IMGT Scientific chart

IMGT numbering for coding regions (Overview)

The IMGT numbering for coding regions is used for the description of mutations, allelic polymorphisms and structural data.

L-PART1

The L-PART1 numbering starts with the first nucleotide of the INIT-CODON (initiation codon, usually 'atg').

L-PART2

The L-PART2 numbering starts with the first nucleotide of the first codon which results from the splicing (this nucleotide is the nucleotide "n" of the DONOR_SPLICE n/gt of the L-PART1.

L-REGION

The L-REGION numbering starts with the first nucleotide of the INIT-CODON (initiation codon, usually 'atg').

V-REGION

The V-REGION numbering (for germline sequences) starts with the first nucleotide of the first codon of the V-REGION. The encoded amino acid at position 1 is the one following the proteolytic cleavage site between the leader peptide and the V-REGION.
The delimitations of the FR-IMGT and CDR-IMGT regions and the amino acid positions are according to the IMGT unique numbering for V-REGIONs.

D-REGION

The D-REGION numbering (for germline sequences) starts with the first nucleotide downstream from the 5'D-HEPTAMER.

J-REGION

The J-REGION numbering (for germline sequences) starts with the first nucleotide of the first codon. The 1 (or 2) nucleotide(s) preceding the first codon (if present) are not numbered.

V-J-REGION, V-D-J-REGION

The V-J-REGION and V-D-J-REGION numbering (for rearranged genomic DNA or in cDNA sequences) starts with the first nucleotide of the first codon of the V-REGION, follows the IMGT unique numbering for V-DOMAIN.

C-REGION

The C-REGION numbering starts with the first nucleotide of the first codon which results from the splicing (this nucleotide is the nucleotide "n" of the DONOR-SPLICE n/gt of the germline J-REGION.

Given that the C-REGION may be encoded by several exons and that these exons may encode different structural parts, two kinds of numbering are used:

The IMGT exon numbering. This numbering starts at the first nucleotide of the first codon of each exon (this nucleotide is the nucleotide "n" of the DONOR-SPLICE n/gt of the preceding exon in the case of splicing).
The IMGT exon numbering is used in Alignments of alleles and Tables of alleles.
Click here for a list of the IGH and TR C-REGION individual exons.
The IMGT unique numbering for C-DOMAIN. This numbering is used for each domain with an Ig fold. The IMGT unique numbering for C-DOMAIN is used in Protein displays and Colliers de Perles.