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Sexual Differences in Cell Loss during the Post-Hatch Development of Song Control Nuclei in the Bengalese Finch.

Chen X, Li J, Zeng L, Zhang X, Lu X, Zuo M, Zhang X, Zeng S - PLoS ONE (2015)

Bottom Line: A corresponding sharp decrease in the density of Bcl-2 after P35 was observed in both sexes, and a greater density of Bid was noted at P45 in males.In addition, we observed that RA volume and the total number of BDNF-expressing cells decreased significantly after unilateral lesion of the LMAN or HVC (two areas that innervate the RA) and that greater numbers of RA-projecting cells were immunoreactive for BDNF in the LMAN than in the HVC.We reasoned that a decrease in the amount of BDNF transported via HVC afferent fibers might result in an increase in cell apoptosis in the female RA.

View Article: PubMed Central - PubMed

Affiliation: Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China.

ABSTRACT
Birdsongs and the regions of their brain that control song exhibit obvious sexual differences. However, the mechanisms underlying these sexual dimorphisms remain unknown. To address this issue, we first examined apoptotic cells labeled with caspase-3 or TUNEL in Bengalese finch song control nuclei - the robust nucleus of the archopallium (RA), the lateral magnocellular nucleus of the anterior nidopallium (LMAN), the high vocal center (HVC) and Area X from post-hatch day (P) 15 to 120. Next, we investigated the expression dynamics of pro-apoptotic (Bid, Bad and Bax) and anti-apoptotic (Bcl-2 and Bcl-xL) genes in the aforementioned nuclei. Our results revealed that the female RA at P45 exhibited marked cell apoptosis, confirmed by low densities of Bcl-xL and Bcl-2. Both the male and female LMAN exhibited apoptotic peaks at P35 and P45, respectively, and the observed cell loss was more extensive in males. A corresponding sharp decrease in the density of Bcl-2 after P35 was observed in both sexes, and a greater density of Bid was noted at P45 in males. In addition, we observed that RA volume and the total number of BDNF-expressing cells decreased significantly after unilateral lesion of the LMAN or HVC (two areas that innervate the RA) and that greater numbers of RA-projecting cells were immunoreactive for BDNF in the LMAN than in the HVC. We reasoned that a decrease in the amount of BDNF transported via HVC afferent fibers might result in an increase in cell apoptosis in the female RA. Our data indicate that cell apoptosis resulting from different pro- and anti-apoptotic agents is involved in generating the differences between male and female song control nuclei.

No MeSH data available.


Related in: MedlinePlus

In situ hybridization for Bcl-2 mRNA in the RA, LMAN, HVC and Area X in the Bengalese finch.A1–D2: Labeled cells in the RA at post-hatching day (P) 45 (A1, A2), the LMAN at P35 (B1, B2), the HVC at P35 (C1, C2), and in Area X at P35 (D1, D2). E-H: Comparisons of the densities of Bcl-2 mRNA-positive cells in the RA (E), LMAN (F), HVC (G) and Area X (H) between males and females. Borders of the song nuclei (dashed lines) were determined with the help of another set of Nissl-stained sections. The Nissl-defined border of the female Area X was difficult to clearly identify, and the dashed lines in D2 indicate the approximate region corresponding to the male Area X. Dorsal is up and caudal is right. Scale bar = 200 μm in A1–C2 and 300 μm in D1–D2. The data are expressed as the mean ± SEM. **P< 0.01.
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pone.0125802.g008: In situ hybridization for Bcl-2 mRNA in the RA, LMAN, HVC and Area X in the Bengalese finch.A1–D2: Labeled cells in the RA at post-hatching day (P) 45 (A1, A2), the LMAN at P35 (B1, B2), the HVC at P35 (C1, C2), and in Area X at P35 (D1, D2). E-H: Comparisons of the densities of Bcl-2 mRNA-positive cells in the RA (E), LMAN (F), HVC (G) and Area X (H) between males and females. Borders of the song nuclei (dashed lines) were determined with the help of another set of Nissl-stained sections. The Nissl-defined border of the female Area X was difficult to clearly identify, and the dashed lines in D2 indicate the approximate region corresponding to the male Area X. Dorsal is up and caudal is right. Scale bar = 200 μm in A1–C2 and 300 μm in D1–D2. The data are expressed as the mean ± SEM. **P< 0.01.

Mentions: As commercial antibodies for Bcl-2, Bid and Bad are not available for avian species, we examined the mRNA expression of these genes in the four song control nuclei at P15, 25, 35, and 45 and in the adult (Bcl-2: Fig 8; Bid: Fig 9; Bad: Fig 10). The densities of Bcl-2, Bid and Bad mRNA-positive cells exhibited significant differences across the five age groups in nearly all of the studied song nuclei, including the RA (Bcl-2: F(4, 20) = 73.630, P<0.001, Fig 8A1, 8A2 and 8E; Bid: F(4, 20) = 202.123, P<0.001, Fig 9A1, 9A2 and 9E), LMAN (Bcl-2: F(4, 20) = 94.570, P<0.001, Fig 8B1, 8B2 and 8F; Bid: F(1, 20) = 74.784, P<0.001, Fig 9B1, 9B2 and 9F; Bad: F(4, 20) = 54.582, P<0.001, Fig 10B1, 10B2 and 10F), HVC (Bcl-2: F(4, 20) = 61.155, P<0.001, Fig 8C1, 8C2 and 8G; Bid: F(4, 20) = 71.859, P<0.001, Fig 9C1, 9C2 and 9G; Bad: F(4, 20) = 237.056, P<0.001, Fig 10C1, 10C2 and 10G), and Area X (Bcl-2: F(4, 20) = 15.974, P<0.001, Fig 8D1, 8D2 and 8H; Bid: F(1, 20) = 1.777, P = 0.197, Fig 9D1, 9D2 and 9H; Bad: F(4, 20) = 59.621, P<0.001, Fig 10D1, 10D2 and 10H). However, the densities of Bad-positive cells did not differ significantly across the five age groups in the RA (F(4, 20) = 0.374, P = 0.824, Fig 10A1, 10A2 and 10E). There were significant sex differences in the densities of Bcl-2-positive cells in the RA at P45 (t = 8.264, P = 0.001, n = 4, Fig 8A1, 8A2 and 8E) and in the HVC at P35 (t = 7.750, P = 0.001, n = 4, Fig 8C1, 8C2 and 8G), P45 (t = 11.664, P<0.001, n = 4, Fig 8G) and in the adult (t = 9.421, P = 0.001, n = 4, Fig 8G). However, no differences were found in any of the studied age groups in the LMAN (F(1, 20) = 1.588, P = 0.222, Fig 8B1, 8B2 and 8F) or Area X (F(1, 20) = 3.125, P = 0.452, Fig 8D1, 8D2 and 8H). The density of Bid-positive cells differed significantly between the sexes in the LMAN at P45 (t = 8.181, P = 0.001, n = 4, Fig 9A1, 9A2 and 9E) and in the HVC at P35 (t = 6.462, P = 0.003, n = 4, Fig 9C1, 9C2 and 9G), P45 (t = 8.344, P = 0.001, n = 4, Fig 9G) and in the adult (t = 15.534, P<0.001, n = 4, Fig 9G), but were not sexually dimorphic in any of the studied age groups in the RA (F(1, 20) = 2.717, P = 0.155, Fig 9E) or Area X (F(1, 20) = 1.777, P = 0.197, Fig 9H). Additionally, there was not a significant sex difference in Bad-positive cell density in any of the studied age groups in the HVC (F(1, 20) = 16.230, P = 0.001, Fig 10C1, 10C2 and 10G), RA (F(1, 20) = 0.288, P = 0.597 Fig 10A1, 10A2 and 10E), LMAN (F(1, 20) = 0.642, P = 0.432 Fig 10B1, 10B2 and 10F) or Area X (F(1, 20) = 0.815, P = 0.377, Fig 10D1, 10D2 and 10H).


Sexual Differences in Cell Loss during the Post-Hatch Development of Song Control Nuclei in the Bengalese Finch.

Chen X, Li J, Zeng L, Zhang X, Lu X, Zuo M, Zhang X, Zeng S - PLoS ONE (2015)

In situ hybridization for Bcl-2 mRNA in the RA, LMAN, HVC and Area X in the Bengalese finch.A1–D2: Labeled cells in the RA at post-hatching day (P) 45 (A1, A2), the LMAN at P35 (B1, B2), the HVC at P35 (C1, C2), and in Area X at P35 (D1, D2). E-H: Comparisons of the densities of Bcl-2 mRNA-positive cells in the RA (E), LMAN (F), HVC (G) and Area X (H) between males and females. Borders of the song nuclei (dashed lines) were determined with the help of another set of Nissl-stained sections. The Nissl-defined border of the female Area X was difficult to clearly identify, and the dashed lines in D2 indicate the approximate region corresponding to the male Area X. Dorsal is up and caudal is right. Scale bar = 200 μm in A1–C2 and 300 μm in D1–D2. The data are expressed as the mean ± SEM. **P< 0.01.
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Related In: Results  -  Collection

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Show All Figures
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pone.0125802.g008: In situ hybridization for Bcl-2 mRNA in the RA, LMAN, HVC and Area X in the Bengalese finch.A1–D2: Labeled cells in the RA at post-hatching day (P) 45 (A1, A2), the LMAN at P35 (B1, B2), the HVC at P35 (C1, C2), and in Area X at P35 (D1, D2). E-H: Comparisons of the densities of Bcl-2 mRNA-positive cells in the RA (E), LMAN (F), HVC (G) and Area X (H) between males and females. Borders of the song nuclei (dashed lines) were determined with the help of another set of Nissl-stained sections. The Nissl-defined border of the female Area X was difficult to clearly identify, and the dashed lines in D2 indicate the approximate region corresponding to the male Area X. Dorsal is up and caudal is right. Scale bar = 200 μm in A1–C2 and 300 μm in D1–D2. The data are expressed as the mean ± SEM. **P< 0.01.
Mentions: As commercial antibodies for Bcl-2, Bid and Bad are not available for avian species, we examined the mRNA expression of these genes in the four song control nuclei at P15, 25, 35, and 45 and in the adult (Bcl-2: Fig 8; Bid: Fig 9; Bad: Fig 10). The densities of Bcl-2, Bid and Bad mRNA-positive cells exhibited significant differences across the five age groups in nearly all of the studied song nuclei, including the RA (Bcl-2: F(4, 20) = 73.630, P<0.001, Fig 8A1, 8A2 and 8E; Bid: F(4, 20) = 202.123, P<0.001, Fig 9A1, 9A2 and 9E), LMAN (Bcl-2: F(4, 20) = 94.570, P<0.001, Fig 8B1, 8B2 and 8F; Bid: F(1, 20) = 74.784, P<0.001, Fig 9B1, 9B2 and 9F; Bad: F(4, 20) = 54.582, P<0.001, Fig 10B1, 10B2 and 10F), HVC (Bcl-2: F(4, 20) = 61.155, P<0.001, Fig 8C1, 8C2 and 8G; Bid: F(4, 20) = 71.859, P<0.001, Fig 9C1, 9C2 and 9G; Bad: F(4, 20) = 237.056, P<0.001, Fig 10C1, 10C2 and 10G), and Area X (Bcl-2: F(4, 20) = 15.974, P<0.001, Fig 8D1, 8D2 and 8H; Bid: F(1, 20) = 1.777, P = 0.197, Fig 9D1, 9D2 and 9H; Bad: F(4, 20) = 59.621, P<0.001, Fig 10D1, 10D2 and 10H). However, the densities of Bad-positive cells did not differ significantly across the five age groups in the RA (F(4, 20) = 0.374, P = 0.824, Fig 10A1, 10A2 and 10E). There were significant sex differences in the densities of Bcl-2-positive cells in the RA at P45 (t = 8.264, P = 0.001, n = 4, Fig 8A1, 8A2 and 8E) and in the HVC at P35 (t = 7.750, P = 0.001, n = 4, Fig 8C1, 8C2 and 8G), P45 (t = 11.664, P<0.001, n = 4, Fig 8G) and in the adult (t = 9.421, P = 0.001, n = 4, Fig 8G). However, no differences were found in any of the studied age groups in the LMAN (F(1, 20) = 1.588, P = 0.222, Fig 8B1, 8B2 and 8F) or Area X (F(1, 20) = 3.125, P = 0.452, Fig 8D1, 8D2 and 8H). The density of Bid-positive cells differed significantly between the sexes in the LMAN at P45 (t = 8.181, P = 0.001, n = 4, Fig 9A1, 9A2 and 9E) and in the HVC at P35 (t = 6.462, P = 0.003, n = 4, Fig 9C1, 9C2 and 9G), P45 (t = 8.344, P = 0.001, n = 4, Fig 9G) and in the adult (t = 15.534, P<0.001, n = 4, Fig 9G), but were not sexually dimorphic in any of the studied age groups in the RA (F(1, 20) = 2.717, P = 0.155, Fig 9E) or Area X (F(1, 20) = 1.777, P = 0.197, Fig 9H). Additionally, there was not a significant sex difference in Bad-positive cell density in any of the studied age groups in the HVC (F(1, 20) = 16.230, P = 0.001, Fig 10C1, 10C2 and 10G), RA (F(1, 20) = 0.288, P = 0.597 Fig 10A1, 10A2 and 10E), LMAN (F(1, 20) = 0.642, P = 0.432 Fig 10B1, 10B2 and 10F) or Area X (F(1, 20) = 0.815, P = 0.377, Fig 10D1, 10D2 and 10H).

Bottom Line: A corresponding sharp decrease in the density of Bcl-2 after P35 was observed in both sexes, and a greater density of Bid was noted at P45 in males.In addition, we observed that RA volume and the total number of BDNF-expressing cells decreased significantly after unilateral lesion of the LMAN or HVC (two areas that innervate the RA) and that greater numbers of RA-projecting cells were immunoreactive for BDNF in the LMAN than in the HVC.We reasoned that a decrease in the amount of BDNF transported via HVC afferent fibers might result in an increase in cell apoptosis in the female RA.

View Article: PubMed Central - PubMed

Affiliation: Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China.

ABSTRACT
Birdsongs and the regions of their brain that control song exhibit obvious sexual differences. However, the mechanisms underlying these sexual dimorphisms remain unknown. To address this issue, we first examined apoptotic cells labeled with caspase-3 or TUNEL in Bengalese finch song control nuclei - the robust nucleus of the archopallium (RA), the lateral magnocellular nucleus of the anterior nidopallium (LMAN), the high vocal center (HVC) and Area X from post-hatch day (P) 15 to 120. Next, we investigated the expression dynamics of pro-apoptotic (Bid, Bad and Bax) and anti-apoptotic (Bcl-2 and Bcl-xL) genes in the aforementioned nuclei. Our results revealed that the female RA at P45 exhibited marked cell apoptosis, confirmed by low densities of Bcl-xL and Bcl-2. Both the male and female LMAN exhibited apoptotic peaks at P35 and P45, respectively, and the observed cell loss was more extensive in males. A corresponding sharp decrease in the density of Bcl-2 after P35 was observed in both sexes, and a greater density of Bid was noted at P45 in males. In addition, we observed that RA volume and the total number of BDNF-expressing cells decreased significantly after unilateral lesion of the LMAN or HVC (two areas that innervate the RA) and that greater numbers of RA-projecting cells were immunoreactive for BDNF in the LMAN than in the HVC. We reasoned that a decrease in the amount of BDNF transported via HVC afferent fibers might result in an increase in cell apoptosis in the female RA. Our data indicate that cell apoptosis resulting from different pro- and anti-apoptotic agents is involved in generating the differences between male and female song control nuclei.

No MeSH data available.


Related in: MedlinePlus