Subtle asymmetry of gene expression in embryonic and foetal human brains

Note: this project is a combination of the data deposited here in GEO and data made available by HDBR in ArrayExpress under E-MTAB-4840. Summary: Brain asymmetry in humans, both structurally and functionally, is observed very early during development, and is important for healthy development. Using RNA sequencing, we investigated gene expression profiles of left and right sides of various brain structures in human foetuses aged 5 to 13 weeks post conception. All brain structures showed significant differences between the expression profiles of left and right sides. The differences partly correlated with gene expression changes with age, suggesting left/right differences in maturation rate. In particular on the faster side (right for cerebral cortex, left for all other investigated tissues), different tissues were lateralised for tissue-specific processes. In the youngest forebrain (5.5 weeks), KCTD12, SNAI1 and GATA1 were significantly right-lateralised. SNAI1 is involved in visceral asymmetry in vertebrates, and KCTD12 is important in lateralisation of fish brains. In the youngest midbrain, SOX1 was significantly left-lateralised. For the part of the project for which data are deposited here, six human embryos in Carnegie stage 15 or 16 were studied. Left and right side of the midbrain and left and right side of the forebrain were dissected, and RNA sequenced. Differential expression analysis per tissue to find left/right differences (paired analysis by embryo).