Fig. 1. Localization of lch5 cells in normal and vvl mutant embryos. (A-C) Dorsal and lateral PNS clusters visualized by mAb 22C10. Anterior is towards the left and dorsal is upwards in all panels. (A) The lch5 neurons (arrows) of a normal embryo are located in the lateral PNS cluster of abdominal segments A1-A7, and their dendrites point dorsally. The v'ch1 neurons can also be observed in these clusters (arrowheads). In ut^H599 (B) and vvl^GA3 (C) homozygous embryos, the lch5 neurons are often aberrantly positioned (arrows). When associated with the dorsal cluster, the dendrites of lch5 neurons point posteriorly or ventrally (compare A1 segments in A-C). The v'ch1 neuron remains in its normal position (arrowheads). (D-G) lch5 organs in normal (D) and ut^H599 embryos (E-G). Neurons in D and E are labeled with mAb 22C10 (red); ligament, cap and attachment cells are labeled with anti-85E (green). a, attachment cells; c, cap cells; n, neurons; l, ligament cells. Yellow labeling of the ligament cells (D,E) is due to the projection of several focal sections. (D) In a normal embryo, the organ is stretched with the ligament and attachment cells at its ventral and dorsal edges respectively. (E) White arrows indicate misplaced lch5 organs, associated with the ventral part of the dorsal cluster. The organs are collapsed. Note the correct orientation of the dendrites in A2, where the ligament cells (yellow arrow) have descended below the level of the dbd neuron (white line). (F) a85E staining of the segments shown in E. All support cells of the misplaced organs can be detected. The attachment cells are in their normal positions (white arrows). The ligament cells (yellow arrow) and cap cells (green arrow) fail to localize to their correct positions. (G) Occasionally the affected lch5 organs are oriented as thoracic dch3 (compare with T3 in D and F). The arrow indicates the five nuclei of the ligament cells, labeled with anti-REPO (red). (H-J) ato-lacZ embryos stained with anti-ß-GAL (red) and anti-REPO (green), revealing the relative position of the ligament cells in developing lch5 organs. (H) Arrows and arrowhead indicate abdominal and thoracic ligament cells, respectively. Square bracket marks the lch5 cells. In A2 the ligament cells (yellow) are at the dorsal edge of the organ as in T3. In A1 and A3, these cells have already started descending (arrows). (I) An early stage 13 embryo. The ligament cells are assuming a more ventral position relative to the other cells of the organ (arrows). (J) At stage 16, the ligament cells are at their final position at the ventral edge of the lch5 organs (arrows).

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