PFA-fixed paraffin-embedded tissue sections were heated at 65°C for 2 hr, and then deparaffinized with xylene, rehydrated with a graded series ethanol, and washed with PBS for 5 min. Subsequently, proteinase K (20 μg/ml) digestion was performed at 37°C for 5 min. After proteinase K digestion, the tissue sections were post-fixed with 4% PFA and then were washed with PBS twice. The tissue sections were further equilibrated in 0.1 M TEA (triethanolamine, pH 8.5) and then incubated with acetic anhydride. The tissue sections were dehydrated through a graded series ethanol and then air dried for 1 hr. Later, the tissue sections were prehybridized with prehybridization buffer (50% deionized formamide, 2× SSC) at 65°C for 2 hr. During the prehybridization step, the DIG-labeled RNA probes were denatured in hybridization solution (50% deionized formamide, 2× SSC, 10% dextran sulfate sodium salt, 1× Denhardt's solution, 10 mM ethylenediaminetetraacetic acid [EDTA], 10 mM DTT, 1 mg/ml yeast-tRNA) at 80°C for 5 min. After prehybridization, the sections were incubated with hybridization solution containing the individual denatured RNA probes at 65°C overnight. On the second day, the slides were rinsed in 5× SSC and then washed in wash buffer (50% deionized formamide, 2× SSC) at 65°C for 30 min. Subsequently, the sections were equilibrated in STE buffer (4× SSC, 20 mM Tris-HCl, 1 mM EDTA, pH 8.0) at 37°C for 10 min. The tissue sections were then incubated in RNaseA solution (20 μg/ml in STE buffer) at 37°C for 30 min. After RNaseA treatment, the samples were washed with STE buffer for 10 min and then washed with FS buffer again at 65°C for 30 min. Next, the slides were washed with 2× SSC, 0.1× SSC and then ddH2O. Subsequently, the sections were equilibrated with 1× MABT (1× MAB: 0.1 M maleic acid, 0.15 M NaCl, pH 7.5, containing 0.1% Tween-20), incubated with blocking solution (10% sheep serum and 2% Roche blocking reagent in 1× MABT) at room temperature for 2 hr, and finally the alkaline phosphatase (AP) -conjugated anti-DIG antibody (1:1,000, Roche, Germany) was added for overnight incubation at 4°C. After labeling, the sections were washed three times (30 min each) with 1× MABT containing 2mM levamisole. Subsequently, the sections were washed and equilibrated in NTMT solution (20 mM NaCl, 100 mM Tris-HCl, 2 mM levamisole, 0.1% Tween-20, pH 9.5) and then color (dark purple) developed using NBT (nitroblue tetrazolium chloride)/BCIP (5-bromo-4-chloro-3-indolyl-phosphate) chromogenic stain for 24 hr. Finally, the sections were washed with PBS, dehydrated with serial concentration of ethanol, cleared in xylene and mounted for viewing.