Assigning pathogenicity for TAB2 variants using a novel scalable functional assay and expanding TAB2 disease spectrum.

Haploinsufficiency of TGF-beta-activated kinase 1 (MAP3K7) binding protein 2 (TAB2) has been associated with congenital heart disease and more recently multiorgan structural abnormalities. Missense variant represents a major proportion of non-synonymous TAB2 variants reported in gnomAD (295/576) and Clinvar (16/73), most of which are variants of uncertain significance (VUSs). However, interpretation of TAB2 missense variants remains challenging because of lack of functional assays. To address this issue, we established a cell-based luciferase assay that enables high-throughput screening of TAB2 variants to assess the functional consequence for predicting variant pathogenicity. Using this platform, we screened 47 TAB2 variants including five pathogenic controls and one benign control, and the results showed that the transcriptional activity of activator protein 1 (AP-1) but not nuclear factor kappa B predicts the TAB2 variant pathogenicity. This assay provides accurate functional readout for both loss-of-function (LOF) and gain-of-function variants, which are associated with distinct phenotypes. In all, 22 out of 32 tested VUSs were reclassified. Genotype-Phenotype association showed that most patients with partial LOF variants do not exhibit congenital heart disease but high frequency of developmental delay, hypotonia and dysmorphic features, which suggests that genetic testing for TAB2 is needed for a broader spectrum of patients with more diverse phenotypes. Molecular modeling with Npl4 zinc finger (NZF) domain variants revealed that the stability of the NZF domain in TAB2 protein is crucial for AP-1 activation. In conclusion, we developed a highly effective functional assay for TAB2 variant prediction and interpretation.

An Integrated Phenotypic and Genotypic Approach Reveals a High-Risk Subtype Association for EBF3 Missense Variants Affecting the Zinc Finger Domain.

OBJECTIVE: Collier/Olf/EBF (COE) transcription factors have distinct expression patterns in the developing and mature nervous system. To date, a neurological disease association has been conclusively established for only the Early B-cell Factor-3 (EBF3) COE family member through the identification of heterozygous loss-of-function variants in individuals with autism spectrum/neurodevelopmental disorders (NDD). Here, we identify a symptom severity risk association with missense variants primarily disrupting the zinc finger domain (ZNF) in EBF3-related NDD. METHODS: A phenotypic assessment of 41 individuals was combined with a literature meta-analysis for a total of 83 individuals diagnosed with EBF3-related NDD. Quantitative diagnostic phenotypic and symptom severity scales were developed to compare EBF3 variant type and location to identify genotype-phenotype correlations. To stratify the effects of EBF3 variants disrupting either the DNA-binding domain (DBD) or the ZNF, we used in vivo fruit fly UAS-GAL4 expression and in vitro luciferase assays. RESULTS: We show that patient symptom severity correlates with EBF3 missense variants perturbing the ZNF, which is a key protein domain required for stabilizing the interaction between EBF3 and the target DNA sequence. We found that ZNF-associated variants failed to restore viability in the fruit fly and impaired transcriptional activation. However, the recurrent variant EBF3 p.Arg209Trp in the DBD is capable of partially rescuing viability in the fly and preserved transcriptional activation. INTERPRETATION: We describe a symptom severity risk association with ZNF perturbations and EBF3 loss-of-function in the largest reported cohort to date of EBF3-related NDD patients. This analysis should have potential predictive clinical value for newly identified patients with EBF3 gene variants. ANN NEUROL 2022;92:138-153.

PRUNE1 c.933G>A synonymous variant induces exon 7 skipping, disrupts the DHHA2 domain, and leads to an atypical NMIHBA syndrome presentation: Case report and review of the literature.

Prune exopolyphosphatase-1 (PRUNE1) encodes a member of the aspartic acid-histidine-histidine (DHH) phosphodiesterase superfamily that regulates cell migration and proliferation during brain development. In 2015, biallelic PRUNE1 loss-of-function variants were identified to cause the neurodevelopmental disorder with microcephaly, hypotonia, and variable brain abnormalities (NMIHBA, OMIM#617481). NMIHBA is characterized by the namesake features and structural brain anomalies including thinning of the corpus callosum, cerebral and cerebellar atrophy, and delayed myelination. To date, 47 individuals have been reported in the literature, but the phenotypic spectrum of PRUNE1-related disorders and their causative variants remains to be characterized fully. Here, we report a novel homozygous PRUNE1 NM_021222.2:c.933G>A synonymous variant identified in a 6-year-old boy with intellectual and developmental disabilities, hypotonia, and spastic diplegia, but with the absence of microcephaly, brain anomalies, or seizures. Fibroblast RNA sequencing revealed that the PRUNE1 NM_021222.1:c.933G>A variant resulted in an in-frame skipping of the penultimate exon 7, removing 53 amino acids from an important protein domain. This case represents the first synonymous variant and the third pathogenic variant known to date affecting the DHH-associated domain (DHHA2 domain). These findings extend the genotypic and phenotypic spectrums in PRUNE1-related disorders and highlight the importance of considering synonymous splice site variants in atypical presentations.

Dihydroquinazolines enhance 20S proteasome activity and induce degradation of α-synuclein, an intrinsically disordered protein associated with neurodegeneration.

Aggregates or oligomeric forms of many intrinsically disordered proteins (IDPs), including α-synuclein, are hallmarks of neurodegenerative diseases, like Parkinson's and Alzheimer's disease, and key contributors to their pathogenesis. Due to their disordered nature and therefore lack of defined drug-binding pockets, IDPs are difficult targets for traditional small molecule drug design and are often referred to as "undruggable". The 20S proteasome is the main protease that targets IDPs for degradation and therefore small molecule 20S proteasome enhancement presents a novel therapeutic strategy by which these undruggable IDPs could be targeted. The concept of 20S activation is still relatively new, with few potent activators having been identified thus far. Herein, we synthesized and evaluated a library of dihydroquinazoline analogues and discovered several promising new 20S proteasome activators. Further testing of top hits revealed that they can enhance 20S mediated degradation of α-synuclein, the IDP associated with Parkinson's disease.

Triflic anhydride mediated synthesis of 3,4-dihydroquinazolines: a three-component one-pot tandem procedure.

A one-pot three-component tandem reaction involving a key Pictet-Spengler-like annulation step has been developed, providing an efficient method for the synthesis of 3,4-dihydroquinazolines in moderate to good yields from amides, aldehydes, and amines. The multicomponent triflic anhydride mediated reaction tolerates the installation of numerous functional groups, affording extensive diversity about the heterocyclic scaffold.