Similarly, COPB2 gene encoding β'-COPI affects brain development: two siblings suffering from microcephaly, cortical blindness, and developmental delay were found to share a large span (16.8 Mega bases) of homozygosity in chromosome 3, including a rare missense variant in COPB2. Moreover, neurospheres derived from animals with Copb2 variants grew less than control. This evidence concerns the gene COPB2 and microcephaly.