FIGURE SUMMARY
Title

Spatiotemporal expression of smooth muscle markers in developing zebrafish gut

Authors
Georgijevic, S., Subramanian, Y., Rollins, E.L., Starovic-Subota, O., Tang, A.C., Childs, S.J.
Source
Full text @ Dev. Dyn.

α-Smooth muscle actinSMA) expression is temporally regulated in the intestine and swim bladder. A,D,G,J,M: αSMA is expressed in the developing gut (arrows) and swim bladder (arrowheads) at 60 (A), 65 (D), and 77 hours postfertilization (hpf) (G), or 4 (J), and 5 days postfertilization (dpf) (M). αSMA expression in the gut is not continuous at 65 hpf (white arrows in inset A), but becomes continuous by 65 hpf (D). G′: αSMA expression is seen in the developing swim bladder at 77 hpf in a dorsal view. B,E,H,K,N: Cross-sections of 60 (B), 65 (E), and 77 hpf (H), or 4 (K) and 5 dpf (N) embryos show αSMA expression in the developing muscularis propria of the gut and swim bladder (arrowhead in E). C,F: Cells expressing αSMA at 60 (C) and 65 hpf (F) are mesenchymal in morphology by hematoxylin and eosin staining. I,L,O: By 77 hpf a layer of circularly arranged cells is seen outside the gut epithelium (arrows in I′ point to nuclei of circularly arranged cells). g, gut; sb, swim bladder.

EXPRESSION / LABELING:
Gene:
Fish:
Anatomical Terms:
Stage Range: Pec-fin to Day 5

Temporal regulation of sm22α-b, smtn-b, cpi-17, and nm-mhc-b during the development of visceral smooth muscle. A-D: nm-mhc-b is first seen in the anterior gut at 50 hours postfertilization (hpf; A, arrow). At 3 days postfertilization (dpf), nm-mhc-b is expressed throughout the gut (B, arrow). By 4 dpf, the expression of nm-mhc-b in the gut (arrows) is down-regulated, but continues in the swim bladder (C, arrowhead). In longitudinal section, nm-mhc-b is expressed in a layer of cells surrounding the gut epithelium (D, arrowheads). E-H: SM22α-b expression at 56 hpf (E), 60 hpf (F), and 4 dpf (G) in the developing gut and swim bladder is similar to that of α-smooth muscle actinSMA). The inset in F is a dorsal view. Like nm-mhc-b, it is expressed in a layer surrounding the gut epithelium at 3 dpf (H). I,J,L,M: cpi-17 is expressed throughout the gut at 3 dpf (I), while smtn-b is expressed in the anterior gut (L). By 4 dpf, cpi-17 (J) and smtn-b (M) are no longer expressed in the gut, but are expressed in the swim bladder. K,N: In longitudinal section, both genes are expressed in a layer surrounding the gut epithelium.

EXPRESSION / LABELING:
Genes:
Fish:
Anatomical Terms:
Stage Range: Long-pec to Day 4

Smooth muscle marker expression in the juvenile gut and swim bladder. A,B: Tropomyosin is expressed in a circular smooth muscle layer at 4 days postfertilization (dpf; A), and in longitudinal and circular layers at 6 dpf (B). C-F: By15 dpf, tropomyosin staining is strong in a layer surrounding both the gut and swim bladder (C). D,E: A higher power image (D) reveals that the swim bladder has a thin epithelial lining and single layer of smooth muscle cells surrounding it, while the gut (E) at similar magnification has developed a columnar epithelium, and a thicker smooth muscle wall. F: In a whole-mount larva, tropomyosin staining is seen around the swim bladder and gut. G: Whole-mount staining of a 20 dpf larva with α-smooth muscle actin (αSMA) reveals a similar pattern to tropomyosin. H: Longitudinal sections of a 22 dpf larva show extensive smooth muscle layers expressing αSMA. L, lumen; sb, swim bladder; g, gut.

Histology of adult zebrafish gut and swim bladder smooth muscle. A,B: The adult gut has a clear laminar structure of smooth muscle adjacent to the columnar epithelium (ce) consisting of an inner circular smooth muscle layer (csm), and an outer longitudinal smooth muscle layer (lsm). C,D: The adult swim bladder shows a slightly different cellular organization. In addition to an epithelial layer, there is an inner circular smooth muscle layer, and a mixed outer layer of radial smooth muscle (rsm), and longitudinal smooth muscle. For direct comparison between gut and swim bladder, A and C are presented at the same magnification, as are B and D. L, lumen.

Acknowledgments
This image is the copyrighted work of the attributed author or publisher, and ZFIN has permission only to display this image to its users. Additional permissions should be obtained from the applicable author or publisher of the image. Full text @ Dev. Dyn.