Monoallelic truncation mutations of IFT140 have recently been shown to be associated with mild late-onset polycystic kidney disease,35 whereas the bi-allelic variants are associated with syndromic ciliopathies such as Mainzer-Saldino Syndrome (also known as SRTD9).34 With fluorescence-detection size-exclusion chromatography (FSEC),56 we revealed that IFT140, a core subunit, is not required for IFT-A assembly like IFT139 (Fig. 6b) and IFT-A subcomplex could be purified without IFT140 (Supplementary information, Fig. S9c). Here, TTC21B is linked to ciliopathy.