SPEF2 and primary ciliary dyskinesia: Genes containing deleterious variants of potential clinical significance identified here included: SPEF2 previously implicated in primary ciliary dyskinesia [101] and vestibular stereocilia function [102], HOMER2 a stereociliary scaffolding protein, essential for normal hearing and vestibular function in humans and mice [103, 104] and PCDH15 implicated in Usher syndrome in humans and balance disorders and deafness in mice [105].