講演情報
[III-TLR-6]Novel Germline Mosaic NKX2-5 Variant in Siblings with LV Noncompaction and AV Block and Functional Analysis Using Zebrafish
○Keiko Uchida1,2, Masaya Kunimatsu3, Iku Ito1,4, Tadashi Inoue2, Shigetomo Fukuhara5, Utako Yokoyama1, Hiroyuki Yamagishi1,2,6 (1.The Department of Physiology, Tokyo Medical University, Tokyo, Japan, 2.The Department of Pediatrics, Keio University School of Medicine, 3.The Department of Pediatrics, Graduate School of Medicine, Chiba University, 4.The Faculty of Medicine, The University of Tokyo, 5.The Department of Molecular Pathophysiology, Institute of Advanced Medical Sciences, Nippon Medical School, 6.Tokyo Metropolitan Children's Medical Center)
キーワード：
genetic analysis、left ventricular noncompaction、atrioventricular block
Background: NKX2-5 is a key cardiac transcription factor essential for heart development and maturation. Variants in NKX2-5 are associated with atrial septal defect, atrioventricular block (AVB), and left ventricular noncompaction (LVNC); however, the genotype-phenotype relationship in NKX2-5 variants remains unclear.
Methods: Whole-exome sequencing was performed in the siblings with LVNC and AVB and their parents. Rare variants (MAF<1%) were filtered using HGVD, Popfreq, and 54KJPN, followed by in silico pathogenicity prediction. To assess functional impact, we generated two independent deletion mutant zebrafish lines carrying deletions at the site homologous to the human variant using genome editing, and cardiac phenotypes were analyzed by fluorescence microscopy.
Results: Both siblings showed progressive AVB, and one required pacemaker implantation at 18 years of age. Echocardiography demonstrated LVNC in both. Among candidate variants, we identified a novel frameshift variant in NKX2-5 present in both siblings but absent in their parents, representing the familial case of germline mosaicism for an NKX2-5 variant. Both deletion mutant zebrafish lines exhibited cardiac dilatation and pericardial effusion at 3 days post-fertilization, consistent with cardiac dysfunction.
Conclusion: We identified a novel NKX2-5 variant transmitted by germline mosaicism and demonstrated its cardiac pathogenicity using two independent deletion mutant zebrafish lines. These findings support the clinical utility of NKX2-5 genetic testing for risk assessment in patients with AVB and LVNC.
Methods: Whole-exome sequencing was performed in the siblings with LVNC and AVB and their parents. Rare variants (MAF<1%) were filtered using HGVD, Popfreq, and 54KJPN, followed by in silico pathogenicity prediction. To assess functional impact, we generated two independent deletion mutant zebrafish lines carrying deletions at the site homologous to the human variant using genome editing, and cardiac phenotypes were analyzed by fluorescence microscopy.
Results: Both siblings showed progressive AVB, and one required pacemaker implantation at 18 years of age. Echocardiography demonstrated LVNC in both. Among candidate variants, we identified a novel frameshift variant in NKX2-5 present in both siblings but absent in their parents, representing the familial case of germline mosaicism for an NKX2-5 variant. Both deletion mutant zebrafish lines exhibited cardiac dilatation and pericardial effusion at 3 days post-fertilization, consistent with cardiac dysfunction.
Conclusion: We identified a novel NKX2-5 variant transmitted by germline mosaicism and demonstrated its cardiac pathogenicity using two independent deletion mutant zebrafish lines. These findings support the clinical utility of NKX2-5 genetic testing for risk assessment in patients with AVB and LVNC.