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First published online September 30, 2004
doi: 10.1242/10.1242/dev.01371

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Developmental architecture of adult-specific lineages in the ventral CNS of Drosophila

¹ Department of Biology, University of Washington, Seattle, WA 98195, USA
² School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK

View larger version (123K): [in a new window]   Fig. 1. Features of the Neurotactin-positive bundles in the thoracic CNS of larval Drosophila. (A) A thick transverse projection of the bundles in one thoracic neuromere. Brackets show the levels of the dorsal (D), intermediate (I) and ventral (V) commissures; VA, ventral arch; tinted region highlights the right ventrolateral (VL) neuropil. (B) Schematic representation of a cross section through the neuropil, showing positions of the commissures, ventrolateral neuropil and dorsal longitudinal tracts (DT). (C,D) Dorsal views of confocal sections through the VL neuropils in T2 and T3 of a nervous system immunostained for (left) Neurotactin (magenta) and with phalloidin (green). Phalloidin staining shows the fine fibrous neuropil characteristic of the VL neuropil, which contains a poorly stained core, the lateral cylinder (LC), that is bounded by the Neurotactin bundles 9i and 1c (right). Several bundles ascend through the cylinder. (E-I) Paired images of thick stack projections of the T2 and T3 neuropils from the levels indicated on (A). The lineage bundles are labeled on the negative version (right panel); the next ventral section is also included as a `ghost' to aid in alignment of the bundles. Brackets show the anterior (aD) and posterior (pD) dorsal commissures, the anterior (aI) and posterior (pI) intermediate commissures, and the anterior ventral (aV) commissure.

View larger version (119K): [in a new window]   Fig. 2. Characteristics of median neuroblast lineage (lineage 0). (A) A thick section projection of confocal slices showing the Neurotactin scaffold between the ventral and intermediate commissures. The neurite bundle from lineage 0 projects to the level of the aI commissure up through T2, but is redirected to the pI commissure in T1. Posterior ventral arch (pVA) is labeled in T3 but is also present in T2 and T1. `0' identifies the ventral base of bundle 0 in each segment. (B-D) Ventral views of projections of full lineage 0 clones in the (B) S3, (C) T1 and (D) T3 neuromeres. Diagrams show the trajectory of the neurite bundle in the Neurotactin scaffold, and the position of the lineage 0 cluster relative to the other clusters in the hemisegmental array. Commissure abbreviations as in Fig. 1

View larger version (119K): [in a new window]   Fig. 3. Characteristics of lineage 1 (NB1-2). (A) Dorsal view of the projection of a lineage 1 clone in T3. (B,C) Thick section projections showing the relationship of the neurite bundles from lineage 1 to features of the Neurotactin scaffold (red) in the ventral neuropil. The contralateral bundle (1c) projects to the contralateral ventrolateral neuropil, whereas the ipsilateral bundle (1i) projects to the ventrolateral neuropil in T2. Progressively ventral sections. (D) Lineage 1 in T1 lacks the anterior 1i bundle. (E) Lineage 1 in A1 lacks the 1c bundle. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (82K): [in a new window]   Fig. 4. Characteristics of lineage 2 (NB 2-1). (A) Ventral view of the projection of paired lineage 2 clones in the T2. (B-D) Thick section projections showing the relationship of the clone to (B) dorsal, (C) intermediate and (D) ventral features of the Neurotactin scaffold (red). Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (99K): [in a new window]   Fig. 5. Characteristics of lineage 3 (NB 7-1). (A,B) Thick section projections showing the relationship of the neurite bundles of lineage 3 clone from C to (A) dorsal and (B) ventral features of the Neurotactin scaffold (red). (C) Ventral view of the projection of a lineage 3 clones in the T3. (D) The intermediate to dorsal region of lineage 3 in T2, showing the expanded 3id bundle. (E) A1 version of lineage 3 lacking the 3il bundle. (F) An Actin-GAL4 based MARCM clone of lineage 3 showing larval neurons as well as the adult-specific cells. The neurons with bright cell bodies are four of the `U' motoneurons made by NB 7-1. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (79K): [in a new window]   Fig. 6. Characteristics of lineage 4 (NB 3-1). (A) Ventral view of the projection of a lineage 4 clone. (B-D) Thick section projections showing the relationship of the neurite bundle from lineage 4 to features of the Neurotactin scaffold (red) in the ventral neuropil. (B-D) Progressively ventral slices. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (128K): [in a new window]   Fig. 7. Characteristics of lineage 5. (A) Ventral view of the projection of a lineage 5 MARCM clone in T1. (B-D) Thick section projections showing the relationship of the neurite bundle from lineage 5 to features of the Neurotactin scaffold (red) in intermediate and ventral neuropils. Progressively ventral slices. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (126K): [in a new window]   Fig. 8. Characteristics of lineage 6 (NB 5-2). (A) Ventral view of the projection of lineage 6 MARCM clones in T3 and A1. (B-E) Thick section projections showing the relationship of the neurite bundles from lineage 6 to features of the Neurotactin scaffold (red). The relationship of the bundles to structures in the (B) dorsal, (C,D) intermediate and (E) ventral neuropils. In the thorax, bundle 6cm forms the middle bundle of the posterior ventral arch and then projects anteriorly in a dorsal tract; bundle 6cd forms the pD commissure. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (107K): [in a new window]   Fig. 9. Characteristics of lineage 7 (NB 3-3). (A) Ventral view of the projection of lineage 7 MARCM clones from the T2 and T3 neuromeres. (B) Lineage 7 clone from A1. (C,D) Thick section projections showing the relationship of the neurite bundle from lineage 7 to features of the Neurotactin scaffold (red) in the (C) intermediate and (D) ventral neuropils. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (62K): [in a new window]   Fig. 10. Characteristics of lineage 8. (A) Ventral view of the projection of a lineage 8 clone. (B,C) Thick section projections showing the relationship of the neurite bundles from lineage 8 to features of the Neurotactin scaffold (red) in (B) intermediate and (C) ventral neuropils. Bundle 8c is one of the 3 paired bundles that constitute the aI commissure; bundle 8i projects to the most dorsal regions of the ventrolateral neuropil. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (112K): [in a new window]   Fig. 11. Characteristics of lineage 9. (A) Ventral view of the projection of MARCM clones of lineage 9 in the T2 and T3 neuromeres. (B) Lineage 9 clone from A1. (C) A thick section projection of confocal slices showing the ventral commissures in T3-A3. In T3, the bundle is the thinnest of the four paired bundles that constitute the aV commissure; it is the only aV bundle that is found in the abdominal segments. (D-F) Thick section projections showing the relationship of the neurite bundles from lineage 9 to features of the Neurotactin scaffold (red) in intermediate (D,E) and ventral (F) neuropils. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (115K): [in a new window]   Fig. 12. Characteristics of lineage 10. (A) Ventral view of the projection of a lineage 10 clone. (B,C) Thick section projections showing the relationship of the neurite bundle from lineage 10 to features of the Neurotactin scaffold (red) in (B) intermediate and (C) ventral neuropils. Bundle 10c is the only bundle of the anterior ventral arch. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1; VA, ventral arch.

View larger version (134K): [in a new window]   Fig. 13. Characteristics of lineage 11. (A) A thick section projection of confocal slices showing a ventral view of the Neurotactin scaffold at the level of the intermediate commissures; brackets identify the pI commissures. The stubby projection of neurite bundle 11im is present in T1 and T2 but absent from T3. (B) Ventral view of the projection a MARCM clone of lineage 11. (C-E) Thick section projections showing the relationship of the neurite bundles from lineage 11 to features of the Neurotactin scaffold (red) in (C) dorsal and (D,E) intermediate neuropils. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (120K): [in a new window]   Fig. 14. Characteristics of lineage 12 (NB 6-1). (A) Ventral view of the projection of a MARCM clone of lineage 12 in T3; the 12i bundles are absent. (B) Lineage 12 clone from T1. (C-F) Thick section projections showing the relationship of the neurite bundle from lineage 12 to features of the Neurotactin scaffold (red) in (C) dorsal, (D,E) intermediate and (F) ventral neuropils. Bundle 12c is the posterior bundle of the posterior ventral arch; the 12i bundle bifurcates with sub-bundles going to intermediate (12im) and dorsal (12id) positions. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (104K): [in a new window]   Fig. 15. Characteristics of lineage 13 (NB 3-4 or 4-4). (A) Ventral view of the projection of a MARCM clone of lineage 13. (B-D) Thick section projections showing the relationship of the neurite bundles from lineage 13 to features of the Neurotactin scaffold (red) in ventral neuropil. (B-D) Successively ventral sections. Bundle 13c is one of four paired bundles in the aV tract; bundle 13i projects to the anterior ventrolateral neuropil. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (74K): [in a new window]   Fig. 16. Characteristics of lineage 14 (NB 4-1). (A) Ventral view of the projection of a MARCM clone of lineage 14. (B,C) Thick section projections showing the relationship of the neurite bundles from lineage 14 to features of the Neurotactin scaffold (red) in ventral neuropil. Successively ventral sections. Bundle 14c is one of four paired bundles in the aV tract. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (92K): [in a new window]   Fig. 17. Characteristics of lineage 15. (A) Ventral view of the projection of a MARCM clone of lineage 15. (B,C) Thick section projections showing the relationship of the neurite bundles from lineage 15 to features of the Neurotactin scaffold (red) in (B) intermediate and (C) ventral neuropils. All of the bundle 15 axons project into the periphery. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (115K): [in a new window]   Fig. 18. Characteristics of lineage 16. (A) Ventral view of the projection of a MARCM clone of lineage 16. (B-E) Thick section projections showing the relationship of the neurite bundles from lineage 16 to features of the Neurotactin scaffold (red) in intermediate (B,C) and ventral (D,E) neuropils. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (133K): [in a new window]   Fig. 19. Characteristics of lineage 17. (A) Ventral view of the projection of a MARCM clone of lineage 17 in A1. (B,C) Thick section projections showing the relationship of the neurite bundles from lineage 17 to features of the Neurotactin scaffold (red) in intermediate neuropil (successively ventral sections). (D) Ventral projection of lineage 17 clone in T2. In both A1 and the thoracic neuromeres, the neurite bundle abruptly hooks dorsally before it reaches the midline. (E) A thick transverse projection of the right hemineuropil showing the characteristic recurved bundle from lineage 17. Arrowhead denotes the midline. (F) A ventral view of a thick section of the Neurotactin scaffold showing a bundle 17 in A1, T3 and T2 but missing from T1. Numbers identify neurite bundles from other lineages; VA, ventral arch. Diagrams as in Fig. 2. D, dorsal commissure; I, intermediate commissures.

View larger version (145K): [in a new window]   Fig. 20. Characteristics of lineage 18. (A) Ventral view of the projection of a MARCM clone of lineage 18 in T2. (B) A mid-sagittal section through the dorsal (Dor), intermediate (Inter) and ventral (Vent) commissural bundles in T1-A1. The neurite bundles for lineages 18 and 10 make up the region of the aI commissure immediately anterior to the ascending bundles from lineage 2. Bundle 18 is absent from T1 whereas bundle 10 is absent in A1. (C) A ventral view of a thick section of the Neurotactin scaffold at the level of the intermediate commissures. There is no lineage 18 bundle in the aI commissure in T1, whereas it is present in the corresponding commissure in posterior neuromeres (brackets). Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2.

View larger version (119K): [in a new window]   Fig. 21. Characteristics of lineage 19 (NB 7-4). (A) Ventral view of the projection of a lineage 19 MARCM clones from T1; inset is a more ventral slice showing bundle 19i. (B) Lineage 19 from T3 showing the contralateral (19c) and ipsilateral (19i) bundles. (C-E) Thick section projections showing the relationship of the neurite bundles from lineage 19 to features of the Neurotactin scaffold (red) in intermediate (C,D) and ventral (E) neuropils. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (125K): [in a new window]   Fig. 22. Characteristics of lineage 20 (NB 5-4). (A) Ventral view of the projection of a MARCM clone of lineage 20. (B-D) Thick section projections showing the relationship of the neurite bundles from lineage 20 to features of the Neurotactin scaffold (red) in intermediate (B) and ventral (C,D) neuropil. Bundle 20 converges with bundles 22 and 21, and projects along the lateral edge of the ventrolateral neuropil. It also contains 2 axons that project to the periphery. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1; VA, ventral arch.

View larger version (90K): [in a new window]   Fig. 23. Characteristics of lineage 21. (A) Ventral view of the projection of a MARCM clone of lineage 21. (B,C) Thick section projections showing the relationship of the neurite bundles from lineage 21 to features of the Neurotactin scaffold (red) in ventral neuropil. (B,C) Progressively more ventral regions of bundle 21. Bundle 21 converges with bundles 20 and 22 but arcs medially, when compared with the lateral arc of the other two bundles. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. VA, ventral arch. Commissure abbreviations as in Fig. 1.

View larger version (142K): [in a new window]   Fig. 24. Characteristics of lineage 22. (A) Ventral view of the projection of a MARCM clone of lineage 22. (B,C) Thick section projections showing the relationship of the neurite bundles from lineage 22 to features of the Neurotactin scaffold (red) in ventral neuropil. Bundle 22 converges with bundles 20 and 21, and projects with 20 along the lateral edge of the ventrolateral neuropil. It also contains at least one motor axon. Numbers identify neurite bundles from other lineages. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (127K): [in a new window]   Fig. 25. Characteristics of lineage 23. (A) Ventral view of the projection of a MARCM clone of lineage 23. (B,C) Thick section projections showing the relationship of the neurite bundles from lineage 23 to features of the Neurotactin scaffold (red) in intermediate (B) and ventral (C) neuropils. Bundle 23c converges with bundles 19c (not shown) to form a posterior segment of the pI commissure. The MARCM clone for lineage 23 has a glial cell (G) associated with it. Diagrams as in Fig. 2. Commissure abbreviations as in Fig. 1.

View larger version (43K): [in a new window]   Fig. 26. Patterns of initial contacts amongst the neurite bundles from the 24 adult-specific lineages. (A) Confocal projection of MARCM clones showing contact between the 14c and 9i bundles. (B) Confocal optical section showing the neurites in bundle 1c terminating adjacent to those in bundle 22. (C) Schematic summary of the initial contacts made by the lineages in T2. Bundles within the pink circle terminate in the ventrolateral neuropil, those in the blue stripe project in dorsal tracts.

View larger version (31K): [in a new window]   Fig. 27. Segment-specific patterns of initial contacts amongst the neurite bundles from the adult-specific lineages. The full complement of bundles is evident in T2. White ovals indicate which lineages or bundles are missing in other segments. Designations as in Fig. 26.

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