Ma. Wride et al., DISTRIBUTION OF TNF-ALPHA-LIKE PROTEINS CORRELATES WITH SOME REGIONS OF PROGRAMMED CELL-DEATH IN THE CHICK-EMBRYO, The International journal of developmental biology, 38(4), 1994, pp. 673-682
Early chick embryos have previously been shown to express tumor necros
is factor-alpha-cross-reactive proteins (TNF alpha-CRPs) in a developm
entally regulated manner, thus implicating these proteins in programme
d cell death and in tissue remodeling. In this study, cells undergoing
DNA fragmentation have been identified, using terminal deoxynucleotid
e transferase (TdT) mediated dUTP-biotin nick-end-labeling (TUNEL), du
ring the embryonic development of the chick, between stages 18 and 29.
DNA fragmentation is indicative of cells undergoing programmed cell d
eath. TUNEL-positive cells were identified in several well documented
areas of programmed cell death, including the limb buds, the heart, sp
inal motoneurons, dorsal root ganglia, and the ventral horn of the neu
ral tube. In addition, other areas of cell death were identified inclu
ding the floor plate a nd the mesonephros. In several locations, a clo
se correlation was noted between the presence of TUNEL-positive cells
and regions of TNF alpha-immunoreactivity. These regions included the
ventral horn and marginal zone of the neural tube, spinal motoneurons,
paravertebral ganglia, parts of the myotome, mesenchyme of the body w
all, and the mesonephros. In addition, using the TNF alpha-sensitive L
929-8 bioassay it was shown that homogenate of stage 18 chick embryos
is cytotoxic to L929-8 cells and that this toxicity can be reduced usi
ng neutralizing antibodies to mouse TNF alpha. This bioassay allowed u
s to estimate the mean concentration of TNF alpha-like activity in emb
ryo homogenate, which is within the range of physiological (pg/ml) lev
els of TNF alpha found in other systems. These results suggest that pr
oteins with TNF alpha-like activity may have a role in programmed cell
death in some tissues during early chick embryo development.