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A septo-temporal molecular gradient of sfrp3 in the dentate gyrus differentially regulates quiescent adult hippocampal neural stem cell activation.

Sun J, Bonaguidi MA, Jun H, Guo JU, Sun GJ, Will B, Yang Z, Jang MH, Song H, Ming GL, Christian KM - Mol Brain (2015)

Bottom Line: Using in situ hybridization and quantitative real-time PCR, we identified an inverse septal-to-temporal increase in the expression of sfrp3 that emerges during postnatal development.Elimination of sfrp3 and its molecular gradient leads to increased RGL activation, preferentially in the temporal region of the adult dentate gyrus.Our study identifies a niche mechanism that contributes to the graded distribution of neurogenesis in the adult dentate gyrus and has important implications for understanding functional differences associated with adult hippocampal neurogenesis along the septo-temporal axis.

View Article: PubMed Central - PubMed

Affiliation: Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, P.R. China.

ABSTRACT

Background: A converging body of evidence indicates that levels of adult hippocampal neurogenesis vary along the septo-temporal axis of the dentate gyrus, but the molecular mechanisms underlying this regional heterogeneity are not known. We previously identified a niche mechanism regulating proliferation and neuronal development in the adult mouse dentate gyrus resulting from the activity-regulated expression of secreted frizzled-related protein 3 (sfrp3) by mature neurons, which suppresses activation of radial glia-like neural stem cells (RGLs) through inhibition of Wingless/INT (WNT) protein signaling.

Results: Here, we show that activation rates within the quiescent RGL population decrease gradually along the septo-temporal axis in the adult mouse dentate gyrus, as defined by MCM2 expression in RGLs. Using in situ hybridization and quantitative real-time PCR, we identified an inverse septal-to-temporal increase in the expression of sfrp3 that emerges during postnatal development. Elimination of sfrp3 and its molecular gradient leads to increased RGL activation, preferentially in the temporal region of the adult dentate gyrus.

Conclusions: Our study identifies a niche mechanism that contributes to the graded distribution of neurogenesis in the adult dentate gyrus and has important implications for understanding functional differences associated with adult hippocampal neurogenesis along the septo-temporal axis.

No MeSH data available.


Related in: MedlinePlus

A gradient of sfrp3 expression in the dentate gyrus of adult mouse hippocampus. a Mid-sagittal section of dissected mouse hippocampus showing in situ hybridization (ISH) for sfrp3 mRNA. Scale bar, 500 μm. b Quantitative analysis of sfrp3 expression by quantitative real-time PCR. Values present mean ± S.E.M. (n = 4; * < 0.05; ANOVA). c. Representative images of ISH for sfrp3 mRNA on twelve serial sections along the septo-temporal axis, with the planes oriented as shown in Fig. 1a. Scale bar, 10 μm. d Quantification of signal intensity for sfrp3 in situ, which was performed on the images shown in Fig. 2c. Open circles, diamonds and triangles represent sfrp3 mRNA from septo-temporal axis of three individual mice. Closed circles are the mean of the three mice. Values represent mean ± S.E.M. (n = 3). e Representative images of sfrp3 mRNA in situ in the dentate gyrus of adult sfrp3 knockout (−/−), heterozygous (+/−), and wild-type (+/+) littermates. Scale bar, 500 μm
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Fig2: A gradient of sfrp3 expression in the dentate gyrus of adult mouse hippocampus. a Mid-sagittal section of dissected mouse hippocampus showing in situ hybridization (ISH) for sfrp3 mRNA. Scale bar, 500 μm. b Quantitative analysis of sfrp3 expression by quantitative real-time PCR. Values present mean ± S.E.M. (n = 4; * < 0.05; ANOVA). c. Representative images of ISH for sfrp3 mRNA on twelve serial sections along the septo-temporal axis, with the planes oriented as shown in Fig. 1a. Scale bar, 10 μm. d Quantification of signal intensity for sfrp3 in situ, which was performed on the images shown in Fig. 2c. Open circles, diamonds and triangles represent sfrp3 mRNA from septo-temporal axis of three individual mice. Closed circles are the mean of the three mice. Values represent mean ± S.E.M. (n = 3). e Representative images of sfrp3 mRNA in situ in the dentate gyrus of adult sfrp3 knockout (−/−), heterozygous (+/−), and wild-type (+/+) littermates. Scale bar, 500 μm

Mentions: Next, we investigated the potential molecular niche mechanism underlying this heterogeneity in neurogenesis along the septo-temporal axis of the adult hippocampus. Several studies have revealed specific molecular domains and regionalization within the dentate gyrus [11, 15]. We focused on sfrp3 based on several of our recent findings. First, we found that in adult mice sfrp3 is highly expressed in mature dentate granule cells and suppresses activation of quiescent RGLs and inhibits maturation of immature neurons [32]. Second, sfrp3 expression is downregulated by various antidepressant treatments, including electroconvulsive treatment and chemical antidepressants, whereas sfrp3 knockout mice exhibit behaviors resembling those following antidepressant treatment [40]. Third, we found that three single-nucleotide polymorphisms (SNPs) in the human SFRP3 gene are significantly associated with early antidepressant responses in a human patient cohort [40]. Given the proposed functional differentiation of the hippocampus along its long axis, we assessed whether the expression pattern of sfrp3 aligns with this dissociation at the molecular level. We examined sfrp3 expression along the longitudinal axis of the adult dentate gyrus using in situ hybridization and quantitative real-time PCR analyses. To directly visualize sfrp3 expression along the septo-temporal axis in a single section, we developed another new approach to section the dissected hippocampus in the sagittal plane (Fig. 2a). Consistent with previous reports [32, 47], sfrp3 expression was enriched in the granule layer of the adult dentate gyrus (Fig. 2a). Interestingly, the sfrp3 in situ signal intensity increased along the longitudinal axis of adult hippocampus from the septal pole to the temporal pole (Fig. 2a). Quantitative real-time PCR in samples of micro-dissected dentate gyrus further confirmed higher sfrp3 expression in the temporal dentate gyrus (Fig. 2b). Notably, in situ analysis showed that the sfrp3 gradient appeared to be continuous across the septo-temporal axis of the hippocampus without sharp step changes suggestive of “border” transitions (Fig. 2a). We confirmed this result with densitometric measurements of in situ signal intensity on coronal sections of dissected hippocampus along the entire axis of hippocampus (Fig. 2c-d). To confirm the specificity of the sfrp3 in situ probe used, we compared wild-type (+/+), heterozygous (+/−) and knockout (−/−) sfrp3 animals. Indeed, no signal was observed in knockout animals in sections processed in parallel with other genotypes (Fig. 2e). Interestingly, a gradient was present in the heterozygous mice, although the expression level appeared to be reduced by ~50 % (Fig. 2e). Together, these results demonstrated that sfrp3 expression in the adult mouse dentate gyrus exhibits a smooth gradient with increasing expression along the septo-temporal axis.Fig. 2


A septo-temporal molecular gradient of sfrp3 in the dentate gyrus differentially regulates quiescent adult hippocampal neural stem cell activation.

Sun J, Bonaguidi MA, Jun H, Guo JU, Sun GJ, Will B, Yang Z, Jang MH, Song H, Ming GL, Christian KM - Mol Brain (2015)

A gradient of sfrp3 expression in the dentate gyrus of adult mouse hippocampus. a Mid-sagittal section of dissected mouse hippocampus showing in situ hybridization (ISH) for sfrp3 mRNA. Scale bar, 500 μm. b Quantitative analysis of sfrp3 expression by quantitative real-time PCR. Values present mean ± S.E.M. (n = 4; * < 0.05; ANOVA). c. Representative images of ISH for sfrp3 mRNA on twelve serial sections along the septo-temporal axis, with the planes oriented as shown in Fig. 1a. Scale bar, 10 μm. d Quantification of signal intensity for sfrp3 in situ, which was performed on the images shown in Fig. 2c. Open circles, diamonds and triangles represent sfrp3 mRNA from septo-temporal axis of three individual mice. Closed circles are the mean of the three mice. Values represent mean ± S.E.M. (n = 3). e Representative images of sfrp3 mRNA in situ in the dentate gyrus of adult sfrp3 knockout (−/−), heterozygous (+/−), and wild-type (+/+) littermates. Scale bar, 500 μm
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Related In: Results  -  Collection

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Fig2: A gradient of sfrp3 expression in the dentate gyrus of adult mouse hippocampus. a Mid-sagittal section of dissected mouse hippocampus showing in situ hybridization (ISH) for sfrp3 mRNA. Scale bar, 500 μm. b Quantitative analysis of sfrp3 expression by quantitative real-time PCR. Values present mean ± S.E.M. (n = 4; * < 0.05; ANOVA). c. Representative images of ISH for sfrp3 mRNA on twelve serial sections along the septo-temporal axis, with the planes oriented as shown in Fig. 1a. Scale bar, 10 μm. d Quantification of signal intensity for sfrp3 in situ, which was performed on the images shown in Fig. 2c. Open circles, diamonds and triangles represent sfrp3 mRNA from septo-temporal axis of three individual mice. Closed circles are the mean of the three mice. Values represent mean ± S.E.M. (n = 3). e Representative images of sfrp3 mRNA in situ in the dentate gyrus of adult sfrp3 knockout (−/−), heterozygous (+/−), and wild-type (+/+) littermates. Scale bar, 500 μm
Mentions: Next, we investigated the potential molecular niche mechanism underlying this heterogeneity in neurogenesis along the septo-temporal axis of the adult hippocampus. Several studies have revealed specific molecular domains and regionalization within the dentate gyrus [11, 15]. We focused on sfrp3 based on several of our recent findings. First, we found that in adult mice sfrp3 is highly expressed in mature dentate granule cells and suppresses activation of quiescent RGLs and inhibits maturation of immature neurons [32]. Second, sfrp3 expression is downregulated by various antidepressant treatments, including electroconvulsive treatment and chemical antidepressants, whereas sfrp3 knockout mice exhibit behaviors resembling those following antidepressant treatment [40]. Third, we found that three single-nucleotide polymorphisms (SNPs) in the human SFRP3 gene are significantly associated with early antidepressant responses in a human patient cohort [40]. Given the proposed functional differentiation of the hippocampus along its long axis, we assessed whether the expression pattern of sfrp3 aligns with this dissociation at the molecular level. We examined sfrp3 expression along the longitudinal axis of the adult dentate gyrus using in situ hybridization and quantitative real-time PCR analyses. To directly visualize sfrp3 expression along the septo-temporal axis in a single section, we developed another new approach to section the dissected hippocampus in the sagittal plane (Fig. 2a). Consistent with previous reports [32, 47], sfrp3 expression was enriched in the granule layer of the adult dentate gyrus (Fig. 2a). Interestingly, the sfrp3 in situ signal intensity increased along the longitudinal axis of adult hippocampus from the septal pole to the temporal pole (Fig. 2a). Quantitative real-time PCR in samples of micro-dissected dentate gyrus further confirmed higher sfrp3 expression in the temporal dentate gyrus (Fig. 2b). Notably, in situ analysis showed that the sfrp3 gradient appeared to be continuous across the septo-temporal axis of the hippocampus without sharp step changes suggestive of “border” transitions (Fig. 2a). We confirmed this result with densitometric measurements of in situ signal intensity on coronal sections of dissected hippocampus along the entire axis of hippocampus (Fig. 2c-d). To confirm the specificity of the sfrp3 in situ probe used, we compared wild-type (+/+), heterozygous (+/−) and knockout (−/−) sfrp3 animals. Indeed, no signal was observed in knockout animals in sections processed in parallel with other genotypes (Fig. 2e). Interestingly, a gradient was present in the heterozygous mice, although the expression level appeared to be reduced by ~50 % (Fig. 2e). Together, these results demonstrated that sfrp3 expression in the adult mouse dentate gyrus exhibits a smooth gradient with increasing expression along the septo-temporal axis.Fig. 2

Bottom Line: Using in situ hybridization and quantitative real-time PCR, we identified an inverse septal-to-temporal increase in the expression of sfrp3 that emerges during postnatal development.Elimination of sfrp3 and its molecular gradient leads to increased RGL activation, preferentially in the temporal region of the adult dentate gyrus.Our study identifies a niche mechanism that contributes to the graded distribution of neurogenesis in the adult dentate gyrus and has important implications for understanding functional differences associated with adult hippocampal neurogenesis along the septo-temporal axis.

View Article: PubMed Central - PubMed

Affiliation: Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, P.R. China.

ABSTRACT

Background: A converging body of evidence indicates that levels of adult hippocampal neurogenesis vary along the septo-temporal axis of the dentate gyrus, but the molecular mechanisms underlying this regional heterogeneity are not known. We previously identified a niche mechanism regulating proliferation and neuronal development in the adult mouse dentate gyrus resulting from the activity-regulated expression of secreted frizzled-related protein 3 (sfrp3) by mature neurons, which suppresses activation of radial glia-like neural stem cells (RGLs) through inhibition of Wingless/INT (WNT) protein signaling.

Results: Here, we show that activation rates within the quiescent RGL population decrease gradually along the septo-temporal axis in the adult mouse dentate gyrus, as defined by MCM2 expression in RGLs. Using in situ hybridization and quantitative real-time PCR, we identified an inverse septal-to-temporal increase in the expression of sfrp3 that emerges during postnatal development. Elimination of sfrp3 and its molecular gradient leads to increased RGL activation, preferentially in the temporal region of the adult dentate gyrus.

Conclusions: Our study identifies a niche mechanism that contributes to the graded distribution of neurogenesis in the adult dentate gyrus and has important implications for understanding functional differences associated with adult hippocampal neurogenesis along the septo-temporal axis.

No MeSH data available.


Related in: MedlinePlus