BioSample

Protocols: Cubes were dissected from prefrontal cortex from human, chimpanzee, bonobo and macaque on dry ice aiming for cubes with few curvature to obtain reproducible slicing results. Briefly, the thickness of grey matter at all facets of the cube was measured to obtain a mean gray matter thickness. The mean thickness was divided by 10 to obtain the thickness for each of the segments, whereby each of the segments consisted of several slices at 50 um thickness. Sectioning was performed in a cryostat (Microm, Thermo Fisher), with slices being alternately immersed in Trizol (Invitrogen) for bulk RNA isolation or transferred to a dry tube (low binding) for single nucleus isolation on dry ice. Segments 11 and 12 were collected as well but were considered being derived from white matter of the cortex. Samples were then stored at -80°C until further use. RNA isolation for bulk-RNA Seq was performed using the Direct-zol 96 RNA kit (Zymo Research) and was quantified using Agilent’s Bioanalyzer RNA 6000 Nano and Pico kit. Libraries were prepared using the NEBNext Ultra Low RNA Library Prep Kit (New England Biolabs). Library quantification was performed using Agilent’s Bioanalyzer DNA 1000 chip kit.