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Updated: Dec 9, 2025
Targeted Next-generation Sequencing and Bioinformatics Pipeline to Evaluate Genetic Determinants of Constitutional Disease
Published on: April 4, 2018
The single nucleotide variant at c.662A>G in human RRM2B is a loss-of-function mutation
Yen-Tzu Tseng1, Shang-Wei Li2,3, Wei-Chun HuangFu2,3
1Department of Animal Science and Technology, National Taiwan University, Taipei, Taiwan.
Background:
Mitochondrial DNA maintenance defects (MDMDs) is one of the critical pediatric dysfunction. One of the recent report indicated that a severe patient of MDMDs carries the NP_056528.2:p.Asn221Ser (N221S) variation in the RRM2B gene (NM_015713.5). However, there is no direct evidence demonstrating the nature of the N221S variation.
Materials And Methods:
This study aimed to utilize zebrafish and morpholino oligomer (MO) knockdown technique to provide direct evidence for the nature of the N221S variation in the RRM2B.
Results:
The results showed that two distinct MOs were both able to perturb the expression of rrm2b in zebrafish and dose-dependently induced morphological defects. Furthermore, co-injection of human wild-type RRM2B mRNA with MO-e4i4 successfully rescued the developmental defects, whereas co-injection of RRM2B/N221S mRNA with MO-e4i4 did not rescue the developmental defects.
Conclusion:
In conclusion, the functional assay in this study provided the direct evidence proving that the N221S variation is a loss-of-function mutation and plausibly related to the pathogenic developmental defects found in the infants of previous clinical reports.
Insights
Mitochondrial DNA maintenance defects (MDMDs) in children can be severe. This study used zebrafish to show that the RRM2B gene
Area of Science:
- Genetics
- Developmental Biology
- Mitochondrial Biology
Background:
- Mitochondrial DNA maintenance defects (MDMDs) are critical pediatric dysfunctions.
- A severe MDMD patient carried the RRM2B gene's Asn221Ser (N221S) variation.
- The functional nature of the N221S variation remained unproven.
Purpose of the Study:
- To provide direct evidence for the functional nature of the RRM2B N221S variation.
- To investigate the role of RRM2B in developmental defects using a zebrafish model.
Main Methods:
- Utilized zebrafish and morpholino oligomer (MO) knockdown technique.
- Perturbed RRM2B expression using two distinct MOs.
- Co-injected wild-type or N221S mutant RRM2B mRNA to assess rescue of developmental defects.
Main Results:
- Morpholino knockdown of rrm2b in zebrafish induced dose-dependent morphological defects.
- Wild-type RRM2B mRNA rescued developmental defects caused by MO-e4i4.
- N221S mutant RRM2B mRNA failed to rescue these developmental defects.
Conclusions:
- The N221S variation in RRM2B represents a loss-of-function mutation.
- This loss-of-function mutation is plausibly linked to pathogenic developmental defects observed in infants.
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