A Novel Frameshift Mutation, KCNH2 [p.Asp896ArgfsX79], Leading to Malignant Ventricular Arrhythmia, Identified After Treatment of Gastrointestinal Bleeding.

A novel frameshift mutation in the KCNH2 gene for long QT syndrome type 2 (LQTS2) was identified after torsades des pointes ventricular tachycardia in a 49-year-old patient managed with octreotide and nadolol for an acute variceal bleed. In spite of removal of offending medications, and correction of underlying electrolyte abnormalities, the patient's QT interval remained prolonged-at 521 ms-raising the suspicion of an underlying channelopathy. Genetic studies confirmed heterozygosity for a novel frameshift mutation for the KCNH2 gene, D896Rfs X79. We explore the pathogenicity and clinical impact of this variant mutation.

Une nouvelle mutation de changement de phase du gène KCNH2 impliqué dans le syndrome du QT long de type 2 (SQTL2) a été trouvée après une tachycardie ventriculaire à torsades de pointes chez un patient de 49 ans traité par octréotide et nadolol en raison d'un saignement variqueux en phase aiguë. En dépit du retrait des médicaments mis en cause et de la correction des anomalies électrolytiques sous-jacentes, l'intervalle du QT du patient qui demeurait prolongé (à 521 ms) a suscité la suspicion d'une canalopathie sous-jacente. Des études génétiques ont permis de confirmer l'hétérozygosité d'une nouvelle mutation de changement de phase du gène KCNH2, D896Rfs X79. Nous examinons la pathogénicité et les répercussions cliniques de cette mutation du variant.

Clinical delineation, sex differences, and genotype-phenotype correlation in pathogenic KDM6A variants causing X-linked Kabuki syndrome type 2.

PURPOSE: The variant spectrum and the phenotype of X-linked Kabuki syndrome type 2 (KS2) are poorly understood. METHODS: Genetic and clinical details of new and published individuals with pathogenic KDM6A variants were compiled and analyzed. RESULTS: Sixty-one distinct pathogenic KDM6A variants (50 truncating, 11 missense) from 80 patients (34 males, 46 females) were identified. Missense variants clustered in the TRP 2, 3, 7 and Jmj-C domains. Truncating variants were significantly more likely to be de novo. Thirteen individuals had maternally inherited variants and one had a paternally inherited variant. Neonatal feeding difficulties, hypoglycemia, postnatal growth retardation, poor weight gain, motor delay, intellectual disability (ID), microcephaly, congenital heart anomalies, palate defects, renal malformations, strabismus, hearing loss, recurrent infections, hyperinsulinism, seizures, joint hypermobility, and gastroesophageal reflux were frequent clinical findings. Facial features of over a third of patients were not typical for KS. Males were significantly more likely to be born prematurely, have shorter stature, and severe developmental delay/ID. CONCLUSION: We expand the KDM6A variant spectrum and delineate the KS2 phenotype. We demonstrate that the variability of the KS2 phenotypic depends on sex and the variant type. We also highlight the overlaps and differences between the phenotypes of KS2 and KS1.

Integrated genome and transcriptome sequencing identifies a noncoding mutation in the genome replication factor DONSON as the cause of microcephaly-micromelia syndrome.

While next-generation sequencing has accelerated the discovery of human disease genes, progress has been largely limited to the "low hanging fruit" of mutations with obvious exonic coding or canonical splice site impact. In contrast, the lack of high-throughput, unbiased approaches for functional assessment of most noncoding variants has bottlenecked gene discovery. We report the integration of transcriptome sequencing (RNA-seq), which surveys all mRNAs to reveal functional impacts of variants at the transcription level, into the gene discovery framework for a unique human disease, microcephaly-micromelia syndrome (MMS). MMS is an autosomal recessive condition described thus far in only a single First Nations population and causes intrauterine growth restriction, severe microcephaly, craniofacial anomalies, skeletal dysplasia, and neonatal lethality. Linkage analysis of affected families, including a very large pedigree, identified a single locus on Chromosome 21 linked to the disease (LOD > 9). Comprehensive genome sequencing did not reveal any pathogenic coding or canonical splicing mutations within the linkage region but identified several nonconserved noncoding variants. RNA-seq analysis detected aberrant splicing in DONSON due to one of these noncoding variants, showing a causative role for DONSON disruption in MMS. We show that DONSON is expressed in progenitor cells of embryonic human brain and other proliferating tissues, is co-expressed with components of the DNA replication machinery, and that Donson is essential for early embryonic development in mice as well, suggesting an essential conserved role for DONSON in the cell cycle. Our results demonstrate the utility of integrating transcriptomics into the study of human genetic disease when DNA sequencing alone is not sufficient to reveal the underlying pathogenic mutation.

A de novo deletion in a boy with cerebral palsy suggests a refined critical region for the 4q21.22 microdeletion syndrome.

We present an 18-year-old boy with cerebral palsy, intellectual disability, speech delay, and seizures. He carries a likely pathogenic 1.3 Mb de novo heterozygous deletion in the 4q21.22 microdeletion syndrome region. He also carries a 436 kb maternally-inherited duplication impacting the first three exons of CHRNA7. The majority of previously published cases with 4q21.22 syndrome shared common features including growth restriction, muscular hypotonia, and absent or severely delayed speech. Using copy number variation (CNV) data available for other subjects, we defined a minimal critical region of 170.8 kb within the syndromic region, encompassing HNRNPD. We also identified a larger 2 Mb critical region encompassing ten protein-coding genes, of which six (PRKG2, RASGEF1B, HNRNPDL, HNRNPD, LIN54, COPS4) have a significantly low number of truncating loss-of-function mutations. Long-range chromatin interaction data suggest that this deletion may alter chromatin interactions at the 4q21.22 microdeletion region. We suggest that the deletion or misregulation of these genes is likely to contribute to the neurodevelopmental and neuromuscular abnormalities in 4q21.22 syndrome.

A novel NDUFS4 frameshift mutation causes Leigh disease in the Hutterite population.

Leigh disease is a progressive, infantile-onset, neurodegenerative disorder characterized by feeding difficulties, failure to thrive, hypotonia, seizures, and central respiratory compromise. Metabolic and neuroimaging investigations typically identify abnormalities consistent with a disorder of mitochondrial energy metabolism. Mutations in more than 35 genes affecting the mitochondrial respiratory chain encoded from both the nuclear and mitochondrial genomes have been associated with Leigh disease. The clinical presentations of five individuals of Hutterite descent with Leigh disease are described herein. An identity-by-descent mapping and candidate gene approach was used to identify a novel homozygous c.393dupA frameshift mutation in the NADH dehydrogenase (ubiquinone) Fe-S protein 4 (NDUFS4) gene. The carrier frequency of this mutation was estimated in >1,300 Hutterite individuals to be 1 in 27. © 2017 Wiley Periodicals, Inc.

The differential diagnosis of spastic diplegia.

Spastic diplegia is the most common form of cerebral palsy worldwide. Many disorders mimic spastic diplegia, which can result in misdiagnosis for the child with resultant negative treatment and family counselling implications. In this paper, the authors provide a brief review of spastic diplegia and the various disorders in the differential diagnosis. We also provide a diagnostic algorithm to assist physicians in making the correct diagnosis.

Disrupted auto-regulation of the spliceosomal gene SNRPB causes cerebro-costo-mandibular syndrome.

Elucidating the function of highly conserved regulatory sequences is a significant challenge in genomics today. Certain intragenic highly conserved elements have been associated with regulating levels of core components of the spliceosome and alternative splicing of downstream genes. Here we identify mutations in one such element, a regulatory alternative exon of SNRPB as the cause of cerebro-costo-mandibular syndrome. This exon contains a premature termination codon that triggers nonsense-mediated mRNA decay when included in the transcript. These mutations cause increased inclusion of the alternative exon and decreased overall expression of SNRPB. We provide evidence for the functional importance of this conserved intragenic element in the regulation of alternative splicing and development, and suggest that the evolution of such a regulatory mechanism has contributed to the complexity of mammalian development.

Complex genomic rearrangements in the dystrophin gene due to replication-based mechanisms.

Genomic rearrangements such as intragenic deletions and duplications are the most prevalent type of mutations in the dystrophin gene resulting in Duchenne and Becker muscular dystrophy (D/BMD). These copy number variations (CNVs) are nonrecurrent and can result from either nonhomologous end joining (NHEJ) or microhomology-mediated replication-dependent recombination (MMRDR). We characterized five DMD patients with complex genomic rearrangements using a combination of MLPA/mRNA transcript analysis/custom array comparative hybridization arrays (CGH) and breakpoint sequence analysis to investigate the mechanisms for these rearrangements. Two patients had complex rearrangements that involved microhomologies at breakpoints. One patient had a noncontiguous insertion of 89.7 kb chromosome 4 into intron 43 of DMD involving three breakpoints with 2-5 bp microhomology at the junctions. A second patient had an inversion of exon 44 flanked by intronic deletions with two breakpoint junctions each showing 2 bp microhomology. The third patient was a female with an inherited deletion of exon 47 in DMD on the maternal allele and a de novo noncontiguous duplication of exons 45-49 in DMD and MID1 on the paternal allele. The other two patients harbored complex noncontiguous duplications within the dystrophin gene. We propose a replication-based mechanisms for all five complex DMD rearrangements. This study identifies additional underlying mechanisms in DMD, and provides insight into the molecular bases of these genomic rearrangements.

Extreme intra-familial variability of congenital central hypoventilation syndrome: a case series.

INTRODUCTION: Congenital central hypoventilation syndrome is an autosomal dominant disorder that classically presents as sudden death in infancy secondary to central hypoventilation. Most cases are caused by polyalanine repeat mutations in the paired-like homeobox 2B gene, PHOX2B. More severe disease is typically associated with nonpolyalanine repeat mutations. We report the case of a family with nonpolyalanine repeat mutations that uncharacteristically has many individuals who were mildly symptomatic and only diagnosed after genetic testing. We highlight the highly variable clinical presentation of this condition and the need for clinicians to remain vigilant. CASE PRESENTATION: We identified 10 individuals in a large extended Caucasian family of German and Austrian background with congenital central hypoventilation syndrome.Case 1: A 16-year old male proband presented for reproductive counseling. He had a previous history of apneic spells and Hirschsprung disease in the neonatal period. A PHOX2B nonpolyalanine repeat mutation was identified in the proband and used to screen his extended family.Cases 2 to 10: Several mildly symptomatic family members (males aged 5, 13, 42 and 80 years; females aged 28, 44, 46 and 48 years) spanning four generations were identified after genetic screening. A newborn boy from this family was also recently diagnosed with Hirschsprung disease and went on to have an abnormal sleep study. CONCLUSIONS: In this report, we highlight the significant phenotypic variability of congenital central hypoventilation syndrome, previously thought to be a rare genetic condition. Given the extreme clinical variability, it is possible that the prevalence of congenital central hypoventilation syndrome in the general population is much higher than previous estimates. This is of major importance to all clinicians who will need to maintain a high index of suspicion for this not so rare and highly clinically variable genetic condition that spans all ages. As the familial mutation has been identified, presymptomatic and prenatal diagnostic testing are available options for family members.

GPSM2 mutations cause the brain malformations and hearing loss in Chudley-McCullough syndrome.

Autosomal-recessive inheritance, severe to profound sensorineural hearing loss, and partial agenesis of the corpus callosum are hallmarks of the clinically well-established Chudley-McCullough syndrome (CMS). Although not always reported in the literature, frontal polymicrogyria and gray matter heterotopia are uniformly present, whereas cerebellar dysplasia, ventriculomegaly, and arachnoid cysts are nearly invariant. Despite these striking brain malformations, individuals with CMS generally do not present with significant neurodevelopmental abnormalities, except for hearing loss. Homozygosity mapping and whole-exome sequencing of DNA from affected individuals in eight families (including the family in the first report of CMS) revealed four molecular variations (two single-base deletions, a nonsense mutation, and a canonical splice-site mutation) in the G protein-signaling modulator 2 gene, GPSM2, that underlie CMS. Mutations in GPSM2 have been previously identified in people with profound congenital nonsyndromic hearing loss (NSHL). Subsequent brain imaging of these individuals revealed frontal polymicrogyria, abnormal corpus callosum, and gray matter heterotopia, consistent with a CMS diagnosis, but no ventriculomegaly. The gene product, GPSM2, is required for orienting the mitotic spindle during cell division in multiple tissues, suggesting that the sensorineural hearing loss and characteristic brain malformations of CMS are due to defects in asymmetric cell divisions during development.

Perinatal and childhood morbidity and mortality in congenital analbuminemia.

Albumin, a serum transport protein, provides 80% of colloid osmotic pressure. Congenital analbuminemia (CAA) is an autosomal recessive disorder characterized by absence of serum albumin. Fifty cases of CAA have been reported throughout the world; however, little is known about its clinical impact. Most reported cases have few clinical signs and symptoms. Twelve local cases from the northwestern central plains region in Saskatchewan were identified and reviewed to ascertain morbidity and mortality related with CAA. All the cases are from two remote First Nations communities. Cases had frequent hospital admissions and recurrent respiratory tract infections. Placental abnormalities included hydropic placentas, placental infarcts and microcalcifications. One-half of the cases were born preterm and one-quarter were small for their gestational age. There were three mortalities in the case series. The present case series suggests increased morbidity and mortality during infancy in patients with CAA. The long-term risks of CAA in this population are unknown and a longitudinal study is recommended.

L'albumine, une protéine du transport sérique, fournit 80 % de la pression colloïdo-osmotique. L'analbuminémie congénitale (AAC) est un trouble autosomique récessif caractérisé par l'absence d'albumine sérique. Cinquante cas d'AAC ont été signalés dans le monde, mais on ne sait pas grand-chose de ses répercussions cliniques. La plupart des cas déclarés s'associaient à peu de signes et symptômes cliniques. Les chercheurs ont dépisté 12 cas locaux, originaires de la région du nord-ouest des plaines centrales, en Saskatchewan, et les ont analysés afin de déterminer la morbidité et la mortalité liées à l'AAC. Tous les cas provenaient de deux communautés éloignées des Premières nations. Ils étaient souvent hospitalisés et avaient des infections respiratoires récurrentes. Les anomalies placentaires incluaient des placentas hydropiques, des infarctus placentaires et des microcalcifications. La moitié des cas étaient prématurés et le quart d'entre eux étaient petits par rapport à leur âge gestationnel. Trois mortalités ont été constatées. Cette série a démontré une augmentation de la morbidité et de la mortalité pendant l'enfance chez les patients ayant une AAC. On ne connaît pas les risques à long terme de l'AAC au sein de cette population. Une étude longitudinale est recommandée.

Further expansion of the phenotypic spectrum associated with mutations in ALDH18A1, encoding Δ¹-pyrroline-5-carboxylate synthase (P5CS).

We report on the third case of cutis laxa and progeroid features caused by a homozygous mutation in ALDH18A1 that encodes Δ¹-pyrroline-5-carboxylate-synthase (P5CS). This severely affected child, born to consanguineous parents of Pakistani origin, presented with lax, wrinkled and thin skin with dilated and tortuous subcutaneous blood vessels, corneal clouding, and hypotonia. The child had severe global developmental delay and feeding difficulties and died in infancy for an unknown reason. The proband was homozygous for a mutation in ALDH18A1, c.1923 + 1G > A which results in the production of two anomalous transcripts that are predicted to encode proteins lacking the catalytic site for the enzyme. The cellular phenotype is characterized by diminished production of collagen types I and III, altered elastin ultrastructure, and diminished cell proliferation of cultured dermal fibroblasts. This severe clinical and cellular phenotype overlaps with a broad group of neurocutaneous syndromes that include cutis laxa type II, wrinkly skin syndrome, de Barsy syndrome, and gerodermia osteodysplastica. The findings presented here emphasize the pleiotropic presentation of this group of conditions and suggest that multiple components of the extracellular matrix are perturbed in these disorders.

Familial interstitial pulmonary fibrosis: a large family with atypical clinical features.

A large kindred of familial pulmonary fibrosis is reported. Six members from the first two generations of this particular kindred were described more than 40 years previously; six more individuals from the third and fourth generations have also been evaluated. The proband, now 23 years of age, has mild disease; the other 11 documented affected family members all died from their disease at an average age of 37 years (range 25 to 50 years). The pathology was that of usual interstitial pneumonia, as is typical in idiopathic pulmonary fibrosis. However, the initial radiographic pattern in many of these individuals was upper lobe and nodular and, along with the young age, was atypical for idiopathic pulmonary fibrosis. Several genetic abnormalities have been associated with familial pulmonary fibrosis. The present study examined the genes coding for surfactant protein-C, ATPbinding cassette protein A3 and telomerase, and found no abnormalities.

Clinical and mutational spectrum of neurofibromatosis type 1-like syndrome.

CONTEXT: Autosomal dominant inactivating sprouty-related EVH1 domain-containing protein 1 (SPRED1) mutations have recently been described in individuals presenting mainly with café au lait macules (CALMs), axillary freckling, and macrocephaly. The extent of the clinical spectrum of this new disorder needs further delineation. OBJECTIVE: To determine the frequency, mutational spectrum, and phenotype of neurofibromatosis type 1-like syndrome (NFLS) in a large cohort of patients. DESIGN, SETTING, AND PARTICIPANTS: In a cross-sectional study, 23 unrelated probands carrying a SPRED1 mutation identified through clinical testing participated with their families in a genotype-phenotype study (2007-2008). In a second cross-sectional study, 1318 unrelated anonymous samples collected in 2003-2007 from patients with a broad range of signs typically found in neurofibromatosis type 1 (NF1) but no detectable NF1 germline mutation underwent SPRED1 mutation analysis. MAIN OUTCOME MEASURES: Comparison of aggregated clinical features in patients with or without a SPRED1 or NF1 mutation. Functional assays were used to evaluate the pathogenicity of missense mutations. RESULTS: Among 42 SPRED1-positive individuals from the clinical cohort, 20 (48%; 95% confidence interval [CI], 32%-64%) fulfilled National Institutes of Health (NIH) NF1 diagnostic criteria based on the presence of more than 5 CALMs with or without freckling or an NF1-compatible family history. None of the 42 SPRED1-positive individuals (0%; 95% CI, 0%-7%) had discrete cutaneous or plexiform neurofibromas, typical NF1 osseous lesions, or symptomatic optic pathway gliomas. In the anonymous cohort of 1318 individuals, 34 different SPRED1 mutations in 43 probands were identified: 27 pathogenic mutations in 34 probands and 7 probable nonpathogenic missense mutations in 9 probands. Of 94 probands with familial CALMs with or without freckling and no other NF1 features, 69 (73%; 95% CI, 63%-80%) had an NF1 mutation and 18 (19%; 95% CI, 12%-29%) had a pathogenic SPRED1 mutation. In the anonymous cohort, 1.9% (95% CI, 1.2%-2.9%) of individuals with the clinical diagnosis of NF1 according to the NIH criteria had NFLS. CONCLUSIONS: A high SPRED1 mutation detection rate was found in NF1 mutation-negative families with an autosomal dominant phenotype of CALMs with or without freckling and no other NF1 features. Among individuals in this study, NFLS was not associated with the peripheral and central nervous system tumors seen in NF1.

Disease-causing 7.4 kb cis-regulatory deletion disrupting conserved non-coding sequences and their interaction with the FOXL2 promotor: implications for mutation screening.

To date, the contribution of disrupted potentially cis-regulatory conserved non-coding sequences (CNCs) to human disease is most likely underestimated, as no systematic screens for putative deleterious variations in CNCs have been conducted. As a model for monogenic disease we studied the involvement of genetic changes of CNCs in the cis-regulatory domain of FOXL2 in blepharophimosis syndrome (BPES). Fifty-seven molecularly unsolved BPES patients underwent high-resolution copy number screening and targeted sequencing of CNCs. Apart from three larger distant deletions, a de novo deletion as small as 7.4 kb was found at 283 kb 5' to FOXL2. The deletion appeared to be triggered by an H-DNA-induced double-stranded break (DSB). In addition, it disrupts a novel long non-coding RNA (ncRNA) PISRT1 and 8 CNCs. The regulatory potential of the deleted CNCs was substantiated by in vitro luciferase assays. Interestingly, Chromosome Conformation Capture (3C) of a 625 kb region surrounding FOXL2 in expressing cellular systems revealed physical interactions of three upstream fragments and the FOXL2 core promoter. Importantly, one of these contains the 7.4 kb deleted fragment. Overall, this study revealed the smallest distant deletion causing monogenic disease and impacts upon the concept of mutation screening in human disease and developmental disorders in particular.

Sotos syndrome: antenatal presentation.

There is little published information regarding the clinical presentation of Sotos syndrome in pregnancy. In this report, we describe the antenatal presentation of a child subsequently diagnosed with Sotos syndrome by molecular analysis. The pregnancy was complicated by a positive maternal serum screen and abnormal ultrasound findings including macrocephaly, polyhydramnios and decreased fetal movements. This is the first report of an elevated Down syndrome risk in a pregnancy with confirmed Sotos syndrome. Sotos syndrome should be included in the differential diagnosis of newborns with a normal karyotype where the pregnancy has demonstrated an increased risk for Down syndrome by maternal serum screening, especially in the presence of supportive ultrasound findings.