Biallelic missense variants in ZBTB11 can cause intellectual disability in humans

Abstract

Exploring genes and pathways underlying intellectual disability (ID) provides insight into brain development and function, clarifying the complex puzzle of how cognition develops. As part of ongoing systematic studies to identify candidate ID genes, linkage analysis and next-generation sequencing revealed Zinc Finger and BTB Domain Containing 11 (ZBTB11) as a novel candidate ID gene. ZBTB11 encodes a little-studied transcription regulator, and the two identified missense variants in this study are predicted to disrupt canonical Zn2+-binding residues of its C2H2 zinc finger domain, leading to possible altered DNA binding. Using HEK293T cells transfected with wild-type and mutant GFP-ZBTB11 constructs, we found the ZBTB11 mutants being excluded from the nucleolus, where the wild-type recombinant protein is predominantly localized. Pathway analysis applied to ChIP-seq data deposited in the ENCODE database supports the localization of ZBTB11 in nucleoli, highlighting associated pathways such as ribosomal RNA synthesis, ribosomal assembly, RNA modification and stress sensing, and provides a direct link between subcellular ZBTB11 location and its function. Furthermore, given the report of prominent brain and spinal cord degeneration in a zebrafish Zbtb11 mutant, we investigated ZBTB11-ortholog knockdown in Drosophila melanogaster brain by targeting RNAi using the UAS/Gal4 system. The observed approximate reduction to a third of the mushroom body size-possibly through neuronal reduction or degeneration-may affect neuronal circuits in the brain that are required for adaptive behavior, specifying the role of this gene in the nervous system. In conclusion, we report two ID families segregating ZBTB11 biallelic mutations disrupting Zn2+-binding motifs and provide functional evidence linking ZBTB11 dysfunction to this phenotype.

The genetics of intellectual disability: advancing technology and gene editing

“…Biological assays can be used to study any undefined variant and its role or pathogenicity. These assays can be used in mutated cells and also directly in patient-derived cells 58 . To identify the pathogenicity of candidate ID genes, electrophysiological studies of SH-SY5Y neuronal cell lines are a very powerful approach 59 to capture early cortical development with high fidelity, thus helping to study genes that are relevant in early cortical development and associated with ID 60 .…”

Intellectual disability-associated factor Zbtb11 cooperates with NRF-2/GABP to control mitochondrial function

“…Two pathogenic mutations were identified, both of which are predicted to disrupt individual Zbtb11 zinc-finger motifs. Affected patients display morphological defects in the brain, including ventriculomegaly and cerebellar atrophy, and also show neuromuscular defects, such as ataxia and facial hypotonia 12 . The molecular and cellular functions of Zbtb11 have hitherto remained unknown, so the aetiology of this disease is not currently understood.…”

The Fuchs corneal dystrophy-associated CTG repeat expansion in the TCF4 gene affects transcription from its alternative promoters

“…According to this mechanism, the TNR-carrying RNAs cluster RNA binding proteins, interfering with the splicing of various mRNAs. Of note, antisense therapy using Fuchs' dystrophy ex vivo cell models leads to inhibition of RNA foci and mis-splicing in Fuchs' dystrophy 34 , 35 . Since the CTG TNR is located in the intron between exons 3 and 4, this repeat is not included in the fully mature TCF4 mRNA 4 , but the CTG TNR is still included in the pre-mRNA of transcripts initiated at the upstream promoters (exon 1a, 1b, 3a, 3b, 3c, 3d promoters).…”