De Novo DNM1L Variant in a Teenager With Progressive Paroxysmal Dystonia and Lethal Super-refractory Myoclonic Status Epilepticus.

J Child Neurol. 2018 Jan 01;:883073818778203

Authors: Ryan CS, Fine AL, Cohen AL, Schiltz BM, Renaud DL, Wirrell EC, Patterson MC, Boczek NJ, Liu R, Babovic-Vuksanovic D, Chan DC, Payne ET

Abstract
BACKGROUND: The dynamin 1-like gene ( DNM1L) encodes a GTPase that mediates mitochondrial and peroxisomal fission and fusion. We report a new clinical presentation associated with a DNM1L pathogenic variant and review the literature.
RESULTS: A 13-year-old boy with mild developmental delays and paroxysmal dystonia presented acutely with multifocal myoclonic super-refractory status epilepticus. Despite sustained and aggressive treatment, seizures persisted and care was ultimately withdrawn in the context of extensive global cortical atrophy. Rapid trio-whole exome sequencing revealed a de novo heterozygous c.1207C>T (p.R403C) pathogenic variant in DNM1L. Immunofluorescence staining of fibroblast mitochondria revealed abnormally elongated and tubular morphology.
CONCLUSIONS: This case highlights the diagnostic importance of rapid whole exome sequencing within a critical care setting and reveals the expanding phenotypic spectrum associated with DNM1L variants. This now includes progressive paroxysmal dystonia and adolescent-onset super-refractory myoclonic status epilepticus contributing to strikingly rapid and progressive cortical atrophy and death.

PMID: 29877124 [PubMed - as supplied by publisher]

Establishing the role of PLVAP in protein-losing enteropathy: a homozygous missense variant leads to an attenuated phenotype.

J Med Genet. 2018 Jun 06;:

Authors: Kurolap A, Eshach-Adiv O, Gonzaga-Jauregui C, Dolnikov K, Mory A, Paperna T, Hershkovitz T, Overton JD, Kaplan M, Glaser F, Zohar Y, Shuldiner AR, Berger G, Baris HN

Abstract
BACKGROUND: Intestinal integrity is essential for proper nutrient absorption and tissue homeostasis, with damage leading to enteric protein loss, that is, protein-losing enteropathy (PLE). Recently, homozygous nonsense variants in the plasmalemma vesicle-associated protein gene (PLVAP) were reported in two patients with severe congenital PLE. PLVAP is the building block of endothelial cell (EC) fenestral diaphragms; its importance in barrier function is supported by mouse models of Plvap deficiency.
OBJECTIVE: To genetically diagnose two first-degree cousins once removed, who presented with PLE at ages 22 and 2.5 years.
METHODS: Family-based whole exome sequencing was performed based on an autosomal recessive inheritance model. In silico analyses were used to predict variant impact on protein structure and function.
RESULTS: We identified a rare homozygous variant (NM_031310.2:c.101T>C;p.Leu34Pro) in PLVAP, which co-segregated with the disease. Leu34 is predicted to be located in a highly conserved, hydrophobic, α-helical region within the protein's transmembrane domain, suggesting Leu34Pro is likely to disrupt protein function and/or structure. Electron microscopy and PLVAP immunohistochemistry demonstrated apparently normal diaphragm morphology, predicted to be functionally affected.
CONCLUSIONS: Biallelic missense variants in PLVAP can cause an attenuated form of the PLE and hypertriglyceridaemia syndrome. Our findings support the role of PLVAP in the pathophysiology of PLE, expand the phenotypic and mutation spectrums and underscore PLVAP's importance in EC barrier function in the gut.

PMID: 29875123 [PubMed - as supplied by publisher]

Identification of rs7350481 at chromosome 11q23.3 as a novel susceptibility locus for metabolic syndrome in Japanese individuals by an exome-wide association study.

Oncotarget. 2017 Jun 13;8(24):39296-39308

Authors: Yamada Y, Sakuma J, Takeuchi I, Yasukochi Y, Kato K, Oguri M, Fujimaki T, Horibe H, Muramatsu M, Sawabe M, Fujiwara Y, Taniguchi Y, Obuchi S, Kawai H, Shinkai S, Mori S, Arai T, Tanaka M

Abstract
We have performed exome-wide association studies to identify genetic variants that influence body mass index or confer susceptibility to obesity or metabolic syndrome in Japanese. The exome-wide association study for body mass index included 12,890 subjects, and those for obesity and metabolic syndrome included 12,968 subjects (3954 individuals with obesity, 9014 controls) and 6817 subjects (3998 individuals with MetS, 2819 controls), respectively. Exome-wide association studies were performed with Illumina HumanExome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. The relation of genotypes of single nucleotide polymorphisms to body mass index was examined by linear regression analysis, and that of allele frequencies of single nucleotide polymorphisms to obesity or metabolic syndrome was evaluated with Fisher's exact test. The exome-wide association studies identified six, 11, and 40 single nucleotide polymorphisms as being significantly associated with body mass index, obesity (P <1.21 × 10-6), or metabolic syndrome (P <1.20 × 10-6), respectively. Subsequent multivariable logistic regression analysis with adjustment for age and sex revealed that three and five single nucleotide polymorphisms were related (P < 0.05) to obesity or metabolic syndrome, respectively, with one of these latter polymorphisms-rs7350481 (C/T) at chromosome 11q23.3-also being significantly (P < 3.13 × 10-4) associated with metabolic syndrome. The polymorphism rs7350481 may thus be a novel susceptibility locus for metabolic syndrome in Japanese. In addition, single nucleotide polymorphisms in three genes (CROT, TSC1, RIN3) and at four loci (ANKK1, ZNF804B, CSRNP3, 17p11.2) were implicated as candidate determinants of obesity and metabolic syndrome, respectively.

PMID: 28445147 [PubMed - indexed for MEDLINE]

Identification of the CFTR c.1666A>G Mutation in Hereditary Inclusion Body Myopathy Using Next-Generation Sequencing Analysis.

Front Neurosci. 2018;12:329

Authors: Lu Y, Da YW, Zhang YB, Li XG, Wang M, Di L, Pang M, Lei L

Abstract
Hereditary inclusion body myopathy (HIBM) is a rare autosomal recessive adult onset muscle disease which affects one to three individuals per million worldwide. This disease is autosomal dominant and occurs in adulthood. Our previous study reported a new subtype of HIBM linked to the susceptibility locus at 7q22.1-31.1. The present study is aimed to identify the candidate gene responsible for the phenotype in HIBM pedigree. After multipoint linkage analysis, we performed targeted capture sequencing on 16 members and whole-exome sequencing (WES) on 5 members. Bioinformatics filtering was performed to prioritize the candidate pathogenic gene variants, which were further genotyped by Sanger sequencing. Our results showed that the highest peak of LOD score (4.70) was on chromosome 7q22.1-31.1.We identified 2 and 22 candidates using targeted capture sequencing and WES respectively, only one of which as CFTRc.1666A>G mutation was well cosegregated with the HIBM phenotype. Using transcriptome analysis, we did not detect the differences of CFTR's mRNA expression in the proband compared with healthy members. Due to low incidence of HIBM and there is no other pedigree to assess, mutation was detected in three patients with duchenne muscular dystrophyn (DMD) and five patients with limb-girdle muscular dystrophy (LGMD). And we found that the frequency of mutation detected in DMD and LGMD patients was higher than that of being expected in normal population. We suggested that the CFTRc.1666A>G may be a candidate marker which has strong genetic linkage with the causative gene in the HIBM family.

PMID: 29872374 [PubMed]

Linkage analysis and whole exome sequencing identify a novel candidate gene in a Dutch multiple sclerosis family.

Mult Scler. 2018 Jun 01;:1352458518777202

Authors: Mescheriakova JY, Verkerk AJ, Amin N, Uitterlinden AG, van Duijn CM, Hintzen RQ

Abstract
BACKGROUND: Multiple sclerosis (MS) is a complex disease resulting from the joint effect of many genes. It has been speculated that rare variants might explain part of the missing heritability of MS.
OBJECTIVE: To identify rare coding genetic variants by analyzing a large MS pedigree with 11 affected individuals in several generations.
METHODS: Genome-wide linkage screen and whole exome sequencing (WES) were performed to identify novel coding variants in the shared region(s) and in the known 110 MS risk loci. The candidate variants were then assessed in 591 MS patients and 3169 controls.
RESULTS: Suggestive evidence for linkage was obtained to 7q11.22-q11.23. In WES data, a rare missense variant p.R183C in FKBP6 was identified that segregated with the disease in this family. The minor allele frequency was higher in an independent cohort of MS patients than in healthy controls (1.27% vs 0.95%), but not significant (odds ratio (OR) = 1.33 (95% confidence interval (CI): 0.8-2.4), p = 0.31).
CONCLUSION: The rare missense variant in FKBP6 was identified in a large Dutch MS family segregating with the disease. This association to MS was not found in an independent MS cohort. Overall, genome-wide studies in larger cohorts are needed to adequately investigate the role of rare variants in MS risk.

PMID: 29873607 [PubMed - as supplied by publisher]

Genetic Analysis of Rare Human Variants of Regulators of G Protein Signaling Proteins and Their Role in Human Physiology and Disease.

Pharmacol Rev. 2018 Jul;70(3):446-474

Authors: Squires KE, Montañez-Miranda C, Pandya RR, Torres MP, Hepler JR

Abstract
Regulators of G protein signaling (RGS) proteins modulate the physiologic actions of many neurotransmitters, hormones, and other signaling molecules. Human RGS proteins comprise a family of 20 canonical proteins that bind directly to G protein-coupled receptors/G protein complexes to limit the lifetime of their signaling events, which regulate all aspects of cell and organ physiology. Genetic variations account for diverse human traits and individual predispositions to disease. RGS proteins contribute to many complex polygenic human traits and pathologies such as hypertension, atherosclerosis, schizophrenia, depression, addiction, cancers, and many others. Recent analysis indicates that most human diseases are due to extremely rare genetic variants. In this study, we summarize physiologic roles for RGS proteins and links to human diseases/traits and report rare variants found within each human RGS protein exome sequence derived from global population studies. Each RGS sequence is analyzed using recently described bioinformatics and proteomic tools for measures of missense tolerance ratio paired with combined annotation-dependent depletion scores, and protein post-translational modification (PTM) alignment cluster analysis. We highlight selected variants within the well-studied RGS domain that likely disrupt RGS protein functions and provide comprehensive variant and PTM data for each RGS protein for future study. We propose that rare variants in functionally sensitive regions of RGS proteins confer profound change-of-function phenotypes that may contribute, in newly appreciated ways, to complex human diseases and/or traits. This information provides investigators with a valuable database to explore variation in RGS protein function, and for targeting RGS proteins as future therapeutic targets.

PMID: 29871944 [PubMed - in process]

Rapid and effective response of the R222Q SCN5A to quinidine treatment in a patient with Purkinje-related ventricular arrhythmia and familial dilated cardiomyopathy: a case report.

BMC Med Genet. 2018 Jun 05;19(1):94

Authors: Zakrzewska-Koperska J, Franaszczyk M, Bilińska Z, Truszkowska G, Karczmarz M, Szumowski Ł, Zieliński T, Płoski R, Bilińska M

Abstract
BACKGROUND: Mutations of the SCN5A gene are reported in 2-4% of patients with dilated cardiomyopathy (DCM). In such cases, DCM is associated with different rhythm disturbances such as the multifocal ectopic Purkinje-related premature contractions and atrial fibrillation. Arrhythmia often occurs at a young age and is the first symptom of heart disease.
CASE PRESENTATION: We present the case of 55-year old male with a 30-year history of heart failure (HF) in the course of familial DCM and complex ventricular tachyarrhythmias, which constituted 50-80% of the whole rhythm. The patient was qualified for heart transplantation because of the increasing symptoms of HF. We revealed the heterozygotic R222Q mutation in SCN5A by means of whole exome sequencing. After the quinidine treatment, a rapid and significant reduction of ventricular tachyarrhythmias and an improvement in the myocardial function were observed and this effect remained constant in the 2.5-year follow-up. This effect was observed even in the presence of concomitant coronary artery disease.
CONCLUSIONS: Patients with familial DCM and Purkinje-related ventricular arrhythmias should be offered genetic screening. The quinidine treatment for the SCN5A R222Q mutation can be life saving for patients.

PMID: 29871609 [PubMed - in process]

Evaluating the Genetics of Common Variable Immunodeficiency: Monogenetic Model and Beyond.

Front Immunol. 2018;9:636

Authors: de Valles-Ibáñez G, Esteve-Solé A, Piquer M, González-Navarro EA, Hernandez-Rodriguez J, Laayouni H, González-Roca E, Plaza-Martin AM, Deyà-Martínez Á, Martín-Nalda A, Martínez-Gallo M, García-Prat M, Del Pino-Molina L, Cuscó I, Codina-Solà M, Batlle-Masó L, Solís-Moruno M, Marquès-Bonet T, Bosch E, López-Granados E, Aróstegui JI, Soler-Palacín P, Colobran R, Yagüe J, Alsina L, Juan M, Casals F

Abstract
Common variable immunodeficiency (CVID) is the most frequent symptomatic primary immunodeficiency characterized by recurrent infections, hypogammaglobulinemia and poor response to vaccines. Its diagnosis is made based on clinical and immunological criteria, after exclusion of other diseases that can cause similar phenotypes. Currently, less than 20% of cases of CVID have a known underlying genetic cause. We have analyzed whole-exome sequencing and copy number variants data of 36 children and adolescents diagnosed with CVID and healthy relatives to estimate the proportion of monogenic cases. We have replicated an association of CVID to p.C104R in TNFRSF13B and reported the second case of homozygous patient to date. Our results also identify five causative genetic variants in LRBA, CTLA4, NFKB1, and PIK3R1, as well as other very likely causative variants in PRKCD, MAPK8, or DOCK8 among others. We experimentally validate the effect of the LRBA stop-gain mutation which abolishes protein production and downregulates the expression of CTLA4, and of the frameshift indel in CTLA4 producing expression downregulation of the protein. Our results indicate a monogenic origin of at least 15-24% of the CVID cases included in the study. The proportion of monogenic patients seems to be lower in CVID than in other PID that have also been analyzed by whole exome or targeted gene panels sequencing. Regardless of the exact proportion of CVID monogenic cases, other genetic models have to be considered for CVID. We propose that because of its prevalence and other features as intermediate penetrancies and phenotypic variation within families, CVID could fit with other more complex genetic scenarios. In particular, in this work, we explore the possibility of CVID being originated by an oligogenic model with the presence of heterozygous mutations in interacting proteins or by the accumulation of detrimental variants in particular immunological pathways, as well as perform association tests to detect association with rare genetic functional variation in the CVID cohort compared to healthy controls.

PMID: 29867916 [PubMed]

Whole-Exome Sequencing in Searching for New Variants Associated With the Development of Parkinson's Disease.

Front Aging Neurosci. 2018;10:136

Authors: Shulskaya MV, Alieva AK, Vlasov IN, Zyrin VV, Fedotova EY, Abramycheva NY, Usenko TS, Yakimovsky AF, Emelyanov AK, Pchelina SN, Illarioshkin SN, Slominsky PA, Shadrina MI

Abstract
Background: Parkinson's disease (PD) is a complex disease with its monogenic forms accounting for less than 10% of all cases. Whole-exome sequencing (WES) technology has been used successfully to find mutations in large families. However, because of the late onset of the disease, only small families and unrelated patients are usually available. WES conducted in such cases yields in a large number of candidate variants. There are currently a number of imperfect software tools that allow the pathogenicity of variants to be evaluated. Objectives: We analyzed 48 unrelated patients with an alleged autosomal dominant familial form of PD using WES and developed a strategy for selecting potential pathogenetically significant variants using almost all available bioinformatics resources for the analysis of exonic areas. Methods: DNA sequencing of 48 patients with excluded frequent mutations was performed using an Illumina HiSeq 2500 platform. The possible pathogenetic significance of identified variants and their involvement in the pathogenesis of PD was assessed using SNP and Variation Suite (SVS), Combined Annotation Dependent Depletion (CADD) and Rare Exome Variant Ensemble Learner (REVEL) software. Functional evaluation was performed using the Pathway Studio database. Results: A significant reduction in the search range from 7082 to 25 variants in 23 genes associated with PD or neuronal function was achieved. Eight (FXN, MFN2, MYOC, NPC1, PSEN1, RET, SCN3A and SPG7) were the most significant. Conclusions: The multistep approach developed made it possible to conduct an effective search for potential pathogenetically significant variants, presumably involved in the pathogenesis of PD. The data obtained need to be further verified experimentally.

PMID: 29867446 [PubMed]

Clinical Report: Warsaw Breakage Syndrome with small radii and fibulae.

Am J Med Genet A. 2017 Nov;173(11):3075-3081

Authors: Eppley S, Hopkin RJ, Mendelsohn B, Slavotinek AM

Abstract
We present two new cases of Warsaw Breakage Syndrome (WABS), an autosomal recessive cohesinopathy, in sisters aged 13 and 11 years who both had compound heterozygous mutations in DDX11. After exclusion of Fanconi anemia, Bloom syndrome and Nijmegen breakage syndrome, whole exome sequencing revealed two novel variants-c.1523T>G, predicting (p.Leu508Arg) and c.1949-1G>A (IVS19-1G>A), that were confirmed with Sanger sequencing in both affected individuals. DDX11 encodes an iron-sulfur-containing DNA helicase, and mutations in this gene have been reported in the five WABS cases previously identified to date. The sisters reported here display the distinguishing clinical features of WABS: pre- and post-natal growth restriction, microcephaly, intellectual disability, sensorineural hearing loss with cochlear abnormalities, and facial dysmorphic features. In addition, our cases had early menarche at 8 and 10 years of age, bilateral small thumbs, and the younger, more severely affected sister had small fibulae. These findings broaden the WABS phenotype and the limb malformations demonstrate further clinical overlap with Fanconi anemia and other cohesinopathies, such as Roberts Syndrome.

PMID: 28960803 [PubMed - indexed for MEDLINE]

Coexistence of mutations in keratin 10 (KRT10) and the mitochondrial genome in a patient with ichthyosis with confetti and Leber's hereditary optic neuropathy.

Am J Med Genet A. 2017 Nov;173(11):3093-3097

Authors: Kalinska-Bienias A, Pollak A, Kowalewski C, Lechowicz U, Stawinski P, Gergont A, Kosinska J, Pronicka E, Kowalski P, Wozniak K, Ploski R

Abstract
Ichthyosis with confetti (IWC) is a severe congenital genodermatosis characterized by ichthyosiform erythroderma since birth and confetti-like spots of normal skin appearing in childhood as a results of revertant mosaicism. This disorder is caused by mutations in KRT10 or KRT1 genes. We report a 16-year-old boy who presented ichthyosiform erythroderma with severe desquamation since birth and gradually worsening psycho-neurological symptoms (mental retardation, ataxia, dystonia, hypoacusis). The patient conspicuously lacked typical confetti-like spots at the age of 16. The molecular diagnostics by the whole exome sequencing showed a novel de novo (c.1374-2A>C) mutation in the KRT10 gene responsible for the development of IWC (KRT10 defect was confirmed by immunofluorescent study). Concurrently, the m.14484T>C mutation in mitochondrial MTND6 gene (characteristic for Leber's hereditary optic neuropathy or LHON) was detected in patient, his mother and brother. LHON causes frequent inherited blindness typically appearing during young adult life whose expression can be triggered by additional factors such as smoking or alcohol exposure. We speculate the effects of KRT10 and LHON mutations influence each other-skin inflammatory reaction due to severe ichthyosis might trigger the development of psychoneurological abnormalities whereas the mitochondrial mutation may reduce revertant mosaicism phenomenon resulting in the lack of confetti-like spots characteristic for IWC. However, based on a single case we should be cautious about attributing phenotypes to digenic mechanisms without functional data.

PMID: 28944608 [PubMed - indexed for MEDLINE]

De novo mutations in HNRNPU result in a neurodevelopmental syndrome.

Am J Med Genet A. 2017 Nov;173(11):3003-3012

Authors: Yates TM, Vasudevan PC, Chandler KE, Donnelly DE, Stark Z, Sadedin S, Willoughby J, Broad Center for Mendelian Genomics, DDD study, Balasubramanian M

Abstract
Exome sequencing in the context of developmental disorders is a useful technique, but variants found need to be interpreted in the context of detailed phenotypic information. Whole gene deletions and loss-of-function-mutations in the HNRNPU gene have been associated with intellectual disability and seizures in some patients. However, a unifying syndromic phenotype has not been previously elucidated. Here, we report a total of seven patients (six patients identified through the Wellcome Trust Deciphering Developmental Disorders study, with one additional patient), who have heterozygous de novo mutations in HNRNPU. These were found via trio-based exome sequencing. All but one of the mutations is predicted to cause loss-of-function. These patients have dysmorphic features in common, including prominent eyebrows, long palpebral fissures, overhanging columella, and thin upper lip. All patients have developmental delay and intellectual disability (ID), ranging from moderate to severe. Seizures are common from early childhood. These initially occur in the context of febrile episodes. This series demonstrates common phenotypic features, including emerging dysmorphism, associated with heterozygous HNRNPU mutations. This allows us to define a novel neurodevelopmental syndrome, with a likely mechanism of haploinsufficiency.

PMID: 28944577 [PubMed - indexed for MEDLINE]

The spectrum of DNMT3A variants in Tatton-Brown-Rahman syndrome overlaps with that in hematologic malignancies.

Am J Med Genet A. 2017 Nov;173(11):3022-3028

Authors: Shen W, Heeley JM, Carlston CM, Acuna-Hidalgo R, Nillesen WM, Dent KM, Douglas GV, Levine KL, Bayrak-Toydemir P, Marcelis CL, Shinawi M, Carey JC

Abstract
De novo, germline variants in DNMT3A cause Tatton-Brown-Rahman syndrome (TBRS). This condition is characterized by overgrowth, distinctive facial appearance, and intellectual disability. Somatic DNMT3A variants frequently occur in hematologic malignances, particularly acute myeloid leukemia. The Arg882 residue is the most common site of somatic DNMT3A variants, and has also been altered in patients with TBRS. Here we present three additional patients with this disorder attributed to DNMT3A germline variants that disrupt the Arg882 codon, suggesting that this codon may be a germline mutation hotspot in this disorder. Furthermore, based on the investigation of previously reported variants in patients with TBRS, we found overlap in the spectrum of DNMT3A variants observed in this disorder and somatic variants in hematological malignancies.

PMID: 28941052 [PubMed - indexed for MEDLINE]

HLX is a candidate gene for a pattern of anomalies associated with congenital diaphragmatic hernia, short bowel, and asplenia.

Am J Med Genet A. 2017 Nov;173(11):3070-3074

Authors: Farrell SA, Sodhi S, Marshall CR, Guerin A, Slavotinek A, Paton T, Chong K, Sirkin WL, Scherer SW, Bérubé-Simard FA, Pilon N

Abstract
Isolated congenital diaphragmatic hernia is often a sporadic event with a low recurrence risk. However, underlying genetic etiologies, such as chromosome anomalies or single gene disorders, are identified in a small number of individuals. We describe two fetuses with a unique pattern of multiple congenital anomalies, including diaphragmatic hernia, short bowel and asplenia, born to first-cousin parents. Whole exome sequencing showed that both were homozygous for a missense variant, c.950A>C, predicting p.Asp317Ala, in the H.20-Like Homeobox 1 (HLX1) gene. HLX is a homeobox transcription factor gene which is relatively conserved across species. Hlx homozygous null mice have a short bowel and reduced muscle cells in the diaphragm, closely resembling the anomalies in the two fetuses and we therefore suggest that the HLX mutation in this family could explain the fetal findings.

PMID: 28898547 [PubMed - indexed for MEDLINE]

De Novo and Inherited Loss-of-Function Variants in TLK2: Clinical and Genotype-Phenotype Evaluation of a Distinct Neurodevelopmental Disorder.

Am J Hum Genet. 2018 May 22;:

Authors: Reijnders MRF, Miller KA, Alvi M, Goos JAC, Lees MM, de Burca A, Henderson A, Kraus A, Mikat B, de Vries BBA, Isidor B, Kerr B, Marcelis C, Schluth-Bolard C, Deshpande C, Ruivenkamp CAL, Wieczorek D, Deciphering Developmental Disorders Study, Baralle D, Blair EM, Engels H, Lüdecke HJ, Eason J, Santen GWE, Clayton-Smith J, Chandler K, Tatton-Brown K, Payne K, Helbig K, Radtke K, Nugent KM, Cremer K, Strom TM, Bird LM, Sinnema M, Bitner-Glindzicz M, van Dooren MF, Alders M, Koopmans M, Brick L, Kozenko M, Harline ML, Klaassens M, Steinraths M, Cooper NS, Edery P, Yap P, Terhal PA, van der Spek PJ, Lakeman P, Taylor RL, Littlejohn RO, Pfundt R, Mercimek-Andrews S, Stegmann APA, Kant SG, McLean S, Joss S, Swagemakers SMA, Douzgou S, Wall SA, Küry S, Calpena E, Koelling N, McGowan SJ, Twigg SRF, Mathijssen IMJ, Nellaker C, Brunner HG, Wilkie AOM

Abstract
Next-generation sequencing is a powerful tool for the discovery of genes related to neurodevelopmental disorders (NDDs). Here, we report the identification of a distinct syndrome due to de novo or inherited heterozygous mutations in Tousled-like kinase 2 (TLK2) in 38 unrelated individuals and two affected mothers, using whole-exome and whole-genome sequencing technologies, matchmaker databases, and international collaborations. Affected individuals had a consistent phenotype, characterized by mild-borderline neurodevelopmental delay (86%), behavioral disorders (68%), severe gastro-intestinal problems (63%), and facial dysmorphism including blepharophimosis (82%), telecanthus (74%), prominent nasal bridge (68%), broad nasal tip (66%), thin vermilion of the upper lip (62%), and upslanting palpebral fissures (55%). Analysis of cell lines from three affected individuals showed that mutations act through a loss-of-function mechanism in at least two case subjects. Genotype-phenotype analysis and comparison of computationally modeled faces showed that phenotypes of these and other individuals with loss-of-function variants significantly overlapped with phenotypes of individuals with other variant types (missense and C-terminal truncating). This suggests that haploinsufficiency of TLK2 is the most likely underlying disease mechanism, leading to a consistent neurodevelopmental phenotype. This work illustrates the power of international data sharing, by the identification of 40 individuals from 26 different centers in 7 different countries, allowing the identification, clinical delineation, and genotype-phenotype evaluation of a distinct NDD caused by mutations in TLK2.

PMID: 29861108 [PubMed - as supplied by publisher]

TRPV6 Variants Interfere with Maternal-Fetal Calcium Transport through the Placenta and Cause Transient Neonatal Hyperparathyroidism.

Am J Hum Genet. 2018 May 23;:

Authors: Suzuki Y, Chitayat D, Sawada H, Deardorff MA, McLaughlin HM, Begtrup A, Millar K, Harrington J, Chong K, Roifman M, Grand K, Tominaga M, Takada F, Shuster S, Obara M, Mutoh H, Kushima R, Nishimura G

Abstract
Transient neonatal hyperparathyroidism (TNHP) is etiologically a heterogeneous condition. One of the etiologies is an insufficient maternal-fetal calcium transport through the placenta. We report six subjects with homozygous and/or compound-heterozygous mutations in the gene encoding the transient receptor potential cation channel, subfamily V, member 6 (TRPV6), an epithelial Ca2+-selective channel associated with this condition. Exome sequencing on two neonates with skeletal findings consistent with neonatal hyperparathyroidism identified homozygous frameshift mutations before the first transmembrane domain in a subject born to first-cousins parents of Pakistani descent as well as compound-heterozygous mutations (a combination of a frameshift mutation and an intronic mutation that alters mRNA splicing) in an individual born to a non-consanguineous couple of African descent. Subsequently, targeted mutation analysis of TRPV6 performed on four other individuals (born to non-consanguineous Japanese parents) with similar X-rays findings identified compound-heterozygous mutations. The skeletal findings improved or resolved in most subjects during the first few months of life. We identified three missense variants (at the outer edges of the second and third transmembrane domains) that alter the localization of the TRPV6: one recurrent variant at the S2-S3 loop and two recurrent variants (in the fourth ankyrin repeat domain) that impair TRPV6 stability. Compound heterozygous loss-of-function mutations for the pathogenic frameshift allele and the allele with an intronic c.607+5G>A mutation resulted in the most severe phenotype. These results suggest that TNHP is an autosomal-recessive disease caused by TRPV6 mutations that affect maternal-fetal calcium transport.

PMID: 29861107 [PubMed - as supplied by publisher]

Genetic Analyses in Small-for-Gestational-Age Newborns.

J Clin Endocrinol Metab. 2018 03 01;103(3):917-925

Authors: Stalman SE, Solanky N, Ishida M, Alemán-Charlet C, Abu-Amero S, Alders M, Alvizi L, Baird W, Demetriou C, Henneman P, James C, Knegt LC, Leon LJ, Mannens MMAM, Mul AN, Nibbering NA, Peskett E, Rezwan FI, Ris-Stalpers C, van der Post JAM, Kamp GA, Plötz FB, Wit JM, Stanier P, Moore GE, Hennekam RC

Abstract
Context: Small for gestational age (SGA) can be the result of fetal growth restriction, which is associated with perinatal morbidity and mortality. Mechanisms that control prenatal growth are poorly understood.
Objective: The aim of the current study was to gain more insight into prenatal growth failure and determine an effective diagnostic approach in SGA newborns. We hypothesized that one or more copy number variations (CNVs) and disturbed methylation and sequence variants may be present in genes associated with fetal growth.
Design: A prospective cohort study of subjects with a low birth weight for gestational age.
Setting: The study was conducted at an academic pediatric research institute.
Patients: A total of 21 SGA newborns with a mean birth weight below the first centile and a control cohort of 24 appropriate-for-gestational-age newborns were studied.
Interventions: Array comparative genomic hybridization, genome-wide methylation studies, and exome sequencing were performed.
Main Outcome Measures: The numbers of CNVs, methylation disturbances, and sequence variants.
Results: The genetic analyses demonstrated three CNVs, one systematically disturbed methylation pattern, and one sequence variant explaining SGA. Additional methylation disturbances and sequence variants were present in 20 patients. In 19 patients, multiple abnormalities were found.
Conclusion: Our results confirm the influence of a large number of mechanisms explaining dysregulation of fetal growth. We concluded that CNVs, methylation disturbances, and sequence variants all contribute to prenatal growth failure. These genetic workups can be an effective diagnostic approach in SGA newborns.

PMID: 29342293 [PubMed - indexed for MEDLINE]

Intellectual Disability & Rare Disorders: A Diagnostic Challenge.

Adv Exp Med Biol. 2017;1031:39-54

Authors: Kvarnung M, Nordgren A

Abstract
Rare disorders constitute a large and heterogeneous group of diagnoses of which many cause chronic disabilities with significant impact on the lives of affected individuals and their families as well as on the health-care system. Each individual disorder is rare, but when considered as a group, rare disorders are common with a total prevalence of approximately 6-8%. The clinical presentation of these disorders includes a broad diversity of symptoms and signs, often involving the nervous system and resulting in symptoms such as intellectual disability, neuropsychiatric disorders, epilepsy and motor dysfunction. The methods for establishing an etiological diagnosis in patients with rare disorders have improved dramatically during recent years. With the introduction of genomic screening methods, it has been shown that the cause is genetic in the majority of the patients and many will receive an etiological diagnosis in a clinical setting. However, there are a lot of challenges in diagnosing these disorders and despite recent years' advances, a large number of patients with rare disorders still go without an etiological diagnosis. In this chapter we will review the etiology of rare disorders with focus on intellectual disability and what has been learned from massive parallel sequencing studies in deciphering the genetic basis. Furthermore, we will discuss challenges in the etiological diagnostics of these disorders including issues that regard interpretation of the numerous genetic variants detected by genomic screening methods and challenges in the translation of massive parallel sequencing technologies into clinical practice.

PMID: 29214565 [PubMed - indexed for MEDLINE]

Clues for Polygenic Inheritance of Pituitary Stalk Interruption Syndrome From Exome Sequencing in 20 Patients.

J Clin Endocrinol Metab. 2018 02 01;103(2):415-428

Authors: Zwaveling-Soonawala N, Alders M, Jongejan A, Kovacic L, Duijkers FA, Maas SM, Fliers E, van Trotsenburg ASP, Hennekam RC

Abstract
Context: Pituitary stalk interruption syndrome (PSIS) consists of a small/absent anterior pituitary lobe, an interrupted/absent pituitary stalk, and an ectopic posterior pituitary lobe. Mendelian forms of PSIS are detected infrequently (<5%), and a polygenic etiology has been suggested. GLI2 variants have been reported at a relatively high frequency in PSIS.
Objective: To provide further evidence for a non-Mendelian, polygenic etiology of PSIS.
Methods: Exome sequencing (trio approach) in 20 patients with isolated PSIS. In addition to searching for (potentially) pathogenic de novo and biallelic variants, a targeted search was performed in a panel of genes associated with midline brain development (223 genes). For GLI2 variants, both (potentially) pathogenic and relatively rare variants (<5% in the general population) were studied. The frequency of GLI2 variants was compared with that of a reference population.
Results: We found four additional candidate genes for isolated PSIS (DCHS1, ROBO2, CCDC88C, and KIF14) and one for syndromic PSIS (KAT6A). Eleven GLI2 variants were present in six patients. A higher frequency of a combination of two GLI2 variants (M1352V + D1520N) was found in the study group compared with a reference population (10% vs 0.68%). (Potentially) pathogenic variants were identified in genes associated with midline brain anomalies, including holoprosencephaly, hypogonadotropic hypogonadism, and absent corpus callosum and in genes involved in ciliopathies.
Conclusion: Combinations of variants in genes associated with midline brain anomalies are frequently present in PSIS and sustain the hypothesis of a polygenic cause of PSIS.

PMID: 29165578 [PubMed - indexed for MEDLINE]

Homozygous mutation in the NPHP3 gene causing foetal nephronophthisis.

Nephrology (Carlton). 2017 Oct;22(10):818-820

Authors: Abdullah U, Farooq M, Fatima A, Tauseef W, Sarwar Y, Nuri M, Tommerup N, Baig SM

Abstract
We present a case of a foetal sonographic finding of hyper-echogenic kidneys, which led to a strategic series of genetic tests and identified a homozygous mutation (c.424C > T, p. R142*) in the NPHP3 gene. Our study provides a rare presentation of NPHP3-related ciliopathy and adds to the mutation spectrum of the gene, being the first one from Pakistani population. With a thorough literature review, it also advocates for molecular assessment of ciliopathies to improve risk estimate for future pregnancies, and identify predisposed asymptomatic carriers.

PMID: 28921755 [PubMed - indexed for MEDLINE]