Pathogenic Somatic Mutation of DICER1 and Clinicopathological Features in Nasal Chondromesenchymal Hamartomas: A Series of Nine Cases.

Nasal chondromesenchymal hamartoma (NCMH) is a rare benign polypoid mesenchymal tumor arising in the nasal cavity and/or paranasal sinuses. Recognizing these sporadic, rare lesions is crucial, as surgical complete removal of the mass is the common treatment approach. This retrospective study analyzed the demographics, symptoms, and imaging data of 9 patients diagnosed with NCMH between January 2017 and June 2023, possibly representing the largest single-center adult case cohort to date. Diagnostic techniques included nasal endoscopy, CT/MRI scan, immunohistological studies, and morphologic comparisons. Pathologic specimens were subjected to Sanger sequencing of exons 24 and 25 of DICER1. The average age of 9 cases was 24.4 years, and the oldest was 55 years. Four of the patients were children, ranging from 1 year old to 11 years old, with an average of 4.5 years. Nasal congestion is the most common registered symptom. Endoscopic findings showed that most patients had smooth pink neoplasms or polypoid masses in the nasal meatus. Radiologic scanning revealed soft-tissue density masses that occupied the nasal cavity. Histologically, the characteristic structure of NCMHs is immature cellular cartilage nodules and mature cartilage nodules distributed in a loose mucoid matrix. Five of the 9 patients had somatic DICER1 missense mutations. Four of the patients with DICER1-mutated NCMH exhibited a p.E1813 missense hotspot mutation. We also report a case of a rare p.P1836H missense mutation. The detected DICER1 somatic mutations provide compelling evidence of an association with the DICER1 tumor family. We emphasize the importance of pathologic consultation and the need for pathologists to accumulate experience in NCMH diagnosis to avoid misdiagnosis.

Bifid nose as the sole manifestation of BNAR syndrome, a FREM1-related condition.

BNAR syndrome (MIM608980) is a very rare condition: nine cases belonging to three unrelated families were reported since its first description in 2002. The distinctive clinical feature is the bifidity of the tip of the nose and its association with anorectal and/or renal anomalies. Its molecular basis consisting of biallelic FREM1 missense or nonsense mutations was elucidated after studying the original Egyptian family and was confirmed in two families originating from Afghanistan and Pakistan. We describe a fourth family originating from Turkey with signs challenging the diagnostic criteria suggested by the description of the three reported families.

Abnormal keratinocyte differentiation in the nasal planum of Labrador Retrievers with hereditary nasal parakeratosis (HNPK).

Hereditary nasal parakeratosis (HNPK) is an inherited disorder described in Labrador Retrievers and Greyhounds. It has been associated with breed-specific variants in the SUV39H2 gene encoding a histone 3 methyltransferase involved in epigenetic silencing. Formalin-fixed biopsies of the nasal planum of Labrador Retrievers were screened by immunofluorescence microscopy for the presence and distribution of epidermal proliferation and differentiation markers. Gene expression of these markers was further analysed using RNA sequencing (RNA-seq) and ultrastructural epidermal differences were investigated by electron microscopy. Differentiation of the nasal planum in the basal and suprabasal epidermal layers of HNPK-affected dogs (n = 6) was similar compared to control dogs (n = 6). In the upper epidermal layers, clear modifications were noticed. Loricrin protein was absent in HNPK-affected nasal planum sections in contrast to sections of the same location of control dogs. However, loricrin was present in the epidermis of paw pads and abdominal skin from HNPK dogs and healthy control dogs. The patterns of keratins K1, K10 and K14, were not markedly altered in the nasal planum of HNPK-affected dogs while the expression of the terminal differentiation marker involucrin appeared less regular. Based on RNA-seq, LOR and IVL expression levels were significantly decreased, while KRT1, KRT10 and KRT14 levels were up-regulated (log2fold-changes of 2.67, 3.19 and 1.71, respectively) in HNPK-affected nasal planum (n = 3) compared to control dogs (n = 3). Electron microscopical analysis revealed structural alterations in keratinocytes and stratum corneum, and disrupted keratinocyte adhesions and distended intercellular spaces in lesional samples (n = 3) compared to a sample of a healthy control dog (n = 1). Our findings demonstrate aberrant keratinocyte terminal differentiation of the nasal planum of HNPK-affected Labrador Retrievers and provide insights into biological consequences of this inactive SUV39H2 gene variant.

Interferon inducible GBPs restrict Burkholderia thailandensis motility induced cell-cell fusion.

Innate immunity responds to pathogens by producing alarm signals and activating pathways that make host cells inhospitable for pathogen replication. The intracellular bacterium Burkholderia thailandensis invades the cytosol, hijacks host actin, and induces cell fusion to spread to adjacent cells, forming multinucleated giant cells (MNGCs) which promote bacterial replication. We show that type I interferon (IFN) restricts macrophage MNGC formation during B. thailandensis infection. Guanylate-binding proteins (GBPs) expressed downstream of type I IFN were required to restrict MNGC formation through inhibition of bacterial Arp2/3-dependent actin motility during infection. GTPase activity and the CAAX prenylation domain were required for GBP2 recruitment to B. thailandensis, which restricted bacterial actin polymerization required for MNGC formation. Consistent with the effects in in vitro macrophages, Gbp2-/-, Gbp5-/-, GbpChr3-KO mice were more susceptible to intranasal infection with B. thailandensis than wildtype mice. Our findings reveal that IFN and GBPs play a critical role in restricting cell-cell fusion and bacteria-induced pathology during infection.

Immunohistochemical and genetic analysis of respiratory epithelial adenomatoid hamartomas and seromucinous hamartomas: are they precursor lesions to sinonasal low-grade tubulopapillary adenocarcinomas?

Respiratory epithelial adenomatoid hamartoma (REAH) and seromucinous hamartoma (SH) are rare tumor-like lesions of the nasal cavity, paranasal sinuses, and nasopharynx. The pathogenesis of REAH/SH is still unclear. Neoplastic proliferation, chronic mechanical irritation, inflammation, or possible embryological tissue misplacement are speculated as possible mechanisms of their development. Low-grade tubulopapillary adenocarcinoma (LGTA) is a rare variant of nonsalivary, nonintestinal type sinonasal adenocarcinoma. The aim of this study was to evaluate the immunohistochemical and genetic profiles of 10 cases of REAH/SH, with serous, mucinous, and respiratory components evaluated separately and to compare these findings with the features of 9 cases of LGTA. All cases of REAH/SH and LGTA were analyzed immunohistochemically with a cocktail of mucin antigens (MUC1, MUC2, MUC4, MUC5AC, MUC6) and with epithelial (CK7, CK20, CDX2, SATB2) and myoepithelial markers (S100 protein, p63, SOX10). The next-generation sequencing assay was performed using FusionPlex Solid Tumor Kit (ArcherDx) in 10 cases of REAH/SH, and the EGFR-ZNF267 gene fusion was detected in 1 of them. Two female REAH/SH cases were assessed for the presence of clonality. Using the human androgen receptor assay, 1 case was proved to be clonal. The serous component of REAH/SH was positive for CK7/MUC1 and SOX10 similarly to LGTA. Although REAH/SH and LGTA are histopathologically and clinically separate entities, the overlap in their morphological and immunohistochemical profiles suggests that REAH/SH might be a precursor lesion of LGTA.

Limiting Dietary Sugar Improves Pediatric Sinonasal Symptoms and Reduces Inflammation.

Excessive sugar consumption is associated with many chronic inflammatory diseases in adults. The effects of excessive sugar consumption in children have not been determined. In this study, we hypothesized that sinonasal symptoms and proinflammatory cytokine levels would be related and could be altered through reduction in sugar-sweetened beverage (SSB) consumption. To test this, we conducted a pilot study involving behavior modification and a 2-week follow-up. Seventeen children participants were recruited, and eleven completed the study. The experimental group presented with chronic nasal congestion or rhinorrhea defined by daily symptoms without acute illness for at least 3 months. The control group presented for non-nasal problems. Both groups received counseling to decrease SSB consumption. The Sinus and Nasal Quality of Life (SN-5) Survey was administered, and a blood sample was obtained by venipuncture at baseline and 2 weeks after counseling. Participants kept a 2-week food diary to document sugar intake. Serum lipid profile and inflammatory cytokines were measured. The experimental group reduced daily sugar intake, 46% versus 11% in the control. Baseline SN-5 scores were significantly worse in the experimental group and normalized to controls after intervention. Inflammatory cytokine levels were not different at baseline, but the experimental group significantly reduced in proinflammatory markers and increased the levels of anti-inflammatory markers after intervention. Our pilot data demonstrate higher sugar consumption may be associated with increased inflammatory stress and sinonasal symptoms. Reducing SSB and controlling inflammation in early childhood may have future health benefits.

Staphylococcus aureus colonization in atopic eczema and its association with filaggrin gene mutations.

BACKGROUND: Atopic dermatitis (AD) is a prevalent disease with significant impact on physical health and quality of life. Staphylococcus aureus has been directly correlated to disease severity, and may also be a contributing causal factor in the pathogenesis of AD. OBJECTIVES: The primary aim was to assess differences in S. aureus colonization in patients with AD with and without filaggrin gene mutations. The secondary aim was to assess disease severity in relation to S. aureus colonization. Exploratory analyses were performed to investigate S. aureus genetic lineages in relation to filaggrin gene (FLG) mutations and disease severity. METHODS: Adult patients with AD (n = 101) were included in the study. Bacterial swabs were taken from lesional skin, nonlesional skin and the nose. Swabs positive for S. aureus were characterized by spa and the respective clonal complex (CC) type assigned. Patients were characterized with respect to disease severity (Scoring Atopic Dermatitis) and FLG mutations (n = 88). Fisher's exact test was used to analyse differences in S. aureus colonization in relation to FLG mutations. RESULTS: Of the 101 patients included, 74 (73%) were colonized with S. aureus. Of the colonized patients, 70 (95%) carried only one CC type in all three different sampling sites. In lesional skin, S. aureus was found in 24 of 31 patients with FLG mutations vs. 24 of 54 wild-type patients (P = 0·0004). Staphylococcus aureusCC1 clonal lineage was more prevalent in patients with FLG mutations (n = 10) than in wild-type patients (n = 2) (P = 0·003). No specific bacterial lineage was linked to disease severity. CONCLUSIONS: Increased S. aureus colonization in patients with AD with FLG mutations, and increased prevalence of CC1 in patients with FLG mutations, suggest that host-microbe interactions and clonal differences in S. aureus are important for colonization of AD skin.

Suplatast tosilate alleviates nasal symptoms through the suppression of nuclear factor of activated T-cells-mediated IL-9 gene expression in toluene-2,4-diisocyanate-sensitized rats.

Histamine H1 receptor (H1R) gene is upregulated in patients with pollinosis; its expression level is highly correlated with the nasal symptom severity. Antihistamines are widely used as allergy treatments because they inhibit histamine signaling by blocking H1R or suppressing H1R signaling as inverse agonists. However, long-term treatment with antihistamines does not completely resolve toluene-2,4-diisocyanate (TDI)-induced nasal symptoms, although it can decrease H1R gene expression to the basal level, suggesting additional signaling is responsible for the pathogenesis of the allergic symptoms. Here, we show that treatment with suplatast tosilate in combination with antihistamines markedly alleviates nasal symptoms in TDI-sensitized rats. Suplatast suppressed TDI-induced upregulation of IL-9 gene expression. Suplatast also suppressed ionomycin/phorbol-12-myristate-13-acetate-induced upregulation of IL-2 gene expression in Jurkat cells, in which calcineurin (CN)/nuclear factor of activated T-cells (NFAT) signaling is known to be involved. Immunoblot analysis demonstrated that suplatast inhibited binding of NFAT to DNA. Furthermore, suplatast suppressed ionomycin-induced IL-9 mRNA upregulation in RBL-2H3 cells, in which CN/NFAT signaling is also involved. These data suggest that suplatast suppressed NFAT-mediated IL-9 gene expression in TDI-sensitized rats and this might be the underlying mechanism of the therapeutic effects of combined therapy of suplatast with antihistamine.

Nasal Chondromesenchymal Hamartoma (NCMH): a systematic review of the literature with a new case report.

BACKGROUND: Nasal chondromesenchymal hamartoma (NCMH) is a very rare, benign tumour of the sinonasal tract usually presenting in infants. We present a systematic review of NCMH cases alongside a case report of an adult with asymptomatic NCMH. METHODS: A systematic review was conducted in accordance with PRISMA guidelines. A PubMed, EMBASE and manual search through references of relevant publications was used to identify all published case-reports of NCMH. Data was collected from each case-report on: patient demographics, laterality, size and location of NCMH, presentation, co-morbidities, investigations, treatment and follow-up. RESULTS: The systematic review identified 48 patients (including ours): 33 male, 15 female. Mean age was 9.6 years (range: 1 day-69 years) with the majority aged 1 year or younger at presentation (n = 18). Presentations included: nasal congestion (n = 17), nasal mass (n = 15) and eye signs (n = 12). NCMH also involved the paranasal sinuses (n = 26), orbit (n = 16) and skull-base (n = 14). All patients underwent operative resection of NCMH. A small 2014 case-series found DICER1 mutations in 6 NCMH patients, establishing a link to the DICER1 tumour spectrum. CONCLUSIONS: NCMH is a rare cause of nasal masses in young children and adults. In light of the newly established link between NCMH and DICER1 mutations surgeons should be vigilant for associated DICER1 tumours, as NCMH may be the 'herald tumour' of this disease spectrum.

Nasal chondromesenchymal hamartomas arise secondary to germline and somatic mutations of DICER1 in the pleuropulmonary blastoma tumor predisposition disorder.

Nasal chondromesenchymal hamartoma (NCMH) is a rare nasal tumor that typically presents in young children. We previously reported on NCMH occurrence in children with pleuropulmonary blastoma (PPB), a rare pulmonary dysembryonic sarcoma that is the hallmark neoplasm in the PPB-associated DICER1 tumor predisposition disorder. Original pathologic materials from individuals with a PPB, PPB-associated tumor and/or a DICER1 mutation were centrally reviewed by the International PPB Registry. Paraffin-embedded NCMH tumor tissue was available in three cases. Laser-capture microdissection was used to isolate mesenchymal spindle cells and cartilage in one case for Sanger sequencing of DICER1. Nine patients (5F/4M) had PPB and NCMH. NCMH was diagnosed at a median age of 10 years (range 6-21 years). NCMH developed 4.5-13 years after PPB. Presenting NCMH symptoms included chronic sinusitis and nasal congestion. Five patients had bilateral tumors. Local NCMH recurrences required several surgical resections in two patients, but all nine patients were alive at 0-16 years of follow-up. Pathogenic germline DICER1 mutations were found in 6/8 NCMH patients tested. In 2 of the patients with germline DICER1 mutations, somatic DICER1 missense mutations were also identified in their NCMH (E1813D; n = 2). Three additional PPB patients developed other nasal lesions seen in the general population (a Schneiderian papilloma, chronic sinusitis with cysts, and allergic nasal polyps with eosinophils). Two of these patients had germline DICER1 mutations. Pathogenic germline and somatic mutations of DICER1 in NCMH establishes that the genetic etiology of NCMH is similar to PPB, despite the disparate biological potential of these neoplasms.

The molecular genetics of inflammatory, autoimmune, and infectious diseases of the sinonasal tract: a review.

CONTEXT: The sinonasal tract is frequently affected by a variety of nonneoplastic inflammatory disease processes that are often multifactorial in their etiology but commonly have a molecular genetic component. OBJECTIVE: To review the molecular genetics of a variety of nonneoplastic inflammatory diseases of the sinonasal tract. DATA SOURCES: Inflammatory lesions of the sinonasal tract can be divided into 3 main categories: (1) chronic rhinosinusitis, (2) infectious diseases, and (3) autoimmune diseases/vasculitides. The molecular diagnosis and pathways of a variety of these inflammatory lesions are currently being elucidated and will shed light on disease pathogenesis and treatment. CONCLUSIONS: The sinonasal tract is frequently affected by inflammatory lesions that arise through complex interactions of environmental, infectious, and genetic factors. Because these lesions are all inflammatory in nature, the molecular pathology surrounding them is most commonly due to upregulation and down-regulation of genes that affect inflammatory responses and immune regulation.

Detection of a latent soluble form of membrane type 1 matrix metalloprotease bound with tissue inhibitor of matrix metalloproteinases-2 in periprosthetic tissues and fluids from loose arthroplasty endoprostheses.

Membrane type 1 matrix metalloproteinase (MT1-MMP) is implicated in pericellular proteolysis, and, together with tissue inhibitor of matrix metalloproteinases-2 (TIMP-2), in the activation of pro-matrix metalloproteinase-2 on the cell surface. It is expressed on the cell surface either activated or as a proenzyme. A soluble form of MT1-MMP (sMT1-MMP) has been previously identified in periprosthetic tissues and fluid of patients with loose arthroplasty endoprostheses. The aim of this study was to examine periprosthetic tissues and fluids from patients with loose arthroplasty endoprostheses, as well as tissues and fluids from patients with other disorders, for the presence of sMT1-MMP, and to investigate its activation state and possible role. With antibody against MT1-MMP, a protein with molecular mass of ~ 57 kDa was detected by western blotting in all samples tested, representing a soluble form of MT1-MMP, which cannot be ascribed to alternative splicing, as northern blotting showed only one transcript. With various biochemical methods, it was shown that this species occurs in a latent form bearing the N-terminal prodomain, and, additionally, it is bound to TIMP-2, which appeared to be bound via its C-terminal domain to a site different from the active site. Cell ELISA and immunohistochemical analysis revealed that, besides fibroblasts, all other cells, such as inflammatory, epithelial, endothelial, giant and cancer cells, express MT1-MMP on their plasma membrane as a proenzyme. Taking into account the proteolytic abilities of MT1-MMP, the latent sMT1-MMP-TIMP-2 complex could be considered as a new interstitial collagenase. However, the exact role, the production mechanism and the cell origin of this complex remain to be elucidated.

Malignant transformation of nasal chondromesenchymal hamartoma in adult: a case report and review of the literature.

Nasal chondromesenchymal hamartoma (NCMH) is an extremely rare benign tumor arising in the sinonasal tract, predominantly involving infants and children. To date, only 27 cases are reported in the international literature and there have been no reported cases of malignant transformation. We present a 40-year-old female patient with nasal obstruction and bloody rhinorrhea. Computed tomography (CT) of the nose and paranasal sinuses confirmed a heterogeneous polypoid soft-tissue mass filling the nasal cavity and extending into the maxillary and ethmoid sinus. The patient underwent a complete radical resection. Histological and immunohistochemical analyses showed a portion of the mass was consistent with typical NCMH. However, some areas of mass exhibited cytological atypia, marked mitotic activity and foci of necrosis. The atypical mesenchymal spindle cells were immunoreactive for vimentin, CD99 and smooth muscle actin (SMA) diffusely. The cartilaginous cells were immunopositive for S-100 protein. Ki-67 index was high in atypical areas, accounting for 50%. A rapid mass recurrence was observed at the original site only 3 months after surgery. The final diagnosis of NCMH with malignant transformation was made. To our knowledge, this is the first report of malignant transformation occurring in an adult with NCMH. Although NCMH commonly develops in the neonate or young infants and exhibits benign histological appearance and favorable prognosis, there is a possibility of malignant transformation in adult patients. Thoroughly histological inspections are suggested to be necessary to accurately diagnose this tumor when it is encountered in adults.

Different expressions of erbB1/2 and tight junction proteins in hypertrophic inferior turbinates and nasal polyps.

Both inferior turbinate hypertrophy and nasal polyp formation entail the enlargement of the nasal mucosa caused by rhinosinusitis, but their macro/microscopic and clinical findings differ markedly. This study aimed at investigating differences in the expressions of erbB1/2 and the tight junction proteins, claudin-1 and tricellulin, in the two tissues. Ten inferior turbinates and ten nasal polyps were collected. The expressions of erbB1/2, claudin-1, and tricellulin were examined by fluorescence immunohistochemistry and by quantitative real-time transcription-polymerase chain reaction (qRT-PCR). The eosinophil count and % of nasal gland area in the mucosa were also measured. The fluorescence intensities in the inferior turbinates were higher for erbB1/2 and lower for claudin-1 than those in the nasal polyps. The results of qRT-PCR were consistent with the immunohistochemical findings for erbB1/2. The quantity of tricellulin mRNA was significantly higher in the inferior turbinates than in the nasal polyps. The % of nasal gland area was significantly higher but the eosinophil count was significantly lower in the inferior turbinate than in the nasal polyp. These results suggest that the underlying pathogenesis of hypertrophic inferior turbinates and nasal polyps is likely to differ with respect to regeneration/proliferation and thus the remodeling process.

Deficiency of FRAS1-related extracellular matrix 1 (FREM1) causes congenital diaphragmatic hernia in humans and mice.

Congenital diaphragmatic hernia (CDH) is a common life-threatening birth defect. Recessive mutations in the FRAS1-related extracellular matrix 1 (FREM1) gene have been shown to cause bifid nose with or without anorectal and renal anomalies (BNAR) syndrome and Manitoba oculotrichoanal (MOTA) syndrome, but have not been previously implicated in the development of CDH. We have identified a female child with an isolated left-sided posterolateral CDH covered by a membranous sac who had no features suggestive of BNAR or MOTA syndromes. This child carries a maternally-inherited ~86 kb FREM1 deletion that affects the expression of FREM1's full-length transcripts and a paternally-inherited splice site mutation that causes activation of a cryptic splice site, leading to a shift in the reading frame and premature termination of all forms of the FREM1 protein. This suggests that recessive FREM1 mutations can cause isolated CDH in humans. Further evidence for the role of FREM1 in the development of CDH comes from an N-ethyl-N-nitrosourea -derived mouse strain, eyes2, which has a homozygous truncating mutation in Frem1. Frem1(eyes2) mice have eye defects, renal agenesis and develop retrosternal diaphragmatic hernias which are covered by a membranous sac. We confirmed that Frem1 is expressed in the anterior portion of the developing diaphragm and found that Frem1(eyes2) embryos had decreased levels of cell proliferation in their developing diaphragms when compared to wild-type embryos. We conclude that FREM1 plays a critical role in the development of the diaphragm and that FREM1 deficiency can cause CDH in both humans and mice.

Spontaneous eosinophilic nasal inflammation in a genetically-mutant mouse: comparative study with an allergic inflammation model.

BACKGROUND: Eosinophilic inflammation is a hallmark of chronic rhinosinusitis with nasal polyps. To model this disease process experimentally, nasal sensitization of mice with ovalbumin or aspergillus has been described. Here, we describe a genetically mutant mouse that develops robust spontaneous nasal eosinophilic inflammation. These mice lack the enzyme SHP-1 that down-regulates the IL-4Rα/stat6 signaling pathway. We compared nasal inflammation and inflammatory mediators in SHP-1 deficient mice (mev) and an ovalbumin-induced nasal allergy model. METHODS: A novel technique of trans-pharyngeal nasal lavage was developed to obtain samples of inflammatory cells from the nasal passages of allergic and mev mice. Total and differential cell counts were performed on cytospin preparations. Expression of tissue mRNA for IL-4, IL-13, and mouse beta-defensin-1 (MBD-1) was determined by quantitative PCR. Eotaxin in the lavage fluid was assessed by ELISA. RESULTS: Allergic and mev mice had increased total cells and eosinophils compared with controls. Expression of IL-4 was similarly increased in both allergic and mev mice, but expression of IL-13 and eotaxin was significantly greater in the allergic mice than mev mice. Eotaxin was significantly up-regulated in both allergic rhinitis and mev mice. In both models of eosinophilic inflammation, down-regulation of the innate immune marker MBD-1 was observed. CONCLUSIONS: The mev mice display spontaneous chronic nasal eosinophilic inflammation with potential utility for chronic rhinosinusitis with nasal polyps research. The eosinophilic infiltrate is more robust in the mev mice than allergic mice, but Th2 cytokine expression is not as pronounced. Decreased MBD-1 expression in both models supports the concept that Th2-cytokines down-regulate sinonasal innate immunity in humans, and suggests a role for mouse models in investigating the interaction between adaptive and innate immunity in the sinonasal mucosa.

Translocation t(12;17)(q24.1;q21) as the sole anomaly in a nasal chondromesenchymal hamartoma arising in a patient with pleuropulmonary blastoma.

The identification of recurrent chromosomal abnormalities in benign and malignant mesenchymal neoplasms has provided important pathogenetic insight as well as powerful diagnostic adjuncts. Nasal chondromesenchymal hamartoma (NCMH), an extremely rare benign tumor arising in the sinonasal tract of infants and children, has not been previously subjected to cytogenetic analysis. Histopathologically composed of mixed mesenchymal elements, NCMH exhibits a relatively wide differential diagnosis to include chondromyxoid fibroma, chondroblastoma, aneurysmal bone cyst, fibrous dysplasia, and osteochondromyxoma. An interesting association with pleuropulmonary blastoma has been reported in a small subset of NCMH patients. In the current study, cytogenetic analysis of a NCMH arising in an 11-year-old boy with a past medical history of pleuropulmonary blastoma revealed a novel 12;17 translocation, t(12;17)(q24.1;q21), as the sole anomaly.

A mild form of SLC29A3 disorder: a frameshift deletion leads to the paradoxical translation of an otherwise noncoding mRNA splice variant.

We investigated two siblings with granulomatous histiocytosis prominent in the nasal area, mimicking rhinoscleroma and Rosai-Dorfman syndrome. Genome-wide linkage analysis and whole-exome sequencing identified a homozygous frameshift deletion in SLC29A3, which encodes human equilibrative nucleoside transporter-3 (hENT3). Germline mutations in SLC29A3 have been reported in rare patients with a wide range of overlapping clinical features and inherited disorders including H syndrome, pigmented hypertrichosis with insulin-dependent diabetes, and Faisalabad histiocytosis. With the exception of insulin-dependent diabetes and mild finger and toe contractures in one sibling, the two patients with nasal granulomatous histiocytosis studied here displayed none of the many SLC29A3-associated phenotypes. This mild clinical phenotype probably results from a remarkable genetic mechanism. The SLC29A3 frameshift deletion prevents the expression of the normally coding transcripts. It instead leads to the translation, expression, and function of an otherwise noncoding, out-of-frame mRNA splice variant lacking exon 3 that is eliminated by nonsense-mediated mRNA decay (NMD) in healthy individuals. The mutated isoform differs from the wild-type hENT3 by the modification of 20 residues in exon 2 and the removal of another 28 amino acids in exon 3, which include the second transmembrane domain. As a result, this new isoform displays some functional activity. This mechanism probably accounts for the narrow and mild clinical phenotype of the patients. This study highlights the 'rescue' role played by a normally noncoding mRNA splice variant of SLC29A3, uncovering a new mechanism by which frameshift mutations can be hypomorphic.

Generation and characterization of a Cyp2f2-null mouse and studies on the role of CYP2F2 in naphthalene-induced toxicity in the lung and nasal olfactory mucosa.

The CYP2F enzymes, abundantly expressed in the respiratory tract, are active toward many xenobiotic compounds, including naphthalene (NA). However, the precise roles of these enzymes in tissue-selective chemical toxicity have been difficult to resolve. A Cyp2f2-null mouse was generated in this study by disrupting the Cyp2f2 fourth exon. Homozygous Cyp2f2-null mice, which had no CYP2F2 expression and showed no changes in the expression of other P450 genes examined, were viable and fertile and had no in utero lethality or developmental deficits. The loss of CYP2F2 expression led to substantial decreases in the in vitro catalytic efficiency of microsomal NA epoxygenases in lung (up to ~160-fold), liver (~3-fold), and nasal olfactory mucosa (OM; up to ~16-fold), and significant decreases in rates of systemic NA (300 mg/kg i.p.) clearance. The Cyp2f2-null mice were largely resistant to NA-induced cytotoxicity, when examined at 24 h after NA dosing (at 300 mg/kg i.p.), and to NA-induced depletion of total nonprotein sulfhydryl (NPSH), examined at 2 h after dosing, in the lungs. In contrast, the loss of CYP2F2 expression did not alleviate NA-induced NPSH depletion or tissue toxicity in the OM. Mouse CYP2F2 clearly plays an essential role in the bioactivation and toxicity of NA in the lung but not in the OM. The Cyp2f2-null mouse should be valuable for studies on the role of CYP2F2 in the metabolism and toxicity of numerous other xenobiotic compounds and for future production of a CYP2F1-humanized mouse.