Deasey, S., Grichenko, O., Du, S., and Nurminskaya, M. (2012) Characterization of the transglutaminase gene family in zebrafish and in vivo analysis of transglutaminase-dependent bone mineralization. Amino Acids. 42(2-3):1065-1075.
We have characterized the protein cross-linking enzyme transglutaminase (TGs) genes in zebrafish, Danio rerio, based on the analysis of their genomic organization and phylogenetics. Thirteen zebrafish TG genes (zTGs) have been identified,
of which 11 show high homology to only 3 mammalian enzymes: TG1, TG2 and FXIIIa. No zebrafish homologues were identified for mammalian TGs 3-7. Real-time PCR analysis demonstrated distinct temporal expression
profiles for zTGs in larvae and adult fish. Analysis by in situ hybridization revealed restricted expression of zTG2b and
zFXIIIa in skeletal elements, resembling expression of their mammalian homologues in osteo-chondrogenic cells. Mammalian TG2
and FXIIIa have been implicated in promoting osteoblast differentiation and bone mineralization in vitro, however, mouse models
lacking either gene have no skeletal phenotype likely due to a compensation effect. We show in this study that mineralization
of the newly formed vertebrae is significantly reduced in fish grown for 5 days in the presence of TG inhibitor KCC-009 added
at 3–5 days post fertilization. This treatment reduces average vertebrae mineralization by 30%, with complete inhibition in
some fish, and no effect on the overall growth and vertebrae number. This is the first in vivo demonstration of the crucial
requirement for the TG-catalyzed cross-linking activity in bone mineralization.