Further studies demonstrated that Col3a1 null mutant mice exhibit overmigration of neurons beyond the pial basement membrane and a cobblestone-like cortical malformation similar to the phenotype seen in Gpr56 null mutant mice.
In the second family, the two affected siblings were homozygous for the missense variant c.145C<G, p.(Pro49Ala) of COL3A1 and showed cobblestone-like cortical malformation, cerebellar cysts, and white matter abnormalities, developmental delay, and seizures.