Expanding the Phenotype of TLK2-Related Neurodevelopmental Disorder: Longitudinal Presentation in Two Young Adult Females.

ZNF148 gene is a Krüppel-type transcription factor that has transcriptional regulatory function. Heterozygous variant in ZNF148 gene causes an intellectual disability syndrome characterized by global developmental delay, absence, or hypoplasia of corpus callosum, wide intracerebral ventricles, and dysmorphic facial features, while its associations with ASD and ADHD have not been reported. We report a new patient with intellectual disability, autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). The patient had a novel heterozygous truncating variant c.1818dupC (p.Lys607Glnfs*11) in the ZNF148 gene. This variation produces a ZNF148 truncated protein with a deletion of the C-terminal activation domain and may destabilize the protein by affecting the transcriptional activation function. Brain MRI shows normal brain development. Here, we identify a novel ZNF148 heterozygous truncating variant in a patient with distinct phenotypes of ASD and ADHD, which expands the genotype-phenotype spectrum of ZNF148, and indicates ZNF148 is also a potential target gene for ASD.

ITSN1 plays an important role in brain development. Recent studies in large cohorts of subjects with neurodevelopmental disorders have identified de novo variants in ITSN1 gene thereby suggesting that this gene is involved in the development of such disorders. The aim of this study is to provide further proof of such a link. We performed trio exome sequencing in a patient presenting autism, intellectual disability, and severe behavioral difficulties. Additional affected patients with a neurodevelopmental disorder harboring a heterozygous variant in ITSN1 (NM_003024.2) were collected through a worldwide collaboration. All patients underwent detailed phenotypic and genetic assessment and data was collected and shared by healthcare givers. We identified ten novel patients from eight families with heterozygous truncating or missense variants in ITSN1 gene. In addition, four previously published patients from large meta-analysis studies were included. In total, 7/14 patients presented a de novo variant in ITSN1. All patients showed neurodevelopmental disorders from autism spectrum disorders (90%), intellectual disability (86%), and epilepsy (30%). We demonstrated that truncating variants are in the first half of ITSN1 whereas missense variants are clustered in C-terminal region. We suggest ITSN1 gene is involved in development of an autism spectrum disorder with variable additional neurodevelopmental deficiency, thus confirming the hypothesis that ITSN1 is important for brain development.

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Purpose Variants in RCBTB1 have been reported in autosomal recessive inherited retinal dystrophies and autosomal dominant familial exudative vitreoretinopathy (FEVR). This study aims to verify the correlation between RCBTB1 variations and phenotypes. Methods Variants in RCBTB1 were selected from 6303 unrelated families with different forms of eye conditions based on whole exome sequencing and targeted exome sequencing. Potential pathogenic truncation variants were filtered by multistep bioinformatics analysis and identified by Sanger sequencing. Segregation and enrichment analysis were used to evaluate the association of truncation variants in RCBTB1 with phenotypes. Results Biallelic damaging variants in RCBTB1 were found in one family while heterozygous truncation variants were detected in 28 unrelated families based on our in-house data from 6303 unrelated families. Totally, 11 variants were present in the 29 families, including seven frameshift variants, three splicing variants, and one nonsense variant. The biallelic variants, c.170delG and c.905_906insTT, were identified in an isolated case with retinitis pigmentosa (RP). Heterozygous truncation variants were distributed in different forms of eye conditions (including normal) without significant enrichment in FEVR, suggesting unrelatedness to specific eye diseases. The frequency and location of truncation variants in the 6303 samples are comparable with the East Asian data from gnomAD. Segregation analysis of available family members further demonstrated the nonpathogenic nature of heterozygous truncation variants. Conclusions Contrary to the previous report, heterozygous truncation variants in RCBTB1 are not associated with FEVR based on our data. The extreme rareness of biallelic truncation variants present in a singleton case with RP further suggests that variants in RCBTB1 are responsible for autosomal recessive RP. This result reminds us that variants of a gene with certain diseases should be thoroughly verified before the use of such information in clinical practice.

Heterozygous variants in the Early B cell factor 3 ( EBF3 ) have been reported in individuals presenting with hypotonia, ataxia and delayed development syndrome (HADDS) (MIM#617330). However, individuals with pathogenic variants in EBF3 show phenotypic heterogeneity and very few variants in the C-terminal domain have been described. We report on a heterozygous de-novo variant in the EBF3 gene in an individual with neurodevelopmental delay and behavioural problems. The proband presented with speech delay, learning disability and behavioural problems that suggest an oppositional defiant disorder. He also has hyperactivity, irritability, hetero-aggressiveness, visual hallucinations, insomnia and decreased pain sensitivity. Whole exome sequencing revealed a de-novo heterozygous nonsense variant - c.1408C>T (p.Arg470*) - in the EBF3 gene, classified as pathogenic. The patient herein described, with a truncating variant in the C-terminal domain of EBF3 , supports the clinical variability of this condition and contributes to genotype-phenotype correlation of this rare disorder.

ABSTRACTKBG syndrome (KBGS, OMIM #148050) is a rare genetic disorder caused by heterozygous truncating or missense variants in the ANKRD11 gene or a deletion of 16q24.3 involving ANKRD11. While truncating variants clearly disrupt protein function, the interpretation of missense variants is more challenging, as many remain variants of uncertain significance (VUS). To address this, we evaluated PhenoScore, an open‐source AI‐based phenomics framework integrating facial recognition and medical data analysis, for predicting the pathogenicity of ANKRD11 missense variants and providing supporting evidence for variant interpretation within the ACMG framework, specifically the PP4 criterion. PhenoScore was trained on 79 individuals with truncating variants in ANKRD11 and age‐, sex‐, and ethnicity‐matched controls with other neurodevelopmental disorders, and its performance was compared to AlphaMissense, REVEL, and the evaluation of a clinical geneticist. Six individuals with functionally confirmed pathogenic missense variants were used for testing. PhenoScore achieved high predictive accuracy with an area under the curve (AUC) of 0.95 and a Brier score of 0.089, and pathogenic missense variants in the test set received a mean prediction score of 0.94. PhenoScore significantly outperformed REVEL (p < 0.01), especially in cases supported by functional and clinical evidence, while no significant difference was observed compared to AlphaMissense (p = 0.63); importantly, the two tools showed complementary strengths. These findings suggest that PhenoScore represents a promising tool for clinical variant interpretation, as it quantifies phenotypic concordance with KBGS and provides objective evidence that can strengthen the PP4 criterion within the ACMG framework. Combined with molecular prediction tools like AlphaMissense, PhenoScore may help reduce uncertainty surrounding VUS in ANKRD11 by complementing these scores.

Women and girls with X-linked Alport syndrome have a risk of disease progression that is difficult to predict. This systematic review examined whether proteinuria correlated with genotype and disease severity in this population. PubMed and Scopus were searched for manuscripts from the past 20 years with "COL4A5," "female," "proteinuria" and related terms. Genotypes and clinical data for women and girls with pathogenic heterozygous COL4A5 variants were extracted. Features were then compared between females with proteinuria or without proteinuria; and genotype-phenotype correlations for age at proteinuria and kidney failure determined. Three-hundred sixty-six women and girls with COL4A5 variants and a median age of 29 years (interquartile range 15-46) were identified. Eighty-eight (24%) had large rearrangements or truncating variants, 63 (17%) had splicing variants, and 215 (59%) had missense changes. In all, 236 (64%) had proteinuria, 56 (16%) had kidney failure, 40 (16%) had a hearing loss, and 15 (7%) had ocular abnormalities. Women and girls with proteinuria were more likely to have large rearrangements or truncating variants (P= 0.005), and less likely to have missense changes (P= 0.0002). Those with proteinuria were also more likely to develop kidney failure (P< 0.0001). Women and girls with truncating, large or splicing variants developed proteinuria earlier than those with missense changes (P= 0.001, P< 0.0001 respectively). Those whose proteinuria was detected before the age of 15 progressed to kidney failure sooner (P< 0.0001). Proteinuria correlates with a more severe genotype in women and girls with X-linked Alport syndrome and is an indicator of disease severity and likely progression.

Cardiac phenotype characterization at magnetic resonance imaging in alpha-protein kinase 3–associated hypertrophic cardiomyopathy

PurposeHeterozygous truncating variants of TOPORS have been reported to cause autosomal dominant retinitis pigmentosa (adRP). The purpose of this study was to investigate whether all heterozygous truncating variants, including copy number variants (CNVs), are pathogenic.MethodsTOPORS truncating variants were collected and reviewed through an in-house dataset and existing databases. Individuals with truncating variants underwent ophthalmological evaluation.ResultsSix truncating variants were detected in seven families. Three N-terminus truncating variants were detected in three families without RP, and the other three were identified in four unrelated families with typical RP. Based on the in-house dataset and published literature, 17 truncating variants were identified in 47 families with RP. All RP-associated truncating alleles, except one, were distributed in the last exon of TOPORS and clustered in amino acid residues 807 to 867 (46/47, 97.9%). Conversely, in the gnomAD database, only one truncating allele (1/27, 3.7%) was in this region, and the others were outside (26/27, 96.3%), suggesting that the pathogenic truncating variants were significantly clustered in residues 807 to 867 (χ2 = 65.6, P = 1.1 × 10–17). Additionally, three CNVs involving the N-terminus of TOPORS were recorded in control populations but were absent in affected patients.ConclusionsThis study suggests that all pathogenic truncating variants of TOPORS were clustered in residues 807 to 867, whereas the truncating variants outside this region and the CNVs involving the N-terminus were not associated with RP. A dominant-negative effect, rather than haploinsufficiency, is speculated to be the underlying pathogenesis. These findings provide valuable information for interpreting variation in TOPORS and other genes in similar situations, especially for CNVs.

Heterozygous variants in Transient receptor potential melastatin type 7 (TRPM7), encoding an essential and ubiquitously expressed cation channel, may cause hypomagnesemia, but current evidence is insufficient to draw definite conclusions and it is unclear whether any other phenotypes can occur. Individuals with unexplained hypomagnesemia underwent whole-exome sequencing which identified TRPM7 variants. Pathogenicity of the identified variants was assessed by combining phenotypic, functional and in silico analyses. We report three new heterozygous missense variants in TRPM7 (p.Met1000Thr, p.Gly1046Arg, p.Leu1081Arg) in individuals with hypomagnesemia. Strikingly, autism spectrum disorder and developmental delay, mainly affecting speech and motor skills, was observed in all three individuals, while two out of three also presented with seizures. The three variants are predicted to be severely damaging by in silico prediction tools and structural modeling. Furthermore, these variants result in a clear loss-of-function of TRPM7-mediated magnesium uptake in vitro, while not affecting TRPM7 expression or insertion into the plasma membrane. This study provides additional evidence for the association between heterozygous TRPM7 variants and hypomagnesemia and adds developmental delay to the phenotypic spectrum of TRPM7-related disorders. Considering that the TRPM7 gene is relatively tolerant to loss-of-function variants, future research should aim to unravel by what mechanisms specific heterozygous TRPM7 variants can cause disease.

SA105 - IDENTIFICATION OF PHENOTYPIC PREDICTORS OF PATHOGENIC COPY NUMBER VARIANTS IN A PSYCHOSIS POPULATION

Novel truncating and missense variants extending the spectrum of EMC1-related phenotypes, causing autism spectrum disorder, severe global development delay and visual impairment.

Sequencing projects have identified large numbers of rare stop-gain and frameshift variants in the human genome. As most of these are observed in the heterozygous state, they test a gene’s tolerance to haploinsufficiency and dominant loss of function. We analyzed the distribution of truncating variants across 16,260 autosomal protein coding genes in 11,546 individuals. We observed 39,893 truncating variants affecting 12,062 genes, which significantly differed from an expectation of 12,916 genes under a model of neutral de novo mutation (p<10−4). Extrapolating this to increasing numbers of sequenced individuals, we estimate that 10.8% of human genes do not tolerate heterozygous truncating variants. An additional 10 to 15% of truncated genes may be rescued by incomplete penetrance or compensatory mutations, or because the truncating variants are of limited functional impact. The study of protein truncating variants delineates the essential genome and, more generally, identifies rare heterozygous variants as an unexplored source of diversity of phenotypic traits and diseases.

Heterozygous nonsense variants in the ferritin heavy-chain gene FTH1 cause a neuroferritinopathy

IntroductionIdiopathic focal epilepsy (IFE) is a group of self-limited epilepsies. The etiology for the majority of the patients with IFE remains elusive. We thus screened disease-causing variants in the patients with IFE.MethodsWhole-exome sequencing was performed in a cohort of 323 patients with IFE. Protein modeling was performed to predict the effects of missense variants. The genotype–phenotype correlation of the newly defined causative gene was analyzed.ResultsFour novel heterozygous variants in PGM3, including two de novo variants, were identified in four unrelated individuals with IFE. The variants included one truncating variant (c.1432C > T/p.Q478X) and three missense variants (c.478C > T/p.P160S, c.1239C > G/p.N413K, and c.1659T > A/p.N553K), which had no allele frequency in the gnomAD database. The missense variants were predicted to be damaging and affect hydrogen bonds with surrounding amino acids. Mutations Q478X, P160S, and N413K were associated with benign childhood epilepsy with centrotemporal electroencephalograph (EEG) spikes. P160S and N413K were located in the inner side of the enzyme active center. Mutation N553K was associated with benign occipital epilepsy with incomplete penetrance, located in the C-terminal of Domain 4. Further analysis demonstrated that previously reported biallelic PGM3 mutations were associated with severe immunodeficiency and/or congenital disorder of glycosylation, commonly accompanied by neurodevelopmental abnormalities, while monoallelic mutations were associated with milder symptoms like IFE.ConclusionThe genetic and molecular evidence from the present study implies that the PGM3 variants identified in IFE patients lead to defects of the PGM3 gene, suggesting that the PGM3 gene is potentially associated with epilepsy. The genotype–phenotype relationship of PGM3 mutations suggested a quantitative correlation between genetic impairment and phenotypic severity, which helps explain the mild symptoms and incomplete penetrance in individuals with IFE.