Jean Brachet Memorial Lecture to the ninth international conference of the International Society of Differentiation: Genomic potential—Acetabularia to mammals
✍ Scribed by Marie A. Di Berardino
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 116 KB
- Volume
- 173
- Category
- Article
- ISSN
- 0021-9541
No coin nor oath required. For personal study only.
✦ Synopsis
It is indeed a distinct honor and pleasure for me to nuclear transplants. Later, Danielli (5,6) and colleagues produced clonal lines of nucleocytoplasmic hy-deliver the 1996 Jean Brachet Memorial Lecture because his research profoundly influenced Develop-brid Amebae to study the relative importance of cytoplasmic inheritance in contrast to nuclear inheritance. mental Biology. Among his prolific and varied investigations extending from oogenesis to organogenesis, Some phenotypic characteristics were found to be controlled exclusively by the nucleus (free amino acid com-Brachet contributed to our knowledge of nucleocytoplasmic interactions in Acetabularia, Ameba, sea ur-position, cytoplasmic crystals, length of cell cycle), whereas several were influenced by both the nucleus chins, and amphibia. It is in the field of nucleocytoplasmic interactions that I have worked and is the subject and the cytoplasm (nuclear diameter, normal shape, resistance to different chemicals, response to different of this paper. Specifically, I shall review the genomic potential of cells revealed through nuclear transplanta-antisera). Nuclear transfers in Ameba combined with autoradiography (7) demonstrated that RNAs are syn-tion experiments in somatic cells of Acetabularia, Ameba, and Stentor, and in the oocytes of Drosophila, thesized in the nucleus and move to the cytoplasm, whereas proteins are synthesized in the cytoplasm. In fish, amphibia, and mammals.
addition, some RNA and protein species shuttle be-ACETABULARIA, AMEBA, AND STENTOR tween the cytoplasm and nucleus, and the cytoplasm exerts a major control on mitosis and DNA synthesis. The first successful recombination of nucleus and cy-Nuclear transplants and grafting experiments in the toplasm was performed by Ha ¨mmerling (1) in the giant unicellular Stentor revealed cytoplasmic inheritance of unicellular green plant, Acetabularia, by means of cortical pattern in the formation of mouthparts (8) and, grafting experiments. The plant consists of three main as in Ameba, the cytoplasm controls macronuclear DNA parts: the rhizoid at the basal end containing the sosynthesis (9). matic nucleus, the stalk, and at the apical end, the
The innovative experiments with unicellular organumbrella expressing the species phenotype. Ha ¨misms, though predating molecular biology, predicted merling (1) found that not only could anucleated fragimportant molecular principles concerning the sites of ments of the stalk regenerate umbrellas, but more sur-RNA and protein synthesis, their translocation within prisingly, fragments farthest removed from the nucleus the cell, and the stability of some RNA species. Equally regenerated the best umbrellas. This finding suggested important, nuclear transfers in unicellular organisms that the stalk contained morphogenetic substances disprovided a conceptual plan for the future analysis of tributed along a linear gradient in which the concentrathe genomic potential of metazoan cells and the cloning tion was lowest at the basal end near the nucleus, and of multicellular organisms. increased toward the apical end near the umbrella. In AMPHIBIA later experiments involving interspecific grafts, Ha ¨mmerling (2) and colleagues showed that the nucleus is Spemann ( 10) proposed that the genomic potential the source of the morphogenetic substances. Subseof amphibian embryonic cells could be determined by quently, Brachet (3, review) and colleagues studied isolating a morula nucleus and introducing it into an RNA and protein synthesis in nucleated and anenucleated egg. He termed this experiment ''fantastiucleated Acetabularia; they concluded that RNA flows cal,'' because at that time it was not technically feasible from the rhizoid's nucleus to the cytoplasm where proto execute the experiment. However, just 14 years later, teins are synthesized and ultimately account for the Briggs and King (11) accomplished the experiment with differentiation of umbrellas.
The unicellular animals, Ameba and Stentor, have been widely used to study nucleocytoplasmic interac-Contract grant sponsor: NIH; Contract grant number: GM23635. tions. Comandon and de Fronbrune (4), the first to