Functional Genomics of Exercise

Introduction to Functional Genomics of Exercise

  • Speaker: Emmeline Hill
  • Purpose: To provide an overview of how functional genomics and specifically transcriptomics are used to study molecular interactions in muscles in response to exercise in horses.

Key Concepts in Functional Genomics

  • Functional Genomics: Field of molecular biology focused on describing gene functions and interactions through transcriptomics data.
  • Transcriptomics: Study of the complete set of RNA molecules produced by a cell or group of cells at a given moment.
  • RNA Sequencing (RNA Seq): A technology used in transcriptomics to enable detailed analysis of gene expression.

Gene Expression

  • Gene Expression: The process by which specific genes are activated and produce their corresponding proteins; crucial for cellular control over structure and function.
  • Genome Definition: The total complement of genetic material in a cell's nucleus, consisting of approximately 3 billion base pairs in horses and around 24,000-25,000 protein-coding genes.
  • Conservation of Genome: Nearly all cells in an organism share the same genome, except for germ cells, though not all genes are expressed simultaneously.
  • Gene Expression Variability: Typically, 3-5% of genes are expressed in a mammalian cell at any given time, differing among cell types due to their specialized functions.

Regulation of Gene Expression

  • Importance of Gene Expression Regulation: Affects cell adaptability to stimuli and environmental changes, determining the phenotype.
  • Central Dogma of Molecular Biology:
    • DNA (blueprint) RNA (precursor) Protein (phenotype).
    • DNA sequence remains unchanged, but gene activity varies across different cells and conditions.
    • mRNA (messenger RNA): The primary type of RNA measured to estimate gene expression levels.

Transcriptome vs. Genome

  • Transcriptome: Dynamic collection of all RNA molecules in a cell, capable of changing in response to environmental stimuli.
  • Other omics fields related to transcriptomics:
    • Proteome: Total protein expression at a specific time.
    • Metabolome: Collection of metabolites within a biological sample.

Skeletal Muscle Responses to Exercise

  • Known adaptations from different types of exercise:
    • Endurance Exercise: Increases mitochondrial biogenesis, ATP generation, improved oxidative efficiency, structural development.
    • Resistance Exercise: Leads to muscle hypertrophy, enhanced protein turnover, reliance on creatine phosphate pathway and glycogenolysis.

Molecular Mechanisms and Experimental Design

  • Investigating differences in gene activity between resting skeletal muscle and exercised state.
  • Experimental design considerations:
    • Treatment Groups: Comparing untrained and trained states.
    • Controlling Non-experimental Factors: Breed, age, sex, time of day, and feeding regime impacts must be controlled.

Candidate Gene Studies and Microarrays

  • Initial studies utilized Candidate Gene Approach: Focused on pre-identified genes via quantitative real-time PCR.
  • Transitioned to Microarrays: Allowed assessment of thousands of genes simultaneously.
    • Developed by labeling resting and exercised RNA samples with different fluorescent dyes and comparing hybridization results on arrays.

RNA Sequencing Advancements

  • RNA Seq: Current gold standard for comprehensive gene expression analysis.
    • Provides detailed transcript profiles and identifies differentially expressed genes in response to exercise.
  • Cost Reduction: Significant decrease in sequencing costs from millions to hundreds of dollars.

Longitudinal Studies on Training Responses

  • Investigating effects of repeated exercise on gene expression:
    • Hypothesized that gene expression does not fully revert to baseline post-exercise but rather primes muscle for future bouts.
    • Collected data post-training period using RNA sequencing technology.
    • Identified important adaptations including differential gene expression results, particularly the myostatin gene.

Myostatin and Training Response

  • Key findings on myostatin gene response show it acts as a negative regulator of muscle development.
  • Notable effects in relation to horse genotype and training responses are documented.

Conclusion and Implications of Functional Genomics

  • Functional Genomics Goals: Understanding dynamic gene expression and interactions within biological systems for phenotype determination.
  • Importance of deciphering Causation versus mere association in genetic studies.
  • Exploration of regulatory regions and transcription binding sites as major contributors to phenotypic expressions in response to exercise and training stimuli.

References for Further Reading

  • Recommendations for searching through PubMed for related studies using keywords: "gene + expression + equine + exercise".