Single nucleotide variants in UNC13C associated with neurodevelopmental disorders affect ethanol sensitivity in Drosophila

Franz Müller  ¹ , Sonja Neuser  ² , Gaurav Shrestha  ³ , Netra P Neupane  ⁴ , Katharina J Götze  ¹ , Nicola Brunetti-Pierri  ^{5   6   7} , Gaetano Terrone  ⁵ , Alexandre Reymond  ⁸ , Koen L van Gassen  ⁹ , Eva Brilstra  ⁹ , Katharina Steindl  ¹⁰ , Anais Begemann  ¹⁰ , Anita Rauch  ¹⁰ , Jonathan Rips  ¹¹ , Duha Fahham  ¹¹ , Tahsin Stefan Barakat  ¹² , Olivier Patat  ¹³ , Jérémie Mortreux  ¹⁴ , Matthew Hoi Kin Chau  ^{15   16   17} , Jill A Rosenfeld  ¹⁸ , Elizabeth Mizerik  ^{18   19} , Swati Srivastava  ^{18   20} , Xi Luo  ^{18   20} , Anne-Kristin Dahse  ¹ , Nicole Scholz  ¹ , Joydip Das  ⁴ , Gregg Roman  ²¹ , Tobias Langenhan  ^{1   22   23} , Rami Abou Jamra  ² , Achmed Mrestani  ^{1   24} , Dmitrij Ljaschenko  ¹

Affiliations

• PMID: 41399760
• PMCID: PMC12702192
• DOI: 10.1016/j.bbrep.2025.102375

Abstract

UNC13s are presynaptic proteins essential for neurotransmitter release at chemical synapses. In this study, we present eleven patients from nine families with severe neurodevelopmental impairments, who carry rare, biallelic UNC13C single-nucleotide variants (SNVs). Six missense variants, each identified in compound heterozygosity in one of three of these patients, were introduced into the Drosophila melanogaster ortholog unc13 using a previously established CRISPR/Cas9-based method for rapid and scarless genomic modifications, hypothesising that they underlie the observed clinical manifestations. However, none of the introduced mutations influenced Mendelian ratios, negative geotaxis, or lifespan of the fruit flies. Interestingly, two variants located outside the gene regions encoding known UNC13C domains caused a decreased ethanol sensitivity in Drosophila, while the Thr1729Met substitution within the C₁ domain resulted in increased ethanol sensitivity. Molecular dynamics simulations of the latter mutant gene product suggested that the altered protein conformation enhances exposure of the ethanol-binding site, thereby increasing sensitivity to ethanol. These findings reinforce previous evidence highlighting the critical role of the C₁ domain in ethanol sensitivity. Given the involvement of the C₁ domain in synaptic plasticity this result might implicate an influence of the Thr1729Met on synaptic function.

Keywords: Chemical synapse; Dunc13; Ethanol sensitivity; Molecular dynamics simulation; Neurodevelopmental disease; UNC13C; Unc13.

© 2025 The Authors.