Activity of rRNA genes in cells of a patient with Down syndrome mosaic

Nucleolus organizing region (NOR) activity in seven probands with Down syndrome due to a de novo (21 ;21) trans-location and their parents was analyzed on the basis of total Ag-NOR size per cell, mean Ag-NOR size per cell (X_c), mean Ag-NOR size per acrocentic (X_a), and the characteristic Ag-NOR number of each subject. The results showed intercellular variations in total Ag-NOR size per cell in all subjects, as well as interindividual variations in mean Ag-NOR size per cell. When the subjects were grouped according to their characteristic Ag-NOR number and the mean Ag-NOR size per cell for each group (GX_c) and the mean Ag-NOR size per acrocentric for each group (GXJ were calculated, a number of interesting and significant correlations were found: (1) GX_c correlated perfectly with the group’s characteristic Ag-NOR number, (2) GX_a varied inversely with the group’s characteristic Ag-NOR number, and (3) GX_c and GX_a varied inversely with each other. These results suggest that if the Ag-NOR number of a cell decreases, the total NOR activity of the cell also decreases, but the NOR activity of its chromosomes increases. This finding supports the existence of a compensatory mechanism that regulates NOR activity on the cellular level.

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“…1979: Zankl andNagl. 1980): the results of others do not (Wegner et al, 1980;Jotterand-Bellomoand van Melle. 1981: Nikolis el al.. 1981 …”

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confidence: 99%

Evidence for a compensatory mechanism regulating Ag-NOR activity in families with de novo 21;21 translocation Down syndrome

Nikoliš

Kekić²

1988

Cytogenet Genome Res

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Down syndrome—a disruption of homeostasis

1983

Am. J. Med. Genet.

272

139

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A major question in human genetics concerns the relationship between the extra chromosome material in the Down syndrome (DS) and its effects. It is suggested here that a generalized disruption of evolved genetic balance in cells of affected individuals leads to decreased developmental and physiological buffering against genetic and environmental forces. Examples of consequences in DS of this model of disruption of homeostasis are presented: i) increased variance for metric traits, ii) amplified instability of developmental pathways, iii) reduced precision of physiological homeostatic controls, and iv) generalized increased morbidity. Evolution has selected for interacting systems. When this evolved balance is disrupted, as in autosomal aneuploidy, the organism is generally disrupted. The model emphasizes the role of environment in producing much of the DS phenotype. Traits less buffered than others in the general population are the ones most disturbed in DS and account for much of the DS phenotype.

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Progress in visualization of eukaryotic gene transcription

Trendelenburg

1983

Hum Genet

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Methods for visualization of the ultrastructure of transcriptionally active eukaryotic genes have been developed using chromatin from giant nuclei of amphibian oocytes (Miller and Beatty 1969). Rapidly isolated chromatin is subjected to low salt treatment in order to dissociate most chromatin associated proteins. As a result, gene-chromatin with associated RNA polymerase particles and RNA transcripts can be directly analysed in electron microscope chromatin spread preparations. More recently, progress has been made in utilising living amphibian oocyte nuclei as a transcription system for cloned eukaryotic genes. In this article, an account of such experiments is given, with emphasis on results and problems of chromatin and transcription organization of microinjected cloned genes. The described transcription assay system possesses important potential for investigation of gene mutations and in particular for the elucidation of molecular aspects of experimental oncology and molecular human genetics.

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Activity of rRNA genes in cells of a patient with Down syndrome mosaic

Cited by 7 publications

References 17 publications

Evidence for a compensatory mechanism regulating Ag-NOR activity in families with de novo 21;21 translocation Down syndrome

Evidence for a compensatory mechanism regulating Ag-NOR activity in families with de novo 21;21 translocation Down syndrome

Down syndrome—a disruption of homeostasis

Progress in visualization of eukaryotic gene transcription

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