FROM PATIENT TO PHENOTYPE: FUNCTIONAL ANALYSIS OF PATIENT-SPECIFIC <EM>DE NOVO</EM> NEURODEVELOPMENTAL DISORDER VARIANT IN A <EM>DROSOPHILA</EM> MODEL

Neurodevelopmental disorders (NDDs), such as Intellectual Disability and Autism Spectrum Disorder, affect 2–3% of the world population and represent a major burden for the affected individuals and their families. Advances in genetic diagnostics have revealed extensive genetic heterogeneity and led to the identification of numerous rare, patient-specific variants. Establishing the pathogenicity of these variants and linking them to altered neural development and cognitive dysfunction remains a challenge.
We investigate a conserved protein-coding gene recently implicated in NDDs through a de novo variant in three unrelated individuals. Despite its evolutionary conservation, the gene’s function in the nervous system is poorly understood. To assess its role in neural development and cognitive function, we use Drosophila melanogaster, a genetically tractable model organism with conserved neurodevelopmental and cognitive pathways. We generated a loss-of-function allele and the precise patient-specific alleles with CRISPR/Cas9 and assessed their effect on neuronal development, lifespan, locomotion and cognitive function. Cognitive function was assessed with habituation, a conserved form of non-associative learning that is frequently affected in NDD individuals and animal models. Flies carrying the patient-specific variants exhibit deficits in NDD-relevant phenotypes, providing functional evidence for variant pathogenicity and supporting a role for this gene in neural development.
This work establishes a proof-of-principle for the use of Drosophila as an efficient platform for functional validation of patient-derived NDD variants. Beyond variant validation, this approach enables systematic investigation of the cellular and molecular mechanisms underlying cognitive dysfunction and can be readily extended to other NDD-associated genes emerging from genomic studies.