Alterations in the relative amounts of specific mRNA species in the developing human brain in Down's syndrome

Abstract

Total cellular polyadenylated RNA [poly(A)+ RNA] was prepared after guanidinium thiocyanate extraction of frozen brain tissue from age-matched normal and Down'ssyndrome (trisomy 21) human foetuses. Poly(A)+ RNA populations were analysed by translation in vitro, followed by two-dimensional gel analysis by using both isoelectric focusing (ISODALT system) and non-equilibrium pH-gradient electrophoresis (BASODALT system) as the first-dimension separation. The relative concentrations of poly(A)+ RNA species coding for seven translation products were significantly altered in Down's syndrome, as determined by both visual comparisons of translation-product fluorograms from normal and Down's-syndrome samples and by quantitative radioactivity determination of individual translation products. The relative concentrations of mRNA species coding for two proteins (68 kDa and 49 kDa) were increased in Down's syndrome and may represent genes located on chromosome 21. The relative concentrations of mRNA species coding for five proteins (37 kDa, 35 kDa, 25.5 kDa, 24.5 kDa, 23 kDa) were decreased in Down's syndrome, these probably representing secondary effects of the trisomy. Six Down'ssyndrome-linked translation products (49 kDa, 37 kDa, 33 kDa, 25.5 kDa, 24.5 kDa, 23 kDa) did not migrate with appreciable amounts of cellular proteins on two-dimensional gels and hence may represent either proteins of high turnover rates or those that are post-translationally modified in vivo. One translation product (68 kDa) comigrated with a major cellular protein species, which was identified as a 68 kDa microtubule-associated protein by limited peptide mapping. The significance of these changes is discussed in relation to the mechanisms whereby the Down's-syndrome phenotype is expressed in the human brain.

The Mouse Brain Transcriptome by SAGE: Differences in Gene Expression between P30 Brains of the Partial Trisomy 16 Mouse Model of Down Syndrome (Ts65Dn) and Normals

“…Several studies have been undertaken to analyze possible alterations of mRNA or protein levels caused by the presence of an additional set of HC21 genes (Weil and Epstein 1979;Van Keuren et al 1982;Whatley et al 1984); however, the precise molecular mechanism that is responsible for the development and maintenance of the complex DS phenotypes remains unclear. The generally accepted working hypothesis is that HC21 contains a certain number of genes that, if present in three copies, will contribute to the DS phenotypes.…”

The characterization of an acidic calmodulin-binding protein in brain cytoskeleton and membrane fractions

“…As noted above, previous work Whatley et al, 1984) showed that the microtubules contain relatively large amounts of the 68K 5.6 protein, which is purified by phosphocellulose chromatography in t (a) 6.0 pH 5.1 the microtubule-associated protein fraction. We also analysed proteins in intermediate-filament preparations by two-dimensional gel electrophoresis, as shown in Fig.…”

“…In the rat, the 68K 5.6 protein is synthesized in the retinal ganglion cells and conveyed down the optic nerve in the slow phase of axonal transport; this protein is also synthesized by glia in the optic-nerve sheath (Strocchi et al, 1984). The 68K 5.6 protein was also found to co-purify with microtubules and microtubule-associated proteins Whatley et al, 1984). In studies of cell-free translation from brain polyribosomes, the 68K 5.6 protein was found to be synthesized exclusively on the free polyribosome population, as are the major cytoskeletal proteins, including tubulin subunits, actin and the neurofilament proteins (Strocchi et al, 1982;Gilbert & Strocchi, 1983).…”

“…The 68K 5.6 protein has been shown to be a microtubule-associated protein, on the basis of its purification properties, Mr, pl and peptide map Whatley et al, 1984). Sobue et al (1981) had identified a group of calmodulinbinding proteins of Mr 55000-62000 in microtubule preparations, and presented evidence that these proteins were tau factors.…”

Dosage effects on gene expression in a maize ploidy series

“…T HE gene dosage changes affecting structural gene expression have been studied in several species including human, mouse, Drosophila and plants (BIRCHLER 1979(BIRCHLER , 1981BIRCHLER and NEWTON 1981;WHATLEY et al 1984;EPSTEIN 1986;REICHERT 1986; DEV- LIN et al 1988;BIRCHLER et al 1990;GUO and BIRCHLER 1994). Changes in dosage include an aneuploid series in which a chromosome or chromosomal segment is added or subtracted relative to the genomic complement or a ploidy series where a complete genomic increment is increased or decreased.…”