Imaging genetics and the sulcal pits

Pits or sulcal roots are the starting marks of the sulcation process on the brain of foetus which occurs in the third semester of gestation. They have for long been assumed to be under tight genetic control, but this was never quantified. Pits are still visible in adult MR images of the brain and we studied them in the Human Connectome Project twin cohort.

© NeuroSpin/CEA. Figure caption: (a) Deep pits frequency and (b) median DPF of the pits selected as phenotypes in each areal. (c) Heritability and (d) associated –log10(p-values) for all the areals being significant without correction (p < 0.05). The areals which are significant after strict Bonferroni are shown with a color above yellow. Both left and right hemisphere results (a, b, c, d) are presented on the symmetrized (left) template.

In a study published in Cerebral Cortex, Y le Guen, and colleagues from Neurospin/Brainomics estimated the pit depth heritability in various brain regions using the high quality and large sample size of the Human Connectome Project pedigree cohort. Analysis of additive genetic variance indicated that their heritability ranges between 0.2 and 0.5 and displays a regional genetic control with an overall symmetric pattern between hemispheres. However, a noticeable asymmetry of heritability estimates is observed in the superior temporal sulcus and could thus be related to language lateralization. The heritability range estimated in this study reinforces the idea that cortical shape variance is determined primarily by nongenetic factors, which is consistent with the important increase of cortical folding from birth to adult life and thus predominantly constrained by environmental factors. Nevertheless, the genetic cues, implicated with various local levels of heritability in the formation of sulcal pits, play a fundamental role in the normal gyral pattern development. Quantifying their influence and identifying the underlying genetic variants would provide insight into neurodevelopmental disorders.

Le Guen, Y., Auzias, G., Leroy, F., Noulhiane, M., Dehaene-Lambertz, G., Duchesnay, Mangin, J-F., Coulon, O., Frouin, V. (2018). Genetic Influence on the Sulcal Pits: On the Origin of the First Cortical Folds. Cerebral Cortex, 28(6), 1922–1933. http://doi.org/10.1093/cercor/bhx098