Abstract
P338: Studying the role of the DIP2C gene in humans and zebrafish
Genetics in Medicine Open, Vol.3(Supplement 2), 102303
2025
DOI: 10.1016/j.gimo.2025.102303
Abstract
Introduction
The disconnected (disco)-interacting protein 2 (DIP2) gene regulates axonal bifurcation of mushroom body neurons in D.melanogaster and is required for axonal regeneration in the neurons of C.elegans. The three human homologues for DIP2, DIP2A, DIP2B, and DIP2C, are highly conserved and widely expressed in the central nervous system. We recently reported 23 individuals with heterozygous variants in DIP2C that all manifest developmental delays primarily affecting expressive language and speech articulation. DIP2 is a regulator of diacylglycerols (DAGs) in yeast, fly, and mouse models and lipidomics analysis in yeast revealed that DIP2 prevents the accumulation of specific DAGs. However, data on the clinical findings resulting from haploinsufficiency for this gene and the mechanism whereby reduced expression for this gene causes speech difficulties are lacking.
Methods
An additional 5 patients with heterozygous, pathogenic DIP2C variants were identified through GeneMatcher. Clinical and variant data were collected after consent from patient families. Five patients gave consent to undergo an assessment for speech apraxia. We studied the effects of 3 missense variants on protein function. CRISPR/Cas9 technology was used to generate zebrafish lines with reduced expression for both zebrafish orthologues of DIP2C, dip2ca and dip2cb. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was performed on RNA obtained at 72 hours post-fertilization (hpf) from control and mutant zebrafish larvae. A diacylglycerol (DAG) fluorescence assay was run on controls and mutant zebrafish larvae at 24 hpf.
Results
In total, we ascertained 16 male and 12 female patients; 11/28 (39%) had an affected family member with the same DIP2C variant. All 28 patients presented with speech difficulties and 19/20 had speech delays (95%). 9/27 (33%) were diagnosed with autism and 22/27 (74%) were described as having behavioral difficulties. 19/26 (73%) walked after the expected age. Five patients developed seizures (21%); similarly; 5/24 had abnormal cardiac findings comprising hypertrophic cardiomyopathy, atrial septal defects, and a bicuspid aortic valve. Minor facial anomalies included high anterior hairlines, broad/long foreheads, bulbous or full nasal tips, and ear anomalies. We generated a dip2ca-/- zebrafish line with a one base pair (bp) insertion and a dip2cb-/- line with a 17 bp deletion; both variants were predicted to cause loss of function from nonsense-mediated decay. Double mutants (dip2ca-/- and dip2cb-/-) had yellow discoloration of the yolk and fins that was suggestive of abnormal fat metabolism. qRT-PCR showed that both mutant zebrafish lines demonstrated downregulation of cnpy, fat2, rfx2, and rfx3.
Conclusion
Our study adds 5 previously unreported patients to the literature on DIP2C variants and confirms that pathogenic variants in this gene are a risk factor for developmental delays with disordered expressive language, seizures and heart malformations. Double mutant zebrafish showed differential expression of fat2, rfx2, and rfx3 that are associated with embryonic brain development. The abnormal yellow discoloration of the double mutant zebrafish is also suggestive of abnormal lipid metabolism. We are continuing with our experiments to determine the effects of reduced dip2ca-/- and dip2cb-/- in the zebrafish lines.
Details
- Title: Subtitle
- P338: Studying the role of the DIP2C gene in humans and zebrafish
- Creators
- Katelyn Beatty - Cincinnati Children's Hospital Medical CenterAjay Deepak Verma - Cincinnati Children's Hospital Medical CenterMadison Moe - Cincinnati Children's Hospital Medical CenterStephanie Htun - University of California, San FranciscoThomas Scerri - Murdoch Children's Research InstituteAlpa Sidhu - University of IowaJacob Ginter - University of IowaLindsey Walker - Children's Hospital of Los AngelesMatthew Deardorff - University of Southern CaliforniaJenny Do - The University of Texas Medical Branch at GalvestonIngrid van de Laar - Erasmus University RotterdamMelissa Pauly - Universitätsklinikum ErlangenGeorgia Vasileiou - Universitätsklinikum ErlangenAngela Morgan - Murdoch Children's Research InstituteAnne Slavotinek - Cincinnati Children's Hospital Medical Center
- Resource Type
- Abstract
- Publication Details
- Genetics in Medicine Open, Vol.3(Supplement 2), 102303
- DOI
- 10.1016/j.gimo.2025.102303
- ISSN
- 2949-7744
- eISSN
- 2949-7744
- Language
- English
- Date published
- 2025
- Academic Unit
- Medical Genetics and Genomics; Stead Family Department of Pediatrics
- Record Identifier
- 9984801614502771
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