Gene Regulation and Thalassemia Study Notes

Learning Objectives

  • Recognize gene expression alterations in genetic diseases.

  • Predict various mechanisms that regulate gene expression.

Gene Regulation Techniques

Northern Blot Analysis

  • Purpose: Detect levels of mRNA, aiding the understanding of gene regulation.

  • Definition: Northern Blotting is a technique used to visualize specific RNA sequences, specifically mRNA.

Steps in Northern Blotting

  1. Isolation of mRNAs:

    • mRNAs are extracted from the specific cells of interest and then run on a gel.

    • All mRNA present in the cell will be portrayed on the gel.

  2. Transfer to Membrane:

    • The mRNAs from the gel are transferred onto a membrane utilizing capillary action.

  3. Probe Hybridization:

    • The membrane is incubated with a labeled probe designed to bind specifically to the target mRNA.

    • The probe can be radioactively labeled or labeled with other methods for visualization.

  4. Visualization:

    • The membrane is exposed to X-ray film, where the radioactive probe creates a dark spot representative of the bound mRNA.

Probe Information

  • Labeled Probe: Radioactively labeled DNA or RNA that hybridizes to complementary mRNA.

  • Unlabeled mRNA Sample: The sample without any label necessary for target visualization, analyzed comparing to labeled probe results.

Applications of Northern Blot Analysis

  • Used to determine if an mRNA is expressed in specific tissues.

    • Example: Measuring the expression of specific mRNA across various tissues such as muscle, liver, small intestine, brain, and white adipose tissue.

  • Close examination of band intensity (thickness) and location on gel provides information about the amount of mRNA present in a sample, though sequencing is required for exact sequences.

Comparison to Modern Techniques

  • RNA Sequencing (RNAseq):

    • A modern technique that allows high-throughput and unbiased transcriptome profiling.

    • Capable of revealing sequence, abundance, splice variants, and novel transcripts.

    • Can detect single-nucleotide variants and editing events.

Case Study: Hemoglobin and Thalassemia

Overview of Thalassemia

  • Thalassemia is characterized as a genetic blood disorder resulting from either inadequate levels or structural abnormalities of the alpha or beta subunits of hemoglobin.

  • Function of Hemoglobin: It binds to and transports oxygen from the lungs to various tissues via blood circulation.

  • Hemoglobin Protein Composition: A tetramer comprised of two alpha and two beta globin polypeptides.

Symptoms of Thalassemia

  • Common Symptoms:

    • Anemia

    • Weakness

    • Poor growth

    • Enlarged liver and spleen

    • Bone deformities

Treatment Options for Thalassemia

  • Blood Transfusion: Management of anemia and blood level requirements.

  • Iron Chelation Therapy: Treatment to reduce iron buildup from repeated transfusions.

  • Cures:

    • Stem cell transplantation.

    • Gene therapy as a potentially curative option.

Activity Section: Analyze Northern Blot Results

Activity Questions

  1. Conduct analysis for patients 1-3 on Northern blot results and propose
    a. A potential mutation location and type which could lead to observed results.
    b. Proposed mutation types for patient 4, possibly leading to their results.
    c. For patient 5:
    i. If patient 5 has normal β globin mRNA levels but a non-functional protein, propose likely mutation type.
    ii. If patient 5 has reduced amounts of β globin protein, propose likely mutation type.
    iii. If patient 5 shows normal mRNA expression yet decreasing protein, analyze potential mutation type causing rapid degradation.

Question Analysis Activities

  • Propose mutations related to patient analyses leading to β thalassemia in case study patient 4:
    A) Nonsense mutation
    B) Frameshift mutation
    C) Missense mutation
    D) Mutation creating an alternate splice site

Mutation Impact Question

  • Identify the likely mutation causing rapid protein degradation:
    A) A stop codon
    B) A mutation in the 5’ UTR
    C) A mutation in the 3’ UTR
    D) A missense mutation resulting in a misfolded protein