PPP1R15B and diabetes mellitus: In humans, a homozygous missense mutation in CReP (R658C) has been found to cause an autosomal recessive condition resulting in multisystem abnormalities: patients present with severe microcephaly, short stature, hypoplastic brainstem and cord, delayed myelination and intellectual disability, pancreatic β-cell failure and diabetes and bone deformities [92,93].