159 Oral - Models of Human Disease I - Diseases with a Neurological Focus
Saturday April 09, 9:45 AM - 10:00 AM

Authors:
Maimuna Paul ^1,2; Anna Duncan ³; Casie Genetti ^3,4,5; Michele Pinelli ^6,7; Nicola Brunetti-Pierri ^6,7; Alexandra Garza-Flores ⁸; Russell Saneto ⁹; Giuseppe Zampino ¹⁰; Emanuele Agolini ¹¹; Ulrike Blümlein ¹²; Rami Abou Jamra ¹³; Raphael Carapito ¹⁴; Bertrand Isidor ¹⁵; Seiamak Bahram ¹⁴; Alyssa Ritter ¹⁶; Kosuke Izumi ¹⁶; Ben Pode Shaked ¹⁷; Ortal Barel ¹⁷; Bruria Ben Zeev ¹⁷; Hongling Pan ^2,18; Hsiao-Tuan Chao ^{1,2,18,19,20,21}; Pankaj Agrawal ^3,4,5

Affiliations:
1) Department of Pediatrics, Baylor College of Medicine, Houston, TX; 2) Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, Tx; 3) Division of Newborn Medicine, Boston Children’s Hospital and Harvard Medical School, Boston, MA; 4) Division of Genetics and Genomics, Boston Children’s Hospital and Harvard Medical School, Boston, MA; 5) The Manton Center for Orphan Disease Research, Boston Children’s Hospital and Harvard Medical School, Boston, MA; 6) Telethon Institute of Genetics and Medicine, Pozzuoli, Italy; 7) University of Naples "Federico II", Pozzuoli, Naples, Italy ; 8) Department of Clinical Genetics, Cook Children’s Hospital, Fort Worth, TX; 9) Departments of Neurology and Pediatrics, Seattle Children's Hospital, University of Washington, Seattle, Washington; 10) Center for Rare Diseases and Birth Defects, Department of Woman and Child Health and Public Health, Fondazione Policlinico Universitario A. Gemelli, Rome, Italy; 11) Translational Cytogenomics Research Unit, Bambino Gesù Children’s Hospital, IRCCS, Rome, Italy; 12) Department of Pediatrics, Carl-Thiem-Klinikum Cottbus, Germany; 13) Institute of Human Genetics, University of Leipzig Medical Center, Leipzig, Germany; 14) Laboratoire 'ImmunoRhumatologie Moléculaire, Plateforme GENOMAX, INSERM UMR_S 1109, Faculté de Médecine, Fédération Hospitalo-Universitaire OMICARE, Fédération de Médecine Translationnelle de Strasbourg (FMTS), ITI TRANSPLANTEX NG, Université de Strasbourg, Strasbourg, France; 15) Service de Génétique Médicale, Hôpital Hôtel-Dieu, Centre Hospitalier Universitaire de Nantes, Nantes, France; 16) Division of Human Genetics and Metabolism, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA; 17) Pediatric Neurology Department, The Edmond and Lilly Safra Pediatric Hospital, Sheba Medical Center, Tel Hashomer, Israel; 18) Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX; 19) Texas Children’s Hospital, Houston, TX; 20) Department of Neuroscience, Baylor College of Medicine, Houston, TX; 21) McNair Medical Institute, The Robert and Janice McNair Foundation, Houston, TX.

Keywords:
b. neural disorder; p. RNA binding proteins

Eukaryotic Initiation Factor-4A2 encodes EIF4A2, an ATP-dependent RNA helicase subunit of the eIF4F complex, which recognizes the 5’cap structure of mRNAs and is required for mRNA binding to the ribosome. The fruit fly homolog eIF4A mediates the negative regulation of Decapentaplegic (Dpp) signaling. In the fly, Dpp-signaling regulates embryo patterning, eye and wing morphogenesis, and stem cell identity determination. The vertebrate homolog of Dpp, TGF-β/BMP, is a key regulator of neuronal differentiation, development, and function and is associated with various neurological disorders. Prior fly studies revealed that both gain and loss of function (GOF and LOF) eIF4A alleles modulate the rough eye and wing serration phenotypes associated with Dpp GOF and LOF, respectively. Despite the role of EIF4A2 homologs in key developmental processes, human disease-causing variants have not previously been identified. Here, we report eleven individuals with extremely rare variants in EIF4A2 who all present with global developmental delay or intellectual disabilities, significant hypotonia, and epilepsy in most cases. To determine the pathogenicity of the EIF4A2 variants in vivo, we generated flies expressing human EIF4A2 wild-type (WT) and variants with a C-terminal HA tag for four de novo variants. We used the GAL4-UAS system to selectively express human EIF4A2 in fly neurons, wing, or eye. First, we conducted climbing assays to determine the impact of neuronal expression of EIF4A2 p.L344F, p.G364E, and p.T243I and found that these variants resulted in motor defects. Second, we found that the wing-specific expression of EIF4A2 p.T216I caused wing serration, which is consistent with loss of Dpp signaling. Third, we found that the eye-specific overexpression of EIF4A2 p.L344F, p.G364E, and p.T243I exacerbates the rough eye phenotypes associated with Dpp GOF, suggesting these variants are loss of function in nature. Finally, GMR GAL4 mediated knockdown of fly eIF4a using two different RNAi lines results in pupal lethality that can be rescued using the expression of human EIF4A2 WT. However, the EIF4A2 p.T243I and p.T216I variants fail to rescue the pupal lethality.
Together, these findings reveal that these de novo EIF4A2 variants are pathogenic and alter fruit fly development in a dominant manner through either GOF or LOF mechanisms. Our work establishes a role for EIF4A2 dysfunction in human neurodevelopmental disorders.