REEV: review, evaluate and explain variants.

In the era of high throughput sequencing, special software is required for the clinical evaluation of genetic variants. We developed REEV (Review, Evaluate and Explain Variants), a user-friendly platform for clinicians and researchers in the field of rare disease genetics. Supporting data was aggregated from public data sources. We compared REEV with seven other tools for clinical variant evaluation. REEV (semi-)automatically fills individual ACMG criteria facilitating variant interpretation. REEV can store disease and phenotype data related to a case to use these for phenotype similarity measures. Users can create public permanent links for individual variants that can be saved as browser bookmarks and shared. REEV may help in the fast diagnostic assessment of genetic variants in a clinical as well as in a research context. REEV (https://reev.bihealth.org/) is free and open to all users and there is no login requirement.

RNA analysis and computer-aided facial phenotyping help to classify a novel TRIO splice site variant.

Pathogenic variants in TRIO, encoding the guanine nucleotide exchange factor, are associated with two distinct neurodevelopmental delay phenotypes: gain-of-function missense mutations within the spectrin repeats are causative for a severe developmental delay with macrocephaly (MIM: 618825), whereas loss-of-function missense variants in the GEF1 domain and truncating variants throughout the gene lead to a milder developmental delay and microcephaly (MIM: 617061). In three affected family members with mild intellectual disability/NDD and microcephaly, we detected a novel heterozygous TRIO variant at the last coding base of exon 31 (NM_007118.4:c.4716G>A). RNA analysis from patient-derived lymphoblastoid cells confirmed aberrant splicing resulting in the skipping of exon 31 (r.4615_4716del), leading to an in-frame deletion in the first Pleckstrin homology subdomain of the GEF1 domain: p.(Thr1539_Lys1572del). To test for a distinct gestalt, facial characteristics of the family members and 41 previously published TRIO cases were systematically evaluated via GestaltMatcher. Computational analysis of the facial gestalt suggests a distinguishable facial TRIO-phenotype not outlined in the existing literature.

Novel mutation and expanding phenotype in IRF2BP2 deficiency.

OBJECTIVES: Inborn errors of immunity manifest with susceptibility to infection but may also present with immune dysregulation only. According to the European Society for Immunodeficiencies Registry about 50% of inborn errors of immunity are classified as common variable immunodeficiencies (CVID). In only few CVID patients are monogenic causes identified. IFN regulatory factor-2 binding protein 2 (IRF2BP2) is one of 20 known genes associated with CVID phenotypes and has only been reported in two families so far. We report another IRF2BP2-deficient patient with a novel pathogenic variant and phenotype and characterize impaired B cell function and immune dysregulation. METHODS: We performed trio whole-exome sequencing, determined B cell subpopulations and intracellular calcium mobilization upon B cell receptor crosslinking in B cells. T cell subpopulations, T cell proliferation and a type I IFN signature were measured. Colonoscopy and gastroduodenoscopy including histopathology were performed. RESULTS: The 33-year-old male presented with recurrent respiratory infections since childhood, colitis and RA beginning at age 25 years. We identified a novel de novo nonsense IRF2BP2 variant c.1618C>T; p.(Q540*). IgG deficiency was detected as consequence of a severe B cell differentiation defect. This was confirmed by impaired plasmablast formation upon stimulation with CpG. No serum autoantibodies were detected. Intracellular cytokine production in CD4+ T cells and CTLA4 expression on FOXP3+ Tregs were impaired. Type I IFN signature was elevated. CONCLUSION: The identified loss-of-function variant in IRF2BP2 severely impairs B cell development and T cell homeostasis, and may be associated with colitis and RA. Our results provide further evidence for association of IRF2BP2 with CVID and contribute to the understanding of the underlying pathomechanisms.

GLI3 variants causing isolated polysyndactyly are not restricted to the protein's C-terminal third.

Loss of function variants of GLI3 are associated with a variety of forms of polysyndactyly: Pallister-Hall syndrome (PHS), Greig-Cephalopolysyndactyly syndrome (GCPS), and isolated polysyndactyly (IPD). Variants affecting the N-terminal and C-terminal thirds of the GLI3 protein have been associated with GCPS, those within the central third with PHS. Cases of IPD have been attributed to variants affecting the C-terminal third of the GLI3 protein. In this study, we further investigate these genotype-phenotype correlations. Sequencing of GLI3 was performed in patients with clinical findings suggestive of a GLI3-associated syndrome. Additionally, we searched the literature for reported cases of either manifestation with mutations in the GLI3 gene. Here, we report 48 novel cases from 16 families with polysyndactyly in whom we found causative variants in GLI3 and a review on 314 previously reported GLI3 variants. No differences in location of variants causing either GCPS or IPD were found. Review of published data confirmed the association of PHS and variants affecting the GLI3 protein's central third. We conclude that the observed manifestations of GLI3 variants as GCPS or IPD display different phenotypic severities of the same disorder and propose a binary division of GLI3-associated disorders in either PHS or GCPS/polysyndactyly.