Biallelic mutations in the cyclin-dependent kinase 5 regulatory subunit-associated protein 2 gene CDK5RAP2 cause autosomal recessive primary microcephaly type 3 (MCPH3). MCPH is characterized by intellectual disability and microcephaly at birth, classically without further organ involvement. Only recently, congenital cataracts were reported in four patients of one pedigree with MCPH3. Given the lack of a further pedigree with this phenotype, it remained unclear whether this was a true causal relationship. Here we support the link between CDK5RAP2 and eye development by showing that most Cdk5rap2 mutant mice (an/an) exhibit eye malformations ranging from reduced size of one or both eyes (microphthalmia) to total absence of both eyes (anophthalmia). We also detected increased apoptosis in the an/an retinal progenitor cells associated with more mitotic cells. This indicates an important role of Cdk5rap2 in physiologic eye development.
