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Figure 2. Localization of targets in unperturbed frog embryos. Polaris: (A) section taken perpendicular to the AV axis in the unfertilized Xenopus egg; (B) section taken parallel to the AV axis in an unfertilized egg; (C) section taken parallel to the AV axis in the fertilized egg; (D) in sections taken perpendicular to the AV axis in the 2-cell embryo, one of the two blastomeres shows strong stain near the cell membrane, although the other blastomere occasionally has some stain as well (E). In the 4-cell embryo, all four blastomeres exhibit cell membrane stain (F). Inversin: (G) section taken along the AV axis in the unfertilized egg; (H) section taken perpendicular to the AV axis in the unfertilized egg; (I) signal is seen in the vegetal cortex in fertilized eggs sectioned parallel to the AV axis, and can be detected in the microtubule organizing center (J; brown stain indicated by the green arrow is pigment brought in by the sperm entry trail); (K) section taken perpendicular to the AV axis at the 4-cell stage; (L) section taken along the AV axis at the 8-cell stage, animal pole is upwards. LRD: (M) section taken along the AV axis of the unfertilized egg; (N) section taken along the AV axis of a fertilized egg; (O) section perpendicular to the AV axis taken close to the animal pole reveals staining throughout one of the two blastomeres. P: sections taken through the equator perpendicular to the AV axis show asymmetric staining near the membrane cortex; (Q) some sections taken perpendicular to the AV axis revealed staining between the blastomeres before the completion of the cleavage furrow; (R) sections parallel to the AV axis reveal a rod of signal from the vegetal pole towards the animal pole, in one of the two blastomeres. KIF3B: (S) section along the AV axis of the unfertilized egg; (T) sectioning perpendicular to the AV axis of the fertilized egg reveals staining in the MTOC at nuclear fusion (brown stain is pigment brought in by the sperm entry trail, green arrowhead). Two-cell embryos sectioned perpendicular to the AV axis exhibit signal in the center (U) or in the membrane cortex (V,W) of one blastomere; (X) sections taken perpendicular to the AV axis at the four-cell stage reveal that staining is often absent from one of the four blastomeres on the right side. Polycystin-2: (Y) sections taken along the AV axis of the unfertilized egg show no signal; (Z) section of fertilized egg taken parallel the AV axis; (Aa) section taken perpendicular to the AV axis at the 2-cell stage; (Ab) section taken parallel to the AV axis at the 2-cell stage; (Ac) section taken across the AV axis at the 4-cell stage. alpha -tubulin: (Ad) antibodies recognizing all tubulin subunits stain throughout the cytoplasm of sections taken across the AV axis of the 2-cell embryo. Acetylated alpha -tubulin: (Ae) sections of fertilized and unfertilized eggs along the AV axis revealed spots of signal at the equator; (Af) sections of 2-cell embryos taken perpendicular to the AV axis revealed signal at the membrane cortex in one of two blastomeres; (Ag) section taken near the animal pole, across the AV axis of the 4-cell embryo. Ah: section taken near the vegetal pole, across the AV axis of the 4-cell embryo. Detyrosinated alpha -tubulin: (Ai) section of an unfertilized egg along the AV axis; (Aj) section taken across the AV axis of embryos at the 4-cell stage; (Ak) sections taken parallel to the AV axis at the 2 cell stage (dashed line indicates embryonic midline); (Al) section taken across the AV axis of a 4-cell embryo. Am: In each panel, yellow ovals with their long axis oriented left to right indicate that the section was taken across the AV axis; yellow ovals with their long axes oriented vertically indicate that the section was taken along the AV axis, with the animal pole being upward. Red arrows, signal; white arrows, lack of signal; green arrows, additional signal. |
