BUTYROPHILIN, SUBFAMILY 2, MEMBER A1; BTN2A1

Alternative titles; symbols

• BT2.1
• BTF1

HGNC Approved Gene Symbol: BTN2A1

Cytogenetic location: 6p22.2 Genomic coordinates (GRCh38): 6:26,457,954-26,476,621 (from NCBI)

▼ Description
The butyrophilin (BTN) genes are a group of major histocompatibility complex (MHC)-associated genes that encode type I membrane proteins with 2 extracellular immunoglobulin (Ig) domains and an intracellular B30.2 (PRYSPRY) domain. Three subfamilies of human BTN genes are located in the MHC class I region: the single-copy BTN1A1 gene (601610) and the BTN2 (e.g., BTN2A1) and BTN3 (e.g., BNT3A1; 613593) genes, which have undergone tandem duplication, resulting in 3 copies of each (summary by Smith et al., 2010).

▼ Cloning and Expression
By genomic sequence analysis, RT-PCR of peripheral blood leukocytes and human cell lines, and 3-prime RACE of a fetal tissue cDNA library, Rhodes et al. (2001) cloned BTN2A1. They also identified alternative splicing affecting the 3-prime end of BTN2A1. Immunofluorescence microscopy showed surface expression of BTN2A1 in transfected HeLa and Chinese hamster ovary cells.

▼ Gene Function
Rigau et al. (2020) identified BTN2A1 as a key ligand that binds to the V-gamma-9-positive TCR-gamma chain (see 615454). BTN2A1 associates with another butyrophilin, BTN3A1 (613593), and these act together to initiate responses to phosphoantigens. Furthermore, binding of a second ligand, possibly BTN3A1, to a separate TCR domain incorporating Vdelta2 is also required.

▼ Gene Structure
Rhodes et al. (2001) determined that the BTN2A1 gene spans approximately 12 kb and contains 7 coding exons.

▼ Mapping
By genomic sequence analysis, Rhodes et al. (2001) mapped the BTN2A1 gene within the BTN gene cluster on chromosome 6p22.1. The BTN gene cluster is located about 4 Mb telomeric to the classical MHC class I genes.