Expanding the genotypic spectrum of ACTG2-related visceral myopathy
James KN, Lau M, Shayan K, Lenberg J, Mardach R, Ignacio R Jr, Halbach J, Choi L, Kumar S, Ellsworth KA.
Cold Spring Harb Mol Case Stud. 2021 Apr 21:mcs.a006085. doi: 10.1101/mcs.a006085. Online ahead of print.
Visceral myopathies (VMs) encompass a spectrum of disorders characterized by chronic disruption of gastrointestinal function, with or without urinary system involvement. Pathogenic missense variation in smooth muscle gamma-actin gene (ACTG2) is associated with autosomal dominant VM. Whole genome sequencing of an infant presenting with chronic intestinal pseudo-obstruction revealed a homozygous 187 base pair (c.589_613+163del188) deletion spanning the exon 6-intron 6 boundary within ACTG2. The patient’s clinical course was marked by prolonged hospitalizations, multiple surgeries, and intermittent total parenteral nutrition dependence. This case supports the emerging understanding of allelic heterogeneity in ACTG2-related VM, in which both homozygous and heterozygous variants in ACTG2 are associated with gastrointestinal dysfunction of similar severity and overlapped clinical presentation. Moreover, it illustrates the clinical utility of rapid whole genome sequencing, which can comprehensively and precisely detect different types of genomic variants including small deletions, leading to guidance of clinical care decisions.
PMID:33883208 | DOI:10.1101/mcs.a006085
April 23, 2021
Rapid whole genome sequencing impacts care and resource utilization in infants with congenital heart disease
Sweeney NM, Nahas SA, Chowdhury S, Batalov S, Clark M, Caylor S, Cakici J, Nigro JJ, Ding Y, Veeraraghavan N, Hobbs C, Dimmock D, Kingsmore SF.
NPJ Genom Med. 2021 Apr 22;6(1):29. doi: 10.1038/s41525-021-00192-x.
Congenital heart disease (CHD) is the most common congenital anomaly and a major cause of infant morbidity and mortality. While morbidity and mortality are highest in infants with underlying genetic conditions, molecular diagnoses are ascertained in only ~20% of cases using widely adopted genetic tests. Furthermore, cost of care for children and adults with CHD has increased dramatically. Rapid whole genome sequencing (rWGS) of newborns in intensive care units with suspected genetic diseases has been associated with increased rate of diagnosis and a net reduction in cost of care. In this study, we explored whether the clinical utility of rWGS extends to critically ill infants with structural CHD through a retrospective review of rWGS study data obtained from inpatient infants < 1 year with structural CHD at a regional children’s hospital. rWGS diagnosed genetic disease in 46% of the enrolled infants. Moreover, genetic disease was identified five times more frequently with rWGS than microarray ± gene panel testing in 21 of these infants (rWGS diagnosed 43% versus 10% with microarray ± gene panels, p = 0.02). Molecular diagnoses ranged from syndromes affecting multiple organ systems to disorders limited to the cardiovascular system. The average daily hospital spending was lower in the time period post blood collection for rWGS compared to prior (p = 0.003) and further decreased after rWGS results (p = 0.000). The cost was not prohibitive to rWGS implementation in the care of this cohort of infants. rWGS provided timely actionable information that impacted care and there was evidence of decreased hospital spending around rWGS implementation.
PMID:33888711 | DOI:10.1038/s41525-021-00192-x
April 23, 2021
Rare deleterious mutations of HNRNP genes result in shared neurodevelopmental disorders
Gillentine MA, Wang T, Hoekzema K, Rosenfeld J, Liu P, Guo H, Kim CN, De Vries BBA, Vissers LELM, Nordenskjold M, Kvarnung M, Lindstrand A, Nordgren A, Gecz J, Iascone M, Cereda A, Scatigno A, Maitz S, Zanni G, Bertini E, Zweier C, Schuhmann S, Wiesener A, Pepper M, Panjwani H, Torti E, Abid F, Anselm I, Srivastava S, Atwal P, Bacino CA, Bhat G, Cobian K, Bird LM, Friedman J, Wright MS, Callewaert B, Petit F, Mathieu S, Afenjar A, Christensen CK, White KM, Elpeleg O, Berger I, Espineli EJ, Fagerberg C, Brasch-Andersen C, Hansen LK, Feyma T, Hughes S, Thiffault I, Sullivan B, Yan S, Keller K, Keren B, Mignot C, Kooy F, Meuwissen M, Basinger A, Kukolich M, Philips M, Ortega L, Drummond-Borg M, Lauridsen M, Sorensen K, Lehman A; CAUSES Study, Lopez-Rangel E, Levy P, Lessel D, Lotze T, Madan-Khetarpal S, Sebastian J, Vento J, Vats D, Benman LM, Mckee S, Mirzaa GM, Muss C, Pappas J, Peeters H, Romano C, Elia M, Galesi O, Simon MEH, van Gassen KLI, Simpson K, Stratton R, Syed S, Thevenon J, Palafoll IV, Vitobello A, Bournez M, Faivre L, Xia K; SPARK Consortium, Earl RK, Nowakowski T, Bernier RA, Eichler EE.
Madelyn A Gillentine
Genome Med. 2021 Apr 19;13(1):63. doi: 10.1186/s13073-021-00870-6.
BACKGROUND: With the increasing number of genomic sequencing studies, hundreds of genes have been implicated in neurodevelopmental disorders (NDDs). The rate of gene discovery far outpaces our understanding of genotype-phenotype correlations, with clinical characterization remaining a bottleneck for understanding NDDs. Most disease-associated Mendelian genes are members of gene families, and we hypothesize that those with related molecular function share clinical presentations.
METHODS: We tested our hypothesis by considering gene families that have multiple members with an enrichment of de novo variants among NDDs, as determined by previous meta-analyses. One of these gene families is the heterogeneous nuclear ribonucleoproteins (hnRNPs), which has 33 members, five of which have been recently identified as NDD genes (HNRNPK, HNRNPU, HNRNPH1, HNRNPH2, and HNRNPR) and two of which have significant enrichment in our previous meta-analysis of probands with NDDs (HNRNPU and SYNCRIP). Utilizing protein homology, mutation analyses, gene expression analyses, and phenotypic characterization, we provide evidence for variation in 12 HNRNP genes as candidates for NDDs. Seven are potentially novel while the remaining genes in the family likely do not significantly contribute to NDD risk.
RESULTS: We report 119 new NDD cases (64 de novo variants) through sequencing and international collaborations and combined with published clinical case reports. We consider 235 cases with gene-disruptive single-nucleotide variants or indels and 15 cases with small copy number variants. Three hnRNP-encoding genes reach nominal or exome-wide significance for de novo variant enrichment, while nine are candidates for pathogenic mutations. Comparison of HNRNP gene expression shows a pattern consistent with a role in cerebral cortical development with enriched expression among radial glial progenitors. Clinical assessment of probands (n = 188-221) expands the phenotypes associated with HNRNP rare variants, and phenotypes associated with variation in the HNRNP genes distinguishes them as a subgroup of NDDs.
CONCLUSIONS: Overall, our novel approach of exploiting gene families in NDDs identifies new HNRNP-related disorders, expands the phenotypes of known HNRNP-related disorders, strongly implicates disruption of the hnRNPs as a whole in NDDs, and supports that NDD subtypes likely have shared molecular pathogenesis. To date, this is the first study to identify novel genetic disorders based on the presence of disorders in related genes. We also perform the first phenotypic analyses focusing on related genes. Finally, we show that radial glial expression of these genes is likely critical during neurodevelopment. This is important for diagnostics, as well as developing strategies to best study these genes for the development of therapeutics.
April 20, 2021
Gene DiscoveryGenetic Neurologic DiseaseNeurogenomics
Abnormal SCID Newborn Screening and Spontaneous Recovery Associated with a Novel Haploinsufficiency IKZF1 Mutation
Kuehn HS, Gloude NJ, Dimmock D, Tokita M, Wright M, Rosenzweig SD, Collins C.
J Clin Immunol. 2021 Apr 14. doi: 10.1007/s10875-021-01035-1. Online ahead of print.
PURPOSE: IKAROS, encoded by IKZF1, is a member of the IKAROS family of zinc-finger transcription factors playing critical roles in lymphocyte development, differentiation, and tumor suppression. Several studies demonstrated that IKZF1 mutations affecting DNA binding or homo-/hetero-dimerization are mostly associated with common variable immunodeficiency, combined immunodeficiency, or hematologic manifestations. Herein we report a likely de novo, nonsense IKZF1 mutation (p.C182*) in a baby with low T cell receptor excision circles (TREC) identified by newborn screening testing for severe combined immunodeficiency. The patient also presented a profound B cell deficiency at birth.
METHODS: Genetic, functional, immunologic, and clinical outcome data associated with this patient and her mutation were evaluated.
RESULTS: Mutant p.C182* was detected in the cytoplasm of the patient’s primary cells, in contrast to wild type (WT) IKAROS protein, only detected in the nucleus. Functional in vitro assessments revealed that p.C182* was less stable than WT IKAROS protein and failed to bind to its target DNA binding sequence and dimerize with WT IKAROS protein, resulting in impaired pericentromeric targeting and transcriptional repression by means of haploinsufficiency. During follow-up, while a spontaneous recovery of TREC and T cells was observed, B cells improved but not to sustained normal ranges.
CONCLUSIONS: Patients with IKAROS-associated diseases can present with SCID-like TREC values through newborn screening testing. IKZF1 mutations should be added to the low TREC differential, although spontaneous recovery has to be considered.
April 15, 2021
Biallelic hypomorphic mutations in HEATR5B, encoding HEAT repeat-containing protein 5B, in a neurological syndrome with pontocerebellar hypoplasia
Ghosh SG, Breuss MW, Schlachetzki Z, Chai G, Ross D, Stanley V, Sonmez FM, Topaloglu H, Zaki MS, Hosny H, Gad S, Gleeson JG.
Eur J Hum Genet. 2021 Apr 6. doi: 10.1038/s41431-021-00832-x. Online ahead of print.
HEAT repeats are 37-47 amino acid flexible tandem repeat structural motifs occurring in a wide variety of eukaryotic proteins with diverse functions. Due to their ability to undergo elastic conformational changes, they often serve as scaffolds at sites of protein interactions. Here, we describe four affected children from two families presenting with pontocerebellar hypoplasia manifest clinically with neonatal seizures, severe intellectual disability, and motor delay. Whole exome sequencing identified biallelic variants at predicted splice sites in intron 31 of HEATR5B, encoding the HEAT repeat-containing protein 5B segregating in a recessive fashion. Aberrant splicing was found in patient fibroblasts, which correlated with reduced levels of HEATR5B protein. HEATR5B is expressed during brain development in human, and we failed to recover live-born homozygous Heatr5b knockout mice. Taken together, our results implicate loss of HEATR5B in pontocerebellar hypoplasia.
PMID:33824466 | DOI:10.1038/s41431-021-00832-x
April 7, 2021
Comprehensive identification of somatic nucleotide variants in human brain tissue
Wang Y, Bae T, Thorpe J, Sherman MA, Jones AG, Cho S, Daily K, Dou Y, Ganz J, Galor A, Lobon I, Pattni R, Rosenbluh C, Tomasi S, Tomasini L, Yang X, Zhou B, Akbarian S, Ball LL, Bizzotto S, Emery SB, Doan R, Fasching L, Jang Y, Juan D, Lizano E, Luquette LJ, Moldovan JB, Narurkar R, Oetjens MT, Rodin RE, Sekar S, Shin JH, Soriano E, Straub RE, Zhou W, Chess A, Gleeson JG, Marquès-Bonet T, Park PJ, Peters MA, Pevsner J, Walsh CA, Weinberger DR; Brain Somatic Mosaicism Network, Vaccarino FM, Moran JV, Urban AE, Kidd JM, Mills RE, Abyzov A. Comprehensive identification of somatic nucleotide variants in human brain tissue. Genome Biol. 2021 Mar 29;22(1):92. doi: 10.1186/s13059-021-02285-3. PMID: 33781308; PMCID: PMC8006362.
Genome Biol. 2021 Mar 29;22(1):92. doi: 10.1186/s13059-021-02285-3.
BACKGROUND: Post-zygotic mutations incurred during DNA replication, DNA repair, and other cellular processes lead to somatic mosaicism. Somatic mosaicism is an established cause of various diseases, including cancers. However, detecting mosaic variants in DNA from non-cancerous somatic tissues poses significant challenges, particularly if the variants only are present in a small fraction of cells.
RESULTS: Here, the Brain Somatic Mosaicism Network conducts a coordinated, multi-institutional study to examine the ability of existing methods to detect simulated somatic single-nucleotide variants (SNVs) in DNA mixing experiments, generate multiple replicates of whole-genome sequencing data from the dorsolateral prefrontal cortex, other brain regions, dura mater, and dural fibroblasts of a single neurotypical individual, devise strategies to discover somatic SNVs, and apply various approaches to validate somatic SNVs. These efforts lead to the identification of 43 bona fide somatic SNVs that range in variant allele fractions from ~ 0.005 to ~ 0.28. Guided by these results, we devise best practices for calling mosaic SNVs from 250× whole-genome sequencing data in the accessible portion of the human genome that achieve 90% specificity and sensitivity. Finally, we demonstrate that analysis of multiple bulk DNA samples from a single individual allows the reconstruction of early developmental cell lineage trees.
CONCLUSIONS: This study provides a unified set of best practices to detect somatic SNVs in non-cancerous tissues. The data and methods are freely available to the scientific community and should serve as a guide to assess the contributions of somatic SNVs to neuropsychiatric diseases.
March 30, 2021
Metagenomic Next-Generation Sequencing for Pathogen Detection and Transcriptomic Analysis in Pediatric Central Nervous System Infections
Ramchandar N, Coufal NG, Warden AS, Briggs B, Schwarz T, Stinnett R, Xie H, Schlaberg R, Foley J, Clarke C, Waldeman B, Enriquez C, Osborne S, Arrieta A, Salyakina D, Janvier M, Sendi P, Totapally BR, Dimmock D, Farnaes L.
Open Forum Infect Dis. 2021 Mar 6;8(6):ofab104. doi: 10.1093/ofid/ofab104. eCollection 2021 Jun.
BACKGROUND: Pediatric central nervous system (CNS) infections are potentially life-threatening and may incur significant morbidity. Identifying a pathogen is important, both in terms of guiding therapeutic management and in characterizing prognosis. Usual care testing by culture and polymerase chain reaction is often unable to identify a pathogen. We examined the systematic application of metagenomic next-generation sequencing (mNGS) for detecting organisms and transcriptomic analysis of cerebrospinal fluid (CSF) in children with central nervous system (CNS) infections.
METHODS: We conducted a prospective multisite study that aimed to enroll all children with a CSF pleocytosis and suspected CNS infection admitted to 1 of 3 tertiary pediatric hospitals during the study timeframe. After usual care testing had been performed, the remaining CSF was sent for mNGS and transcriptomic analysis.
RESULTS: We screened 221 and enrolled 70 subjects over a 12-month recruitment period. A putative organism was isolated from CSF in 25 (35.7%) subjects by any diagnostic modality. Metagenomic next-generation sequencing of the CSF samples identified a pathogen in 20 (28.6%) subjects, which were also all identified by usual care testing. The median time to result was 38 hours.
CONCLUSIONS: Metagenomic sequencing of CSF has the potential to rapidly identify pathogens in children with CNS infections.
March 21, 2021
Correction to: De novo variants in SNAP25 cause an early-onset developmental and epileptic encephalopathy
Klöckner C, Sticht H, Zacher P, Popp B, Babcock HE, Bakker DP, Barwick K, Bonfert MV, Bönnemann CG, Brilstra EH; Care4Rare Canada Consortium, Chung WK, Clarke AJ, Devine P, Donkervoort S, Fraser JL, Friedman J, Gates A, Ghoumid J, Hobson E, Horvath G, Keller-Ramey J, Keren B, Kurian MA, Lee V, Leppig KA, Lundgren J, McDonald MT, McLaughlin HM, McTague A, Mefford HC, Mignot C, Mikati MA, Nava C, Raymond FL, Sampson JR, Sanchis-Juan A, Shashi V, Shieh JTC, Shinawi M, Slavotinek A, Stödberg T, Stong N, Sullivan JA, Taylor AC, Toler TL, van den Boogaard MJ, van der Crabben SN, van Gassen KLI, van Jaarsveld RH, Van Ziffle J, Wadley AF, Wagner M, Wigby K, Wortmann SB, Zarate YA, Møller RS, Lemke JR, Platzer K. Correction to: De novo variants in SNAP25 cause an early-onset developmental and epileptic encephalopathy. Genet Med. 2021 Apr;23(4):796. doi: 10.1038/s41436-020-01090-w. Erratum for: Genet Med. 2021 Apr;23(4):653-660. PMID: 33686260.
Genet Med. 2021 Mar 8. doi: 10.1038/s41436-020-01090-w. Online ahead of print.
PMID:33686260 | DOI:10.1038/s41436-020-01090-w
March 9, 2021
Paternal genetic variants and risk of obstructive heart defects: A parent-of-origin approach
Patel J, Bircan E, Tang X, Orloff M, Hobbs CA, Browne ML, Botto LD, Finnell RH, Jenkins MM, Olshan A, Romitti PA, Shaw GM, Werler MM, Li J, Nembhard WN; National Birth Defects Prevention Study.
PLoS Genet. 2021 Mar 8;17(3):e1009413. doi: 10.1371/journal.pgen.1009413. eCollection 2021 Mar.
Previous research on risk factors for obstructive heart defects (OHDs) focused on maternal and infant genetic variants, prenatal environmental exposures, and their potential interaction effects. Less is known about the role of paternal genetic variants or environmental exposures and risk of OHDs. We examined parent-of-origin effects in transmission of alleles in the folate, homocysteine, or transsulfuration pathway genes on OHD occurrence in offspring. We used data on 569 families of liveborn infants with OHDs born between October 1997 and August 2008 from the National Birth Defects Prevention Study to conduct a family-based case-only study. Maternal, paternal, and infant DNA were genotyped using an Illumina Golden Gate custom single nucleotide polymorphism (SNP) panel. Relative risks (RR), 95% confidence interval (CI), and likelihood ratio tests from log-linear models were used to estimate the parent-of-origin effect of 877 SNPs in 60 candidate genes in the folate, homocysteine, and transsulfuration pathways on the risk of OHDs. Bonferroni correction was applied for multiple testing. We identified 3 SNPs in the transsulfuration pathway and 1 SNP in the folate pathway that were statistically significant after Bonferroni correction. Among infants who inherited paternally-derived copies of the G allele for rs6812588 in the RFC1 gene, the G allele for rs1762430 in the MGMT gene, and the A allele for rs9296695 and rs4712023 in the GSTA3 gene, RRs for OHD were 0.11 (95% CI: 0.04, 0.29, P = 9.16×10-7), 0.30 (95% CI: 0.17, 0.53, P = 9.80×10-6), 0.34 (95% CI: 0.20, 0.57, P = 2.28×10-5), and 0.34 (95% CI: 0.20, 0.58, P = 3.77×10-5), respectively, compared to infants who inherited maternally-derived copies of the same alleles. We observed statistically significant decreased risk of OHDs among infants who inherited paternal gene variants involved in folate and transsulfuration pathways.
March 8, 2021
Author Correction: Loss of NARS1 impairs progenitor proliferation in cortical brain organoids and leads to microcephaly
Ghosh SG, Breuss MW, Schlachetzki Z, Chai G, Ross D, Stanley V, Sonmez FM, Topaloglu H, Zaki MS, Hosny H, Gad S, Gleeson JG.
February 16, 2021