Hiroki Morizono, PhD

Dr Morizono is a Research Professor in Biochemistry and Molecular Medicine and Pediatrics at The George Washington University (GW) and a Principal Investigator in the Center for Translational Research at Children’s National Hospital. He is an internationally recognized expert in urea cycle disorders with a focus on the effects of mutation on structure function relationships in the enzymes of the proximal urea cycle. He has been studying ornithine transcarbamylase (OTC) for 27 years. During his Ph.D., he built the first homology model of human OTC to rationalize how known patient mutations affect catalytic activity and protein stability. He developed a purification strategy for recombinant human OTC, which yielded protein in quantities needed to solve the first X ray crystallography structures of human OTC, and confirmed the accuracy of his homology model. His subsequent mining of genomic datasets uncovered several bacteria which had an OTC-like gene that lacked a strongly conserved motif . He showed that these species had transcarbamylases that required either acetyl- or succinyl- ornithine as a substrate by synthesizing specific substrates and inhibitors. Crystallization of these enzymes showed they had a rare trefoil knot in their tertiary structure. He has continued to curate OTC variants identified in patients, and has curated a website for OTC mutations, and developed approaches to evaluate the effect of mutation on OTC enzyme function and stability. He began work on AAV-based gene therapy to treat OTC deficiency in collaboration with James Wilson which led to the development of a clinical candidate vector that is currently in Phase III clinical trials. In related work, he showed the CRISPR could be used to correctly edit the OTC mutation in a spf-ash OTC mouse model, and subsequently developed a CAS9 based approach to insert a full length OTC into the defective OTC gene locus. Mutation analysis of OTC led to several collaborations involving homology modeling of genes involved in Sanfilippo syndrome and leukodystrophies. Dr Morizono’s work with N-acetylglutamate synthase (NAGS) spans the T0-T4 spectrum. In collaboration with Dr Caldovic, he discovered the vertebrate gene for NAGS prior to the completion of the human genome. Although all other urea cycle genes resemble their bacterial counterparts, NAGS had diverged greatly. Knowledge of the gene sequence has allowed patients with NAGS deficiency to be identified, led to clinical trials to treat NAGS deficiency using N-carbamylglutamate (NCG), FDA approval of NCG and currently, evaluation of NCG for treating other diseases resulting in hyperammonemia. He was a member of the IEEE BioCompute Objects Working Group that described the specifications to ensure reproducibility of bioinformatics experiments for FDA submission. He has been the Director of the Children's National Research Institute Bioinformatics Unit which oversees the Bioinformatics Core since 2018. The Core has provided services for over 100 projects ranging from bulk RNA-Seq, Single Cell RNA-Seq, metagenomics and microarrays. He has experience managing and securing data for Big Data projects through his work with the Clinical Translational Science Institute at Children’s National (CTSI-CN). Since 2011, Dr Morizono has been the lead of the CTSI-CN Informatics component. In this capacity, he grown the informatics infrastructure of the CTSI-CN, provided additional resources to the CTSI-CN REDCap team, and designed extensions to REDCap needed for the multisite trial of NCG. He is very familiar with data governance and management at scale having initiated the creation of a research data warehouse from the inpatient electronic medical record, which indexes and retrieves unstructured information from the EMR.
Financial relationships
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Type of financial relationship:There are no financial relationships to disclose.Date added:05/05/2025Date updated:05/05/2025