Functional Analysis of TFAP2E as a Gene for Human Central Nervous System Malformations

Jeshurun C. Kalanithy1, Gabriel C. Dworschak2, Benjamin Odermatt3, Heiko Reutter4

1 Institute of Human Genetics and Institute of Anatomy, University of Bonn, Bonn, Germany
2 Department of Pediatrics, Children's Hospital, Institute of Human Genetics, Institute of Anatomy, University of Bonn, Bonn, Germany
3 Institute of Anatomy, University of Bonn, Bonn, Germany
4 Institute of Human Genetics and Department of Neonatology and Pediatric Intensive Care, University Hospital Bonn, Bonn, Germany

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Introduction: Congenital malformations of the central nervous system (CNS) do affect the brain and/or the neural tube. The underlying causes are extremely heterogenous, including environmental risk factors and genetic factors. Trio whole exome sequencing in a fetus with distinct brain malformations identified a novel germline de novo missense variant in TFAP2E. TFAP2E encodes for the transcription factor AP-2. Among brain malformations, the fetus was diagnosed with microlissencephaly, severe cerebellar hypoplasia and additionally the fetus presented with micrognathia.

Materials and Methods: We initiated functional studies in zebrafish (zf) using 2 different Morpholinos® (MO) against tfap2e in different transgenic neuronal, glial and neural crest cells reporter lines.

Results: We have performed functional analysis of zebrafish larvae after Tfap2e Morpholino knockdown (MO KD) and were able to reproduce the human phenotype in the zebrafish model. Both the CNS and the jaw have been evaluated and are significantly affected in MO-injected zfl in comparison to controls, indicating a crucial role of TFAP2E in neuronal and neural crest cell formation and maturation. Major effects on vasculogenesis were excluded after MO KD experiments in vascular reporter lines, suggesting the cell specificity of the observed effects. Additionally, behavior analysis revealed rarified movements of the MO KD zebrafish larvae.

Conclusion: Our findings indicate that TFAP2E is linked to neural crest development and maturation of the CNS and hence is a novel human neuronal disease causing gene. Further experiments including Chromatin Immunoprecipitation to identify binding targets and underlying pathways of the transcription factor are ongoing.