Prenylation enzymes HMGR-1, FCE-1, and ICMT-1 polarize towards BM. (A) A schematic diagram showing the mevalonate/HMGR-1 prenylation pathway (see text for detailed description). (B) Left: Sum intensity z-projected images show AC localization and invasive enrichment (arrows) of the endogenously tagged membrane-associated prenylation enzymes mNG::HMGR-1 and mNG::FCE-1, and AC expressed ICMT-1::mScarlet (lin-29p::icmt-1::mScarlet, inset shows spectral fluorescence-intensity map displaying the minimum and maximum pixel value range of the acquired data) from the P6.p 1-cell to 4-cell stages. All the subsequent spectral fluorescence-intensity maps also display the maximum (H) and minimum (L) pixel value range of the acquired data, which was independently determined for each image. Right: Boxplots show the AC basal/apical ratios of mNG::HMGR-1, mNG::FCE-1, and ICMT-1::mScarlet fluorescence intensity ([HMGR-1] n = 12 1-cell, 16 2-cell, 9 2–4-cell, and 11 4-cell stage animals; [FCE-1] n = 9 1-cell, 14 2-cell, 13 2–4-cell, and 16 4-cell stage animals; [ICMT-1] n = 10 1-cell, 15 2-cell, 10 2–4-cell, and 11 4-cell stage animals, **** P ≤ 0.0001, ns [not statistically significant], P > 0.05, Brown-Forsythe and Welch ANOVA tests followed by Dunnett’s T3 multiple comparisons test and Kruskal–Wallis test followed by Dunn’s multiple comparisons test). (C) Top: Single slice confocal images of IMCT-1::mScarlet (magenta), mNG::KDEL (cyan, ER marker) and overlay in the AC show tight overlap of localization of ICMT-1 throughout the ER (white arrows). Bottom: Insets highlight the AC basal ER region and show a puncta of intense IMCT-1 enrichment within the ER (left arrow) and a region of similar intensity to the mNG::KDEL marker (right arrow) (similar localization observed in n = 25/25 animals). All data are from two or more replicates. Scale bars, 5 µm.