Previous studies of the orthologous ODA β-HC in the flagellated unicellular algae Chlamydomonas reinhardtii demonstrated an essential role for flagella movement.3, 43 To determine whether DNAH9 plays a similar role in human respiratory cells, we next investigated motile cilia function and structure in individuals with DNAH9 mutations and we obtained nasal brush biopsies of three individuals: OP-2905 II1, OP-1226 II1, and MS-SI46 II1.