For example, mutations in the gene encoding CReP, a constitutively expressed phosphatase that dephosphorylates phospho-eIF2α in unstressed conditions and during acute ER stress (Jousse et al. 2003), cause developmental delays in white matter myelination in addition to microcephaly, short stature and learning disability (Kernohan et al. 2015). The gene discussed is PPP1R15B; the disease is microcephaly.