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Phenotypes

Mouse phenotype:

increased heart weight, increased circulating bilirubin level

Subcellular localization

Ciliary associated gene, Nucleoplasm, Plasma membrane, Cytosol

Functional category

• Non-motile cilium / primary cilium
• Signaling (Hedgehog
• GPCRs
• ion channels)

Function

Protein kinase TAOK2 and phosphatase PPP4C were found to regulate primary cilia length. NPCs lacking TAOK2 exhibited elongated cilia, aberrant IFT88 and pericentrin (PCNT) accumulation, and were impaired in sonic hedgehog (SHH) signaling. These findings implicate aberrant cilia length in the pathophysiology of 16p11.2 copy number variation and establish TAOK2 kinase as a regulator of primary cilium length. We found that shRNA against TAOK2 (mean = 5.43 μm, n = 26 NPCs, SEM = 0.32) and PPP4C (mean = 4.35 μm, n = 27 NPCs, SEM = 0.27) significantly increased cilia length compared to control shRNA (mean = 3.43 μm, n = 29 NPCs, SEM = 0.15) in WTC11-derived NPCs (Figures 3B and 3C). Similarly, in the RMK0119b-derived NPCs, shRNA against TAOK2 (mean = 4.82 μm, n = 24 NPCs, SEM = 0.25) and PPP4C (mean = 4.60 μm, n = 16 NPCs, SEM = 0.43) significantly increased the cilia length compared to control shRNA (mean = 3.21 μm, n = 19 NPCs, SEM = 0.19) (Figure 3D). Next, we tested in an overexpression screen, the impact of increased gene expression on cilia length. Briefly, we generated mammalian expression vector with a BFP-tag inserted at the N-terminal of TAOK2 and PPP4C along with six other genes in the 16p11.2 locus. NPCs derived from WTC11 line were transfected with either control-BFP construct or constructs expressing the 16p11.2 genes, starved for 24 h, and immunostained with ARL13B antibody 48 h after transfection (Figure 3E). Overexpression of TAOK2 had the strongest effect in decreasing cilia length (mean = 1.66 μm, n = 25 NPCs, SEM = 0.08), followed by PPP4C (mean = 2.39 μm, n = 19 NPCs, SEM = 0.15), while control (mean = 3.19 μm, n = 22 NPCs, SEM = 0.16) and none of the other six 16p11.2 genes had a significant effect on cilia length (Figure 3F). Therefore, gene dosage of TAOK2, and to a lesser extent PPP4C, drives opposing cilia length changes in NPCs derived from 16p11.2 CNV carriers(40882641).