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"+" or "-" indicates if the gene sequences have been found (+) or not been found (-) transcribed (T) and/or translated into protein (Pr). Arbitrarily that information is shown on the first line of each gene when the data have been confirmed by several studies.

Functionality is shown between parentheses, (F) and (P), when the accession number refers to rearranged genomic DNA or cDNA and the corresponding germline gene has not yet been isolated.
Functionality is shown between brackets, [F] and [P], when the accession number refers to genomic DNA, but not known as being germline or rearranged.

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IMGT gene name IMGT allele name Fct T Pr Positions in the locus IMGT/LIGM-DB reference sequences IMGT/LIGM-DB sequences from the literature
Strain Clone names Exons Accession numbers Positions in the sequence Secondary accession numbers Strain Clone names Accession numbers Positions in the sequence
IGHM1 IGHM1*01 (F) IgM-A CH1 AF228580 [1] c (s)
CH2 AF228580 [1] c (s)
CH3 (1) AF228580 [1] c (s)
CH4 (1) AF228580 [1] c (s)
M1 (1)
M2
IGHM2 IGHM2*01 (F) IgM-B CH1 AF228581 [1] c (s)
CH2 AF228581 [1] c (s)
CH3 (1) AF228581 [1] c (s)
CH4 (1) AF228581 [1] c (s)
M1 (1)
M2

c: cDNA sequence.
(s): transcript of a secreted chain.

IMGT notes:
  1. (1) As in other Teleostei, CH3 is spliced to CH4 in secretory mu cDNA, whereas it is probably spliced to the M1 exon in membrane mu cDNA.
IMGT references:
  1. [1] Hordvik I. et al., Mol. Immunol., 39, 313-321 (2002). PMID: 12220889
See also (IMGT Scientific chart):