Fig. 5. mps1 is induced in the proximal blastemal proliferative zone during regenerative outgrowth. (A) Northern analysis of mps1 expression using several adult tissues as well as regenerating caudal fin tissue. Blots were also probed for ß-actin expression as a control to indicate the amounts of RNA loaded. (B) Whole-mount in situ hybridization of mps1 in wild-type 1-day and 3-day postamputation fin regenerates (violet stain indicated by arrowhead). mps1 RNA levels were increased in the newly-formed blastema at 1 day postamputation (top) and these levels were maintained in the blastema during regenerative outgrowht (bottom). Whole-mount mps1 signals appeared stronger than section mps1 signals in 1-day regenerates, an observation that is common at that timepoint for other genes. This likely represents somewhat weak but widespread signals in individual blastemal cells that appear stronger when visualized en masse. (C) (Left and center) Longitudinal sections of wild-type 1- and 3-day fin regenerates co-stained for mps1 RNA and PCNA protein (green). mps1 was upregulated in the most highly proliferative cells during outgrowth (brackets), but was absent from the distal blastema. (Right) msxb RNA localization (violet, arrowhead at 3 days) in the newly formed blastema at 1 day and the distal blastema at 3 days postamputation. Thus, in the new blastema, mps1 colocalizes with PCNA and msxb. However, mps1 is specifically induced in the proximal blastema during outgrowth. The morphological difference between 3-day regenerates shown in Fig. 5C represents variation commonly seen in fin regenerates during outgrowth. Original magnifications: 50x in B and 110x in C.

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