MYD88 Gene

The MYD88 gene (MYD88 stands for "Innate Immune Signal Transduction Adaptor") is a protein coding gene located at chromosome 3p22.2. Alternative splicing results in multiple transcript variants.

The MYD88 gene encodes a cytosolic adaptor protein that plays a central role in innate and adaptive immune responses . The encoded protein consists of an N-terminal death domain and a C-terminal Toll interleukin-1 receptor domain. It functions as an essential signal transducer in the interleukin-1 and Toll-like receptor signaling pathways. These pathways regulate the activation of numerous proinflammatory genes.

Specifically, the adapter protein acts through IRAK1, IRAK2, IRF7, and TRAF6, leading to NF-kappa-B activation, cytokine secretion, and inflammatory response. It increases IL-8 transcription and participates in IL-18-mediated signaling.

Furthermore, the protein activates IRF1, leading to its rapid migration into the nucleus to cause efficient induction of IFN-beta, NOS2/INOS, and IL12A genes. Upon TLR8 activation by GU-rich single-stranded RNA (GU-rich RNA) derived from viruses such as SARS-CoV-2, SARS-CoV, and HIV-1, it induces the release of IL1B by activating the NLRP3 inflammasome. MyD88-mediated signaling in intestinal epithelial cells is critical for maintaining intestinal homeostasis and controls the expression of the antimicrobial lectin REG3G in the small intestine.

Patients with defects in the MYD88 gene have an increased susceptibility to pyogenic bacterial infections.

Diseases associated with MYD88 include:

• Immunodeficiency 68
• Macroglobulinemia, Waldenström 1 (Familial Waldenström's disease).

1. Braggio E et al (2009) Identification of copy number abnormalities and inactivating mutations in two negative regulators of nuclear factor-kappa-B signaling pathways in Waldenstrom's macroglobulinemia. Cancer Res 69: 3579-3588.
2. Conway DH et al (2010) Myeloid differentiation primary response gene 88 (MyD88) deficiency in a large kindred. (Letter) J Allergy Clin Immun 126: 172-175.
3. Kyle RA et al (2003) Long-term follow-up of IgM monoclonal gammopathy of undetermined significance. Blood 102: 3759-3764.
4. McMaster ML et al (2006) Genomewide linkage screen for Waldenstrom macroglobulinemia susceptibility loci in high-risk families. Am J Hum Genet 79: 695-701.
5. Picard C et al (2010) Clinical features and outcome of patients with IRAK-4 and MyD88 deficiency. Medicine 89: 403-425.
6. Platt CD et al (2019) A novel truncating mutation in MYD88 in a patient with BCG adenitis, neutropenia and delayed umbilical cord separation. Clin Immun 207: 40-42.