EIF3F-related neurodevelopmental disorder: refining the phenotypic and expanding the molecular spectrum

Abstract Background An identical homozygous missense variant in EIF3F, identified through a large-scale genome-wide sequencing approach, was reported as causative in nine individuals with a neurodevelopmental disorder, characterized by variable intellectual disability, epilepsy, behavioral problems and sensorineural hearing-loss. To refine the phenotypic and molecular spectrum of EIF3F-related neurodevelopmental disorder, we examined independent patients. Results 21 patients were homozygous and one compound heterozygous for c.694T>G/p.(Phe232Val) in EIF3F. Haplotype analyses in 15 families suggested that c.694T>G/p.(Phe232Val) was a founder variant. All affected individuals had developmental delays including delayed speech development. About half of the affected individuals had behavioral problems, altered muscular tone, hearing loss, and short stature. Moreover, this study suggests that microcephaly, reduced sensitivity to pain, cleft lip/palate, gastrointestinal symptoms and ophthalmological symptoms are part of the phenotypic spectrum. Minor dysmorphic features were observed, although neither the individuals’ facial nor general appearance were obviously distinctive. Symptoms in the compound heterozygous individual with an additional truncating variant were at the severe end of the spectrum in regard to motor milestones, speech delay, organic problems and pre- and postnatal growth of body and head, suggesting some genotype–phenotype correlation. Conclusions Our study refines the phenotypic and expands the molecular spectrum of EIF3F-related syndromic neurodevelopmental disorder.

Download Full-text

Molecular basis of ciliary defects caused by compound heterozygous IFT144/WDR19 mutations found in cranioectodermal dysplasia

Human Molecular Genetics ◽

10.1093/hmg/ddab034 ◽

2021 ◽

Author(s):

Yamato Ishida ◽

Takuya Kobayashi ◽

Shuhei Chiba ◽

Yohei Katoh ◽

Kazuhisa Nakayama

Keyword(s):

Protein Trafficking ◽

Primary Cilia ◽

Intraflagellar Transport ◽

Missense Variant ◽

Cellular Level ◽

Compound Heterozygous ◽

Hypomorphic Allele ◽

Genes Encoding ◽

Specific Proteins ◽

Compound Heterozygous Mutations

Abstract Primary cilia contain specific proteins to achieve their functions as cellular antennae. Ciliary protein trafficking is mediated by the intraflagellar transport (IFT) machinery containing the IFT-A and IFT-B complexes. Mutations in genes encoding the IFT-A subunits (IFT43, IFT121/WDR35, IFT122, IFT139/TTC21B, IFT140, and IFT144/WDR19) often result in skeletal ciliopathies, including cranioectodermal dysplasia (CED). We here characterized the molecular and cellular defects of CED caused by compound heterozygous mutations in IFT144 [the missense variant IFT144(L710S) and the nonsense variant IFT144(R1103*)]. These two variants were distinct with regard to their interactions with other IFT-A subunits and with the IFT-B complex. When exogenously expressed in IFT144-knockout (KO) cells, IFT144(L710S) as well as IFT144(WT) rescued both moderately compromised ciliogenesis and the abnormal localization of ciliary proteins. As the homozygous IFT144(L710S) mutation was found to cause autosomal recessive retinitis pigmentosa, IFT144(L710S) is likely to be hypomorphic at the cellular level. In striking contrast, the exogenous expression of IFT144(R1103*) in IFT144-KO cells exacerbated the ciliogenesis defects. The expression of IFT144(R1103*) together with IFT144(WT) restored the abnormal phenotypes of IFT144-KO cells. However, the coexpression of IFT144(R1103*) with the hypomorphic IFT144(L710S) variant in IFT144-KO cells, which mimics the genotype of compound heterozygous CED patients, resulted in severe ciliogenesis defects. Taken together, these observations demonstrate that compound heterozygous mutations in IFT144 cause severe ciliary defects via a complicated mechanism, where one allele can cause severe ciliary defects when combined with a hypomorphic allele.

Download Full-text

Reprogramming of human peripheral blood mononuclear cell (PBMC) from a patient suffering from hearing loss into iPSC line (SDQLCHi035-A) maintaining compound heterozygous variations in GJB2 gene

Stem Cell Research ◽

10.1016/j.scr.2021.102188 ◽

2021 ◽

Vol 51 ◽

pp. 102188

Author(s):

Xiaomeng Yang ◽

Ning Liu ◽

Hong Mu ◽

Yuqiang Lv ◽

Haiyan Zhang ◽

...

Keyword(s):

Hearing Loss ◽

Peripheral Blood Mononuclear Cell ◽

Mononuclear Cell ◽

Peripheral Blood ◽

Human Peripheral Blood ◽

Gjb2 Gene ◽

Compound Heterozygous ◽

Ipsc Line ◽

Peripheral Blood Mononuclear

Download Full-text

Emerging Role of ODC1 in Neurodevelopmental Disorders and Brain Development

Genes ◽

10.3390/genes12040470 ◽

2021 ◽

Vol 12 (4) ◽

pp. 470

Author(s):

Jeremy W. Prokop ◽

Caleb P. Bupp ◽

Austin Frisch ◽

Stephanie M. Bilinovich ◽

Daniel B. Campbell ◽

...

Keyword(s):

Brain Development ◽

Neural Progenitor Cells ◽

Neurodevelopmental Disorder ◽

Fetal Brain ◽

Missense Variant ◽

Neural Progenitor ◽

Loss Of Function ◽

Gain Of Function ◽

Systematic Analysis ◽

Function Expression

Ornithine decarboxylase 1 (ODC1 gene) has been linked through gain-of-function variants to a rare disease featuring developmental delay, alopecia, macrocephaly, and structural brain anomalies. ODC1 has been linked to additional diseases like cancer, with growing evidence for neurological contributions to schizophrenia, mood disorders, anxiety, epilepsy, learning, and suicidal behavior. The evidence of ODC1 connection to neural disorders highlights the need for a systematic analysis of ODC1 genotype-to-phenotype associations. An analysis of variants from ClinVar, Geno2MP, TOPMed, gnomAD, and COSMIC revealed an intellectual disability and seizure connected loss-of-function variant, ODC G84R (rs138359527, NC_000002.12:g.10444500C > T). The missense variant is found in ~1% of South Asian individuals and results in 2.5-fold decrease in enzyme function. Expression quantitative trait loci (eQTLs) reveal multiple functionally annotated, non-coding variants regulating ODC1 that associate with psychiatric/neurological phenotypes. Further dissection of RNA-Seq during fetal brain development and within cerebral organoids showed an association of ODC1 expression with cell proliferation of neural progenitor cells, suggesting gain-of-function variants with neural over-proliferation and loss-of-function variants with neural depletion. The linkage from the expression data of ODC1 in early neural progenitor proliferation to phenotypes of neurodevelopmental delay and to the connection of polyamine metabolites in brain function establish ODC1 as a bona fide neurodevelopmental disorder gene.

Download Full-text

UTMOST, a single and cross-tissue TWAS (Transcriptome Wide Association Study), reveals new ASD (Autism Spectrum Disorder) associated genes

Translational Psychiatry ◽

10.1038/s41398-021-01378-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Cristina Rodriguez-Fontenla ◽

Angel Carracedo

Keyword(s):

In Silico ◽

Association Studies ◽

Meta Analysis ◽

Neurodevelopmental Disorder ◽

Gastrointestinal Symptoms ◽

Tissue Expression ◽

Autism Spectrum ◽

Biological Characterization ◽

Large Size ◽

Body Tissues

AbstractAutism spectrum disorders (ASD) is a complex neurodevelopmental disorder that may significantly impact on the affected individual’s life. Common variation (SNPs) could explain about 50% of ASD heritability. Despite this fact and the large size of the last GWAS meta-analysis, it is believed that hundreds of risk genes in ASD have yet to be discovered. New tools, such as TWAS (Transcriptome Wide Association Studies) which integrate tissue expression and genetic data, are a great approach to identify new ASD susceptibility genes. The main goal of this study is to use UTMOST with the publicly available summary statistics from the largest ASD GWAS meta-analysis as genetic input. In addition, an in silico biological characterization for the novel associated loci was performed. Our results have shown the association of 4 genes at the brain level (CIPC, PINX1, NKX2-2, and PTPRE) and have highlighted the association of NKX2-2, MANBA, ERI1, and MITF at the gastrointestinal level. The gastrointestinal associations are quite relevant given the well-established but unexplored relationship between ASD and gastrointestinal symptoms. Cross-tissue analysis has shown the association of NKX2-2 and BLK. UTMOST-associated genes together with their in silico biological characterization seems to point to different biological mechanisms underlying ASD etiology. Thus, it would not be restricted to brain tissue and it will involve the participation of other body tissues such as the gastrointestinal.

Download Full-text

A biallelic variant in CLRN2 causes non-syndromic hearing loss in humans

Human Genetics ◽

10.1007/s00439-020-02254-z ◽

2021 ◽

Author(s):

Barbara Vona ◽

Neda Mazaheri ◽

Sheng-Jia Lin ◽

Lucy A. Dunbar ◽

Reza Maroofian ◽

...

Keyword(s):

Hearing Loss ◽

Amino Acid ◽

Rna Splicing ◽

Stop Codon ◽

Missense Variant ◽

Homozygosity Mapping ◽

Deafness Gene ◽

Expression Studies ◽

Hearing Function

AbstractDeafness, the most frequent sensory deficit in humans, is extremely heterogeneous with hundreds of genes involved. Clinical and genetic analyses of an extended consanguineous family with pre-lingual, moderate-to-profound autosomal recessive sensorineural hearing loss, allowed us to identify CLRN2, encoding a tetraspan protein, as a new deafness gene. Homozygosity mapping followed by exome sequencing identified a 14.96 Mb locus on chromosome 4p15.32p15.1 containing a likely pathogenic missense variant in CLRN2 (c.494C > A, NM_001079827.2) segregating with the disease. Using in vitro RNA splicing analysis, we show that the CLRN2 c.494C > A variant leads to two events: (1) the substitution of a highly conserved threonine (uncharged amino acid) to lysine (charged amino acid) at position 165, p.(Thr165Lys), and (2) aberrant splicing, with the retention of intron 2 resulting in a stop codon after 26 additional amino acids, p.(Gly146Lysfs*26). Expression studies and phenotyping of newly produced zebrafish and mouse models deficient for clarin 2 further confirm that clarin 2, expressed in the inner ear hair cells, is essential for normal organization and maintenance of the auditory hair bundles, and for hearing function. Together, our findings identify CLRN2 as a new deafness gene, which will impact future diagnosis and treatment for deaf patients.

Download Full-text

UNC13B variants associated with partial epilepsy with favourable outcome

Brain ◽

10.1093/brain/awab164 ◽

2021 ◽

Author(s):

Jie Wang ◽

Jing-Da Qiao ◽

Xiao-Rong Liu ◽

De-Tian Liu ◽

Yan-Hui Chen ◽

...

Keyword(s):

Neuronal Excitability ◽

Brain Mri ◽

Missense Variant ◽

Febrile Seizures ◽

Favourable Outcome ◽

Partial Epilepsy ◽

Favorable Outcome ◽

Compound Heterozygous ◽

Developmental Abnormalities ◽

Seizure Rate

Abstract The unc-13 homolog B (UNC13B) gene encodes a presynaptic protein, mammalian uncoordinated 13–2 (Munc13-2), that is highly expressed in the brain—predominantly in the cerebral cortex—and plays an essential role in synaptic vesicle priming and fusion, potentially affecting neuronal excitability. However, the functional significance of UNC13B mutation in human disease is not known. In this study we screened for novel genetic variants in a cohort of 446 unrelated cases (families) with partial epilepsy without acquired causes by trio-based whole-exome sequencing. UNC13B variants were identified in 12 individuals affected by partial epilepsy and/or febrile seizures from eight unrelated families. The eight probands all had focal seizures and focal discharges in EEG recordings, including two patients who experienced frequent daily seizures and one who showed abnormalities in the hippocampus by brain MRI; however, all of the patients showed favorable outcome without intellectual or developmental abnormalities. The identified UNC13B variants included one nonsense variant, two variants at or around a splice site, one compound heterozygous missense variant, and four missense variants that cosegregated in the families. The frequency of UNC13B variants identified in the present study was significantly higher than that in a control cohort of Han Chinese and controls of the East Asian and all populations in the Genome Aggregation Database. Computational modeling, including hydrogen bond and docking analyses, suggested that the variants lead to functional impairment. In Drosophila, seizure rate and duration were increased by Unc13b knockdown compared to wild-type flies, but these effects were less pronounced than in sodium voltage-gated channel alpha subunit 1 (Scn1a) knockdown Drosophila. Electrophysiologic recordings showed that excitatory neurons in Unc13b-deficient flies exhibited increased excitability. These results suggest that UNC13B is potentially associated with epilepsy. The frequent daily seizures and hippocampal abnormalities but ultimately favorable outcome under antiepileptic therapy in our patients indicate that partial epilepsy caused by UNC13B variant is a clinically manageable condition.

Download Full-text

Contribution of Multiple Inherited Variants to Autism Spectrum Disorder (ASD) in a Family with 3 Affected Siblings

Genes ◽

10.3390/genes12071053 ◽

2021 ◽

Vol 12 (7) ◽

pp. 1053

Author(s):

Jasleen Dhaliwal ◽

Ying Qiao ◽

Kristina Calli ◽

Sally Martell ◽

Simone Race ◽

...

Keyword(s):

Autism Spectrum Disorder ◽

Rare Variants ◽

Neurodevelopmental Disorder ◽

Autism Spectrum ◽

Spectrum Disorder ◽

Compound Heterozygous ◽

Variable Effect ◽

Gabaergic Neurotransmission ◽

High Heritability ◽

Compound Heterozygous Variants

Autism Spectrum Disorder (ASD) is the most common neurodevelopmental disorder in children and shows high heritability. However, how inherited variants contribute to ASD in multiplex families remains unclear. Using whole-genome sequencing (WGS) in a family with three affected children, we identified multiple inherited DNA variants in ASD-associated genes and pathways (RELN, SHANK2, DLG1, SCN10A, KMT2C and ASH1L). All are shared among the three children, except ASH1L, which is only present in the most severely affected child. The compound heterozygous variants in RELN, and the maternally inherited variant in SHANK2, are considered to be major risk factors for ASD in this family. Both genes are involved in neuron activities, including synaptic functions and the GABAergic neurotransmission system, which are highly associated with ASD pathogenesis. DLG1 is also involved in synapse functions, and KMT2C and ASH1L are involved in chromatin organization. Our data suggest that multiple inherited rare variants, each with a subthreshold and/or variable effect, may converge to certain pathways and contribute quantitatively and additively, or alternatively act via a 2nd-hit or multiple-hits to render pathogenicity of ASD in this family. Additionally, this multiple-hits model further supports the quantitative trait hypothesis of a complex genetic, multifactorial etiology for the development of ASDs.

Download Full-text