DNA SIZE: 4545 bp DNA linear (hg38), plus strand.
This gene has 13 transcripts (splice variants), 202 orthologues, no paralogues and it is associated with 77 phenotypes.
It starts at 38138661 and ends at 38143021 bp from pter. (according to hg38-Dec_2013).
Chr 3 (hg38), Starts at 38138661 and ends at 38143022 bp from pter.              https://www.ncbi.nlm.nih.gov/genome/gdv/browser/gene/?id=4615

Figure 1. MYD88 gene.

MyD88, Myeloid differentiation primary response protein, is an adapter protein with a crucial role in the innate and adaptive immune response. This protein regulates the activation of numerous proinflammatory genes acting as an essential signal transducer in the interleukin-1 and Toll-like receptor signaling pathways.
https://www.proteinatlas.org/ENSG00000172936-MYD88                               

MyD88 is composed by 296 amino acid and its molecular mass is 33233 Da.                                                  https://www.genecards.org/cgi-bin/carddisp.pl?gene=MYD88#proteins

The quaternary structure consists in an homodimer. MyD88 also forms heterodimers with MyD88 adapte-like (Mal), also termed TIRAP, which connect MyD88 to the receptor complex for TLR-2 and TLR4 signaling in response to bacterial infections. ¹

In human, MyD88 is characterized by a ubiquitous expression in appendix (RPKM 32.5), bone marrow (RPKM 32.2) and 25 other tissues including adrenal, brain, colon, duodenum, endometrium, esophagus, fat, gall bladder, heart, kidney, liver, lung, lymph node, ovary, pancreas, placenta, prostate, salivary gland, skin, small intestine, spleen, stomach, testis, thyroid, urinary bladder.
https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=DetailsSearch&Term=4615#gene-expression

Figure 2. Bulk tissue gene expression for MyD88.                                                                            https://www.gtexportal.org/home/gene/MYD88

MyD88 is mainly localizated in the cytoplasm (cytosol, mithocondria and vesicles) and nucleus.                          https://www.genecards.org/cgi-bin/carddisp.pl?gene=MYD88#localization

Interacting with transcriptional repressors as LRRFIP1 and LRRFIP2 (Leucine-rich repeat flightless-interacting protein 1 and 2), MyD88 positively regulates Toll-like receptor (TLR) signaling in response to agonist by competing with the negative FLII (Flightless-I) regulator for MyD88-binding.                                                                      https://www.ebi.ac.uk/interpro/entry/InterPro/IPR019139/

It has also an influence on the interleukins, increasing IL-8 transcription ² and being involved in IL-18-mediated signaling pathway. Activating IRF1 allows its rapid migration into the nucleus to mediate the induction of IFN-beta, NOS2/INOS, and IL12A genes. ³
It interacts with many receptors and regulatory factors such as bone marrow tyrosine kinase on chromosome X (BMX), interleukin 1 receptor-like 1 (IL1RL1) against Helicobacter pylori infection ⁴, and a serine/threonine protein kinase (IKBKE), that belongs to the IKK family. ⁵
It induces IL1B release through NLRP3 inflammasome activation 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. ³
IL1B treatment allows the formation of a complex with PELI1, IRAK1, IRAK4 and TRAF6 leading to NF-kappa-B activation with the recruitment of MAP3K7/TAK1, TAB1 and TAB2, cytokine secretion and the inflammatory response. ^6-8 The complex formation can be blocked through the binding of SMAD6 to PELI1 negatively regulating IL1R-TLR signaling and eventually NF-kappa-B-mediated gene expression. MyD88 may also interact with Phosphoinositide-3-Kinase Adaptor Protein 1 (PIK3AP1). This protein has a direct interaction via TIR domain with DHX9 (via H2A and OB-fold regions). ⁹
It directly interacts with OTUD4 deubiquitinase. ¹⁰
In case of microbial infection, interacts with uropathogenic E. Coli protein TcpC or uropathogenic E. Faecalis protein TcpF suppressing Toll-like receptor (TLR)-mediated cytokine production.                                                            https://www.genecards.org/cgi-bin/carddisp.pl?gene=MYD88#proteins

MyD88 has also a role in the maintenance of gut homeostasis and in the control of the expression of the antimicrobial lectin REG3G in the small intestine (By similarity).

Figure 3. MyD88-dependent TLR/IL-1R signaling.

Figure 4. String Interaction Network for MyD88.                                                                                                          https://www.genecards.org/cgi-bin/carddisp.pl?gene=MYD88

The MYD88 gene is conserved in chimpanzee, Rhesus monkey, dog, cow, mouse, rat, chicken, zebrafish, mosquito and frog.
https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=DetailsSearch&Term=4615

In the first report of MYD88 L265P somatic mutation in IgM-associated light-chain amyloidosis has been demonstrated that this mutation, which lead to constitutive activation of the nuclear factor kB pathway, was oncogenically active in 29% of patients with activated B-cell type diffuse large B-cell lymphoma. ¹¹ The substitution of leucine by proline at position 265 (L265P) is the most common somatic variant of MYD88 mutation ¹¹ because of a single nucleotide change (T→C) in chromosome 3p22.2. ¹² This mutation was detected in 86% to 100% of patients with WM or lymphoplasmacytic lymphoma, ^12,13 at a lower frequency in patients with IgM MGUS, from 10% to 87%, ^12,14 in a percentage ranging from 36% to 38% as regards primary central nervous system lymphoma; ^15,16 6% to 21% of splenic marginal zone lymphoma, ^13,14,17 a lower percentage, 9%, of gastric mucosa associated lymphoid tissue lymphomas, and in 2.9% to 4% of the patients with chronic lymphocytic leukemia. ^17,18

Figure 5. The most common somatic variant of MYD88 mutation is the substitution of leucine by proline at position 265 (L265P). 

Germline loss-of-function mutations in MYD88 lead to immunodeficiency with recurrent pyogenic infections. ¹⁹
Somatic gain-of-function mutations contribute to certain B cell malignancies. ^11,12,18