The phenotypic spectrum of contiguous deletion of CYP21A2 and tenascin XB: quadricuspid aortic valve and other midline defects

Pediatric Quadricuspid Aortic Valve: Morphology, Characteristics, Clinical Outcomes, and Literature Review

BACKGROUND

Quadricuspid aortic valve (QAV) is an exceedingly rare congenital heart defect (CHD) which has not been well-defined in a pediatric population.

METHODS

The Mayo Clinic echocardiography database was retrospectively analyzed to identify patients ≤18 years diagnosed with QAV from January 1990 to December 2023. Patients with truncus arteriosus were excluded. All images were independently reviewed to define morphology of the QAV by using the Hurwitz and Roberts classification.

RESULTS

Fourteen patients with QAV were identified with a median age at time of diagnosis being 10.5 years (interquartile range [IQR] 6-14 years). Male-to-female ratio was 3:1. Associated CHDs were present in 50% (n = 7) patients. The most common morphological subtypes of QAV were Type D in 43% (n = 6) and Type B in 29% (n = 4). Aortic regurgitation was the most frequently associated valvular abnormality affecting 86% (n = 12) cases, with greater than moderate regurgitation in only two patients. Aortic valve stenosis was observed in 14% (n = 2) patients. Ascending aortic dilatation was present in 21% (3/14) of the cohort, but only 14% (1/7) of isolated QAV patients. At a mean follow up of 11 ± 6.6 years and a median follow-up age of 22 years (IQR 14-27 years), survival was 100% with no primary interventions on the aortic valve or aorta. However, four patients required surgical interventions for associated CHDs.

CONCLUSION

Among children with QAV, almost half of the patients had additional CHD. Aortic regurgitation was the predominant hemodynamic abnormality. Long-term survival was excellent with minimal progression during childhood and adolescence.

Mitral valve transcriptome analysis in thirty-four age-matched Cavalier King Charles Spaniels with or without congestive heart failure caused by myxomatous mitral valve disease

We here report the results of a mitral valve transcriptome study designed to identify genes and molecular pathways involved in development of congestive heart failure (CHF) following myxomatous mitral valve disease (MMVD) in dogs. The study is focused on a cohort of elderly age-matched dogs (n = 34, age ~ 10 years) from a single breed-Cavalier King Charles Spaniels (CKCS)-with a high incidence of MMVD. The cohort comprises 19 dogs (10♀, 9♂) without MMVD-associated CHF, and 15 dogs (6♀, 9♂) with CHF caused by MMVD; i.e., we compare gene expression in breed and age-matched groups of dogs, which only differ with respect to CHF status. We identify 56 genes, which are differentially expressed between the two groups. In this list of genes, we confirm an enrichment of genes related to the TNFβ-signaling pathway, extracellular matrix organization, vascular development, and endothelium damage, which also have been identified in previous studies. However, the genes with the greatest difference in expression between the two groups are CNTN3 and MYH1. Both genes encode proteins, which are predicted to have an effect on the contractile activity of myocardial cells, which in turn may have an effect on valvular performance and hemodynamics across the mitral valve. This may result in shear forces with impact on MMVD progression.

Case report: A novel compound heterozygous variant in the TNXB gene causes single kidney agenesis and vesicoureteral reflux

Primary vesicoureteral reflux (VUR) is the prevailing congenital anomaly of the kidneys and urinary tract, posing a significant risk for pyelonephritis scarring and chronic renal insufficiency in pediatric patients. Nevertheless, the precise genetic etiology of VUR remains enigmatic. In this current investigation, we conducted whole-exome sequencing on a child exhibiting single kidney, devoid of any familial VUR background, along with both biological parents. Two missense variants (NM_019105.8: exon11: c.4111G>A and NM_019105.8: exon2: c.31A>T) in the TNXB gene were identified through whole-exome sequencing of the child. These variants were found to be inherited from the child's parents, with each parent carrying one of the variants. Molecular dynamics simulations were conducted to assess the impact of these variants on the tenascin XB proteins encoded by them, revealing varying degrees of impairment. Based on our findings, it is suggested that the TNXB compound heterozygous variant, consisting of c.4111G>A and c.31A>T, may be the underlying cause of right renal agenesis and left hydronephrosis in afflicted child. This discovery broadens the genetic range of the TNXB gene and establishes a genetic foundation for disease-specific preimplantation genetic diagnosis (PGD) in prospective pregnancies involving the parents of this afflicted child.

Congenital adrenal hyperplasia with a CYP21A2 deletion overlapping the tenascin-X gene: an atypical presentation

OBJECTIVES

Congenital Adrenal Hyperplasia (CAH) is a group of genetic diseases characterized by impaired cortisol biosynthesis. 95% of CAH cases result from mutation in the CYP21A2 gene encoding 21-hydroxilase. TNX-B gene partially overlaps CYP21A2 and encodes a matrix protein called Tenascin-X (TNX). Complete tenascin deficiency causes Enlers-Danlos syndrome (EDS). A mono allelic variant called CAH-X CH-1 was recently described, resulting from a CYP21A2 complete deletion that extends into the TNXB. This haploinsufficiency of TNX may be associated with a mild hypermobility form of EDS, as well as other connective tissue comorbidities such as hernia, cardiac defects and chronic arthralgia.

CASE PRESENTATION

We report four patients heterozygous for a CAH-X CH-1 allele that do not present clinical manifestations of the EDS.

CONCLUSIONS

All CAH patients, carriers of these TNXA/TNXB chimeras, should be evaluated for clinical manifestations related to connective tissue hypermobility, cardiac abnormalities and other EDS features, allowing for better clinical surveillance management.

Pseudogene TNXA Variants May Interfere with the Genetic Testing of CAH-X

CAH-X is a hypermobility-type Ehlers-Danlos syndrome connective tissue dysplasia affecting approximately 15% of patients with 21-hydroxylase deficiency (21-OHD) congenital adrenal hyperplasia (CAH) due to contiguous deletion of CYP21A2 and TNXB genes. The two most common genetic causes of CAH-X are CYP21A1P-TNXA/TNXB chimeras with pseudogene TNXA substitution for TNXB exons 35-44 (CAH-X CH-1) and TNXB exons 40-44 (CAH-X CH-2). A total of 45 subjects (40 families) from a cohort of 278 subjects (135 families of 21-OHD and 11 families of other conditions) were found to have excessive TNXB exon 40 copy number as measured by digital PCR. Here, we report that 42 subjects (37 families) had at least one copy of a TNXA variant allele carrying a TNXB exon 40 sequence, whose overall allele frequency was 10.3% (48/467). Most of the TNXA variant alleles were in cis with either a normal (22/48) or an In2G (12/48) CYP21A2 allele. There is potential interference with CAH-X molecular genetic testing based on copy number assessment, such as with digital PCR and multiplex ligation-dependent probe amplification, since this TNXA variant allele might mask a real copy number loss in TNXB exon 40. This interference most likely happens amongst genotypes of CAH-X CH-2 with an in trans normal or In2G CYP21A2 allele.

Extracellular Matrix Remodeling During Palate Development

The morphogenesis of the mammalian secondary plate is a series of highly dynamic developmental process, including the palate shelves vertical outgrowth, elevation to the horizontal plane and complete fusion in the midline. Extracellular matrix (ECM) proteins not only form the basic infrastructure for palatal mesenchymal cells to adhere via integrins but also interact with cells to regulate their functions such as proliferation and differentiation. ECM remodeling is essential for palatal outgrowth, expansion, elevation, and fusion. Multiple signaling pathways important for palatogenesis such as FGF, TGF β, BMP, and SHH remodels ECM dynamics. Dysregulation of ECM such as HA synthesis or ECM breakdown enzymes MMPs or ADAMTS causes cleft palate in mouse models. A better understanding of ECM remodeling will contribute to revealing the pathogenesis of cleft palate.

High-Throughput Screening for CYP21A1P-TNXA/TNXB Chimeric Genes Responsible for Ehlers-Danlos Syndrome in Patients with Congenital Adrenal Hyperplasia

Many patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency have CAH-X syndrome, a connective tissue dysplasia consistent with hypermobility-type Ehlers-Danlos syndrome due to a contiguous gene deletion involving the adjacent CYP21A2 and TNXB genes. CAH-X syndrome is caused by carrying CYP21A1P-TNXA/TNXB chimeric genes [CAH-X chimera 1 (CH-1) and chimera 2 (CH-2)] on one or more alleles. Genetic analysis is cumbersome due to pseudogene interference. We developed a PCR-based CAH-X high-throughput screening method to assess the copy numbers of TNXB exons 35 and 40; this method is amenable to either real-time quantitative PCR or droplet digital PCR (ddPCR). The assay was validated in a cohort of 278 subjects from 146 unrelated CAH families. Results were confirmed by a validated Sanger sequencing platform. A total of 44 CAH-X-positive calls were made, with 42 (26 CH-1 and 16 CH-2) confirmed. The assay had 100% sensitivity (42 true/42 positives), 99.2% specificity (234 true/236 negatives), and an overall 99.3% accuracy (276/278). Calls made by real-time quantitative PCR and ddPCR were consistent (100%), and ddPCR offered easier data interpretation. The CAH-X prevalence was 15.6% (21/135 probands), higher than the previously estimated 8.5%, and was particularly high (29.2% or 21/72) in those with a 30-Kb deletion. This assay is suitable for high-throughput CAH-X screening, especially in subjects testing positive for CAH in neonatal screening.

Genetic risk factors for eating disorders: an update and insights into pathophysiology

Genome-wide-association studies (GWASs), epigenetic, gene-expression and gene-gene interaction projects, nutritional genomics and investigations of the gut microbiota have increased our knowledge of the pathophysiology of eating disorders (EDs). However, compared with anorexia nervosa, genetic studies in patients with bulimia nervosa and binge-eating disorder are relatively scarce, with the exception of a few formal genetic and small-sized candidate-gene-association studies. In this article, we review important findings derived from formal and molecular genetics in order to outline a genetics-based pathophysiological model of EDs. This model takes into account environmental and nutritional factors, genetic factors related to the microbiome, the metabolic and endocrine system, the immune system, and the brain, in addition to phenotypical traits of EDs. Shortcomings and advantages of genetic research in EDs are discussed against the historical background, but also in light of potential future treatment options for patients with EDs.

From Bicuspid to Quadricuspid Aortic Valve: The Clinical Case of a 38-year-old Woman with Chest Pain

We report a case of a 38-year-old woman with an alleged diagnosis of bicuspid aortic valve disease that was correctly identified as quadricuspid aortic valve (QAV) disease in our cardiology unit. In this case report, we focus on echocardiographic features of this rare congenital valve disease aiming to provide useful tips to achieve correct differential diagnosis according to the updated echocardiographic international guidelines and recommendations, briefly reviewing other QAV cases reported in the current literature as well. In conclusion, we strongly recommend adhering to practical echocardiographic guidelines to reduce interobserver variability, not to miss the diagnosis of rare congenital defects like the one we reported.

High-throughput DNA methylation analysis in anorexia nervosa confirms TNXB hypermethylation

OBJECTIVES

Patients with anorexia nervosa (AN) are ideally suited to identify differentially methylated genes in response to starvation.

METHODS

We examined high-throughput DNA methylation derived from whole blood of 47 females with AN, 47 lean females without AN and 100 population-based females to compare AN with both controls. To account for different cell type compositions, we applied two reference-free methods (FastLMM-EWASher, RefFreeEWAS) and searched for consensus CpG sites identified by both methods. We used a validation sample of five monozygotic AN-discordant twin pairs.

RESULTS

Fifty-one consensus sites were identified in AN vs. lean and 81 in AN vs. population-based comparisons. These sites have not been reported in AN methylation analyses, but for the latter comparison 54/81 sites showed directionally consistent differential methylation effects in the AN-discordant twins. For a single nucleotide polymorphism rs923768 in CSGALNACT1 a nearby site was nominally associated with AN. At the gene level, we confirmed hypermethylated sites at TNXB. We found support for a locus at NR1H3 in the AN vs. lean control comparison, but the methylation direction was opposite to the one previously reported.

CONCLUSIONS

We confirm genes like TNXB previously described to comprise differentially methylated sites, and highlight further sites that might be specifically involved in AN starvation processes.

An overview of inborn errors of metabolism manifesting with primary adrenal insufficiency

Primary adrenal insufficiency (PAI) results from an inability to produce adequate amounts of steroid hormones from the adrenal cortex. The most common causes of PAI are autoimmune adrenalitis (Addison's disease), infectious diseases, adrenalectomy, neoplasia, medications, and various rare genetic syndromes and inborn errors of metabolism that typically present in childhood although late-onset presentations are becoming increasingly recognized. The prevalence of PAI in Western countries is approximately 140 cases per million, with an incidence of 4 per 1,000,000 per year. Several pitfalls in the genetic diagnosis of patients with PAI exist. In this review, we provide an in-depth discussion and overview on the inborn errors of metabolism manifesting with PAI, including genetic diagnosis, genotype-phenotype relationships and counseling of patients and their families with a focus on various enzymatic deficiencies of steroidogenesis.

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.

Genetics of Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) refers to a group of autosomal recessive disorders due to single-gene defects in the various enzymes required for cortisol biosynthesis. CAH represents a continuous phenotypic spectrum with more than 95% of all cases caused by 21-hydroxylase deficiency. Genotyping is an important tool in confirming the diagnosis or carrier state, provides prognostic information on disease severity, and is essential for genetic counseling. In this article, the authors provide an in-depth discussion on the genetics of CAH, including genetic diagnosis, molecular analysis, genotype-phenotype relationships, and counseling of patients and their families.

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.

Tenascin-X haploinsufficiency associated with Ehlers-Danlos syndrome in patients with congenital adrenal hyperplasia

CONTEXT

The gene for congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, CYP21A2, is flanked by the gene encoding tenascin-X (TNXB), a connective tissue extracellular matrix protein that has been linked to both autosomal dominant and autosomal recessive Ehlers-Danlos syndrome (EDS). A contiguous deletion of CYP21A2 and TNXB has been described.

OBJECTIVE

The objective of the study was to determine the frequency and clinical significance of TNXB haploinsufficiency in CAH patients.

DESIGN, SETTING, AND PARTICIPANTS

A total of 192 consecutive unrelated CAH patients being seen as part of an observational study at the National Institutes of Health Clinical Center (Bethesda, MD) were prospectively studied during 2006-2010. Patients were evaluated for clinical evidence of EDS, including cardiac evaluation. DNA was analyzed by PCR, multiplex ligation-dependent probe amplification, Southern blot, and TNXB sequencing. Tenascin-X expression was evaluated by Western blot analysis of fibroblasts and immunostaining of the skin. CAH patients with TNXB haploinsufficiency were compared with age-matched CAH patients with normal TNXB (controls). Phenotyping of 7 parents with TNXB haploinsufficiency was performed.

MAIN OUTCOME MEASURES

The frequency of TNXB haploinsufficiency among CAH patients and the frequency of EDS symptomatology among CAH patients with TNXB haploinsufficiency and controls.

RESULTS

TNXB haploinsufficiency, here termed CAH-X syndrome, was present in 7% of CAH patients. Twelve of 91 patients carrying a CYP21A2 deletion (13%) carried a contiguous deletion that extended into TNXB. One patient carried a TNXB premature stop codon. Twelve of 13 patients with CAH-X had EDS clinical features. Patients with CAH-X were more likely than age-matched controls to have joint hypermobility (P < .001), chronic joint pain (P = .003), multiple joint dislocations (P = .004), a structural cardiac valve abnormality by echocardiography (P = .02), and reduced tenascin-X expression by Western blot and immunostaining. A subset of parents had clinical findings.

CONCLUSIONS

Clinical evaluation for connective tissue dysplasia should be routinely performed in CAH patients, especially those harboring a CYP21A2 deletion.

Complement component 4 copy number variation and CYP21A2 genotype associations in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is an autosomal recessive disorder of cortisol biosynthesis caused by CYP21A2 mutations. An increase in gene copy number variation (CNV) exists at the CYP21A2 locus. CNV of C4, a neighboring gene that encodes complement component 4, is associated with autoimmune disease susceptibility. In this study, we performed comprehensive genetic analysis of the RP-C4-CYP21-TNX (RCCX) region in 127 unrelated 21-OHD patients (100 classic, 27 nonclassic). C4 copy number was determined by Southern blot. C4 CNV and serum C4 levels were evaluated in relation to CYP21A2 mutations and relevant phenotypes. We found that the most common CYP21A2 mutation associated with the nonclassic form of CAH, V281L, was associated with high C4 copy number (p = 7.13 × 10(-16)). Large CYP21A2 deletion, a common mutation associated with the classic form of CAH, was associated with low C4 copy number (p = 1.61 × 10(-14)). Monomodular RCCX with a short C4 gene, a risk factor for autoimmune disease, was significantly less frequent in CAH patients compared to population estimates (2.8 vs. 10.6 %; p = 1.08 × 10(-4)). In conclusion, CAH patients have increased C4 CNV, with mutation-specific associations that may be protective for autoimmune disease. The study of CYP21A2 in relation to neighboring genes provides insight into the genetics of CNV hotspots, an important determinant of human health.

Comprehensive genetic analysis of 182 unrelated families with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

BACKGROUND

Genetic analysis is commonly performed in patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency.

STUDY OBJECTIVE

The objective of the study was to describe comprehensive CYP21A2 mutation analysis in a large cohort of CAH patients.

METHODS

Targeted CYP21A2 mutation analysis was performed in 213 patients and 232 parents from 182 unrelated families. Complete exons of CYP21A2 were sequenced in patients in whom positive mutations were not identified by targeted mutation analysis. Copy number variation and deletions were determined using Southern blot analysis and PCR methods. Genotype was correlated with phenotype.

RESULTS

In our heterogeneous U.S. cohort, targeted CYP21A2 mutation analysis did not identify mutations on one allele in 19 probands (10.4%). Sequencing identified six novel mutations (p.Gln262fs, IVS8+1G>A, IVS9-1G>A, p.R408H, p.Gly424fs, p.R426P) and nine previously reported rare mutations. The majority of patients (79%) were compound heterozygotes and 69% of nonclassic (NC) patients were compound heterozygous for a classic and a NC mutation. Duplicated CYP21A2 haplotypes, de novo mutations and uniparental disomy were present in 2.7% of probands and 1.9 and 0.9% of patients from informative families, respectively. Genotype accurately predicted phenotype in 90.5, 85.1, and 97.8% of patients with salt-wasting, simple virilizing, and NC mutations, respectively.

CONCLUSIONS

Extensive genetic analysis beyond targeted CYP21A2 mutational detection is often required to accurately determine genotype in patients with CAH due to the high frequency of complex genetic variation.

Nonclassic congenital adrenal hyperplasia

Nonclassic congenital adrenal hyperplasia (NCAH) due to P450c21 (21-hydroxylase deficiency) is a common autosomal recessive disorder. This disorder is due to mutations in the CYP21A2 gene which is located at chromosome 6p21. The clinical features predominantly reflect androgen excess rather than adrenal insufficiency leading to an ascertainment bias favoring diagnosis in females. Treatment goals include normal linear growth velocity and "on-time" puberty in affected children. For adolescent and adult women, treatment goals include regularization of menses, prevention of progression of hirsutism, and fertility. This paper will review key aspects regarding pathophysiology, diagnosis, and treatment of NCAH.

Genetics of congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is one of the most common inherited metabolic disorders. It comprises a group of autosomal recessive disorders caused by the deficiency of one of four steroidogenic enzymes involved in cortisol biosynthesis or in the electron donor enzyme P450 oxidoreductase (POR) that serves as electron donor to steroidogenic cytochrome P450 (CYP) type II enzymes. The biochemical and clinical phenotype depends on the specific enzymatic defect and the impairment of specific enzyme activity. Defects of steroid 21-hydroxylase (CYP21A2) and 11beta-hydroxylase (CYP11B1) only affect adrenal steroidogenesis, whereas 17alpha-hydroxylase (CYP17A1) and 3beta-hydroxysteroid dehydrogenase type 2 (HSD3B2) deficiency also impact on gonadal steroid biosynthesis. Inactivating POR gene mutations are the cause of CAH manifesting with apparent combined CYP17A1-CYP21A2 deficiency. P450 oxidoreductase deficiency (ORD) has a complex phenotype including two unique features not observed in any other CAH variant: skeletal malformations and severe genital ambiguity in both sexes.