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Updated: Jun 17, 2026
Skeletal Muscle Gender Dimorphism from Proteomics
Published on: December 14, 2011
Differential expression of choline kinase isoforms in skeletal muscle explains the phenotypic variability in the
Gengshu Wu1, Roger B Sher, Gregory A Cox
1Group on the Molecular and Cell Biology of Lipids and Department of Biochemistry, University of Alberta, Edmonton, Alberta Canada T6G 2S2.
Abstract:
Choline kinase in mammals is encoded by two genes, Chka and Chkb. Disruption of murine Chka leads to embryonic lethality, whereas a spontaneous genomic deletion in murine Chkb results in neonatal forelimb bone deformity and hindlimb muscular dystrophy. Surprisingly, muscular dystrophy isn't significantly developed in the forelimb. We have investigated the mechanism by which a lack of choline kinase beta, encoded by Chkb, results in minimal muscular dystrophy in forelimbs. We have found that choline kinase beta is the major isoform in hindlimb muscle and contributes more to choline kinase activity, while choline kinase alpha is predominant in forelimb muscle and contributes more to choline kinase activity. Although choline kinase activity is decreased in forelimb muscles of Chkb(-/-) mice, the activity of CTP:phosphocholine cytidylyltransferase is increased, resulting in enhanced phosphatidylcholine biosynthesis. The activity of phosphatidylcholine phospholipase C is up-regulated while the activity of phospholipase A(2) in forelimb muscle is not altered. Regeneration of forelimb muscles of Chkb(-/-) mice is normal when challenged with cardiotoxin. In contrast to hindlimb muscle, mega-mitochondria are not significantly formed in forelimb muscle of Chkb(-/-) mice. We conclude that the relative lack of muscle degeneration in forelimbs of Chkb(-/-) mice is due to abundant choline kinase alpha and the stable homeostasis of phosphatidylcholine.
Insights
Choline kinase beta deficiency causes severe hindlimb muscular dystrophy but mild forelimb effects. This is due to abundant choline kinase alpha in forelimbs, maintaining phosphatidylcholine homeostasis and muscle integrity.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Choline kinase (CK) is crucial for cell membrane synthesis, encoded by Chka and Chkb genes.
- Disruption of Chka causes embryonic lethality; Chkb disruption leads to skeletal and muscle defects.
- Chkb deficiency results in hindlimb muscular dystrophy but surprisingly mild forelimb muscle degeneration.
Purpose of the Study:
- To investigate the mechanism behind the differential impact of Chkb deficiency on forelimb versus hindlimb muscles.
- To understand how choline kinase alpha (Chka) compensates for the lack of choline kinase beta (Chkb) in forelimb muscles.
Main Methods:
- Comparative analysis of choline kinase isoforms (Chka and Chkb) expression and activity in forelimb and hindlimb muscles of Chkb(-/-) mice.
- Assay of phosphatidylcholine biosynthesis pathway enzymes, including CTP:phosphocholine cytidylyltransferase, phospholipase C, and phospholipase A(2).
- Assessment of muscle regeneration capacity and mitochondrial morphology in Chkb(-/-) mice.
Main Results:
- Choline kinase beta is the predominant isoform in hindlimb muscle, while choline kinase alpha dominates in forelimb muscle.
- Despite reduced overall CK activity in forelimb muscles of Chkb(-/-) mice, CTP:phosphocholine cytidylyltransferase activity is upregulated, enhancing phosphatidylcholine synthesis.
- Forelimb muscles show normal regeneration and lack mega-mitochondria formation, unlike hindlimb muscles.
Conclusions:
- The relative preservation of forelimb muscle in Chkb(-/-) mice is attributed to the compensatory upregulation of choline kinase alpha.
- Abundant choline kinase alpha ensures stable phosphatidylcholine homeostasis, protecting forelimb muscles from degeneration.
- Differential expression of CK isoforms dictates tissue-specific susceptibility to Chkb deficiency.
