Muscle Genetics

Genetic markers and the evolution of motility

During anthropogenesis, specific marker genes became fixed that directly influenced the development of the muscular apparatus and fine motor skills.

• The FOXP2 gene is critical for word articulation. Its mutations make rapid facial muscle movements impossible, without which modern speech cannot form.
• The HAR2 gene regulates the activity of other genes during the formation of the wrist and thumb. This genetic feature provided human ancestors with unique manual dexterity, enabling the manufacture and use of complex tools.

Genetically determined metabolism

Energy supply for muscle contractions is based on the breakdown of reserve polysaccharide (glycogenolysis) and subsequent carbohydrate oxidation (glycolysis). Glycogen is stored as granules directly within the sarcoplasm of the fibers, forming a tight complex with the enzymes of its synthesis and degradation.

Although the specific concentration of glycogen per 1 gram of tissue is higher in the liver (up to 5–6%), the total mass of skeletal muscle accounts for about 40% of an adult's body weight. As a result, the muscles store twice as much total carbohydrate.

The main genetic feature of muscles is the complete absence of the enzyme glucose-6-phosphatase. As a result, glucose-6-phosphate cannot be dephosphorylated and diffuse into the bloodstream. All muscle glycogen serves as an energy source exclusively for the muscles themselves.

Molecular limitations of anaerobic glycolysis

During intense short-term exertion (sprinting, weightlifting), metabolism switches to anaerobic glycolysis. It generates ATP at a high rate, but has significant biochemical limitations:

1. Low efficiency. Free blood glucose yields only 2 ATP molecules. When utilizing its own glycogen, the yield is 3 ATP (no energy is spent on the hexokinase reaction).
2. Delayed start. The glycolytic pathway reaches maximum power only 10–15 seconds after work begins. In the first seconds, energy supply depends on the phosphagen system (ready reserves of ATP and creatine phosphate).
3. Lactate accumulation. Pyruvate is reduced to lactic acid (lactate). This lowers intracellular pH, inhibits enzymes (e.g., phosphofructokinase), and disrupts the binding of calcium ions to the protein troponin C (troponin C), leading to muscle fatigue.

Viral lesions of the muscular system

Some infections can cause pronounced muscular symptoms. Human herpesvirus type 7 (HHV-7 / HHV-7) is considered a possible etiological factor in chronic fatigue syndrome.

In this pathology, the musculoskeletal system is specifically affected: generalized muscle weakness and migrating pains in muscles (myalgia) and joints (arthralgia) occur. The condition is accompanied by rapid physical exhaustion, sleep disorders, lymphadenopathy, and prolonged low-grade fever.

Class and exam questions

What else to study on this topic

• Molecular markers of anthropogenesis (HAR1, AMY1, ASPM, LCT)
• Mitochondrial DNA and the Y chromosome in the study of human evolution
• Cytogenetic evidence for the fusion of chromosome 2
• Clinical presentation and diagnosis of exanthema subitum
• Oncogenic subtypes of human herpesvirus type 8 (HHV-8)

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.