Restoring de novo coenzyme Q biosynthesis in Caenorhabditis elegans coq-3 mutants yields profound rescue compared to exogenous coenzyme Q supplementation

Abstract

Coenzyme Q (ubiquinone or Q) is an essential lipid component of the mitochondrial electron transport chain. In Caenorhabditis elegans Q biosynthesis involves at least nine steps, including the hydroxylation of the hydroquinone ring by CLK-1 and two O-methylation steps mediated by COQ-3. We characterize two C. elegans coq-3 deletion mutants, and show that while each has defects in Q synthesis, their phenotypes are distinct. First generation homozygous coq-3(ok506) mutants are fertile when fed the standard lab diet of Q-replete OP50 E. coli, but their second generation homozygous progeny do not reproduce. In contrast, the coq-3(qm188) deletion mutant remains sterile when fed Q-replete OP50. Quantitative PCR analyses suggest that the longer qm188 deletion may alter expression of the flanking nuo-3 and gdi-1 genes, located 5′ and 3′, respectively of coq-3 within an operon. We surmise that variable expression of nuo-3, a subunit of complex I, or of gdi-1, a guanine nucleotide dissociation inhibitor, may act in combination with defects in Q biosynthesis to produce a more severe phenotype. The phenotypes of both coq-3 mutants are more drastic as compared to the C. elegans clk-1 mutants. When fed OP50, clk-1 mutants reproduce for many generations, but show reduced fertility, slow behaviors, and enhanced life span. The coq-3 and clk-1 mutants all show arrested development and are sterile when fed the Q-deficient E. coli strain GD1 (harboring a mutation in the ubiG gene). However, unlike clk-1 mutant worms, neither coq-3 mutant strain responded to dietary supplementation with purified exogenous Q10. Here we show that the Q9 content can be determined in lipid extracts from just 200 individual worms, enabling the determination of Q content in the coq-3 mutants unable to reproduce. An extra-chromosomal array expressing wild-type C. elegans coq-3 rescued fertility of both coq-3 mutants and partially restored steady-state levels of COQ-3 polypeptide and Q9 content, indicating that primary defect in both is limited to coq-3. The limited response of the coq-3 mutants to dietary supplementation with Q provides a powerful model to probe the effectiveness of exogenous Q supplementation as compared to restoration of de novo Q biosynthesis.

Invertebrate Models for Coenzyme Q₁₀ Deficiency

“…Similarly to clk-1 mutants, coq-1, coq-2, or coq-3 mutant worms fed with a diet containing the CoQ-defective bacteria GD1 failed in larval development. However, if this diet was supplemented with NovaSOL ® Q10, about 30% of the clk-1 larvae completed development, although no rescue was achieved for any coq-1, coq-2, or coq-3 mutants [Gomez et al, 2012]. Nevertheless, a full rescue of the coq-3 mutant phenotype was achieved by an extra-chromosomal array containing the own C. elegans coq-3 gene despite the phenotypic disparity shown by coq-3(qm188) and coq-3(ok506) strains [Gomez et al, 2012].…”

“…However, if this diet was supplemented with NovaSOL ® Q10, about 30% of the clk-1 larvae completed development, although no rescue was achieved for any coq-1, coq-2, or coq-3 mutants [Gomez et al, 2012]. Nevertheless, a full rescue of the coq-3 mutant phenotype was achieved by an extra-chromosomal array containing the own C. elegans coq-3 gene despite the phenotypic disparity shown by coq-3(qm188) and coq-3(ok506) strains [Gomez et al, 2012]. Both transgenic worms showed a dramatic rescue, illustrating the crucial role the endogenous synthesized CoQ 9 isoform plays in fertility and development.…”

“…elegans harboring partial deletions of the coq-3 gene show a more diverse phenotype: coq-3(qm188) mutants do not develop reproductive organs and subsequently become sterile [Hihi et al, 2002], whereas coq-3(ok506) mutants retain fertility for the first generation, although only a small fraction of the second generation survives into adulthood [Gomez et al, 2012].…”

“…One third of the coq-3(ok506) larvae developed if fed with OP50 bacteria, although no successful development was achieved in the coq-3(qm188) strain [Gomez et al, 2012]. Similarly to clk-1 mutants, coq-1, coq-2, or coq-3 mutant worms fed with a diet containing the CoQ-defective bacteria GD1 failed in larval development.…”

Electrochemical Investigation of Coenzyme Q10 on Silver Electrode in Ethanol Aqueous Solution and Its Determination Using Differential Pulse Voltammetry

“…[1][2][3][4] CoQ 10 is the most common coenzyme Q in animals and coexists with its reduced form (CoQ 10 H 2 or ubiquinol-10) that is the predominant form in the tissues of living beings (Fig. 1A).…”