Mosaic RASopathies concept: different skin lesions, same systemic manifestations?

BACKGROUND: Cutaneous epidermal nevi are genotypically diverse mosaic disorders. Pathogenic hotspot variants in HRAS, KRAS, and less frequently, NRAS and BRAF may cause isolated keratinocytic epidermal nevi and sebaceous nevi or several different syndromes when associated with extracutaneous anomalies. Therefore, some authors suggest the concept of mosaic RASopathies to group these different disorders. METHODS: In this paper, we describe three new cases of syndromic epidermal nevi caused by mosaic HRAS variants: one associating an extensive keratinocytic epidermal nevus with hypomastia, another with extensive mucosal involvement and a third combining a small sebaceous nevus with seizures and intellectual deficiency. Moreover, we performed extensive literature of all cases of syndromic epidermal nevi and related disorders with confirmed pathogenic postzygotic variants in HRAS, KRAS, NRAS or BRAF. RESULTS: Most patients presented with bone, ophthalmological or neurological anomalies. Rhabdomyosarcoma, urothelial cell carcinoma and pubertas praecox are also repeatedly reported. KRAS pathogenic variants are involved in 50% of the cases, especially in sebaceous nevi, oculoectodermal syndrome and encephalocraniocutaneous lipomatosis. They are frequently associated with eye and brain anomalies. Pathogenic variants in HRAS are rather present in syndromic keratinocytic epidermal nevi and phacomatosis pigmentokeratotica. CONCLUSION: This review delineates genotype/phenotype correlations of syndromic epidermal nevi with somatic RAS and BRAF pathogenic variants and may help improve their follow-up.

[Management of genetic renal disorders: local experience and importance of the network]. / Prise en charge des maladies rénales génétiques : expérience locale et importance du réseau.

In nephrology, rare disorders are frequently encountered. In children, about 60% of the renal disorders are rare, with congenital abnormalities of the kidney and urinary tract disorders (CAKUT), being highly prevalent. In adults, about 22% of the disorders leading to renal replacement therapies are rare and include glomerulonephritis and genetic disorders. Rarity may preclude the rapid and extensive access to care for patients suffering of renal disorders, especially in Switzerland, which is small and fragmented. Only collaborative network and access to databases, shared resources and to specific competence may help patient management. Lausanne and Geneva University Hospitals have started specialized outpatient clinics for rare renal disorders several years ago and are part of national and international networks.

Dans le domaine des maladies rénales, la rareté est fréquente. Chez l'enfant, 60 % des maladies touchant les reins sont rares et les malformations de l'axe urinaire sont prépondérantes. Chez l'adulte, près de 22 % des pathologies qui mènent à la maladie rénale terminale sont rares et incluent les glomérulonéphrites et les maladies génétiques. La rareté de ces pathologies fait que les compétences médicales peuvent être difficiles à trouver et l'expérience locale insuffisante. Ainsi, seule la mise en réseau des données, des ressources et des compétences peut permettre d'améliorer la prise en charge de ces patients. Le CHUV et les HUG ont mis en place des consultations spécialisées pour les maladies rénales rares. Elles s'inscrivent dans un réseau national et international.

Homozygous GLI3 variants observed in three unrelated patients presenting with syndromic polydactyly.

Polydactyly is a hallmark of GLI3 pathogenic variants, with Greig cephalopolysyndactyly syndrome and Pallister-Hall syndrome being the two main associated clinical presentations. Homozygous GLI3 variants are rare instances in the literature, and mendelian dominance is the accepted framework for GLI3-related diseases. Herein, we report three unrelated probands, presenting with polydactyly, and homozygous variants in the GLI3 gene. First, a 10-year-old girl, whose parents were first-degree cousins, presented with bilateral postaxial polydactyly of the hands, developmental delay and multiple malformations. Second, a male newborn, whose parents were first-degree cousins, presented with isolated bilateral postaxial polysyndactyly of the hands and the feet. Third, an adult male, whose parents were first-degree cousins, had bilateral mesoaxial polydactyly of the hands, with severe intellectual disability and multiple malformations. All three probands carried homozygous GLI3 variants. Strikingly, the parents also carried the child's variant, in the heterozygous state, without any clinical sign of GLI3 disease. Given the clinical presentation of our patients, the rarity and predicted high pathogenicity of the variants observed, and the absence of other pathogenic variants, we suggest that these GLI3 homozygous variants are causal. Moreover, the parents were heterozygous for the observed variants, but were clinically unremarkable, suggesting that these variants are hypomorphic alleles.

Genotype-phenotype correlations in recessive titinopathies.

PURPOSE: High throughput sequencing analysis has facilitated the rapid analysis of the entire titin (TTN) coding sequence. This has resulted in the identification of a growing number of recessive titinopathy patients. The aim of this study was to (1) characterize the causative genetic variants and clinical features of the largest cohort of recessive titinopathy patients reported to date and (2) to evaluate genotype-phenotype correlations in this cohort. METHODS: We analyzed clinical and genetic data in a cohort of patients with biallelic pathogenic or likely pathogenic TTN variants. The cohort included both previously reported cases (100 patients from 81 unrelated families) and unreported cases (23 patients from 20 unrelated families). RESULTS: Overall, 132 causative variants were identified in cohort members. More than half of the cases had hypotonia at birth or muscle weakness and a delayed motor development within the first 12 months of life (congenital myopathy) with causative variants located along the entire gene. The remaining patients had a distal or proximal phenotype and a childhood or later (noncongenital) onset. All noncongenital cases had at least one pathogenic variant in one of the final three TTN exons (362-364). CONCLUSION: Our findings suggest a novel association between the location of nonsense variants and the clinical severity of the disease.

Childhood neurodegeneration associated with a specific UBTF variant: a new case report and review of the literature.

BACKGROUND: A new monogenic neurodegenerative disease affecting ribosomal metabolism has recently been identified in association with a monoallelic UBTF putative gain of function variant (NM_001076683.1:c.628G>A, hg19). Phenotype is consistent among these probands with progressive motor, cognitive, and behavioural regression in early to middle childhood. CASE PRESENTATION: We report on a child with this monoallelic UBTF variant who presented with progressive disease including regression, episodes of subacute deterioration during febrile illnesses and a remarkable EEG pattern with a transient pattern of semi-periodic slow waves. CONCLUSIONS: This case further supports the phenotype-genotype correlation of neurodegeneration associated with UBTF c.628G>A. Moreover, it brings new insights into the clinical features and EEG that could possibly serve as diagnostic markers of this otherwise nonspecific phenotype.

[Multidisciplinary cardiogenetic counselling]. / Consultation multidisciplinaire de cardiogénétique.

Multidisciplinary cardiogenetic consulting offers a global clinical approach to patients suffering from channelopathies or hereditary cardiomyopathies. Mutation is discovered in around 50 % of the cases. Several experts are working together to bring probands and their families useful and necessary informations to help them understanding causes, consequences and support of their disease. This approach is developped in close collaboration with the treating physician.

La consultation multidisciplinaire de cardiogénétique offre une approche globale spécialisée aux patients souffrant de canalopathies ou de cardiomyopathies héréditaires. Une mutation génétique est identifiée dans près de 50 % des cas. Les différents experts engagés travaillent conjointement pour apporter aux patients et à leurs familles les renseignements utiles et nécessaires pour comprendre les causes, les conséquences et la prise en charge de la maladie concernée. La consultation se fait en étroite collaboration avec les médecins traitants.

The neurodevelopmental and facial phenotype in individuals with a TRIP12 variant.

Haploinsufficiency of TRIP12 causes a neurodevelopmental disorder characterized by intellectual disability associated with epilepsy, autism spectrum disorder and dysmorphic features, also named Clark-Baraitser syndrome. Only a limited number of cases have been reported to date. We aimed to further delineate the TRIP12-associated phenotype and objectify characteristic facial traits through GestaltMatcher image analysis based on deep-learning algorithms in order to establish a TRIP12 gestalt. 38 individuals between 3 and 66 years (F = 20, M = 18) - 1 previously published and 37 novel individuals - were recruited through an ERN ITHACA call for collaboration. 35 TRIP12 variants were identified, including frameshift (n = 15) and nonsense (n = 6) variants, as well as missense (n = 5) and splice (n = 3) variants, intragenic deletions (n = 4) and two multigene deletions disrupting TRIP12. Though variable in severity, global developmental delay was noted in all individuals, with language deficit most pronounced. About half showed autistic features and susceptibility to obesity seemed inherent to this disorder. A more severe expression was noted in individuals with a missense variant. Facial analysis showed a clear gestalt including deep-set eyes with narrow palpebral fissures and fullness of the upper eyelids, downturned corners of the mouth and large, often low-set ears with prominent earlobes. We report the largest cohort to date of individuals with TRIP12 variants, further delineating the associated phenotype and introducing a facial gestalt. These findings will improve future counseling and patient guidance.

Chronic potassium depletion increases adrenal progesterone production that is necessary for efficient renal retention of potassium.

Modern dietary habits are characterized by high-sodium and low-potassium intakes, each of which was correlated with a higher risk for hypertension. In this study, we examined whether long-term variations in the intake of sodium and potassium induce lasting changes in the plasma concentration of circulating steroids by developing a mathematical model of steroidogenesis in mice. One finding of this model was that mice increase their plasma progesterone levels specifically in response to potassium depletion. This prediction was confirmed by measurements in both male mice and men. Further investigation showed that progesterone regulates renal potassium handling both in males and females under potassium restriction, independent of its role in reproduction. The increase in progesterone production by male mice was time dependent and correlated with decreased urinary potassium content. The progesterone-dependent ability to efficiently retain potassium was because of an RU486 (a progesterone receptor antagonist)-sensitive stimulation of the colonic hydrogen, potassium-ATPase (known as the non-gastric or hydrogen, potassium-ATPase type 2) in the kidney. Thus, in males, a specific progesterone concentration profile induced by chronic potassium restriction regulates potassium balance.

Case Report: A Rare Truncating Variant of the CFHR5 Gene in IgA Nephropathy.

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Despite appropriate therapy, 20-40% of affected-patients evolve toward end-stage kidney disease (ESKD). Mesangial IgA deposits are the hallmark of IgAN, and complement deposition (C3) seems to differentiate latent IgA mesangial deposits from active IgAN. Atypical hemolytic uremic syndrome (aHUS), another disease in which complement plays an important role, is caused by inherited or acquired deregulation of the alternative pathway (AP) of complement. A subgroup of IgAN shows thrombotic microangiopathy (TMA) lesions in kidney biopsies, the histological characteristic of aHUS. Genetic variants of complement Factor H (CFH), known to be present in aHUS, have been associated with rapidly progressive forms of IgAN and a clinical pattern of aHUS. Genome-wide association studies (GWAS) have confirmed that the 1q32 region, encoding for CFH and its related proteins, is an IgAN susceptibility locus. A 30 year-old man was admitted for seizures and malignant hypertension. The kidney biopsy showed IgAN associated with features of TMA. Despite five plasma exchanges, the patient remained dialysis-dependent, and ESKD was diagnosed. Functional and genetic complement analysis were performed. A monoallelic protein-truncating, likely loss-of-function variant was identified in the CFHR5 gene. Eculizumab is the treatment of aHUS. As it has been successfully used in a few cases of rapidly progressive IgAN, it was decided to administer eculizumab over a period of 12 months in addition to the usual immunosuppression for renal transplantation. After a follow-up of 3 years, there was no clinical disease recurrence. Systematic biologic and genetic screening of complement in individuals with IgAN might be useful to better delineate the role of the AP of complement in renal disease progression, and this may have therapeutic implications.

CNV Detection from Exome Sequencing Data in Routine Diagnostics of Rare Genetic Disorders: Opportunities and Limitations.

To assess the potential of detecting copy number variations (CNVs) directly from exome sequencing (ES) data in diagnostic settings, we developed a CNV-detection pipeline based on ExomeDepth software and applied it to ES data of 450 individuals. Initially, only CNVs affecting genes in the requested diagnostic gene panels were scored and tested against arrayCGH results. Pathogenic CNVs were detected in 18 individuals. Most detected CNVs were larger than 400 kb (11/18), but three individuals had small CNVs impacting one or a few exons only and were thus not detectable by arrayCGH. Conversely, two pathogenic CNVs were initially missed, as they impacted genes not included in the original gene panel analysed, and a third one was missed as it was in a poorly covered region. The overall combined diagnostic rate (SNVs + CNVs) in our cohort was 36%, with wide differences between clinical domains. We conclude that (1) the ES-based CNV pipeline detects efficiently large and small pathogenic CNVs, (2) the detection of CNV relies on uniformity of sequencing and good coverage, and (3) in patients who remain unsolved by the gene panel analysis, CNV analysis should be extended to all captured genes, as diagnostically relevant CNVs may occur everywhere in the genome.

Clinical and Genetic Findings in a Series of Eight Families with Arthrogryposis.

The term "arthrogryposis" is used to indicate multiple congenital contractures affecting two or more areas of the body. Arthrogryposis is the consequence of an impairment of embryofetal neuromuscular function and development. The causes of arthrogryposis are multiple, and in newborns, it is difficult to predict the molecular defect as well as the clinical evolution just based on clinical findings. We studied a consecutive series of 13 participants who had amyoplasia, distal arthrogryposis (DA), or syndromic forms of arthrogryposis with normal intellectual development and other motor abilities. The underlying pathogenic variants were identified in 11 out of 13 participants. Correlating the genotype with the clinical features indicated that prenatal findings were specific for DA; this was helpful to identify familial cases, but features were non-specific for the involved gene. Perinatal clinical findings were similar among the participants, except for amyoplasia. Dilatation of the aortic root led to the diagnosis of Loeys-Dietz syndrome (LDS) in one case. The phenotype of DA type 5D (DA5D) and Escobar syndrome became more characteristic at later ages due to more pronounced pterygia. Follow-up indicated that DA type 1 (DA1)/DA type 2B (DA2B) spectrum and LDS had a more favorable course than the other forms. Hand clenching and talipes equinovarus/rocker bottom foot showed an improvement in all participants, and adducted thumb resolved in all forms except in amyoplasia. The combination of clinical evaluation with Next Generation Sequencing (NGS) analysis in the newborn may allow for an early diagnosis and, particularly in the DAs, suggests a favorable prognosis.

Common genetic variation of beta1- and beta2-adrenergic receptor and response to four classes of antihypertensive treatment.

Varying results have been reported on the association of beta-adrenergic receptor polymorphisms with blood pressure (BP) response to beta-blockers. We investigated the influence of ADRB1 Ser49Gly and Arg389Gly, and ADRB2 Gly16Arg and Glu27Gln polymorphisms on ambulatory BP response to bisoprolol and three other antihypertensive drug monotherapies in a placebo-controlled, double-blind, cross-over study with 233 moderately hypertensive men. ADRB1 Ser49Ser homozygotes tended to have a better ambulatory BP response to bisoprolol but the difference was statistically nonsignificant. ADRB1 Arg389Arg homozygotes did not show better BP response to bisoprolol than the other genotypes. There were no significant associations of ADRB2 polymorphisms with BP responses to any of the study drugs. The results from this controlled study in hypertensive men do not support clinical use of common polymorphisms in ADRB1 and ADRB2 in predicting BP responses to beta-blockers or to three other antihypertensive drugs.

Further evidence of inherited long QT syndrome gene mutations in antiarrhythmic drug-associated torsades de pointes.

BACKGROUND: Pathophysiologically significant ion-channel mutations have been detected in only a minority of cases of acquired long QT syndrome (LQTS). OBJECTIVE: The aim of this study was to clarify the putative role of subclinical inherited LQTS in drug-associated torsades de pointes (TdP) and to assess the concomitant proarrhythmic factors. METHODS: We evaluated 16 consecutive cases with documented, antiarrhythmic drug-induced TdP who were referred to the Laboratory of Molecular Medicine at Helsinki University for LQTS genetic testing between September 2000 and August 2005. RESULTS: A prolonged QTc interval was observed in 56% of the patients before administration of the drug. TdP was associated with amiodarone in seven, sotalol in six, flecainide in two, and propafenone in one of the cases. Except for the culprit drug, one or more risk factors such as female sex, congestive heart failure, and atrial fibrillation were present in each drug-associated TdP. DNA samples were screened for the four common Finnish founder mutations (KCNQ1 G589D and IVS7-2A-->G, HERG L552S, and R176W), which are known to account for the majority of inherited LQTS in Finland. A total of three (19%) individuals carried one of these four mutations. CONCLUSIONS: Our data show that previously unsuspected LQTS mutations may be present in patients with antiarrhythmic drug-associated TdPs. A normal QTc interval does not exclude the risk of proarrhythmia.

Association between HERG K897T polymorphism and QT interval in middle-aged Finnish women.

OBJECTIVES: The aim of this study was to test whether a recently reported polymorphism in the HERG gene coding for the rapidly activating delayed rectifier K+ channel has influence on myocardial repolarization. BACKGROUND: The length of myocardial repolarization, measured as the QT interval, has a hereditary component, but no genes that would explain the variability of repolarization have been identified in healthy subjects. METHODS: QT intervals were measured from the 12-lead electrocardiogram in a random middle-aged population (226 men/187 women). The longest QT interval at any of the 12 leads (QTmax), QTV(2), and the Tpeak-Tend interval were used as measures of repolarization. Deoxyribonucleic acid samples were genotyped for the nucleotide 2690A>C variation of the HERG gene, corresponding to the HERG K(lysine)897T(threonine) amino acid polymorphism. RESULTS: The allele frequencies were 0.84 (A) and 0.16 (C). Females with the genotype AC or CC had longer QTcmax (477 +/- 99 ms) and Tpeak-Tend intervals (143 +/- 95 ms) than females with the genotype AA (441 +/- 69 ms and 116 +/- 65 ms, p = 0.005 and p = 0.025, respectively). In males, the QTcmax and the Tpeak-Tend intervals did not differ between the genotypes. After adjustment for echocardiographic and various laboratory variables, the HERG K897T polymorphism remained as an independent predictor of QTcmax (p = 0.009) and the Tpeak-Tend intervals (p = 0.026) in females. CONCLUSIONS; The common K897T polymorphism of the HERG channel is associated with the maximal duration and transmural dispersion of ventricular repolarization in middle-aged females.

Common variants of the beta and gamma subunits of the epithelial sodium channel and their relation to plasma renin and aldosterone levels in essential hypertension.

BACKGROUND: Rare mutations of the epithelial sodium channel (ENaC) result in the monogenic hypertension form of Liddle's syndrome. We decided to screen for common variants in the ENaC beta and gamma subunits in patients with essential hypertension and to relate their occurrence to the activity of circulating renin-angiotensin-aldosterone system. METHODS: Initially, DNA samples from 27 patients with low renin/low aldosterone hypertension were examined. The DNA variants were subsequently screened for in 347 patients with treatment-resistant hypertension, 175 male subjects with documented long-lasting normotension and 301 healthy Plasma renin and aldosterone levels were measured under baseline conditions and during postural and captopril challenge tests. RESULTS: Two commonly occurring betaENaC variants (G589S and a novel intronic i12-17CT substitution) and one novel gammaENaC variant (V546I) were detected. One of these variants occurred in a heterozygous form in 32 patients, a prevalence (9.2%) significantly higher than that in normotensive males (2.9%, p = 0.007) and blood donors (3.0%, p = 0.001). betaENaC i12-17CT was significantly more prevalent in the hypertension group than in the two control groups combined (4.6% vs. 1.1%, p = 0.001). When expressed in Xenopus oocytes, neither of the two ENaC amino acid-changing variants showed a significant difference in activity compared with ENaC wild-type. No direct evidence for a mRNA splicing defect could be obtained for the betaENaC intronic variant. The ratio of daily urinary potassium excretion to upright and mean (of supine and upright values) plasma renin activity was higher in variant allele carriers than in non-carriers (p = 0.034 and p = 0.048). CONCLUSIONS: At least 9% of Finnish patients with hypertension admitted to a specialized center carry genetic variants of beta and gammaENaC, a three times higher prevalence than in the normotensive individuals or in random healthy controls. Patients with the variant alleles showed an increased urinary potassium excretion rate in relation to their renin levels.

Functional characterization of the common amino acid 897 polymorphism of the cardiac potassium channel KCNH2 (HERG).

OBJECTIVE: To determine whether the amino acid 897 threonine (T) to lysine (K) polymorphism of the KCNH2 (HERG) potassium channel influences channel performance or patient phenotype. METHODS: The phenotypic effects of this polymorphism were investigated in vitro by electrophysiological experiments in HEK-293 cells and in vivo by exercise electrocardiography in a group of LQTS patients carrying the same genetically proven KCNQ1 mutation. RESULTS: When expressed in HEK-293 cells, the 897T isoform of the KCNH2 channel exhibited changes in inactivation and deactivation properties, and a smaller current density than the more common 897K isoform. Western blot experiments indicated that the decreased current density associated with 897T was caused by reduced channel expression. During a maximal exercise test in 39 LQT1 patients carrying an identical KCNQ1 mutation (G589D) and showing a prolonged QT interval (>440 ms), QT intervals were longer in patients carrying the 897T allele than in those homozygous for the 897K allele. CONCLUSIONS: The K897T variation has an effect on channel function and clinical phenotype. Our data warrant further investigations into the significance of this polymorphism in drug-induced and inherited LQTS.

Renin-angiotensin system and alpha-adducin gene polymorphisms and their relation to responses to antihypertensive drugs: results from the GENRES study.

BACKGROUND: Polymorphisms in genes coding for components of the renin-angiotensin system (RAS) and alpha-adducin (ADD1) have been reported to be associated with blood pressure (BP) responses to antihypertensive agents. The results, however, have not been consistent and most of the earlier studies have been small and lacked placebo-control. Therefore, the association of common polymorphisms in these genes with BP responses to four different antihypertensive drugs was analyzed in a controlled study. METHODS: The study included 208 hypertensive Finnish men from the GENRES study. All of them used amlodipine 5 mg, bisoprolol 5 mg, hydrochlorothiazide (HCT) 25 mg, and losartan 50 mg daily, each for 4 weeks as a monotherapy in a double-blind, randomized, study. The treatment periods were separated by 4-week placebo periods. Both 24-h ambulatory (ABP) and office BP (OBP) measurements were carried out. The polymorphisms analyzed were ADD1 Gly460Trp, angiotensinogen (AGT) Met235Thr, angiotensin converting enzyme (ACE) insertion/deletion (I/D), and angiotensin II type 1 receptor (AGTR1) 1166A/C. RESULTS: The presence of 460Trp allele of ADD1, previously suggested to be a marker of thiazide responsiveness, did not predict a better response to HCT. There was no significant association of AGT Met235Thr, ACE I/D, and AGTR1 1166A/C polymorphisms with BP responses to the study drugs. ADD1 460Trp and AGT 235Thr alleles were associated with higher systolic white coat effect (WCE) during the placebo periods (P values 0.03 and 0.01, respectively). CONCLUSIONS: Common polymorphisms of ADD1, AGT, ACE, and AGTR1 do not markedly predict BP responses to amlodipine, bisoprolol, HCT, and losartan, at least in white hypertensive men.

Effects of mineralocorticoid and K+ concentration on K+ secretion and ROMK channel expression in a mouse cortical collecting duct cell line.

The cortical collecting duct (CCD) plays a key role in regulated K(+) secretion, which is mediated mainly through renal outer medullary K(+) (ROMK) channels located in the apical membrane. However, the mechanisms of the regulation of urinary K(+) excretion with regard to K(+) balance are not well known. We took advantage of a recently established mouse CCD cell line (mCCD(cl1)) to investigate the regulation of K(+) secretion by mineralocorticoid and K(+) concentration. We show that this cell line expresses ROMK mRNA and a barium-sensitive K(+) conductance in its apical membrane. As this conductance is sensitive to tertiapin-Q, with an apparent affinity of 6 nM, and to intracellular acidification, it is probably mediated by ROMK. Overnight exposure to 100 nM aldosterone did not significantly change the K(+) conductance, while it increased the amiloride-sensitive Na(+) transport. Overnight exposure to a high K(+) (7 mM) concentration produced a small but significant increase in the apical membrane barium-sensitive K(+) conductance. The mRNA levels of all ROMK isoforms measured by qRT-PCR were not changed by altering the basolateral K(+) concentration but were decreased by 15-45% upon treatment with aldosterone (0.3 or 300 nM for 1 and 3 h). The paradoxical response of ROMK expression to aldosterone could possibly work as a preventative mechanism to avoid excessive K(+) loss which would otherwise result from the increased electrogenic Na(+) transport and associated depolarization of the apical membrane in the CCD. In conclusion, mCCD(cl1) cells demonstrate a significant K(+) secretion, probably mediated by ROMK, which is not stimulated by aldosterone but increased by overnight exposure to a high K(+) concentration.