Development of coordinated motility patterns in zebrafish larvae. A 7 dpf larvae is shown in panel A. The anterior bulb and mid-distal intestine are indicated with gray and black bars, respectively. Standard length is shown in panel A and was measured from the snout to the posterior end of the notochord. The region of interest used to construct STMaps is outlined in black in images shown above the STMaps in panels B, C, and D. Patterns of propagating contractions are revealed in STMaps as dark ridges. Short contractions beginning in the mid- and distal intestine and propagating toward the anus are seen at 5 dpf (B). Retrograde contractions are apparent in the anterior region, and short, rapid contractions are apparent near the anal region (arrows, B). Contraction patterns in the mid- and distal intestine were more consistent and individual contractions were longer and more frequent at 7 and 9 dpf (C, D). The motility index, a measure of contraction coordination, increased from 36% (n = 14) at 5 dpf to 88% (n = 8) at 7 dpf and 86% at 9 dpf (n = 7) (E). The number of STMaps showed coordinated motor patterns increased (black bars) and the number of maps scored as uncoordinated decreased (gray bars) between 5 and 7 dpf. The number of propagating contractions per 10 min recording also increased from 5 to 7 dpf and 9 dpf (n = 7) (F); *p < 0.05.

Treatment with imatinib mesylate inhibits development of coordinated motility patterns. STMaps from treated larvae (n = 16) show fewer contractions that appear disorganized when compared to age-matched control larvae (N= 9) (A, B, C, compared to Fig. 1). Imatinib mesylate decreased the number of coordinated motor patterns (black, D), contraction number (E), distance (F), and velocity (G) at 9 dpf; *p < 0.05.

Development of GI motor patterns is incomplete in Sparse mutants. STMaps at 5 dpf (A), 7 dpf (B), and 9 dpf (C) show relatively few contractions when compared to control larvae (see Fig. 1). Motor patterns are poorly coordinated with propagating contractions moving in the oral and the aboral directions (see A). Coordinated motility patterns were observed in 1 of 4 larvae at 5 dpf, 5 of 12 larvae at 7 dpf, and 4 out of 14 larvae at 9 dpf (D). The total number of contractions did not change during development (E); p > 0.05.