“…In this study, we demonstrate by using MRI that the microcephaly of Trappc9 KO mice has a postnatal onset and is clearly established at weaning age. These findings are in line with TRAPPC9 patient data, which show microcephaly within the first year of life (Amin et al, 2022; Aslanger et al, 2022; Ben Ayed et al, 2021; Bolat et al, 2022; Hnoonual et al, 2019; Koifman et al, 2010; Penon-Portmann et al, 2023; Radenkovic et al, 2022) as well as data from other recently published Trappc9 KO mouse studies, which reported differences at postnatal days 7, 15 and 20, but not at birth (Hu et al, 2023; Ke et al, 2020). Monogenic disorders causing postnatal-onset microcephaly are less common than those causing primary microcephaly, which are mostly due to cell proliferation defects during embryogenesis.…”