Does ADP‐Ribosylation of Proteins in Nuclei Contribute to Ectoderm Cell Differentiation in Sea Urchin Embryos?

Abstract

In nuclei of sea urchin embryos, marked increase in ADP-ribosyltransferase activity followed by its decrease occurrs in the pre-hatching and post-hatching periods with peaks of activity at the morula and gastrula stages. Increase in its activity was blocked by cycloheximide in the pre-and post-hatching periods and by actinomycin D only in the post-hatching period. Embryo wall cells (ectoderm cells) isolated from gastrulae exhibited markedly higher activity of this enzyme than archenteron cells and mesenchyme cells. Probably, the increase in the activity of this enzyme in the post-hatching period results from expression of the gene for this enzyme mainly in ectoderm cells. In the post-hatching period, the activity increased more in animalized embryos than in normal ones, and increased little in vegetalized embryos. 3-Aminobenzamide (3-ABA), as well as luminol and nicotinamide, inhibited formation of ectoderm structures more than that of endoderm structures, such as the archenteron, in normal and animalized embryos, but had no appreciable effect on morphogenesis in vegetalized embryos. The reaction catalyzed by ADP-ribosyltransferase probably contributes to ectoderm cell differentiation. Treatment of embryos with 3-ABA in the pre-hatching period had little inhibitory effect on the morphogenesis in the post-hatching period, though it caused death of many embryos. introductiontion more than endoderm cell differentiation.

Proteins ADP‐ribosylated in Nuclei and Plasma Membrane Vesicles Isolated from Sea Urchin Embryos at Various Stages of Early Development

“…Almost the same change as above in the rate of ADP-ribosylation has been found in the posthatching period, in which the rate is maximal in the late gastrula stage (24 hr after fertilization). These observations are consistent with those reported previously (1 5, 16). The rate of ADP-ribosylation did not change so much in the histone fraction of nuclei incubated with [aden~sine-'~C]NAD as in their acid-insoluble protein fraction during early development (shown by a dashed line in Fig.…”

“…In the present study, we confirmed that ADPribosylation of proteins occurs in the plasma membrane fraction (1 7) and the nuclear fraction isolated from sea urchin embryos (15,16). We also found that scarcely any ADP-ribosylation of proteins occurs in mitochondria, microsome vesicles or the soluble fraction.…”

“…Previously, we reported that ADP-ribosylation of proteins in nuclei isolated from sea urchin .embryos increases during development between the time of fertilization and the morula stage and decreases thereafter in the pre-hatching period (15,16). In the post-hatching period, the rate of ADP-ribosylation increases again between the mesenchyme blastula and the gastrula stage (1 5, 16).…”

ADP‐Ribosylation of Histones in Nuclei Isolated from Embryos of the Sea Urchin, Hemicentrotus pulcherrimus

“…2). It has been demonstrated that the rate of protein ADP-ribosylation in the precipitate obtained by adding trichloroacetic acid to the suspension of nuclei is higher than that in the histone fraction at all stages examined (9), and is also markedly higher at the morula and the gastrula stages than at the swimming blastula stage (10). The rate of ADP-ribosylation of histones seems to alter during early development in a manner different from that of other nuclear proteins in the TCA-insoluble fraction.…”

“…Recently, we reported that ADP-ribosylation of proteins in sea urchin embryos occurs in nuclear fractions (9,10) and plasma membrane fractions (8,10) but is not detectable in mitochondria, microsome vesicles or the soluble fraction (10). In sea urchin embryos, the rate of ADP-ribosylation in the plasma membrane fraction is quite low compared to that in the nuclear fraction (10).…”