Nuclear gene mutations as the cause of mitochondrial complex III deficiency
Erika Fernández-Vizarra1, Massimo Zeviani1
1Mitochondrial Biology Unit, Medical Research Council Cambridge, UK.
Insights
Mitochondrial Complex III (CIII) deficiency, a rare oxidative phosphorylation defect, has seen recent breakthroughs. Advances in genetic analysis have identified seven new genes linked to CIII defects, resolving previously unexplained cases.
Area of Science:
- Mitochondrial biology
- Human genetics
- Biochemistry
Background:
- Complex III (CIII) deficiency is a rare cause of mitochondrial disease, impacting oxidative phosphorylation.
- Historically, only three genes (MT-CYB, BCS1L, UQCRB) were linked to CIII defects, leaving many cases unresolved.
- CIII is central to the mitochondrial respiratory chain and metabolic pathways.
Purpose of the Study:
- To review recent strategies for discovering mutations in CIII assembly and activity factors.
- To highlight new genetic discoveries associated with CIII deficiency.
- To present data on LYRM7/MZM1L's role in CIII biogenesis.
Main Methods:
- Review of recent genetic studies and literature.
- Analysis of mutation discovery strategies.
- Functional characterization of CIII assembly factors.
Main Results:
- Seven additional genes have been identified in recent years, significantly expanding the genetic landscape of CIII deficiency.
- New insights into the function of CIII assembly and structural factors have been gained.
- The molecular role of LYRM7/MZM1L as a chaperone in CIII biogenesis is further elucidated.
Conclusions:
- Recent advances in genetic technologies have dramatically improved the diagnosis of Complex III deficiency.
- Understanding the function of novel genes is crucial for resolving unresolved cases and understanding CIII assembly.
- LYRM7/MZM1L plays a key role in the proper formation of Complex III.
Abstract:
Complex III (CIII) deficiency is one of the least common oxidative phosphorylation defects associated to mitochondrial disease. CIII constitutes the center of the mitochondrial respiratory chain, as well as a crossroad for several other metabolic pathways. For more than 10 years, of all the potential candidate genes encoding structural subunits and assembly factors, only three were known to be associated to CIII defects in human pathology. Thus, leaving many of these cases unresolved. These first identified genes were MT-CYB, the only CIII subunit encoded in the mitochondrial DNA; BCS1L, encoding an assembly factor, and UQCRB, a nuclear-encoded structural subunit. Nowadays, thanks to the fast progress that has taken place in the last 3-4 years, pathological changes in seven more genes are known to be associated to these conditions. This review will focus on the strategies that have permitted the latest discovery of mutations in factors that are necessary for a correct CIII assembly and activity, in relation with their function. In addition, new data further establishing the molecular role of LYRM7/MZM1L as a chaperone involved in CIII biogenesis are provided.
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