Figure 3.

Expression level of hatching enzyme genes and distribution of hatching gland cells (HGCs). (A) Comparison of the relative expression levels of hatching enzyme genes (MHCE and MLCE) and housekeeping genes (β-actin and GAPDH) in medaka embryos performed by Northern blot. The relative expression level of mRNA was estimated by densitometry and represented relative to an intensity of 1 for β-actin. (B) Expression analysis of hatching enzyme genes performed by Northern blot. Gene names are shown at the top of the lane, and clade I genes are underlined. Triangles indicate the positions of 28 S and 18 S rRNAs. (C) A section of the lower jaw of medaka embryo stained with toluidine blue. HGCs (arrowheads) are filled with many of zymogen granules. pc, pharyngeal cavity. Scale bar, 10 μm. (D-H) Distribution of HGCs were observed by whole-mount in situ hybridization using pre-hatching embryos of milkfish (D), loach (E), catfish (F), rainbow trout (G) and Pacific cod (H). Dorsal (D and H) and ventral (F and G) views of the head region, and lateral view (E). Scale bars, 200 μm.