RTTN and microcephaly: Mutations in numerous centriolar proteins have been linked to microcephaly (Barbelanne and Tsang, 2014; Kaindl et al., 2010), including components involved in centriole elongation such as CPAP (Leal et al., 2003) and RTTN (Care4Rare Canada Consortium et al., 2015; Grandone et al., 2016).