Tenascin-X deficiency is associated with Ehlers-Danlos syndrome

Complement component 4 variations may influence psychopathology risk in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

CYP21A2 defects result in congenital adrenal hyperplasia (CAH), an autosomal recessive disorder characterized by impaired adrenal steroidogenesis. CYP21A2 lies within the major histocompatibility complex in an area of the genome highly susceptible to genetic variation. Alterations in the neighboring complement component 4 isotypes C4A and C4B have been associated with psychiatric and autoimmune disease. The purpose of this study was to evaluate C4A and C4B in patients with CAH in relation to CYP21A2 genotype and psychiatric and autoimmune comorbidity. We determined the copy numbers of C4A and C4B in 145 patients with CAH (median age: 15.5 years, IQR: 16.8) and 108 carrier relatives (median age: 41.5 years, IQR: 12.0) and evaluated serum C4 concentrations. Comorbidity was determined by medical record review. Only 30% of subjects had the expected two copies each of the two C4 genes. C4B copy number determined total C4 copy number and serum C4 concentration, negatively correlated with carriership of a 30-kb deletion (P < 10^- 5), and positively correlated with carriership of p.V281L (P < 10^- 5). High C4A copy number (≥ 3) was associated with increased risk of having an externalizing psychiatric condition (relative risk: 2.67, 95% CI: 1.03-6.89, P = 0.04). No association was found between C4 copy number and autoimmune disease. Mutation-specific C4 structural variations commonly occur in patients with CAH and may have important clinical consequences, including increased risk of psychiatric morbidity. Trial registration NCT00250159 (November 7, 2005).

Potential biomarkers of the mature intervertebral disc identified at the single cell level

Intervertebral disc (IVD) degeneration and trauma is a major socio-economic burden and the focus of cell-based regenerative medicine approaches. Despite numerous ongoing clinical trials attempting to replace ailing IVD cells with mesenchymal stem cells, a solid understanding of the identity and nature of cells in a healthy mature IVD is still in need of refinement. Although anatomically simple, the IVD is comprised of heterogeneous cell populations. Therefore, methods involving cell pooling for RNA profiling could be misleading. Here, by using RNA in situ hybridization and z proportion test, we have identified potential novel biomarkers through single cell assessment. We quantified the proportion of RNA transcribing cells for 50 genetic loci in the outer annulus fibrosus (AF) and nucleus pulposus (NP) in coccygeal bovine discs isolated from tails of four skeletally mature animals. Our data reconfirm existing data and suggest 10 novel markers such as Lam1 and Thy1 in the outer AF and Gli1, Gli3, Noto, Scx, Ptprc, Sox2, Zscan10 and LOC101904175 in the NP, including pluripotency markers, that indicate stemness potential of IVD cells. These markers could be added to existing biomarker panels for cell type characterization. Furthermore, our data once more demonstrate heterogeneity in cells of the AF and NP, indicating the need for single cell assessment by methods such as RNA in situ hybridization. Our work refines the molecular identity of outer AF and NP cells, which can benefit future regenerative medicine and tissue engineering strategies in humans.

The extracellular matrix glycoprotein tenascin-X regulates peripheral sensory and motor neurones

KEY POINTS

Tenascin-X (TNX) is an extracellular matrix glycoprotein with anti-adhesive properties in skin and joints. Here we report the novel finding that TNX is expressed in human and mouse gut tissue where it is exclusive to specific subpopulations of neurones. Our studies with TNX-deficient mice show impaired defecation and neural control of distal colonic motility that can be rescued with a 5-HT₄ receptor agonist. However, colonic secretion is unchanged. They are also susceptible to internal rectal intussusception. Colonic afferent sensitivity is increased in TNX-deficient mice. Correspondingly, there is increased density of and sensitivity of putative nociceptive fibres in TNX-deficient mucosa. A group of TNX-deficient patients report symptoms highly consistent with those in the mouse model. These findings suggest TNX plays entirely different roles in gut to non-visceral tissues - firstly a role in enteric motor neurones and secondly a role influencing nociceptive sensory neurones Studying further the mechanisms by which TNX influences neuronal function will lead to new targets for future treatment.

ABSTRACT

The extracellular matrix (ECM) is not only an integral structural molecule, but is also critical for a wide range of cellular functions. The glycoprotein tenascin-X (TNX) predominates in the ECM of tissues like skin and regulates tissue structure through anti-adhesive interactions with collagen. Monogenic TNX deficiency causes painful joint hypermobility and skin hyperelasticity, symptoms characteristic of hypermobility Ehlers Danlos syndrome (hEDS). hEDS patients also report consistently increased visceral pain and gastrointestinal (GI) dysfunction. We investigated whether there is a direct link between TNX deficiency and GI pain or motor dysfunction. We set out first to learn where TNX is expressed in human and mouse, then determine how GI function, specifically in the colon, is disordered in TNX-deficient mice and humans of either sex. In human and mouse tissue, TNX was predominantly associated with cholinergic colonic enteric neurones, which are involved in motor control. TNX was absent from extrinsic nociceptive peptidergic neurones. TNX-deficient mice had internal rectal prolapse and a loss of distal colonic contractility which could be rescued by prokinetic drug treatment. TNX-deficient patients reported increased sensory and motor GI symptoms including abdominal pain and constipation compared to controls. Despite absence of TNX from nociceptive colonic neurones, neuronal sprouting and hyper-responsiveness to colonic distension was observed in the TNX-deficient mice. We conclude that ECM molecules are not merely support structures but an integral part of the microenvironment particularly for specific populations of colonic motor neurones where TNX exerts functional influences.

Multiple Roles of Tenascins in Homeostasis and Pathophysiology of Aorta

Tenascins are a family of large extracellular matrix (ECM) glycoproteins. Four family members (tenascin-C, -R, -X, and -W) have been identified to date. Each member consists of the same types of structural domains and exhibits time- and tissue-specific expression patterns, suggesting their specific roles in embryonic development and tissue remodeling. Among them, the significant involvement of tenascin-C (TNC) and tenascin-X (TNX) in the progression of vascular diseases has been examined in detail. TNC is strongly up-regulated under pathological conditions, induced by a number of inflammatory mediators and mechanical stress. TNC has diverse functions, particularly in the regulation of inflammatory responses. Recent studies suggest that TNC is involved in the pathophysiology of aneurysmal and dissecting lesions, in part by protecting the vascular wall from destructive mechanical stress. TNX is strongly expressed in vascular walls, and its distribution is often reciprocal to that of TNC. TNX is involved in the stability and maintenance of the collagen network and elastin fibers. A deficiency in TNX results in a form of Ehlers–Danlos syndrome (EDS). Although their exact roles in vascular diseases have not yet been elucidated, TNC and TNX are now being recognized as promising biomarkers for diagnosis and risk stratification of vascular diseases.

Vascular aspects of the Ehlers-Danlos Syndromes

The Ehlers-Danlos Syndromes comprise a heterogeneous group of rare monogenic conditions that are characterized by joint hypermobility, skin and vascular fragility and generalized connective tissue friability. The latest classification recognizes 13 clinical subtypes, with mutations identified in 19 different genes. Besides defects in fibrillar collagens (collagen types I, III and V), their modifying enzymes (ADAMTS-2, lysylhydroxylase 1 (LH1)), and molecules involved in collagen folding (FKBP22), defects have recently been identified in other constituents of the extracellular matrix (e.g. Tenascin-X, collagen type XII), enzymes involved in glycosaminoglycan biosynthesis (β4GalT7 and β3GalT6), dermatan 4-O-sulfotransferase-1 (D4ST1), dermatan sulfate epimerase (DSE)), (putative) transcription factors (ZNF469, PRDM5), components of the complement pathway (C1r, C1s) and an intracellular Zinc transporter (ZIP13). Easy bruising is, to a variable degree, present in all subtypes of EDS. A variable bleeding tendency, manifesting e.g. as gum bleeding, menometrorraghia, postnatal or peri-operative hemorrhage is observed in many EDS-patients of varying EDS subtypes. Life-threatening arterial aneurysms, dissections and ruptures of medium-sized and large arteries are a hallmark of the vascular subtype of EDS, caused by a molecular defect in collagen type III, an important constituent of blood vessel walls and hollow organs. They may however also occur in other EDS subtypes, especially in classical EDS, caused by defects in type V collagen or, rarely, type I collagen, and in kyphoscoliotic EDS, caused by defects in LH1 or FKBP22. These manifestations of vascular fragility and bleeding are usually attributed to fragility of the blood vessel walls and the perivascular connective tissues, but the molecular pathomechanisms underlying these complications are poorly studied. This review summarizes current knowledge on manifestations of vascular fragility in the different EDS subtypes.

Matricellular Proteins: Functional Insights From Non-mammalian Animal Models

The extracellular matrix (ECM) has central roles in tissue integrity and remodeling throughout the life span of animals. While collagens are the most abundant structural components of ECM in most tissues, tissue-specific molecular complexity is contributed by ECM glycoproteins. The matricellular glycoproteins are categorized primarily according to functional criteria and represented predominantly by the thrombospondin, tenascin, SPARC/osteonectin, and CCN families. These proteins do not self-assemble into ECM fibrils; nevertheless, they shape ECM properties through interactions with structural ECM proteins, growth factors, and cells. Matricellular proteins also promote cell migration or morphological changes through adhesion-modulating or counter-adhesive actions on cell-ECM adhesions, intracellular signaling, and the actin cytoskeleton. Typically, matricellular proteins are most highly expressed during embryonic development. In adult tissues, expression is more limited unless activated by cues for dynamic tissue remodeling and cell motility, such as occur during inflammatory response and wound repair. Many insights in the complex roles of matricellular proteins have been obtained from studies of gene knockout mice. However, with the exception of chordate-specific tenascins, these are highly conserved proteins that are encoded in many animal phyla. This review will consider the increasing body of research on matricellular proteins in nonmammalian animal models. These models provide better access to the very earliest stages of embryonic development and opportunities to study biological processes such as limb and organ regeneration. In aggregate, this research is expanding concepts of the functions and mechanisms of action of matricellular proteins.

A 3-gene panel improves the prediction of left ventricular dysfunction after acute myocardial infarction

BACKGROUND

Identification of patients at risk of poor outcome after acute myocardial infarction (MI) would allow tailoring healthcare to each individual. However, lack of prognostication tools renders this task challenging. Previous investigations suggested that blood transcriptome analysis may inform about prognosis after MI. We aim to independently confirm the value of gene expression profiles in the blood to predict left ventricular (LV) dysfunction after MI.

METHODS AND RESULTS

Five genes (LMNB1, MMP9, TGFBR1, LTBP4 and TNXB) selected from previous studies were measured in peripheral blood samples obtained at reperfusion in 449 MI patients. 79 patients had LV dysfunction as attested by an ejection fraction (EF) ≤40% at 4-month follow-up and 370 patients had a preserved LV function (EF>40%). LMNB1, MMP9 and TGFBR1 were up-regulated in patients with LV dysfunction and LTBP4 was down-regulated, as compared with patients with preserved LV function. The 5 genes were significant univariate predictors of LV dysfunction. In multivariable analyses adjusted with traditional risk factors and corrected for model overfitting, a panel of 3 genes - TNXB, TGFBR1 and LTBP4 - improved the prediction of a clinical model (p=0.00008) and provided a net reclassification index of 0.45 [0.23-0.69], p=0.0002 and an integrated discrimination improvement of 0.05 [0.02-0.09], p=0.001. Bootstrap internal validation confirmed the incremental predictive value of the 3-gene panel.

CONCLUSION

A 3-gene panel can aid to predict LV dysfunction after MI. Further independent validation is required before considering these findings for molecular diagnostic assay development.

Tenascin-X, Congenital Adrenal Hyperplasia, and the CAH-X Syndrome

Mutations of the CYP21A2 gene encoding adrenal 21-hydroxylase cause congenital adrenal hyperplasia (CAH). The CYP21A2 gene is partially overlapped by the TNXB gene, which encodes an extracellular matrix protein called Tenascin-X (TNX). Mutations affecting both alleles of TNXB cause a severe, autosomal recessive form of Ehlers-Danlos syndrome (EDS). Rarely, patients with severe, salt-wasting CAH have deletions of CYP21A2 that extend into TNXB, resulting in a "contiguous gene syndrome" consisting of CAH and EDS. Heterozygosity for TNXB mutations causing haploinsufficiency of TNX may be associated with the mild "hypermobility form" of EDS, which principally affects small and large joints. Studies of patients with salt-wasting CAH found that up to 10% had clinical features of EDS, associated joint hypermobility, haploinsufficiency of TNX and heterozygosity for TNXB mutations, now called "CAH-X." These patients have joint hypermobility and a spectrum of other comorbidities associated with their connective tissue disorder, including chronic arthralgia, joint subluxations, hernias, and cardiac defects. Other disorders are beginning to be associated with TNX deficiency, including familial vesicoureteral reflux and neurologic disorders. Further work is needed to delineate the full spectrum of TNX-deficient disorders, with and without associated CAH.

Wound healing-related properties detected in an experimental model with a collagen gel contraction assay are affected in the absence of tenascin-X

Patients with tenascin-X (TNX)-deficient type Ehlers-Danlos syndrome (EDS) do not exhibit delayed wound healing, unlike classic type EDS patients, who exhibit mutations in collagen genes. Similarly, in TNX-knockout (KO) mice, wound closure of the skin is normal even though these mice exhibit a reduced breaking strength. Therefore, we speculated that the wound healing process may be affected in the absence of TNX. In this study, to investigate the effects of TNX absence on wound healing-related properties, we performed collagen gel contraction assays with wild-type (WT) and TNX-KO mouse embryonic fibroblasts (MEFs). Collagen gels with embedded TNX-KO MEFs showed significantly greater contraction than those containing WT MEFs. Subsequently, we assessed collagen gel contraction-related properties, such as the activities of matrix metalloproteinase (MMP)-2 and MMP-9 and the protein and mRNA expression levels of transforming growth factor β1 (TGF-β1) in the collagen gels. The activities of MMP-2 and MMP-9 and the expression level of TGF-β1 were elevated in the absence of TNX. Furthermore, filopodia-like protrusion formation, cell proliferation, migration, and collagen expression in MEFs were promoted in the absence of TNX. These results indicate that these wound healing-related properties are affected in a TNX-deficient extracellular environment.

Congenital adrenal hyperplasia

Congenital adrenal hyperplasia is a group of autosomal recessive disorders encompassing enzyme deficiencies in the adrenal steroidogenesis pathway that lead to impaired cortisol biosynthesis. Depending on the type and severity of steroid block, patients can have various alterations in glucocorticoid, mineralocorticoid, and sex steroid production that require hormone replacement therapy. Presentations vary from neonatal salt wasting and atypical genitalia, to adult presentation of hirsutism and irregular menses. Screening of neonates with elevated 17-hydroxyprogesterone concentrations for classic (severe) 21-hydroxylase deficiency, the most common type of congenital adrenal hyperplasia, is in place in many countries, however cosyntropin stimulation testing might be needed to confirm the diagnosis or establish non-classic (milder) subtypes. Challenges in the treatment of congenital adrenal hyperplasia include avoidance of glucocorticoid overtreatment and control of sex hormone imbalances. Long-term complications include abnormal growth and development, adverse effects on bone and the cardiovascular system, and infertility. Novel treatments aim to reduce glucocorticoid exposure, improve excess hormone control, and mimic physiological hormone patterns.

The Ehlers-Danlos syndromes, rare types

The Ehlers-Danlos syndromes comprise a clinically and genetically heterogeneous group of heritable connective tissue disorders, which are characterized by joint hypermobility, skin hyperextensibility, and tissue friability. In the Villefranche Nosology, six subtypes were recognized: The classical, hypermobile, vascular, kyphoscoliotic, arthrochalasis, and dermatosparaxis subtypes of EDS. Except for the hypermobile subtype, defects had been identified in fibrillar collagens or in collagen-modifying enzymes. Since 1997, a whole spectrum of novel, clinically overlapping, rare EDS-variants have been delineated and genetic defects have been identified in an array of other extracellular matrix genes. Advances in molecular testing have made it possible to now identify the causative mutation for many patients presenting these phenotypes. The aim of this literature review is to summarize the current knowledge on the rare EDS subtypes and highlight areas for future research. © 2017 Wiley Periodicals, Inc.

[Ehlers-Danlos syndromes]

Ehlers-Danlos syndromes (EDS) are a heterogeneous group of inheritable connective tissue disorders characterized by skin hyperextensibility, joint hypermobility and cutaneous fragility with delayed wound healing. Over and above these common features, they differ in the presence or absence of various organ and tissue abnormalities, and differences in genetic causal mechanisms and degree of severity. They are complex and multisystem diseases, with the majority being highly disabling because of major joint problems and neurosensory deficiencies, and in some cases, they may be life-threatening due to associated complications, especially vascular disorders. In 1997, the Villefranche classification defined 6 subtypes of EDS. However, many other new variants have been described over the last years. The "historical" EDS were characterized by abnormalities in fibrillar collagen protein synthesis. More recently, disorders of synthesis and organization of the extracellular matrix have been shown to be responsible for other types of EDS. Thus, many EDS are in fact metabolic diseases related to enzymatic defects. While there is no curative treatment for any type of EDS, early diagnosis is of utmost importance in order to optimize the symptomatic management of patients and to prevent avoidable complications. Patients must be treated and monitored by multidisciplinary teams in highly specialized reference centers. In this article, we present the current state of knowledge on these diseases that continue to be elucidated thanks to new molecular genetic techniques.

Mobile Cecum in a Young Woman with Ehlers-Danlos Syndrome Hypermobility type: A Case Report and Review of the Literature

Ehlers-Danlos syndrome, hypermobility type (EDS-HT) is unexpectedly common and is associated with a high rate of gastrointestinal manifestations. We herein report the first documented case of mobile cecum associated with EDS-HT. A 21-year-old woman with repeated right lower abdominal pain was initially diagnosed with EDS-HT. Abdominal examinations performed in the supine position, such as CT and ultrasonography, showed no gross abnormalities. In contrast, oral barium gastrointestinal transit X-ray images obtained with changes in the patient's body position revealed position-dependent cecal volvulus with mobile cecum. She was finally discharged with a dramatic resolution of her symptoms after laparoscopic cecopexy for mobile cecum.

Vascular phenotypes in nonvascular subtypes of the Ehlers-Danlos syndrome: a systematic review

Purpose

Within the spectrum of the Ehlers-Danlos syndromes (EDS), vascular complications are usually associated with the vascular subtype of EDS. Vascular complications are also observed in other EDS subtypes, but the reports are anecdotal and the information is dispersed. To better document the nature of vascular complications among “nonvascular” EDS subtypes, we performed a systematic review.

Methods

We queried three databases for English-language studies from inception until May 2017, documenting both phenotypes and genotypes of patients with nonvascular EDS subtypes. The outcome included the number and nature of vascular complications.

Results

A total of 112 papers were included and data were collected from 467 patients, of whom 77 presented with a vascular phenotype. Severe complications included mainly hematomas (53%), frequently reported in musculocontractural and classical-like EDS; intracranial hemorrhages (18%), with a high risk in dermatosparaxis EDS; and arterial dissections (16%), frequently reported in kyphoscoliotic and classical EDS. Other, more minor, vascular complications were reported in cardiac-valvular, arthrochalasia, spondylodysplastic, and periodontal EDS.

Conclusion

Potentially life-threatening vascular complications are a rare but important finding in several nonvascular EDS subtypes, highlighting a need for more systematic documentation. This review will help familiarize clinicians with the spectrum of vascular complications in EDS and guide follow-up and management.

Suppression of hepatic dysfunction in tenascin‑X‑deficient mice fed a high‑fat diet

Extracellular matrix glycoprotein tenascin‑X (TNX) is the largest member of the tenascin family. In the present study, the contribution of TNX to liver dysfunction was investigated by administration of high‑fat and high‑cholesterol diet with high levels of phosphorus and calcium (HFCD) to wild‑type (WT) and TNX‑knockout (KO) mice. After 16 weeks of HFCD administration, the ratio of liver weight to body weight was approximately 22% higher in the HFCD‑fed WT mice compared with the HFCD‑fed TNX‑KO mice, indicating hepatomegaly in HFCD‑fed WT mice. Histological analyses with hematoxylin and eosin staining at 21 weeks revealed that hepatocyte hypertrophy in HFCD‑fed TNX‑KO mice was suppressed to 85% of that in HFCD‑fed WT mice. By contrast, there was a 1.2‑fold increase in lipid deposition in hepatocytes from HFCD‑fed TNX‑KO mice compared with HFCD‑fed WT mice at 18 weeks, as demonstrated by Oil Red O staining. In addition, TNX‑KO mice at 21 weeks and 27 weeks post‑HFCD administration exhibited significant suppression of inflammatory cell infiltrate to 51 and 24% of that in WT mice, respectively. Immunofluorescence analysis for type I collagen and Elastica van Gieson staining demonstrated a clear hepatic fibrosis progression in HFCD‑fed WT mice at 27 weeks, whereas hepatic fibrosis was undetected in HFCD‑fed TNX‑KO mice. The present findings indicated that TNX deficiency suppressed hepatic dysfunction induced by HFCD administration.

A potential contribution of tenascin-X to blood vessel formation in peripheral nerves

Tenascin-X (TNX), an extracellular matrix protein, is abundantly expressed in peripheral nerves. However, the physiological role of TNX in peripheral nerves remains unknown. In this study, we found that actin levels in sciatic nerves of TNX-deficient mice were markedly decreased. Since actin was highly expressed in endothelial cells in wild-type sciatic nerves, we assessed morphological alterations of blood vessels in TNX-null sciatic nerves. The density of blood vessels was significantly decreased and the size of blood vessels was larger than those in wild-type sciatic nerves. Immunofluorescence showed that TNX was expressed by Schwann cells and fibroblasts in sciatic nerves. The results suggest that TNX secreted from Schwann cells and/or fibroblasts is involved in blood vessel formation in peripheral nerves.

Vesicoureteral reflux and the extracellular matrix connection

Primary vesicoureteral reflux (VUR) is a common pediatric condition due to a developmental defect in the ureterovesical junction. The prevalence of VUR among individuals with connective tissue disorders, as well as the importance of the ureter and bladder wall musculature for the anti-reflux mechanism, suggest that defects in the extracellular matrix (ECM) within the ureterovesical junction may result in VUR. This review will discuss the function of the smooth muscle and its supporting ECM microenvironment with respect to VUR, and explore the association of VUR with mutations in ECM-related genes.

The association between Ehlers-Danlos syndrome-hypermobility type and gastrointestinal symptoms in university students: a cross-sectional study

BACKGROUND

Patients with Ehlers-Danlos syndrome-hypermobility type (EDS-HT) have increased prevalence of gastrointestinal (GI) symptoms, particularly reflux and dyspepsia. EDS-HT is associated with dysautonomia, psychopathology, and chronic pain which can be associated with GI symptoms. The association between GI symptoms and EDS-HT in a 'non-patient' population and the effect of the above-mentioned factors has never been studied.

METHODS

In a cross sectional study, a hypermobility questionnaire was used to screen university students; further clinical examination established the diagnosis of EDS-HT. Validated questionnaires assessed for GI, somatic, pain and autonomic symptoms, psychopathology and quality of life (QOL). These were compared in students with and without EDS-HT; logistic regression analysis examined associations between EDS-HT, GI symptoms and other variables.

KEY RESULTS

Of 1998 students screened, 162 were included: 74 EDS-HT (21.0 years, 53% female) vs 88 Non-EDS-HT (21.5 years, 65% female). Compared to non-EDS-HT students, EDS-HT students were more likely to have multiple GI symptoms (41.9% vs 27.3% P=.05), particularly postprandial fullness (34.4% vs 15.9%, P=.01) and early satiety (32% vs 17%, P=.03), greater autonomic (P<.001) and somatic symptoms (P=.04) but not psychopathology (P>.8). The association between EDS-HT and postprandial symptoms was dependent on autonomic factors but independent of pain and psychopathology. Pain-related QOL scores were reduced in the EDS-HT group (80 vs 90, P=.03).

CONCLUSIONS AND INFERENCES

The previously described association between EDS-HT, dyspepsia, pain and autonomic symptoms in patients is also present in non-patient groups. Future studies are necessary to explore the etiological role of connective tissue in GI and extra intestinal symptoms.

Overview of Wound Healing and Management

Wound healing is a highly complex chain of events, and although it may never be possible to eliminate the risk of experiencing a wound, clinicians' armamentarium continues to expand with methods to manage it. The phases of wound healing are the inflammatory phase, the proliferative phase, and the maturation phase. The pathway of healing is determined by characteristics of the wound on initial presentation, and it is vital to select the appropriate method to treat the wound based on its ability to avoid hypoxia, infection, excessive edema, and foreign bodies.

Recognizing the tenascin-X deficient type of Ehlers-Danlos syndrome: a cross-sectional study in 17 patients

The tenascin-X (TNX) deficient type Ehlers-Danlos syndrome (EDS) is similar to the classical type of EDS. Because of the limited awareness among geneticists and the challenge of the molecular analysis of the TNXB gene, the TNX-deficient type EDS is probably to be under diagnosed. We therefore performed an observational, cross-sectional study. History and physical examination were performed. Results of serum TNX measurements were collected and mutation analysis was performed by a combination of next-generation sequencing (NGS), Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). Included were 17 patients of 11 families with autosomal recessive inheritance and childhood onset. All patients had hyperextensible skin without atrophic scarring. Hypermobility of the joints was observed in 16 of 17 patients. Deformities of the hands and feet were observed frequently. TNX serum level was tested and absent in 11 patients (seven families). Genetic testing was performed in all families; 12 different mutations were detected, most of which are suspected to lead to non-sense mRNA mediated decay. In short, patients with the TNX-deficient type EDS typically have generalized joint hypermobility, skin hyperextensibility and easy bruising. In contrast to the classical type, the inheritance pattern is autosomal recessive and atrophic scarring is absent. Molecular analysis of TNXB in a diagnostic setting is challenging.

Decorin interacting network: A comprehensive analysis of decorin-binding partners and their versatile functions

Decorin, a prototype small leucine-rich proteoglycan, regulates a vast array of cellular processes including collagen fibrillogenesis, wound repair, angiostasis, tumor growth, and autophagy. This functional versatility arises from a wide array of decorin/protein interactions also including interactions with its single glycosaminoglycan side chain. The decorin-binding partners encompass numerous categories ranging from extracellular matrix molecules to cell surface receptors to growth factors and enzymes. Despite the diversity of the decorin interacting network, two main roles emerge as prominent themes in decorin function: maintenance of cellular structure and outside-in signaling, culminating in anti-tumorigenic effects. Here we present contemporary knowledge regarding the decorin interacting network and discuss in detail the biological relevance of these pleiotropic interactions, some of which could be targeted by therapeutic interventions.

A method for quantification of serum tenascin-X by nano-LC/MS/MS

BACKGROUND

Complete deficiency of an extracellular matrix tenascin-X (TNX) leads to a classical type of Ehlers-Danlos syndrome (EDS). TNX haploinsufficiency is a cause of hypermobility type of EDS. Human TNX is also present in a serum form (sTNX) with a molecular size of 140kDa. In this study, we established a method for quantification of sTNX using nano-liquid chromatography tandem mass spectrometry (LC/MS/MS) with selected/multiple reaction monitoring.

METHODS

Twelve abundant protein-depleted sera were reduced, alkylated, and digested with Lys-C and trypsin. Subsequently, the digests were fractionated by strong cation exchange chromatography. Optimal and validated transitions of precursor and product ions of the peptides from sTNX were developed on a triple quadrupole mass spectrometer.

RESULTS

Serum concentrations of sTNX of healthy individuals were quantified as an average of 144ng/ml. However, sTNX was not detected by this method in serum from a patient with a classical type of EDS in whom sTNX was not found by Western blot analysis. The limit of quantification (LOQ) of sTNX by nano-LC/MS/MS method was 2.8pg whereas the detection sensitivity of sTNX by Western blot analysis was 19pg. The nano-LC/MS/MS method is more sensitive than Western blot analysis.

CONCLUSIONS

The quantification method will be useful for diagnosis and risk stratification of EDS caused by TNX deficiency and haploinsufficiency.

Identification of Biomarkers for Footpad Dermatitis Development and Wound Healing

Footpad dermatitis (FPD) is a type of skin inflammation that causes necrotic lesions on the plantar surface of the footpads in commercial poultry, with significant animal welfare, and economic implications. To identify biomarkers for FPD development and wound healing, a battery cage trial was conducted in which a paper sheet was put on the bottom of cages to hold feces to induce FPD of broilers. Day-of-hatch Ross 308 male broiler chicks were fed a corn–soybean meal diet and assigned to 3 treatments with 8 cages per treatment and 11 birds per cage. Cages without paper sheets were used as a negative control (NEG). Cages with paper sheets during the entire growth period (d 0–30) were used as a positive control (POS) to continually induce FPD. Cages with paper sheets during d 0–13 and without paper sheets during d 14–30 were used to examine the dynamic of FPD development and lesion wound healing (LWH). Footpad lesions were scored to grade (G) 1–5 with no lesion in G1 and most severe lesion in G5. Covering with paper sheets in POS and LWH induced 99% incidence of G3 footpads on d 13. Removing paper sheets from LWH healed footpad lesions by d 30. One representative bird, with lesions most close to pen average lesion score, was chosen to collect footpad skin samples for biomarker analysis. Total collagen protein and mRNA levels of tenascin X (TNX), type I α1 collagen (COL1A1), type III α1 collagen (COL3A1), tissue inhibitor of metalloproteinase 3 (TIMP3), and integrin α1 (ITGA1) mRNA levels were decreased (P < 0.05), while mRNA levels of tenascin C (TNC), tumor necrosis factor (TNF) α, Toll-like receptor (TLR) 4 and vascular endothelial growth factor (VEGF), IL-1β, and the ratio of MMP2 to all TIMP were increased (P < 0.03) in G3 footpads in POS and LWH compared to G1 footpads in NEG on d 14. These parameters continued to worsen with development of more severe lesions in POS. After paper sheets were removed (i.e., LWH), levels of these parameters gradually or rapidly returned to levels measured in NEG. Regression analysis indicated significant quadratic changes of these parameters to footpad lesion scores. In summary, these biomarkers were interrelated with dynamic changes of footpad lesion scores, suggesting they may be used as potential biomarkers for footpad lesion development and wound healing process.

Tenascins in fibrotic disorders-from bench to bedside

Although fibrosis is becoming increasingly recognized as a major cause of morbidity and mortality in chronic inflammatory diseases, available treatment strategies are limited. Tenascins constitute a family of matricellular proteins, primarily modulating interactions of cells with other matrix components and growth factors. Data obtained from tenascin C deficient mice show important roles of this molecule in several models of fibrosis. Moreover there is growing evidence that tenascin C has a strong impact on chronic inflammation, myofibroblast differentiation and recruitment. Tenascin C as well as tenascin X has furthermore been shown to affect TGF-β activation and signaling. Taken together these data suggest that these proteins might be important factors in fibrosis development and make them attractive both as biological markers and as targets for therapeutical intervention. So far most clinical research in fibrosis has been focused on tenascin C. This review aims at summarizing our up-to-date knowledge on the involvement of tenascin C in the pathogenesis of fibrotic disorders.

Transcriptional regulation of tenascin genes

Extracellular matrix proteins of the tenascin family resemble each other in their domain structure, and also share functions in modulating cell adhesion and cellular responses to growth factors. Despite these common features, the 4 vertebrate tenascins exhibit vastly different expression patterns. Tenascin-R is specific to the central nervous system. Tenascin-C is an “oncofetal” protein controlled by many stimuli (growth factors, cytokines, mechanical stress), but with restricted occurrence in space and time. In contrast, tenascin-X is a constituitive component of connective tissues, and its level is barely affected by external factors. Finally, the expression of tenascin-W is similar to that of tenascin-C but even more limited. In accordance with their highly regulated expression, the promoters of the tenascin-C and -W genes contain TATA boxes, whereas those of the other 2 tenascins do not. This article summarizes what is currently known about the complex transcriptional regulation of the 4 tenascin genes in development and disease.

Tenascin-X: beyond the architectural function

Tenascin-X is the largest member of the tenascin (TN) family of evolutionary conserved extracellular matrix glycoproteins, which also comprises TN-C, TN-R and TN-W. Among this family, TN-X is the only member described so far to exert a crucial architectural function as evidenced by a connective tissue disorder (a recessive form of Ehlers-Danlos syndrome) resulting from a loss-of-function of this glycoprotein in humans and mice. However, TN-X is more than an architectural protein, as it displays features of a matricellular protein by modulating cell adhesion. However, the cellular functions associated with the anti-adhesive properties of TN-X have not yet been revealed. Recent findings indicate that TN-X is also an extracellular regulator of signaling pathways. Indeed, TN-X has been shown to regulate the bioavailability of the Transforming Growth Factor (TGF)-β and to modulate epithelial cell plasticity. The next challenges will be to unravel whether the signaling functions of TN-X are functionally linked to its matricellular properties.

Bilateral closed flexor pollicis longus musculotendinous junction ruptures

We present a case of bilateral closed flexor pollicis longus musculotendinous junction ruptures. Our case suggests multifactorial aetiology and provides further evidence for genetic influences in musculotendinous junction injuries.

Bruch's membrane abnormalities in PRDM5-related brittle cornea syndrome

Background

Brittle cornea syndrome (BCS) is a rare, generalized connective tissue disorder associated with extreme corneal thinning and a high risk of corneal rupture. Recessive mutations in transcription factors ZNF469 and PRDM5 cause BCS. Both transcription factors are suggested to act on a common pathway regulating extracellular matrix genes, particularly fibrillar collagens. We identified bilateral myopic choroidal neovascularization as the presenting feature of BCS in a 26-year-old-woman carrying a novel PRDM5 mutation (p.Glu134*). We performed immunohistochemistry of anterior and posterior segment ocular tissues, as expression of PRDM5 in the eye has not been described, or the effects of PRDM5-associated disease on the retina, particularly the extracellular matrix composition of Bruch’s membrane.

Methods

Immunohistochemistry using antibodies against PRDM5, collagens type I, III, and IV was performed on the eyes of two unaffected controls and two patients (both with Δ9-14 PRDM5). Expression of collagens, integrins, tenascin and fibronectin in skin fibroblasts of a BCS patient with a novel p.Glu134* PRDM5 mutation was assessed using immunofluorescence.

Results

PRDM5 is expressed in the corneal epithelium and retina. We observe reduced expression of major components of Bruch’s membrane in the eyes of two BCS patients with a PRDM5 Δ9-14 mutation. Immunofluorescence performed on skin fibroblasts from a patient with p.Glu134* confirms the generalized nature of extracellular matrix abnormalities in BCS.

Conclusions

PDRM5-related disease is known to affect the cornea, skin and joints. Here we demonstrate, to the best of our knowledge for the first time, that PRDM5 localizes not only in the human cornea, but is also widely expressed in the retina. Our findings suggest that ECM abnormalities in PRDM5-associated disease are more widespread than previously reported.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-015-0360-4) contains supplementary material, which is available to authorized users.

Broadening the Spectrum of Ehlers Danlos Syndrome in Patients With Congenital Adrenal Hyperplasia

CONTEXT

The contiguous gene deletion syndrome (CAH-X) was described in a subset (7%) of congenital adrenal hyperplasia (CAH) patients with a TNXA/TNXB chimera, resulting in deletions of CYP21A2, encoding 21-hydroxylase necessary for cortisol biosynthesis, and TNXB, encoding the extracellular matrix glycoprotein tenascin-X (TNX). This TNXA/TNXB chimera is characterized by a 120-bp deletion in exon 35 and results in TNXB haploinsufficiency, disrupted TGF-β signaling, and an Ehlers Danlos syndrome phenotype.

OBJECTIVE

The objective of the study was to determine the genetic status of TNXB and resulting protein defects in CAH patients with a CAH-X phenotype but not the previously described TNXA/TNXB chimera. Design, Settings, Participants, and Intervention: A total of 246 unrelated CAH patients were screened for TNXB defects. Genetic defects were investigated by Southern blotting, multiplex ligation-dependent probe amplification, Sanger, and next-generation sequencing. Dermal fibroblasts and tissue were used for immunoblotting, immunohistochemical, and coimmunoprecipitation experiments.

MAIN OUTCOME MEASURES

The genetic and protein status of tenascin-X in phenotypic CAH-X patients was measured.

RESULTS

Seven families harbor a novel TNXB missense variant c.12174C>G (p.C4058W) and a clinical phenotype consistent with hypermobility-type Ehlers Danlos syndrome. Fourteen CAH probands carry previously described TNXA/TNXB chimeras, and seven unrelated patients carry the novel TNXB variant, resulting in a CAH-X prevalence of 8.5%. This highly conserved pseudogene-derived variant in the TNX fibrinogen-like domain is predicted to be deleterious and disulfide bonded, results in reduced dermal elastin and fibrillin-1 staining and altered TGF-β1 binding, and represents a novel TNXA/TNXB chimera. Tenascin-X protein expression was normal in dermal fibroblasts, suggesting a dominant-negative effect.

CONCLUSIONS

CAH-X syndrome is commonly found in CAH due to 21-hydroxylase deficiency and may result from various etiological mechanisms.

Functional gastrointestinal disorders are associated with the joint hypermobility syndrome in secondary care: a case-control study

BACKGROUND

The overlap of unexplained gastrointestinal (GI) and somatic symptoms is well established in patients with functional gastrointestinal disorders (FGID). Joint hypermobility syndrome (JHS) is a non-inflammatory connective tissue disorder associated with GI and somatic symptoms. We aimed to determine whether there is an association between diagnosis of JHS and FGID and the impact of this association on comorbidities and quality of life (QOL).

METHODS

Prospective case-control study in secondary care GI clinics over 2 years. JHS was assessed by the first author prior to consultation in 641 consecutive new patients. Diagnosis of FGID (cases, n = 336) or organic disorders (controls, n = 305) was established blind to JHS status. JHS prevalence was compared in cases (FGID patients) and controls (organic disorders patients). Extra-intestinal comorbidity and QOL were compared in FGID patients with and without JHS.

KEY RESULTS

JHS prevalence was higher in FGID compared to organic GI disorders (39.0% vs 27.5%, ORadj: 1.51, CI: 1.07-2.12, p = 0.02), and particularly associated with functional gastroduodenal disorders (44.1%, ORadj: 2.08, CI: 1.25-3.46, p = 0.005), specifically postprandial distress syndrome (51%, ORadj: 1.99, CI: 1.06-3.76, p = 0.03). FGID patients with JHS had increased chronic pain (23.2% vs 11.9%, p = 0.01), fibromyalgia (10.5% vs 3.1%, p = 0.01), somatization scores (13 vs 10, p < 0.001), urinary autonomic scores (30.5 vs 20.7, p = 0.03), and worse pain-related QOL scores (45.0 vs 63.5, p = 0.004).

CONCLUSIONS & INFERENCES

JHS is significantly associated with FGID, and this subgroup of patients have increased comorbidity and decreased QOL. Further research is required to understand the pathophysiological basis of this association.

A prospective evaluation of undiagnosed joint hypermobility syndrome in patients with gastrointestinal symptoms

BACKGROUND & AIMS

The Joint Hypermobility Syndrome (JHS) is a common connective tissue disorder characterized by joint hyperflexibility, dysautonomia, and chronic pain. Gastrointestinal (GI) symptoms are reported in JHS patients attending rheumatology clinics, but the prevalence and symptom pattern of previously undiagnosed JHS in GI clinics are unknown.

METHODS

By using validated questionnaires, a prospective cross-sectional study in secondary care GI clinics estimated the prevalence of JHS in new consecutively referred patients, compared GI symptoms in patients with and without JHS, and by using multiple regression determined whether the burden of GI symptoms in JHS patients was dependent on chronic pain, autonomic, psychological, and medication related factors. A positive control group consisted of JHS patients referred from rheumatology clinics with GI symptoms (JHS-Rh).

RESULTS

From 552 patients recruited, 180 (33%) had JHS (JHS-G) and 372 did not (non-JHS-G). Forty-four JHS-Rh patients were included. JHS-G patients were more likely to be younger, female with poorer quality of life (P = .02) than non-JHS-G patients. After age and sex matching, heartburn (odds ratio [OR], 1.66; confidence interval [CI], 1.1-2.5; P = .01), water brash (OR, 2.02; CI, 1.3-3.1; P = .001), and postprandial fullness (OR, 1.74; CI, 1.2-2.6; P = .006) were more common in JHS-G vs non-JHS-G. Many upper and lower GI symptoms increased with increasing severity of JHS phenotype. Upper GI symptoms were dependent on autonomic and chronic pain factors.

CONCLUSIONS

JHS is common in GI clinics, with increased burden of upper GI and extraintestinal symptoms and poorer quality of life. Recognition of JHS will facilitate multidisciplinary management of GI and extra-GI manifestations.

Ehlers-Danlos syndrome: a cause of epilepsy and periventricular heterotopia

PURPOSE

Ehlers-Danlos syndrome (EDS) comprises a variety of inherited connective tissue disorders that have been described in association with various neurological features. Until now the neurological symptoms have not been studied in detail; therefore, the aim of this review is to analyze the possible association between EDS, epilepsy and periventricular heterotopia (PH).

METHODS

We have carried out a critical review of all cases of epilepsy in EDS patients with and without PH.

RESULTS

Epilepsy is a frequent neurological manifestation of EDS; generally, it is characterized by focal seizures with temporo-parieto-occipital auras and the most common EEG findings epileptiform discharges and slow intermittent rhythm with delta-theta waves. Epilepsy in EDS patients is usually responsive to common antiepileptic therapy; very few cases of drug resistant focal epilepsy requested surgical treatment, with favorable results in terms of outcome. Epilepsy is the most common presenting neurological manifestation associated with PH in EDS patients. Abnormal anatomic circuitries (including heterotopic nodules) could generate epilepsy in patients with PH.

CONCLUSION

Among the principal neurological manifestations, epilepsy and PH have a considerable importance and can influence the long-term evolution of these patients. We hypothesize that PH may determine the epileptic manifestations in patients with EDS; much remains to be learnt about the relationships between nodules and the epileptic manifestations in EDS syndrome.

Revisiting the matricellular concept

The concept of a matricellular protein was first proposed by Paul Bornstein in the mid-1990s to account for the non-lethal phenotypes of mice with inactivated genes encoding thrombospondin-1, tenascin-C, or SPARC. It was also recognized that these extracellular matrix proteins were primarily counter or de-adhesive. This review reappraises the matricellular concept after nearly two decades of continuous investigation. The expanded matricellular family as well as the diverse and often unexpected functions, cellular location, and interacting partners/receptors of matricellular proteins are considered. Development of therapeutic strategies that target matricellular proteins are discussed in the context of pathology and regenerative medicine.

Congenital adrenal hyperplasia, ovarian failure and Ehlers-Danlos syndrome due to a 6p deletion

Cryptic deletions in balanced de novo translocations represent a frequent cause of abnormal phenotypes, including Mendelian diseases. In this study, we describe a patient with multiple congenital abnormalities, such as late-onset congenital adrenal hyperplasia (CAH), primary ovarian failure and Ehlers-Danlos syndrome (EDS), who carries a de novo t(6;14)(p21;q32) translocation. Genomic array analysis identified a cryptic 1.1-Mb heterozygous deletion, adjacent to the breakpoint on chromosome 6, extending from 6p21.33 to 6p21.32 and affecting 85 genes, including CYP21A2,TNXB and MSH5. Multiplex ligation-dependent probe amplification analysis of the 6p21.3 region was performed in the patient and her family and revealed a 30-kb deletion in the patient's normal chromosome 6, inherited from her mother, resulting in homozygous loss of genes CYP21A1P and C4B. CYP21A2 sequencing showed that its promoter region was not affected by the 30-kb deletion, suggesting that the deletion of other regulatory sequences in the normal chromosome 6 caused a loss of function of the CYP21A2 gene. EDS and primary ovarian failure phenotypes could be explained by the loss of genes TNXB and MSH5, a finding that may contribute to the characterization of disease-causing genes. The detection of this de novo microdeletion drastically reduced the estimated recurrence risk for CAH in the family.

Matricellular proteins in the trabecular meshwork: review and update

Abstract Primary open-angle glaucoma (POAG) is a leading cause of blindness worldwide, and intraocular pressure (IOP) is an important modifiable risk factor. IOP is a function of aqueous humor production and aqueous humor outflow, and it is thought that prolonged IOP elevation leads to optic nerve damage over time. Within the trabecular meshwork (TM), the eye's primary drainage system for aqueous humor, matricellular proteins generally allow cells to modulate their attachments with and alter the characteristics of their surrounding extracellular matrix (ECM). It is now well established that ECM turnover in the TM affects outflow facility, and matricellular proteins are emerging as significant players in IOP regulation. The formalized study of matricellular proteins in TM has gained increased attention. Secreted protein acidic and rich in cysteine (SPARC), myocilin, connective tissue growth factor (CTGF), and thrombospondin-1 and -2 (TSP-1 and -2) have been localized to the TM, and a growing body of evidence suggests that these matricellular proteins play an important role in IOP regulation and possibly the pathophysiology of POAG. As evidence continues to emerge, these proteins are now seen as potential therapeutic targets. Further study is warranted to assess their utility in treating glaucoma in humans.

Tenascin C protects aorta from acute dissection in mice

Acute aortic dissection (AAD) is caused by the disruption of intimomedial layer of the aortic walls, which is immediately life-threatening. Although recent studies indicate the importance of proinflammatory response in pathogenesis of AAD, the mechanism to keep the destructive inflammatory response in check is unknown. Here, we report that induction of tenascin-C (TNC) is a stress-evoked protective mechanism against the acute hemodynamic and humoral stress in aorta. Periaortic application of CaCl₂ caused stiffening of abdominal aorta, which augmented the hemodynamic stress and TNC induction in suprarenal aorta by angiotensin II infusion. Deletion of Tnc gene rendered mice susceptible to AAD development upon the aortic stress, which was accompanied by impaired TGFβ signaling, insufficient induction of extracellular matrix proteins and exaggerated proinflammatory response. Thus, TNC works as a stress-evoked molecular damper to maintain the aortic integrity under the acute stress.

Transforming growth factor-β (TGF-β) pathway abnormalities in tenascin-X deficiency associated with CAH-X syndrome

Patients with congenital adrenal hyperplasia (CAH) with tenascin-X deficiency (CAH-X syndrome) have both endocrine imbalances and characteristic Ehlers Danlos syndrome phenotypes. Unlike other subtypes, tenascin-X-related Ehlers Danlos syndrome is caused by an extracellular matrix protein deficiency rather than a defect in fibrillar collagen or a collagen-modifying enzyme, and the understanding of the disease mechanisms is limited. We hypothesized that transforming growth factor-β pathway dysregulation may, in part, be responsible for connective tissue phenotypes observed in CAH-X, due to this pathway's known role in connective tissue disorders. Fibroblasts and direct tissue from human skin biopsies from CAH-X probands and age- and sex-matched controls were screened for transforming growth factor-β biomarkers known to be dysregulated in other hereditary disorders of connective tissue. In CAH-X fibroblast lines and dermal tissue, pSmad1/5/8 was significantly upregulated compared to controls, suggesting involvement of the bone morphogenetic protein pathway. Additionally, CAH-X samples compared to controls exhibited significant increases in fibroblast-secreted TGF-β3, a cytokine important in secondary palatal development, and in plasma TGF-β2, a cytokine involved in cardiac function and development, as well as palatogenesis. Finally, MMP-13, a matrix metalloproteinase important in secondary palate formation and tissue remodeling, had significantly increased mRNA and protein expression in CAH-X fibroblasts and direct tissue. Collectively, these results demonstrate that patients with CAH-X syndrome exhibit increased expression of several transforming growth factor-β biomarkers and provide a novel link between this signaling pathway and the connective tissue dysplasia phenotypes associated with tenascin-X deficiency.

Mutations in the collagen XII gene define a new form of extracellular matrix-related myopathy

Bethlem myopathy (BM) [MIM 158810] is a slowly progressive muscle disease characterized by contractures and proximal weakness, which can be caused by mutations in one of the collagen VI genes (COL6A1, COL6A2 and COL6A3). However, there may be additional causal genes to identify as in ∼50% of BM cases no mutations in the COL6 genes are identified. In a cohort of -24 patients with a BM-like phenotype, we first sequenced 12 candidate genes based on their function, including genes for known binding partners of collagen VI, and those enzymes involved in its correct post-translational modification, assembly and secretion. Proceeding to whole-exome sequencing (WES), we identified mutations in the COL12A1 gene, a member of the FACIT collagens (fibril-associated collagens with interrupted triple helices) in five individuals from two families. Both families showed dominant inheritance with a clinical phenotype resembling classical BM. Family 1 had a single-base substitution that led to the replacement of one glycine residue in the triple-helical domain, breaking the Gly-X-Y repeating pattern, and Family 2 had a missense mutation, which created a mutant protein with an unpaired cysteine residue. Abnormality at the protein level was confirmed in both families by the intracellular retention of collagen XII in patient dermal fibroblasts. The mutation in Family 2 leads to the up-regulation of genes associated with the unfolded protein response (UPR) pathway and swollen, dysmorphic rough-ER. We conclude that the spectrum of causative genes in extracellular matrix (ECM)-related myopathies be extended to include COL12A1.

Comprehensive mutation analysis of the CYP21A2 gene: an efficient multistep approach to the molecular diagnosis of congenital adrenal hyperplasia

Congenital adrenal hyperplasia, due to 21-hydroxylase deficiency (21-OHD) is an autosomal recessive disorder of adrenal steroidogenesis caused by mutations in the CYP21A2 gene. Direct comparison of established and novel methodologies of CYP21A2 genetic analysis in a large cohort representing a wide range of genotypes has not been previously reported. We genotyped a cohort of 129 unrelated patients with 21-OHD, along with 145 available parents, using Southern blot (SB) analysis, multiplex ligation-dependent probe amplification (MLPA), PCR-based restriction fragment length polymorphism (RFLP) analysis, multiplex minisequencing and conversion-specific PCR, duplication-specific amplification, and DNA sequencing. CYP21A2 genotyping identified four duplicated CYP21A2 genes (1.53%) and 79 chimeric CYP21A1P/CYP21A2 genes (30.15%). Parental SB data were essential for determining the CYP21 haplotype in three cases, whereas PCR-based RFLP analysis was necessary for MLPA results to be accurately interpreted in the majority of cases. The comparison of different methods in detecting deletion and duplication showed that MLPA with PCR-based RFLP was comparable with SB analysis, with parental data of 100% sensitivity and specificity. DNA sequencing was required for the identification of 16 (6.1%) rare point mutations and determination of clinically significant chimera junction sites. MLPA with PCR-based RFLP analysis is an excellent substitute for SB analysis in detecting CYP21A2 deletion and duplication and a combination of MLPA, PCR-based RFLP, duplication-specific amplification, and DNA sequencing is a convenient and comprehensive strategy for mutation analysis of the CYP21A2 gene in patients with 21-OHD.

A novel TaqI polymorphism in the coding region of the ovine TNXB gene in the MHC class III region: morphostructural and physiological influences

The tenascin-XB (TNXB) gene has antiadhesive effects, functions in matrix maturation in connective tissues, and localizes to the major histocompatibility complex class III region. We hypothesized that it may influence adaptive physiological response through an effect on blood vessel function. We identified a novel g.1324 A→G polymorphism at a TaqI recognition site in a 454 bp fragment of ovine TNXB and genotyped it in 150 Nigerian sheep using PCR-RFLP. The missense mutation changes glutamic acid (GAA) to glycine (GGA). Among SNP genotypes, significant differences (P < 0.05) were observed in body weight and fore cannon bone length. Interaction effects of breed, SNP genotype, and geographic location had a significant effect (P < 0.05) on chest girth. The SNP genotype was significantly (P < 0.05) associated with physiological traits of pulse rate and skin temperature. The observed effect of this novel polymorphism may be mediated through its role in connective tissue biology, requiring further association and functional studies.

Tenascin-X, collagen, and Ehlers-Danlos syndrome: tenascin-X gene defects can protect against adverse cardiovascular events

Long thought to be two separate syndromes, Ehlers-Danlos syndrome hypermobility type (EDS-HT) and benign joint hypermobility syndrome (BJHS) appear on close examination to represent the same syndrome, with virtually identical clinical manifestations. While both EDS-HT and BJHS were long thought to lack the genetic loci of other connective tissue disorders, including all other types of EDS, researchers have discovered a genetic locus that accounts for manifestations of both EDS-HT and BJHS in a small population of patients. However, given the modest sample size of these studies and the strong correlation between serum levels of tenascin-X with clinical symptoms of both EDS-HT and BJHS, strong evidence exists for the origins of both types of hypermobility originating in haploinsufficiency or deficiency of the gene TNXB, responsible for tenascin-X. Tenascin-X regulates both the structure and stability of elastic fibers and organizes collagen fibrils in the extra-cellular matrix (ECM), impacting the rigidity or elasticity of virtually every cell in the body. While the impacts of tenascin-X insufficiency or deficiency on the skin and joints have received some attention, its potential cardiovascular impacts remain relatively unexplored. Here we set forth two novel hypotheses. First, TNXB haploinsufficiency or deficiency causes the range of clinical manifestations long identified with both EDS-HT and BJHS. And, second, that haploinsufficiency or deficiency of TNXB may provide some benefits against adverse cardiovascular events, including heart attack and stroke, by lowering levels of arterial stiffness associated with aging, as well as by enhancing accommodation of accrued atherosclerotic plaques. This two-fold hypothesis provides insights into the mechanisms underlying the syndromes previous identified with joint hypermobility, at the same time the hypothesis also sheds light on the role of the composition of the extracellular matrix and its impacts on endothelial sheer stress in adverse cardiovascular events.