Spliceosome malfunction causes neurodevelopmental disorders with overlapping features.

Pre-mRNA splicing is a highly coordinated process. While its dysregulation has been linked to neurological deficits, our understanding of the underlying molecular and cellular mechanisms remains limited. We implicated pathogenic variants in U2AF2 and PRPF19, encoding spliceosome subunits in neurodevelopmental disorders (NDDs), by identifying 46 unrelated individuals with 23 de novo U2AF2 missense variants (including 7 recurrent variants in 30 individuals) and 6 individuals with de novo PRPF19 variants. Eight U2AF2 variants dysregulated splicing of a model substrate. Neuritogenesis was reduced in human neurons differentiated from human pluripotent stem cells carrying two U2AF2 hyper-recurrent variants. Neural loss of function (LoF) of the Drosophila orthologs U2af50 and Prp19 led to lethality, abnormal mushroom body (MB) patterning, and social deficits, which were differentially rescued by wild-type and mutant U2AF2 or PRPF19. Transcriptome profiling revealed splicing substrates or effectors (including Rbfox1, a third splicing factor), which rescued MB defects in U2af50-deficient flies. Upon reanalysis of negative clinical exomes followed by data sharing, we further identified 6 patients with NDD who carried RBFOX1 missense variants which, by in vitro testing, showed LoF. Our study implicates 3 splicing factors as NDD-causative genes and establishes a genetic network with hierarchy underlying human brain development and function.

Genomic profiling informs diagnoses and treatment in vascular anomalies.

Vascular anomalies are malformations or tumors of the blood or lymphatic vasculature and can be life-threatening. Although molecularly targeted therapies can be life-saving, identification of the molecular etiology is often impeded by lack of accessibility to affected tissue samples, mosaicism or insufficient sequencing depth. In a cohort of 356 participants with vascular anomalies, including 104 with primary complex lymphatic anomalies (pCLAs), DNA from CD31+ cells isolated from lymphatic fluid or cell-free DNA from lymphatic fluid or plasma underwent ultra-deep sequencing thereby uncovering pathogenic somatic variants down to a variant allele fraction of 0.15%. A molecular diagnosis, including previously undescribed genetic causes, was obtained in 41% of participants with pCLAs and 72% of participants with other vascular malformations, leading to a new medical therapy for 63% (43/69) of participants and resulting in improvement in 63% (35/55) of participants on therapy. Taken together, these data support the development of liquid biopsy-based diagnostic techniques to identify previously undescribed genotype-phenotype associations and guide medical therapy in individuals with vascular anomalies.

Lymphatic disorders caused by mosaic, activating KRAS variants respond to MEK inhibition.

Central conducting lymphatic anomaly (CCLA) due to congenital maldevelopment of the lymphatics can result in debilitating and life-threatening disease with limited treatment options. We identified 4 individuals with CCLA, lymphedema, and microcystic lymphatic malformation due to pathogenic, mosaic variants in KRAS. To determine the functional impact of these variants and identify a targeted therapy for these individuals, we used primary human dermal lymphatic endothelial cells (HDLECs) and zebrafish larvae to model the lymphatic dysplasia. Expression of the p.Gly12Asp and p.Gly13Asp variants in HDLECs in a 2­dimensional (2D) model and 3D organoid model led to increased ERK phosphorylation, demonstrating these variants activate the RAS/MAPK pathway. Expression of activating KRAS variants in the venous and lymphatic endothelium in zebrafish resulted in lymphatic dysplasia and edema similar to the individuals in the study. Treatment with MEK inhibition significantly reduced the phenotypes in both the organoid and the zebrafish model systems. In conclusion, we present the molecular characterization of the observed lymphatic anomalies due to pathogenic, somatic, activating KRAS variants in humans. Our preclinical studies suggest that MEK inhibition should be studied in future clinical trials for CCLA due to activating KRAS pathogenic variants.

Single Cell Transcriptome Analysis of Peripheral Blood Mononuclear Cells in Freshly Isolated versus Stored Blood Samples.

BACKGROUND: Peripheral blood mononuclear cells (PBMCs) are widely used as a model in the study of different human diseases. There is often a time delay from blood collection to PBMC isolation during the sampling process, which can result in an experimental bias, particularly when performing single cell RNA-seq (scRNAseq) studies. METHODS: This study examined the impact of different time periods from blood draw to PBMC isolation on the subsequent transcriptome profiling of different cell types in PBMCs by scRNAseq using the 10X Chromium Single Cell Gene Expression assay. RESULTS: Examining the five major cell types constituting the PBMC cell population, i.e., CD4+ T cells, CD8+ T cells, NK cells, monocytes, and B cells, both common changes and cell-type-specific changes were observed in the single cell transcriptome profiling over time. In particular, the upregulation of genes regulated by NF-kB in response to TNF was observed in all five cell types. Significant changes in key genes involved in AP-1 signaling were also observed. RBC contamination was a major issue in stored blood, whereas RBC adherence had no direct impact on the cell transcriptome. CONCLUSIONS: Significant transcriptome changes were observed across different PBMC cell types as a factor of time from blood draw to PBMC isolation and as a consequence of blood storage. This should be kept in mind when interpreting experimental results.

Interstitial deletion 4p15.32p16.1 and complex chromoplexy in a female proband with severe neurodevelopmental delay, growth failure and dysmorphism.

Complex chromosomal rearrangements involve the restructuring of genetic material within a single chromosome or across multiple chromosomes. These events can cause serious human disease by disrupting coding DNA and gene regulatory elements via deletions, duplications, and structural rearrangements. Here we describe a 5-year-old female with severe developmental delay, dysmorphic features, multi-suture craniosynostosis, and growth failure found to have a complex series of balanced intra- and inter-chromosomal rearrangements involving chromosomes 4, 11, 13, and X. Initial clinical studies were performed by karyotype, chromosomal microarray, and FISH with research-based short-read genome sequencing coupled with sanger sequencing to precisely map her breakpoints to the base pair resolution to understand the molecular basis of her phenotype. Genome analysis revealed two pathogenic deletions at 4p16.1-p15.32 and 4q31.1, accounting for her developmental delay and dysmorphism. We identified over 60 breakpoints, many with blunt ends and limited homology, supporting a role for non-homologous end joining in restructuring and resolution of the seminal chromoplexy event. We propose that the complexity of our patient's genomic rearrangements with a high number of breakpoints causes dysregulation of gene expression by three-dimensional chromatin interactions or topologically associating domains leading to growth failure and craniosynostosis. Our work supports an important role for genome sequencing in understanding the molecular basis of complex chromosomal rearrangements in human disease.

Identification of Novel Loci Shared by Juvenile Idiopathic Arthritis Subtypes Through Integrative Genetic Analysis.

OBJECTIVE: Juvenile idiopathic arthritis (JIA) is the most common chronic immune-mediated joint disease among children and encompasses a heterogeneous group of immune-mediated joint disorders classified into 7 subtypes according to clinical presentation. However, phenotype overlap and biologic evidence suggest a shared mechanistic basis between subtypes. This study was undertaken to systematically investigate shared genetic underpinnings of JIA subtypes. METHODS: We performed a heterogeneity-sensitive genome-wide association study encompassing a total of 1,245 JIA cases (classified into 7 subtypes) and 9,250 controls, followed by fine-mapping of candidate causal variants at each genome-wide significant locus, functional annotation, and pathway and network analysis. We further identified candidate drug targets and drug repurposing opportunities by in silico analyses. RESULTS: In addition to the major histocompatibility complex locus, we identified 15 genome-wide significant loci shared between at least 2 JIA subtypes, including 10 novel loci. Functional annotation indicated that candidate genes at these loci were expressed in diverse immune cell types. CONCLUSION: This study identified novel genetic loci shared by JIA subtypes. Our findings identified candidate mechanisms underlying JIA subtypes and candidate targets with drug repurposing opportunities for JIA treatment.

Identification of Mitochondrial DNA Variants Associated With Risk of Neuroblastoma.

Neuroblastoma is a childhood cancer that originates in the developing sympathetic nervous system. We previously reported a crucial role of mitochondrial DNA haplogroups in the pathology of neuroblastoma. To pinpoint mitochondrial DNA variants associated with neuroblastoma risk, we applied a mitochondrial genome imputation pipeline to the single nucleotide polymorphisms array data of 2 pediatric cohorts containing a total of 2404 neuroblastoma patients and 9310 cancer-free controls. All statistical tests were 2-sided. The single nucleotide variant, rs2853493, was statistically significantly associated with neuroblastoma risk in the discovery cohort (odds ratio = 0.62, 95% confidence interval = 0.53 to 0.72, P < .001) and further confirmed in the replication cohort (odds ratio = 0.75, 95% confidence interval = 0.62 to 0.90, P = .002). Further, expression quantitative trait loci analysis indicated genotypes of rs2853493 were associated with expression levels of MT-CYB gene expression in neuroblastoma cells, suggesting rs2853493 may confer risk to neuroblastoma via regulating the expression level of its nearby genes.

A novel MBTPS2 variant associated with BRESHECK syndrome impairs sterol-regulated transcription and the endoplasmic reticulum stress response.

Ichthyosis follicularis, atrichia, and photophobia syndrome (IFAP syndrome) is a rare, X-linked disorder caused by pathogenic variants in membrane-bound transcription factor protease, site 2 (MBTPS2). Pathogenic MBTPS2 variants also cause BRESHECK syndrome, characterized by the IFAP triad plus intellectual disability and multiple congenital anomalies. Here we present a patient with ichthyosis, sparse hair, pulmonic stenosis, kidney dysplasia, hypospadias, growth failure, thrombocytopenia, anemia, bone marrow fibrosis, and chronic diarrhea found by research-based exome sequencing to harbor a novel, maternally inherited MBTPS2 missense variant (c.766 G>A; (p.Val256Leu)). In vitro modeling supports variant pathogenicity, with impaired cell growth in cholesterol-depleted media, attenuated activation of the sterol regulatory element-binding protein pathway, and failure to activate the endoplasmic reticulum stress response pathway. Our case expands both the genetic and phenotypic spectrum of BRESHECK syndrome to include a novel MBTPS2 variant and cytopenias, bone marrow fibrosis, and chronic diarrhea.

Further supporting SMARCC2-related neurodevelopmental disorder through exome analysis and reanalysis in two patients.

BAFopathies are a heterogenous group of neurodevelopmental disorders caused by mutations in genes encoding subunits of the BAF complex, and they exhibit a broad clinical phenotypic spectrum. Pathogenic heterozygous variants in SMARCC2 have been implicated in Coffin-Siris syndrome 8 (MIM 618362) with variable neurodevelopmental presentations. We report here two relatively severely affected patients with two different SMARCC2 variants: one has de novo pathogenic variant, c.1824_1826del, p.(Leu609del), in a suspected hotspot region through reanalysis of previously negative clinical exome data, and the other has a likely pathogenic loss-of-function variant, c.1094_1097delAGAA, p.(Lys365Thrfs*12) through exome analysis in an adopted subject. Regardless of variant type, both patients have severe developmental delays, severe speech delay, short stature, hypotonia, seizures, and craniofacial dysmorphisms, blurring previously speculated genotype-phenotype correlation on missense and loss-of-function variants. This report extends our understanding of the genotypic and phenotypic spectrums of the SMARCC2-related neurodevelopmental disorder.

A new syndrome of moyamoya disease, kidney dysplasia, aminotransferase elevation, and skin disease associated with de novo variants in RNF213.

Ring-finger protein 213 (RNF213) encodes a protein of unknown function believed to play a role in cellular metabolism and angiogenesis. Gene variants are associated with susceptibility to moyamoya disease. Here, we describe two children with moyamoya disease who also demonstrated kidney disease, elevated aminotransferases, and recurrent skin lesions found by exome sequencing to have de novo missense variants in RNF213. These cases highlight the ability of RNF213 to cause Mendelian moyamoya disease in addition to acting as a genetic susceptibility locus. The cases also suggest a new, multi-organ RNF213-spectrum disease characterized by liver, skin, and kidney pathology in addition to severe moyamoya disease caused by heterozygous, de novo C-terminal RNF213 missense variants.

Mononuclear calcium complex as effective catalyst for alkenes hydrogenation.

Hydrogenolysis of the scorpionate-supported calcium benzyl complex [(TpAd,iPr)Ca(p-CH2C6H4-Me)(THP)] (TpAd,iPr = hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate, THP = tetrahydropyran) (2-THP) afforded the mononuclear calcium hydrido complex [(TpAd,iPr)Ca(H)(THP)] (3). Under mild conditions (40 °C, 10 atm H2, 5 mol% cat.), complex 3 effectively catalyzed the hydrogenation of a variety of alkenes, including activated alkenes, semi-activated alkenes, non-activated terminal and internal alkenes. Mononuclear calcium unsubstituted alkyl complex [(TpAd,iPr)Ca{(CH2)4Ph}(THP)] (6), proposed as the catalytic hydrogenation intermediate, was isolated and structurally characterized.

Mitochondrial DNA Haplogroups and Susceptibility to Neuroblastoma.

BACKGROUND: Neuroblastoma is a childhood malignancy that arises from the developing sympathetic nervous system. Although mitochondrial dysfunctions have been implicated in the pathophysiology of neuroblastoma, the role of mitochondrial DNA (mtDNA) has not been extensively investigated. METHODS: A total of 2404 Caucasian children diagnosed with neuroblastoma and 9310 ancestry-matched controls were recruited at the Children's Hospital of Philadelphia. The mtDNA haplogroups were identified from SNP array data of two independent cohorts. We conducted a case-control study to explore potential associations of mtDNA haplogroups with the susceptibility of neuroblastoma. The genetic effect of neuroblastoma was measured by odds ratios (ORs) of mitochondrial haplogroups. All tests were two-sided. RESULTS: Haplogroup K was statistically significantly associated with reduced risk of neuroblastoma in the discovery cohort consisting of 1474 cases and 5699 controls (OR = 0.72, 95% confidence interval [CI] = 0.57 to 0.90; P = 4.8 × 10-3). The association was replicated in an independent cohort (OR = 0.69, 95% CI = 0.53 to 0.92; P = .01) of 930 cases and 3611 controls. Pooled analysis was performed by combining the two data sets. The association remained highly statistically significant after correction for multiple testing (OR = 0.71, 95% CI = 0.59 to 0.84, P = 1.96 × 10-4, Pcorrected = .002). Further analysis focusing on neuroblastoma subtypes indicated haplogroup K was more associated with high-risk neuroblastoma (OR = 0.57, 95% CI = 0.43 to 0.76; P = 1.46 × 10-4) than low-risk and intermediate-risk neuroblastoma. CONCLUSIONS: Haplogroup K is an independent genetic factor associated with reduced risk of developing neuroblastoma in European descents. These findings provide new insights into the genetic basis of neuroblastoma, implicating mitochondrial DNA encoded proteins in the etiology of neuroblastoma.

Rare copy number variants in over 100,000 European ancestry subjects reveal multiple disease associations.

Copy number variants (CNVs) are suggested to have a widespread impact on the human genome and phenotypes. To understand the role of CNVs across human diseases, we examine the CNV genomic landscape of 100,028 unrelated individuals of European ancestry, using SNP and CGH array datasets. We observe an average CNV burden of ~650 kb, identifying a total of 11,314 deletion, 5625 duplication, and 2746 homozygous deletion CNV regions (CNVRs). In all, 13.7% are unreported, 58.6% overlap with at least one gene, and 32.8% interrupt coding exons. These CNVRs are significantly more likely to overlap OMIM genes (2.94-fold), GWAS loci (1.52-fold), and non-coding RNAs (1.44-fold), compared with random distribution (P < 1 × 10-3). We uncover CNV associations with four major disease categories, including autoimmune, cardio-metabolic, oncologic, and neurological/psychiatric diseases, and identify several drug-repurposing opportunities. Our results demonstrate robust frequency definition for large-scale rare variant association studies, identify CNVs associated with major disease categories, and illustrate the pleiotropic impact of CNVs in human disease.

Microduplications at the 15q11.2 BP1-BP2 locus are enriched in patients with anorexia nervosa.

Microduplication at 15q11.2 have been reported in genetic association studies of schizophrenia and autism. Given the potential overlap in psychiatric symptoms of schizophrenia and autism with anorexia nervosa (AN), we were inspired to test the association of this CNV locus with the genetic susceptibility of AN using ParseCNV, a highly quality controlled CNV pipeline developed by our group. The CNV analysis was performed in 1017 AN cases and 7250 controls using the Illumina HumanHap610 SNP arrays data. We uncovered association of the 15q11.2 microduplication with AN with P = 0.00023, while no genetic association between the microdeletion of this region and AN was identified. Among four genes in this region that are not imprinted, NIPA1 has the highest expression in brain and encodes a magnesium transporter protein on early endosomes and the cell surface in neurons. Targeting at Mg2+ uptake mediated by NIPA1 presents an interesting research topic for the explorations of novel therapy for AN and other neurobehavioral diseases, such as schizophrenia and autism.

Common variants at 5q33.1 predispose to migraine in African-American children.

BACKGROUND: Genome-wide association studies (GWASs) have identified multiple susceptibility loci for migraine in European adults. However, no large-scale genetic studies have been performed in children or African Americans with migraine. METHODS: We conducted a GWAS of 380 African-American children and 2129 ancestry-matched controls to identify variants associated with migraine. We then attempted to replicate our primary analysis in an independent cohort of 233 African-American patients and 4038 non-migraine control subjects. RESULTS: The results of this study indicate that common variants at 5q33.1 associated with migraine risk in African-American children (rs72793414, p=1.94×10-9). The association was validated in an independent study (p=3.87×10-3) for an overall meta-analysis p value of 3.81×10-10. eQTL (Expression quantitative trait loci) analysis of the Genotype-Tissue Expression data also shows the genotypes of rs72793414 were strongly correlated with the mRNA expression levels of NMUR2 at 5q33.1. NMUR2 encodes a G protein-coupled receptor of neuromedin-U (NMU). NMU, a highly conserved neuropeptide, participates in diverse physiological processes of the central nervous system. CONCLUSIONS: This study provides new insights into the genetic basis of childhood migraine and allow for precision therapeutic development strategies targeting migraine patients of African-American ancestry.

Pathogenic variant in EPHB4 results in central conducting lymphatic anomaly.

Central conducting lymphatic anomaly (CCLA) is one of the complex lymphatic anomalies characterized by dilated lymphatic channels, lymphatic channel dysmotility and distal obstruction affecting lymphatic drainage. We performed whole exome sequencing (WES) of DNA from a four-generation pedigree and examined the consequences of the variant by transfection of mammalian cells and morpholino and rescue studies in zebrafish. WES revealed a heterozygous mutation in EPHB4 (RefSeq NM_004444.4; c.2334 + 1G>C) and RNA-Seq demonstrated that the EPHB4 mutation destroys the normal donor site, which leads to the use of a cryptic splice donor that results in retention of the intervening 12-bp intron sequence. Transient co-expression of the wild-type and mutant EPHB4 proteins showed reduced phosphorylation of tyrosine, consistent with a loss-of-function effect. Zebrafish ephb4a morpholino resulted in vessel misbranching and deformities in the lymphatic vessel development, indicative of possible differentiation defects in lymphatic vessels, mimicking the lymphatic presentations of the patients. Immunoblot analysis using zebrafish lysates demonstrated over-activation of mTORC1 as a consequence of reduced EPHB4 signaling. Strikingly, drugs that inhibit mTOR signaling or RAS-MAPK signaling effectively rescued the misbranching phenotype in a comparable manner. Moreover, knock-in of EPHB4 mutation in HEK293T cells also induced mTORC1 activity. Our data demonstrate the pathogenicity of the identified EPHB4 mutation as a novel cause of CCLA and suggesting that ERK inhibitors may have therapeutic benefits in such patients with complex lymphatic anomalies.

Heterozygous Deletion Impacting SMARCAD1 in the Original Kindred with Absent Dermatoglyphs and Associated Features (Baird, 1964).

In 1964, Baird described a family with adermatoglyphia, facial milia, and skin fragility. Using whole exome sequencing, genotyping, and Sanger sequencing, we identified a 116-kb heterozygous deletion involving exons 1-9 of SMARCAD1 in descendants of this kindred. This contrasts with point mutations within exon 9 in all other reported families.

A Molecular Barium Hydrido Complex Stabilized by a Super-Bulky Hydrotris(pyrazolyl)borate Ligand.

Hydrogenolysis of the scorpionate-supported barium alkyl complex (TpAd,iPr )Ba[CH(SiMe3 )2 ](THF) (TpAd,iPr =hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate) afforded the dinuclear barium hydrido complex [(TpAd,iPr )Ba(µ-H)]2 (2), which was characterized by NMR spectroscopy and single-crystal X-ray analysis. Exposure of 2 with 1 atm of CO resulted in a reductive coupling process to form the cis-ethendiolate dianion (3). Reaction of 2 with one equivalent of PhC≡C-C≡CPh gave barium 1,4-diphenyl-2-butyne-1,4-diyl complex {[(TpAd,iPr )Ba]2 (PhCH-C≡C-CHPh) (4).

Common variants in MMP20 at 11q22.2 predispose to 11q deletion and neuroblastoma risk.

MYCN amplification and 11q deletion are two inversely correlated prognostic factors of poor outcome in neuroblastoma. Here we identify common variants at 11q22.2 within MMP20 that associate with neuroblastoma cases harboring 11q deletion (rs10895322), using GWAS in 113 European-American cases and 5109 ancestry-matched controls. The association is replicated in 44 independent cases and 1902 controls. Our study yields novel insights into the genetic underpinnings of neuroblastoma, demonstrating that the inherited common variants reported contribute to the origin of intra-tumor genetic heterogeneity in neuroblastoma.Chromosomal abnormalities such as 11q deletion are associated with poor prognosis in neuroblastoma. Here, the authors perform a genome-wide association study and identify an association between a variant within a Matrix metalloproteinase (MMP) gene member, MMP20, and 11q-deletion subtype neuroblastoma.

Erratum: A genome-wide association study of anorexia nervosa suggests a risk locus implicated in dysregulated leptin signaling.

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