Gene expression in sexually dimorphic muscles in sheep

Area of Science:

• Animal Science
• Molecular Biology
• Genetics

Background:

• Testosterone exhibits region-specific effects on skeletal muscle.
• Insulin-like growth factor I (IGF-I), androgen receptor (AR), and myostatin are key genes involved in regulating skeletal muscle mass and growth.
• Differential gene expression may explain variations in muscle development.

Purpose of the Study:

• To quantify and compare the expression of IGF-I, AR, and myostatin mRNA in two distinct sheep skeletal muscles: splenius and semitendinosus.
• To investigate the role of these genes in mediating testosterone's differential effects on muscle growth.

Main Methods:

• Gene expression analysis using quantitative reverse-transcription-polymerase chain reaction (RT-PCR) for IGF-I.
• Gene expression analysis using ribonuclease protection assay (RPA) with standard curves for AR and myostatin.
• Extraction and measurement of total RNA from semitendinosus and splenius muscles of eleven post-pubertal Dorset rams.

Main Results:

• Significantly higher mRNA levels of IGF-I and AR were observed in the splenius muscle compared to the semitendinosus muscle.
• No significant difference in myostatin mRNA levels was found between the two muscles.
• Mean values (attomoles/µg RNA) for splenius vs. semitendinosus were: IGF-I (1.39 vs. 1.02), AR (4.05 vs. 2.96), and myostatin (4.30 vs. 3.85).

Conclusions:

• Local IGF-I production and androgen receptor (AR) expression regulation are likely crucial for sexually dimorphic muscle growth patterns in sheep.
• The differential expression of IGF-I and AR contributes to regional variations in skeletal muscle development.
• Myostatin's role in differential muscle growth between these specific regions requires further investigation.