Transient expression of transglutaminase C during prenatal development of human muscles.

Tissue transglutaminase (TGase C, TGase II) is known to participate in cellular processes during morphogenesis, differentiation, and development of various prenatal tissues and organs. The expression of TGase C during myoblast proliferation and attachment to external laminae was examined by immunohistochemical (IH) localization at 5-12 weeks of developmental stages of prenatal human muscle in 23 embryos. IH detection using a monospecific antibody to TGase C showed a prominent expression of TGase C in muscle cells as stage- and spatial-specific patterns during an early embryonal period. The myoblasts of intervertebral, tongue, and limb muscles, attached to adjacent cartilaginous skeletons or fibrous fascia, showed a pronounced expression of TGase C at 5-6, 6-7, and 7-8 weeks after fertilization, respectively. The most intense activity of TGase C was observed in some cardiac myoblasts infiltrating into endocardial mesenchyme at 6-7 weeks after fertilization. Although weak staining was detected until 14 weeks after fertilization, the level of TGase C expression in all muscles was significantly decreased after 6-7 weeks, with the exception that the smooth muscle cells of blood vessels and gastrointestinal tract showed diffusely intense staining of TGase C between 5 and 12 weeks after fertilization. Western blotting analysis of the cellular extracts of pooled samples showed a single strong band at 80 kD at 6 weeks after fertilization. This band became weaker after 8-10 weeks of prenatal development. These findings of transient expression of TGase C, which coincides with the development of myoblast anchoring and differentiation, suggest that TGase C plays a role in myoblast attachment to the extracellular laminae during the early embryonal period.