Loss of Macf1 abolishes ciliogenesis and disrupts apicobasal polarity establishment in the retina

Microtubule actin crosslinking factor 1 (Macf1) plays a role in coordinated actions of actin and microtubules in multiple cellular processes. Here we show that Macf1 is also critical for ciliogenesis in multiple cell types. Ablation of Macf1 in the developing retina abolishes ciliogenesis and basal bodies fail to dock to ciliary vesicles or migrate apically. Photoreceptor polarity is randomized while inner retinal cells laminate correctly, suggesting that photoreceptor maturation is guided by polarity cues provided by cilia. Deletion of Macf1 in adult photoreceptors caused reversal of basal body docking and loss of outer segments, reflecting a continuous requirement for Macf1 function. Macf1 was also shown to interact with ciliary proteins Mkks and Talpid3. We propose that a disruption of trafficking across microtubles to actin filaments underlies the ciliogenesis defect in cells lacking Macf1, and that Mkks and Talpid3 are involved in the coordination of microtubule and actin interactions. Overall design: RNA was isolated from confluent mouse embryonic fibroblasts (3 clones per genotype). MEFs where generated from Macf1flox/flox and Macf1flox/+ mice, and immortalized via transfection with the SV40 large T antigen. Cells were grown to 75% confluency and treated with AAV8-CMV-Cre (1.2x10e13vg/ml) overnight. Single cell colonies were generated and recombination for the Macf1 knockout allele (Macf1-/-) and heterozygous control (Macf1-/+) was confirmed by sequencing. Loss of protein expression was confirmed by western blot. Cells were grown to confluency and serum starved on gelatin coated glass coverslips prior to fixing and immunostaining as described for the retina.

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May-Simera HL, Gumerson JD, Gao C, Campos M, Cologna SM, Beyer T, Boldt K, Kaya KD, Patel N, Kretschmer F, Kelley MW, Petralia RS, Davey MG, Li T