Morphologic transformation of the thymus in developing zebrafish.
The morphologic transformation of the developing zebrafish thymus from 1 week postfertilization (wpf) to 15 wpf is described. The thymus overall morphology changed from a small pouch-like shape at 1 wpf to a conical shape between 2 and 3 wpf before acquiring a more complex shape from 4 wpf onward. Rapid growth rate along the lateral axis at the region near the pharyngeal epithelium occurred between 1 and 2 wpf, whereas rapid growth rate along the dorsal-ventral axis occurred between 3 and 6 wpf. Expansion of thymocyte population beginning from 1 wpf became more evident by 2 to 3 wpf, as indicated by the apparent increase of different sizes of lymphocytes, recombination activating gene-1 (rag-1), and T-cell antigen receptor alpha chain constant region (TCRAC) -positive cells. Tissue section in situ hybridization (ISH) analysis with rag-1 probe reveals that cortex-medullary regionalization has begun between 1 and 2 wpf as rag-1 expression clearly demarcated the cortex, whereas the medulla was rag-1 negative. The presence of TCRAC-positive cells in the medulla by 2-3 wpf, suggests that the thymic selection processes had begun. The zebrafish thymus is morphologically mature by 3 wpf. Early signs of thymic involution were observed in zebrafish aged 15 wpf.
Department of Biological Sciences, The National University of Singapore, Singapore.
S H
SH
Lam
H L
HL
Chua
Z
Z
Gong
Z
Z
Wen
T J
TJ
Lam
Y M
YM
Sin
D000818:Animals; D016654:Genes, RAG-1 / Q000235:genetics*; D017403:In Situ Hybridization; D008954:Models, Biological; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D012984:Software; D013950:Thymus Gland / Q000166:cytology / Q000196:embryology*; D013997:Time Factors; D015027:Zebrafish / Q000196:embryology*
D011948:Receptors, Antigen, T-Cell