2. Academic Validation
  3. A novel stoploss mutation CYB5R3 c.906A>G(p.*302Trpext*42) involved in the pathogenesis of hereditary methemoglobinemia

A novel stoploss mutation CYB5R3 c.906A>G(p.*302Trpext*42) involved in the pathogenesis of hereditary methemoglobinemia

  • Clin Chim Acta. 2025 Jan 1:564:119930. doi: 10.1016/j.cca.2024.119930.
Kai-Ying He 1,  Hong-Ping Yu 2,  Jing Zou 2,  Xiang Chen 3,  Li Chen 2,  Dan-Dan Ruan 2,  Ting Chen 4,  Qian Chen 2,  Li Zhang 5,  Mei-Zhu Gao 5,  Xin-Fu Lin 6,  Hong Li 2,  Zhu-Ting Fang 7,  Jing Wu 8,  Jie-Wei Luo 9,  Li-Sheng Liao 10
Affiliations

Affiliations

  • 1 Fujian University of Traditional Chinese Medicine, Fuzhou 350122, China; Department of Traditional Chinese Medicine, Shengli Clinical Medical College of Fujian Medical University, Fujian Provincial Hospital, Fuzhou 350001, China.
  • 2 Department of Traditional Chinese Medicine, Shengli Clinical Medical College of Fujian Medical University, Fujian Provincial Hospital, Fuzhou 350001, China.
  • 3 The First Clinical Medical College, Nanchang University, Nanchang 330006, China.
  • 4 School of Medicine, Shanghai University, Shanghai 200444, China.
  • 5 Nephrology Department, Fujian Provincial Hospital, Fuzhou 350001, China.
  • 6 Pediatrics Department, Fujian Provincial Hospital, Fuzhou 350001, China.
  • 7 Department of Traditional Chinese Medicine, Shengli Clinical Medical College of Fujian Medical University, Fujian Provincial Hospital, Fuzhou 350001, China; Clinical School of Oncology, Fujian Medical University, Fuzhou 350001, China. Electronic address: 470389481@qq.com.
  • 8 Fujian University of Traditional Chinese Medicine, Fuzhou 350122, China; Department of Traditional Chinese Medicine, Shengli Clinical Medical College of Fujian Medical University, Fujian Provincial Hospital, Fuzhou 350001, China. Electronic address: fz4212@yeah.net.
  • 9 Department of Traditional Chinese Medicine, Shengli Clinical Medical College of Fujian Medical University, Fujian Provincial Hospital, Fuzhou 350001, China. Electronic address: docluo0421@aliyun.com.
  • 10 Department of Traditional Chinese Medicine, Shengli Clinical Medical College of Fujian Medical University, Fujian Provincial Hospital, Fuzhou 350001, China; Department of Hematology, Fujian Provincial Hospital, Fuzhou 350001, China. Electronic address: liaolisheng@126.com.
PMID: 39154701 DOI: 10.1016/j.cca.2024.119930
Abstract

Recessive congenital methemoglobinemia (RCM) is a hereditary autosomal disorder with an extremely low incidence rate. Here, we report a case of methemoglobinemia type I in a patient with congenital persistent cyanosis. The condition was attributed to a novel compound heterozygous mutation in CYB5R3, characterized by elevated methemoglobin levels (13.4 % of total hemoglobin) and undetectable NADH cytochrome b5 reductase (CYB5R3) activity. Whole-exome Sequencing (WES) revealed two heterozygous mutations in CYB5R3: a previously reported pathogenic missense mutation c.611G>A(p.Cys204Tyr) inherited from the father, and a novel stop codon mutation c.906A>G(p.*302Trpext*42) from the mother, the latter mutation assessed as likely pathogenic according to ACMG guidelines. In cells overexpressing the CYB5R3 c.906A>G mutant construct, the CYB5R3 mRNA level was significantly lower than in cells overexpressing the wild-type (WT) CYB5R3 construct. However, there was no significant difference in protein expression levels between the mutant and WT constructs. Notably, an additional protein band of approximately 55 kDa was detected in the mutant cells. Immunofluorescence localization showed that, compared to wild-type CYB5R3, the subcellular localization of the CYB5R3 p.*302Trpext*42 mutant protein did not show significant changes and remained distributed in the endoplasmic reticulum and mitochondria. However, the c.906A>G(p.*302Trpext*42) mutation resulted in increased intracellular Reactive Oxygen Species (ROS) levels and decreased NAD+/NADH ratio, suggesting impaired CYB5R3 function and implicating this novel mutation as likely pathogenic.

Keywords

CYB5R3; Hereditary; Methemoglobinemia; Mutation; Stoploss.

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