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Jacob, M.* ; Badmann, S.* ; Bigoni, S.* ; Iascone, M.* ; Vivaldi, I.* ; Mayerhanser, K.* ; Kopajtich, R. ; Prokisch, H. ; Forest, C.* ; Eck, S. ; Zech, M. ; Graf, E.* ; Wagner, M. ; Winkelmann, J. ; Brunet, T.* ; Brugger, M.*

Pathogenicity of NUSAP1 variants is defined by NMD-Escape: Evidence from two novel cases and systematic population-based variant analysis.

Clin. Genet., DOI: 10.1111/cge.70244 (2026)
Publ. Version/Full Text Research data DOI PMC
Open Access Hybrid
Creative Commons Lizenzvertrag
Protein-truncating variants in the 3' region of a transcript, evading mRNA degradation and giving rise to aberrant truncated proteins, are an underrecognized cause in Mendelian diseases. Here, we report two individuals with heterozygous de novo nonsense variants in the penultimate and last exon of NUSAP1, both presenting with early-onset refractory epilepsy, global developmental delay, congenital microcephaly, and a recognizable facial gestalt. RNA sequencing performed in one individual did not show a reduction in expression, compatible with escape of aberrant transcripts from nonsense mediated mRNA decay (NMD). We systematically analyzed gnomAD population data to delineate a critical region at the 3' region of NUSAP1, where nonsense variants introduce a premature termination codon and escape NMD. Such variants are absent from healthy controls, while frameshift variants producing C-terminal elongations appear tolerated. This position-dependent model provides guidance for diagnostic variant interpretation.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Nusap1 ; Microcephaly ; Nonsense‐mediated Decay ; Protein‐truncating Variants; Messenger-rna Decay; Nonsense; Binding; Genes
ISSN (print) / ISBN 0009-9163
e-ISSN 1399-0004
Publisher Wiley
Publishing Place 111 River St, Hoboken 07030-5774, Nj Usa
Reviewing status Peer reviewed
Grants Technical University of Munich-Institute for Advanced Study