No abstract

Investigations into the genetic basis of neuronal damage following spinal cord injury have thus far been limited to the acute phase after the injury. Using microarray analysis, the present study compared the spinal-cord-injury-induced gene expression changes in adult rats at the epicenter and rostral segments of spinal cord at acute (12 h) and delayed (42 days) time points. We have previously reported that the acute response to spinal cord injury involves alterations in genes responsible for inflammation, cell cycle alteration, and altered receptor function. In contrast, the delayed response includes changes in the expression of HSP27, MAG, MAP-2, IGF-1 and ApoE. The alteration in expression of these genes suggests an ongoing repair process in animals whose functional recovery has reached a plateau.

No abstract

The sex-linked gene, brindled, in the mouse produces a coat-colour variegation in heterozygous females. There is much individual variation in the relative areas of mutant and wild-type colour, but it was not known if any of this variation was genetic. The main object, when the experiments were started, was to test the simple expectation of the Lyon hypothesis, that if X-inactivation is random the variegation should not be modifiable by selection. On the assumption that the variegation is due to X-chromosome inactivation, modification by selection would show that the inactivation process, or some property of the derived cell populations, is under genetic control. Heterozygous females were accordingly selected for the area of coat showing the mutant colour. Selection based on individual phenotypes was ineffective, but four cycles of reciprocal recurrent selection based on progeny-means produced a 'High' line with 64% mutant area and a ' Low' line with 30 % mutant area, from a base population with 53 % mutant area. Autosomal modifiers were not responsible for the response; the difference between the selected lines was entirely due to properties of the X chromosomes carrying the brindled gene. The changed properties of the X chromosomes were not restricted to the locus of brindled, but extended at least as far as the locus of tabby. The chromosomes carrying the wild-type allele of brindled were not altered by the selection, but normal X chromosomes from other strains affected the degree of variegation. It was concluded that the difference between the selected lines was due either to non-random inactivation or to somatic cell selection. It was not possible to distinguish between these two mechanisms. The results obtained in these experiments with a structurally normal X chromosome were in all essentials similar to those obtained by Cattanach with his X-autosome translocation.