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Fig. 2 Occurrence of vessel pruning in the midbrain vasculature during development.
(A) Projected confocal image of a left midbrain vasculature in a 3-dpf Tg(kdrl:eGFP) larva. (B) Serial images showing that a vessel segment (arrow) underwent pruning in the midbrain vasculature shown in (A, square). Time, hour:minute. Scales, 25 μm in (A) and 10 μm in (B). (C) Temporal distribution of vessel pruning events observed from eight larvae at each data point. (D and E) An example (D) and summary (E) of data showing that vessel segments formed at 2-dpf underwent extensive pruning during 2.0–7.0 dpf. The data in (E) were obtained from six larvae. (D) Centerline of a 2-dpf midbrain vasculature in which red and blue mark segments were pruned or unpruned during 2.0–7.0 dpf, respectively. The black dots represent branch points between the CVP and midbrain vessel segments. (F and G) Local structural features of pruned vessel segments. (F) Percentages of pruned segments that did not link to the CVP and were located in H-type (87/107) or O-type (19/107) of vascular microcircuits or directly linked to the CVP (1/107). The data were obtained from 18 larvae. Inset, schematic of H-type and O-type of vascular microcircuits. The dashed arrows in the inset indicate the direction of blood flow, and the red and blue lines represent pruned and unpruned vessel segments, respectively. (G) Percentage of pruned segments that were located in internal vessel loop. Error bars, ± SEM.