A molecule in teleost fish, related with human MHC-encoded G6F, has a cytoplasmic tail with ITAM and marks the surface of thrombocytes and in some fishes also of erythrocytes.
In teleost fish, a novel gene G6F-like was identified, encoding a type I transmembrane molecule with four extracellular Ig-like domains and a cytoplasmic tail with putative tyrosine phosphorylation motifs including YxN and an immunoreceptor tyrosine-based activation motif (ITAM). G6F-like maps to a teleost genomic region where stretches corresponding to human chromosomes 6p (with the MHC), 12p (with CD4 and LAG-3), and 19q are tightly linked. This genomic organization resembles the ancestral "Ur-MHC" proposed for the jawed vertebrate ancestor. The deduced G6F-like molecule shows sequence similarity with members of the CD4/LAG-3 family and with the human major histocompatibility complex-encoded thrombocyte marker G6F. Despite some differences in molecular organization, teleost G6F-like and tetrapod G6F seem orthologous as they map to similar genomic location, share typical motifs in transmembrane and cytoplasmic regions, and are both expressed by thrombocytes/platelets. In the crucian carps goldfish (Carassius auratus auratus) and ginbuna (Carassius auratus langsdorfii), G6F-like was found expressed not only by thrombocytes but also by erythrocytes, supporting that erythroid and thromboid cells in teleost fish form a hematopoietic lineage like they do in mammals. The ITAM-bearing of G6F-like suggests that the molecule plays an important role in cell activation, and G6F-like expression by erythrocytes suggests that these cells have functional overlap potential with thrombocytes.
Ohashi
Ken
K
Department of Veterinary Medicine, Nihon University, Fujisawa, Kanagawa, Japan.
Takizawa
Fumio
F
Tokumaru
Norihiro
N
Nakayasu
Chihaya
C
Toda
Hideaki
H
Fischer
Uwe
U
Moritomo
Tadaaki
T
Hashimoto
Keiichiro
K
Nakanishi
Teruyuki
T
Dijkstra
Johannes Martinus
JM
D000595:Amino Acid Sequence; D000818:Animals; D001792:Blood Platelets / Q000276:immunology; D002874:Chromosome Mapping; D004912:Erythrocytes / Q000276:immunology; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D005399:Fishes / Q000235:genetics* / Q000276:immunology*; D050982:GATA1 Transcription Factor / Q000235:genetics; D015870:Gene Expression; D006054:Goldfish / Q000235:genetics / Q000276:immunology; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry / Q000235:genetics*; D008285:Major Histocompatibility Complex; D008969:Molecular Sequence Data; D050983:NF-E2 Transcription Factor / Q000235:genetics; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000276:immunology; D009990:Oryzias / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D029941:Fish Proteins; D050982:GATA1 Transcription Factor; D007136:Immunoglobulins; C477999:LY6G6F protein, human; D050983:NF-E2 Transcription Factor