Mutations in the IL2RG gene cause approximately 30 percent of severe combined immunodeficiency disorder (SCID) cases in humans. These mutations result in alterations to a protein component of cytokine receptors that are essential for proper development of the immune system. The IL2RG gene is composed of eight exons and contains upstream and downstream sequences that are necessary for proper transcription and translation. Below are some of the mutations observed. For each, explain its likely influence on the IL2RG gene product (assume its length to be 375 amino acids).

Nonsense mutation in a coding region

Key Concepts

Nonsense Mutation

A nonsense mutation is a type of point mutation where a single nucleotide change results in the formation of a premature stop codon in the mRNA sequence. This leads to the truncation of the protein, often resulting in a nonfunctional product. In the context of the IL2RG gene, such a mutation could severely impair the function of the cytokine receptor, disrupting immune system development and contributing to severe combined immunodeficiency disorder (SCID).

Cytokine Receptors

Cytokine receptors are proteins located on the surface of cells that bind to cytokines, which are signaling molecules crucial for immune responses. The IL2RG gene encodes a component of these receptors, and proper functioning is essential for the signaling pathways that regulate immune cell development and activity. Mutations affecting these receptors can lead to impaired immune responses, as seen in SCID cases linked to IL2RG mutations.

Gene Structure and Function

The IL2RG gene consists of eight exons, which are the coding regions that dictate the amino acid sequence of the protein, along with regulatory sequences that control transcription and translation. Understanding the gene's structure is vital for comprehending how mutations can affect the gene product. Disruptions in the gene's coding or regulatory regions can lead to altered protein function, impacting the immune system's development and response.