Conservation and evolution of gene coexpression networks in human and chimpanzee brains - PubMed (original) (raw)

Fig. 2.

Modules correspond to functional subdivisions of the brain. (A–G) (Upper) Heat maps depicting expression levels for all genes (rows) in all human and chimpanzee brain regions (columns; black labels are human samples and red are chimpanzee) for each module: turquoise (A), blue (B), brown (C), yellow (D), green (E), red (F), and black (G). Red, increased expression; black, neutral expression; green, decreased expression. (Lower) Barplots of the values of the module eigengene (i.e., the first principal component) derived from singular value decomposition are displayed for each module. Black horizontal lines beneath the barplots denote indicator variables (line = 1, no line = 0). Modules were characterized as follows (Kruskal–Wallis test): cerebellum (1,001 genes, P = 0.00013; A), cortex (360 genes, P = 0.00089; B), cortex (343 genes, P = 0.0000014; C), caudate nucleus (200 genes, P = 0.00013; D), cortex and cerebellum (126 genes, P = 0.003; E), and anterior cingulate cortex and caudate nucleus (122 genes, P = 0.008; F). The black module (G), consisting of 50 genes, is a white matter module as characterized by manual inspection of its constituent genes (see text and Table 1). To assess module conservation between humans and chimpanzees, the Spearman correlations in intramodular connectivity (_k_in) were calculated for each module between the species: r = 0.55 (A), r = 0.30 (B), r = 0.39 (C), r = 0.51 (D), NS (E), r = 0.42 (F), and r = 0.62 (G). All correlations were highly significant (P < 10E-6), with the exception of the green module (P = 0.32). H1, human 1; C1, chimp 1, etc.; Broca, Broca's area; acc, anterior cingulate cortex; prv, primary visual cortex; prf, prefrontal cortex; cn, caudate nucleus; vc, cerebellum; NS, not significant. (H) Upon removal of the cerebellar samples from the dataset, an additional module specific to primary visual cortex was identified (P = 0.0011, Kruskal–Wallis test). The Spearman correlation in _k_in between humans and chimpanzees was 0.54 (P = 1.36E-6).