated with epidermal dysplasias to peptidoglycan derived from Staphylococcus aureus and Staphylococcus epidermidis

Mutations in Connexin26 (Cx26) give rise to a spectrum of dominantly inherited hyperproliferating skin disorders, the severest being keratitis-ichthyosis-deafness (KID) syndrome, an inflammatory skin disorder, with patients prone to opportunistic infections. We compared the effects of peptidoglycan (PGN) extracted from the skin commensal Staphylococcus epidermidis and the opportunistic pathogen Staphylococcus aureus on interleukin-6 and connexin expression in HaCaT cells (a keratinocyte cell line) and connexin channel activity in HaCaT and HeLa (connexin deficient) cells transfected to express KID and non-KID Cx26 mutations. In both cell types, PGN from S. aureus induced hemichannel activity in cells expressing KID mutants as monitored by ATP release assays following 15-min challenge, while that from S. epidermidis evoked a response in HeLa cells. In KID mutant expressing cells, ATP release was significantly higher than in cells transfected with wild-type Cx26. No ATP release was observed in non-KID mutant transfected cells or in the presence of carbenoxolone, a connexin channel blocker. PGN isolated from S. aureus but not S. epidermidis induced interleukin-6 and Cx26 expression in HaCaT cells following 6-h challenge. Challenge by PGN from S. aureus evoked a greater interleukin-6 response in cells expressing KID mutants than in cells expressing wtCx26 or non-KID mutants. This response returned to basal levels if acute KID hemichannel signalling was blocked prior to PGN challenge. Thus, KID mutants form channels that can be triggered by the pro-inflammatory mediator PGN from opportunistic pathogens but not skin commensals, providing further insight into the genotype-phenotype relationship of Cx26 disorders.

Porokeratotic eccrine nevus may be caused by somatic connexin26 mutations

Porokeratotic eccrine ostial and dermal duct nevus, or porokeratotic eccrine nevus (PEN), is a hyperkeratotic epidermal nevus. Several cases of widespread involvement have been reported, including one in association with the keratitis–ichthyosis–deafness (KID) syndrome (OMIM #148210), a rare disorder caused by mutations in the GJB2 gene coding for the gap junction protein connexin26 (Cx26). The molecular cause is, as yet, unknown. We have noted that PEN histopathology is shared by KID. The clinical appearance of PEN can resemble that of KID syndrome. Furthermore, a recent report of cutaneous mosaicism for a GJB2 mutation associated with KID describes linear hyperkeratotic skin lesions that might be consistent with PEN. From this, we hypothesized that PEN might be caused by Cx26 mutations associated with KID or similar gap junction disorders. Thus, we analyzed the GJB2 gene in skin samples from two patients referred with generalized PEN. In both, we found GJB2 mutations in the PEN lesions but not in unaffected skin or peripheral blood. One mutation was already known to cause the KID syndrome, and the other had not been previously associated with skin symptoms. We provide extensive functional data to support its pathogenicity. We conclude that PEN may be caused by mosaic GJB2 mutations.

[Conradi-Hünermann-Happle syndrome]

BACKGROUND

Conradi-Hünermann-Happle syndrome is caused by a mutation in the emopanil binding protein-gene (EBP), which encodes the enzyme 3β-hydroxysteroid-dehydrogenase-δ8,7 isomerase. This gene is involved in cholesterol metabolism.

CASE DESCRIPTION

In this case report we describe a girl aged 19 months with Conradi-Hünermann-Happle syndrome. This syndrome was characterized in this patient by a complete erythrodermia directly after birth, followed by linear ichthyosis, shortened upper arms and thighs, vertebral anomalies resulting in progressive scoliosis and cataract. The patient's mother was found also to suffer from the Conradi-Hünermann-Happle syndrome. As a child she had linear ichthyosis, difference in leg length and congenital alopecia in a linear pattern.

CONCLUSION

For diagnosis and treatment of children with such a rare syndrome a multidisciplinary approach is essential. Multidisciplinary collaboration guarantees an appropriate follow-up for the patient and the family.

Repetitive disruptions of the nuclear envelope invoke temporary loss of cellular compartmentalization in laminopathies

The nuclear lamina provides structural support to the nucleus and has a central role in nuclear organization and gene regulation. Defects in its constituents, the lamins, lead to a class of genetic diseases collectively referred to as laminopathies. Using live cell imaging, we observed the occurrence of intermittent, non-lethal ruptures of the nuclear envelope in dermal fibroblast cultures of patients with different mutations of lamin A/C. These ruptures, which were absent in normal fibroblasts, could be mimicked by selective knockdown as well as knockout of LMNA and were accompanied by the loss of cellular compartmentalization. This was demonstrated by the influx of cytoplasmic transcription factor RelA and regulatory protein Cyclin B1 into the nucleus, and efflux of nuclear transcription factor OCT1 and nuclear structures containing the promyelocytic leukemia (PML) tumour suppressor protein to the cytoplasm. While recovery of enhanced yellow fluorescent protein-tagged nuclear localization signal in the nucleus demonstrated restoration of nuclear membrane integrity, part of the mobile PML structures became permanently translocated to the cytoplasm. These satellite PML structures were devoid of the typical PML body components, such as DAXX, SP100 or SUMO1. Our data suggest that nuclear rupture and loss of compartmentalization may add to cellular dysfunction and disease development in various laminopathies.

Pathogenesis-based therapy reverses cutaneous abnormalities in an inherited disorder of distal cholesterol metabolism

Identification of the underlying genetic, cellular, and biochemical basis of lipid metabolic disorders provides an opportunity to deploy corrective, mechanism-targeted, topical therapy. We assessed this therapeutic approach in two patients with Congenital Hemidysplasia with Ichthyosiform Erythroderma and Limb Defects (CHILD) syndrome, an X-linked dominant disorder of distal cholesterol metabolism. Based upon the putative pathogenic role of both pathway-product deficiency of cholesterol and accumulation of toxic metabolic intermediates, we assessed the efficacy of combined therapy with lovastatin and cholesterol. We also evaluated the basis for the poorly understood, unique lateralization of the cutaneous and bone malformations of CHILD syndrome by analyzing gene activation in abnormal and unaffected skin. Ultrastructural analysis of affected skin showed evidence of both cholesterol depletion and toxic metabolic accumulation. Topical treatment with lovastatin/cholesterol (but not cholesterol alone) virtually cleared skin lesions by 3 months, accompanied by histologic and ultrastructural normalization of epidermal structure and lipid secretion. The unusual lateralization of abnormalities in CHILD syndrome reflects selective clearance of keratinocytes and fibroblasts that express the mutant allele from the unaffected side. These findings validate pathogenesis-based therapy that provides the deficient end-product and prevents accumulation of toxic metabolites, an approach of potential utility for other syndromic lipid metabolic disorders.

A proposal for classification of entities combining vascular malformations and deregulated growth

BACKGROUND

Agreement on terminology and nomenclature is fundamental and essential for effective exchange of information between clinicians and researchers. An adequate terminology to describe all patients showing vascular malformations combined with deregulated growth is at present not available.

OBJECTIVES

To propose a classification of patients with vascular malformations, not restricted to the face, and growth disturbances based on simple, clinically visible characteristics, on which clinicians and researchers can comment and which should eventually lead to an internationally accepted classification.

METHODS

Rooted in our joint experience we established a classification of vascular malformation not limited to the face, with growth disturbances. It is based on the nature and localization of the vascular malformations; the nature, localization and timing of growth disturbances; the nature of co-localization of the vascular malformations and growth disturbances; the presence or absence of other features. Subsequently a mixed (experienced and non-experienced) group of observers evaluated 146 patients (106 from the Netherlands; 40 from the UK) with vascular malformations and disturbed growth, using the classification. Inter-observer variability was assessed by estimating the Intra-Class Correlation (ICC) coefficient and its 95% confidence interval.

RESULTS

We defined 6 subgroups within the group of entities with vascular malformation-deregulated growth. Scoring the patients using the proposed classification yielded a high inter-observer reproducibility (ICC varying between 0.747 and 0.895 for all levels of flow).

CONCLUSIONS

The presently proposed classification was found to be reliable and easy to use for patients with vascular malformations with growth disturbances. We invite both clinicians and researchers to comment on the classification, in order to improve it further. This way we may obtain our final aim of an internationally accepted classification of patients, which should facilitate both clinical treatment and care of, as well as research into the molecular background of entities combining vascular malformation and deregulated growth.

A de novo p.Asp18Asn mutation in TREX1 in a patient with Aicardi-Goutières syndrome

Aicardi-Goutières syndrome is a rare, genetically determined encephalopathy often resembling congenital infection. Mutations in the TREX1 gene are found in approximately 25% of patients. Aicardi-Goutières syndrome is usually inherited as an autosomal recessive trait, although a single case of a heterozygous TREX1 mutation associated with the syndrome has been reported. We present a second case of a de novo heterozygous TREX1 mutation causing an autosomal dominant phenotype of Aicardi-Goutières syndrome with additional features indicative of mitochondrial dysfunction. This report serves to enhance awareness of de novo heterozygous mutations underlying Aicardi-Goutières syndrome-with a concomitant low risk of recurrence.

[Birt-Hogg-Dubé syndrome]

Birt-Hogg-Dubé (BHD) is a rare autosomal dominant genodermatosis, characterized by cutaneous hamartomas, pulmonary cysts, spontaneous pneumothorax and kidney tumours. BHD is caused by mutation in the gene which codes for folliculin (FLCN). FLCN is part of the mTOR-AMPK signal transduction pathway. Genetic testing of patients is now possible. Furthermore, understanding of the biology and mechanisms behind BHD-associated disease provides an opportunity for development of new treatment options.

Birt-Hogg-Dubé syndrome: diagnosis and management

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant condition characterised clinically by skin fibrofolliculomas, pulmonary cysts, spontaneous pneumothorax, and renal cancer. The condition is caused by germline mutations in the FLCN gene, which encodes folliculin; the function of this protein is largely unknown, although FLCN has been linked to the mTOR pathway. The availability of DNA-based diagnosis has allowed insight into the great variation in expression of FLCN, both within and between families. Patients can present with skin signs and also with pneumothorax or renal cancer. Preventive measures are aimed mainly at early diagnosis and treatment of renal cancer. This Review gives an overview of current diagnosis and management of BHD.

T-cell large granular lymphocytic leukaemia with an uncommon clinical and immunological phenotype

A 39-year-old man presented with a rapidly growing unilateral painless nodule on the right cheek. Histopathological examination and peripheral blood analysis both showed a population of T-cell large granular lymphocytes, which were CD1+, CD2+, CD5+, CD7+ and CD16+, with expression of cutaneous lymphocyte-associated antigen. Further laboratory examination revealed severe neutropaenia, relative lymphocytosis and a clonally rearranged T-cell receptor. The cutaneous manifestation of T-cell large granular lymphocytic leukaemia is very rare. In this particular patient, however, it was instrumental in establishing the diagnosis and may have been enabled by the expression of cutaneous lymphocyte-associated antigen on the cell surface.

Neonatal Langerhans' cell histiocytosis: a rare and potentially life-threatening disease

A 5-day-old girl presented with thrombocytopenia, leukopenia, anemia and crusted purpura on the skin. The diagnosis Langerhans' cell histiocytosis (LCH) was suspected on clinical grounds and subsequently confirmed by histopathological examination of a skin biopsy. Cytological examination of a bone marrow aspirate revealed numerous histiocytes, which is suspect for bone-marrow infiltration by LCH. LCH is a condition in which a clonal population of Langerhans' cells accumulates in various tissues, causing tissue damage and/or dysfunction. The prognosis of this disease depends on the age of the patient, the extent of the disease and the presence of vital organ failure. In case of organ dysfunction, systemic chemotherapy is indicated. Although very rare, LCH can be a life-threatening disease. Early diagnosis can improve chances of survival. We briefly discuss diagnostic procedures and treatment.

Connexin mimetic peptides improve cell migration rates of human epidermal keratinocytes and dermal fibroblasts in vitro

Nonhealing cutaneous wounds, a major cause of morbidity and mortality, are difficult to treat. Recent studies suggest that significant increases in skin wound-healing rates occur by altering gap junction intercellular communication (GJIC). As migration of keratinocytes and fibroblasts is an important feature of wound healing, this study investigated whether migration rates in cultured normal human epidermal keratinocytes and dermal fibroblasts could be altered by modulating GJIC via connexin mimetic peptides. First, HeLa cells stably transfected with connexin43 (Cx43), Cx40, or Cx26 were used as a model to determine connexin specificity and the doses of connexin mimetic peptides required to attenuate GJIC. Gap26 and Gap26M inhibited GJIC dose dependently and were nonconnexin specific, whereas Gap27 was Cx43-selective. Skin keratinocytes and fibroblasts expressed a variety of connexins, with Cx43 predominating. Cx43 protein expression was reduced at leading edges 3 hours after scraping confluent monolayers, resolving at 24 hours. Gap26M and Gap27 significantly increased migration rates across scrapes in keratinocytes and fibroblasts by blocking gap junction functionality. GJIC inhibition can thus directly influence keratinocyte and fibroblast migration. Furthermore, our results support the therapeutic potential of connexin mimetic peptides to aid wound closure, and provide a simple approach to screening new agents.