We found that, in both general population cohorts, polygenic-based prediction of LIMK1 expression in the cortex was very strongly dependent on haplotype group in a manner that echoed the situation in Williams syndrome itself [52]: the Hap1 group (with reduced IPS gray matter) had lower estimated expression scores (p = 10−15 for the NIMH group, p = 10−23 for the PNC group) than the Hap2 group (see Fig. 4). Here, LIMK1 is linked to Williams syndrome.