1. Volume 23, Issue 20, Pages 2063-2070 (October 2013)
Visualization of Neural Activity in Insect Brains Using a Conserved Immediate Early Gene, Hr38 
Nozomi Fujita, Yuka Nagata, Takumi Nishiuchi, Makoto Sato, Masafumi Iwami, Taketoshi Kiya 
Current Biology 
Volume 23, Issue 20, Pages (October 2013)
DOI: /j.cub
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2. Figure 1
Identification of Bmhr38 as a Gene Whose Expression Is Transiently Induced by Exposure to Female Odor or Sex Pheromones
(A) Validation of the microarray results with quantitative RT-PCR (qRT-PCR). Males were exposed to female odor for 30 min. Relative value of BmHr38 expression to the no-stimulation control is shown. ∗∗p < 0.001, Student’s t test. n = 5, each.
(B) Time course of BmHr38 expression in the male silkmoth brain was analyzed by qRT-PCR. Male silkmoths were exposed to female odor for 30 min and then placed in normal air. BmHr38 expression peaked at 60 min and decreased at 180 min. n = 6, each.
(C) Western blot analysis of BmHR38. Male silkmoths were stimulated with the same condition as (B). Affinity-purified anti-Hr38 peptide antibody detected an approximately 60 kDa protein, whose expression level was increased by female odor stimulation.
(D) The dose-response relationship of BmHr38 expression and pheromone stimulation intensity was analyzed by qRT-PCR. The BmHr38 expression level increased in a dose-dependent manner for bombykol. In addition, the duration of sexual behavior, which was observed with a 5 to 15 min time window, increased dose dependently. In contrast, application of bombykol (90 ng) in combination with bombykal (10 ng) decreased both the BmHr38 expression level and sexual behavior duration, indicating the suppressive effect of bombykal. Application of both bombykal (100 ng) and bombykol (900 ng), however, did not decrease either the BmHr38 expression level or sexual behavior duration, suggesting that bombykal (100 ng) is not sufficient to suppress the effect of high concentrations of bombykol. Statistically different groups are indicated by different letters (p < 0.05, Tukey-Kramer’s honestly significant difference [HSD] test after ANOVA. n = 3, each). Data are shown as mean ± SE throughout the study.
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3. Figure 2
Comprehensive Neural Activity Map of a Male Silkmoth Brain in Response to Sex Pheromones
From rostral to caudal, coronal brain sections were cut successively.
(A) Camera lucida drawings of the BmHr38 mRNA expression pattern in the brain of bombykol-stimulated male silkmoths. Consecutive sections from rostral to caudal are shown from 1 to 16. Signals are indicated by red dots.
(B) A schematic drawing of a male silkmoth brain from the lateral view.
(C) Camera lucida drawings of the BmHr38 mRNA expression pattern in the brain of bombykal-stimulated male silkmoths. Two different individuals (1 and 2) at different section depths [1–3] are shown. Signals are indicated by blue dots.
(D) Representative pictures of in situ hybridization for BmHr38 are shown (from left to right; no stimulation control, 100 ng bombykol stimulation, and 100 ng bombykal stimulation). BmHr38-expressing cells are depicted by red (bombykol) and blue (bombykal) circles. The areas corresponding to the pictures are shown in light blue boxes in (A) and (C).
(E) Quantitative analysis of BmHr38-positive cell densities. BmHr38-positive cells were manually counted and divided by the area of the soma region (excluding the neuropil regions). Each group was stimulated with bombykol (100 ng), bombykal (100 ng), or female odor for 30 min and then placed in normal air for 30 min. Control with no stimulation is shown as a negative control. Statistically different groups are indicated by different letters (p < 0.05, Tukey-Kramer’s HSD test after ANOVA).
(F) BmHr38 expression in the antennae was also upregulated by female odor exposure. ∗p < 0.05, U test. n = 3, each.
(G and H) BmHr38 can also be used as a neural activity marker in the male silkmoth antennae.
(G) Double in situ hybridization of BmHr38 and BmOR1 (bombykol receptor; left panels) or BmOR3 (bombykal receptor; right panels) in the antennae. Male antennae with no stimulation (control; top panels), bombykol stimulation (100 ng; middle panels), or bombykal stimulation (100 ng; bottom panels) are shown. BmOR1- or BmOR3-expressing cells without BmHr38 expression are highlighted by white circles. Cells double positive for BmHr38 and BmOR1 or BmOR3 are highlighted by yellow circles. BmHr38-positive, but BmOR1- or BmOR3-negative, cells are highlighted by light blue circles.
(H) Percentage of BmHr38-positive cells in BmOR1- or BmOR3-expressing cells ± 0.63 receptor cells per picture were analyzed. The number of pictures analyzed is shown in parentheses. Statistically different groups are indicated by different letters (P < 0.05, Tukey-Kramer’s HSD test after ANOVA). AN, antennal nerve; MGC, macro glomerular complex; Gs, ordinary glomeruli; PC, protocerebrum; SOG, suboesophageal ganglion; MB, mushroom body; OL, optic lobe. The probe specificity test confirmed that signal was detected only when antisense probes were used (Figure S2). Scale bar, (A)–(D) 100 μm, (G) 10 μm.
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4. Figure 3
Dhr38 Expression Is Transiently Increased in a Neural Activity-Dependent Manner and Can Be Used as a Neural Activity Marker in the Fly Brains
(A) Neural stimulation by warming (31°C) for 1 hr increased Dhr38 expression in the heads of elav-GAL4/+; UAS-dTrpA1/+ and UAS-dTrpA1/+; OK107-GAL4/+, as revealed by qRT-PCR. No increase in Dhr38 expression was observed in control flies (UAS-dTrpA1/+, elav-GAL4/+, and OK107-GAL4/+). ∗p < 0.02, ∗∗p < 0.005, Welch’s t test. n = 4, each.
(B) Continuous neural stimulation by warming (31°C) and quantification of Dhr38 expression by qRT-PCR in the heads of elav-GAL4/+; UAS-dTrpA1/+ flies. Dhr38 expression peaked at 120 min and maintained the maximum expression level. n = 4, each.
(C) Time course of Dhr38 expression. Flies expressing dTrpA1 in the central nervous system (elav-GAL4/+; UAS-dTrpA1/+) were stimulated at 31°C for 30 min and then returned to the permissive temperature (23°C). As in silkmoths, Dhr38 expression was transiently upregulated by neural stimulation. n = 4, each.
(D) Western blot analysis of DHR38. Heads of flies stimulated with the same condition as (C) were used. Affinity-purified anti-Hr38 peptide antibody detected an approximately 70 kDa protein whose band intensity increased in a neural activity-dependent manner. The same membrane was used to detect Synapsin as a loading control.
(E) Dhr38 mRNA expression can be induced by short-term (5 min) stimulation. n = 3, each.
(F–I, K, L, N, O, Q, and R) In situ hybridization of Dhr38 in the brains of elav-GAL4/+; UAS-dTrpA1/+ (F–I), UAS-dTrpA1/UAS-GFP; OK107-GAL4/+ (K and L), and GH146-GAL4, UAS-GFP/UAS-dTrpA1 (N, O, Q, and R). Neural stimulation was induced by warming at 31°C for 2 hr (H, I, L, O, and R). Dhr38 expression was detected in a stimulation-dependent manner. Stimulated cells were visualized with anti-ELAV (F–I) or anti-GFP (K, L, N, O, Q, and R) antibody staining. Central brain area (F and H, anterior view; G and I, posterior view), calyx of the mushroom body (MB) (K and L), AL (N and O), and MB-LH areas (Q and R) are shown. Left is lateral and right is medial. One confocal optical section (2 μm thickness; F–I, K, L, N, and O) and stack of three optical sections (6 μm thickness; Q and R) are shown. Asterisks indicate nonspecific signals. Scale bar, 100 μm (F–I), 20 μm (K, L, N, O, Q, and R). AL, antennal lobe; LH, lateral horn.
(J) Ratio of Dhr38-stained area to anti-ELAV-stained area measured from anterior or posterior side.
(M and P) Percentage of Dhr38-positive cells in GFP-positive cells ± 17.7 (M) and ± 1.93 (P) GFP-positive cells per picture were analyzed.
(S) Number of Dhr38-positive cells in the MB and LH areas. The number of pictures analyzed is shown in parentheses. ∗p < , Welch’s t test.
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5. Figure 4
A Neural Activity Map of the Male Adult Fly Brain in Response to Female Body Stimulation
(A–E) Schematic summary of the distribution pattern of Dhr38-positive cells in the brain of an adult Canton-S (CS) male stimulated with a freshly decapitated virgin CS female body for 2 hr. Anterior (A) and posterior (E) views are shown.
(B–D and F–H) Representative pictures of in situ hybridization for Dhr38 in the brain of the no-stimulation control (B and F), one virgin female body stimulation (C and G), and three virgin female body stimulation (D and H). Brain structures were visualized with anti-nc82 antibody staining (blue). Dhr38-positive cells are indicated by yellow arrows. Asterisks indicate nonspecific signals. Areas corresponding to (B–D) and (F–H) are indicated by boxes in (A) and (E), respectively.
(I–L) Number of Dhr38-positive cells in CS males (I and J), Orco mutant males (K), or Or47b mutant males (L) under various stimulus conditions counted in five reproducibly stained brain areas defined as in (A) and (E). The numbers of analyzed samples are shown in parentheses. Statistically different groups are indicated by different letters (p < 0.05, Tukey-Kramer’s HSD test after ANOVA).
(M–Q) Colocalization analysis of Dhr38 and fruitless-expressing neurons. The nomenclature of cell clusters follows that used in the previous paper [15]. In situ hybridization of Dhr38 (magenta) and antibody staining of GFP (green) in the brain of a NP21/20xUAS-IVS-mCD8GFP male stimulated with one decapitated virgin female body is shown. Double-positive cells for Dhr38 and GFP are indicated by white arrows. Scale bar, 50 μm (B–D and F–H), 10 μm (M–Q).
Current Biology  , DOI: ( /j.cub )
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