Differentially Expressed Genes.

A total of 6216 or 31.4% of gene symbols represented on the Affymetrix mouse array displayed expression changes in at least one pairwise comparison. All percentages displayed here are based on this total 6216 gene count. For both forelimbs (FL) and hindlimbs (HL) at each time point the number of up-regulated (>2X) and down-regulated (<2X) genes in relationship to whole embryo total RNA levels are indicated. Gene cohorts relevant to particular developmental stages were determined by comparing up-regulated genes between pairs of successive time points; genes exclusively up-regulated at each of the two time points considered (i.e., down-regulated or unchanged at the other) are indicated for each comparison (E9.5 vs E10.5; E10.5 vs E11.5; E11.5 vs E12.5 and E12.5 vs E13.5). Genes up-regulated only at one particular time point were identified by comparing the genes up-regulated at a given limb stage with those up-regulated at any other stage.