Other PRRs, such as the RLRs RIG-I and MDA5 (melanoma differentiation-associated protein 5), have also been found on NSCs as part of a defense system against infection by viruses such as Japanese encephalitis and Zika, the latter of which has been associated with dramatically impaired embryonic neurogenesis that culminates in microcephaly [173]. Here, IFIH1 is linked to microcephaly.