We ring in #2022 by introducing a new member of the mucin (MUC) family. Say hello to MUC3B that now joins 3 annotated membrane mucin genes in human chr 7q22! biorxiv.org/content/10.110… 🧵👇#mucins #glycotime
1/6: GRCh38 human genome assembly contains 3 membrane mucin genes (MUC3, MUC12 and MUC17) in chr 7q22. This “MUC3 cluster” is flanked by 3 genes ACHE, TRIM56 and SERPINE1. 
2/6: We used ACHE, TRIM56 and SERPINE1 as genetic landmarks to search primate genomes for conserved MUC3 clusters. To our surprise all primates carry 4 MUC genes sandwiched between landmark genes, including a MUC3B gene that we could not find in human GRCh38!
3/6: A large portion of a typical MUC gene consists of repetitive sequences called tandem repeats, which are particularly difficult to sequence with standard methods. We hypothesized that the GRCh38 assembly suffers from significant gaps in MUC gene sequences.
4/6: So we used a recent human T2T-CHM13 assembly to fill the sequence gaps in chr 7q22. Notably, we identified a human MUC3B gene and filled a gap of over 80,000 nucleotide in repetitive exons of other MUC3 cluster genes.
5/6: Finally, we used RNA-seq data and quantitative PCR to measure and validate MUC3B transcripts in human intestine. The related MUC17 mucin acts as a cell-attached barrier that blocks bacterial binding to gut epithelial cells. The function of MUC3B remains to be determined!
6/6: We hope our work facilitates the discovery of disease-associated MUC gene polymorphism, and development of experimental models for studying MUC gene function. With that we welcome MUC3B to the mucin family! 🥳🥳🥳
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