The developmental expression of taxon-specific crystallins in the duck lens

The three crystallins, alpha B-crystallin, tau-crystallin/alpha-enolase and epsilon-crystallin/lactate dehydrogenase B are all stress induced proteins and may thus share common regulatory elements. However, no evidence was found for coordinate expression of these three genes during duck lens development. The alpha B- and alpha-enolase/tau-crystallin mRNAs accumulate with similar kinetics between day 12 and day 24 of embryonic development but differ in their epithelial versus fibre cell location; the LDH-B/epsilon-crystallin transcript shares its preferential location in the fibre cell with alpha B-crystallin but differs in its developmental pattern of expression. The accumulation of LDH-B/epsilon-crystallin mRNA in heart and lens followed a similar developmental pattern. In contrast, the alpha-enolase/tau-crystallin mRNA level in heart decreases while the level in lens rises. The LDH-B gene is used as a crystallin gene in duck but not in chicken. This species-specific difference may correlate with the difference in LDH-B activity between various chicken and duck tissues: the retina and pancreas in duck have significantly higher LDH-B activity than in chick, while heart, muscle, stomach, liver, intestine and kidney all have much higher LDH-B activity in chicken than in duck.