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. 2015 May 12;11(6):944-956.
doi: 10.1016/j.celrep.2015.04.019. Epub 2015 Apr 30.

The Parvalbumin/Somatostatin Ratio Is Increased in Pten Mutant Mice and by Human PTEN ASD Alleles

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Free PMC article

The Parvalbumin/Somatostatin Ratio Is Increased in Pten Mutant Mice and by Human PTEN ASD Alleles

Daniel Vogt et al. Cell Rep. .
Free PMC article

Abstract

Mutations in the phosphatase PTEN are strongly implicated in autism spectrum disorder (ASD). Here, we investigate the function of Pten in cortical GABAergic neurons using conditional mutagenesis in mice. Loss of Pten results in a preferential loss of SST(+) interneurons, which increases the ratio of parvalbumin/somatostatin (PV/SST) interneurons, ectopic PV(+) projections in layer I, and inhibition onto glutamatergic cortical neurons. Pten mutant mice exhibit deficits in social behavior and changes in electroencephalogram (EEG) power. Using medial ganglionic eminence (MGE) transplantation, we test for cell-autonomous functional differences between human PTEN wild-type (WT) and ASD alleles. The PTEN ASD alleles are hypomorphic in regulating cell size and the PV/SST ratio in comparison to WT PTEN. This MGE transplantation/complementation assay is efficient and is generally applicable for functional testing of ASD alleles in vivo.

Figures

Figure 1
Figure 1. Nkx2.1-Cre; Pten conditional mutants exhibit reduced interneuron numbers, increased PV/SST ratio and ectopic PV+ processes in layer I
(A) Images of postnatal day (P) 30 mice and brains (superior and lateral views) from Pten+/+, PtenFlox/+ and PtenFlox/Flox (Nkx2.1-Cre+; Ai14Flox/+) genotypes. Coronal immunofluorescent images of P30 somatosensory cortices show co-expression of tdTomato with SST (B–D) or with PV (E–G). (E′-G′) Higher magnification images of neocortical layer I from images E–G that have been merged with DAPI. Brackets to the right of each panel denote the boundaries of layer I. (H) Quantification of the number of tdTomato+ cells per square millimeter (mm2) in the somatosensory cortex over time. Quantification of the % tdTomato+ cells that express either SST (I) or PV (J). (K) Ratio of tdTomato+/PV+ cells per mm2 over tdTomato+/SST+ cells per mm2 in the neocortex. Data are represented as mean ± SEM. *p < 0.05, **p < 0.01. Scale bars in (G and G′) = 100 μm. See also Figures S1, and S2, and Tables S1 and S2.
Figure 2
Figure 2. Normal interneuron numbers and morphology in SST-IRES-Cre; Pten cKOs
(A) Coronal immunofluorescent image of SST-IRES-Cre+; Ai14Flox/+ showing the pattern of SST-lineage cells (tdtomato+) at embryonic day (E) 15.5. Coronal immunofluorescent images of P30 somatosensory cortices from SST-IRES-Cre+; Ai14Flox/+;Pten+/+, PtenFlox/+ and PtenFlox/Flox show expression of tdTomato with SST (B–D) or with PV (E–G). Brackets to the right of each panel denote the boundaries of layer I. (H) Quantification of the total number of tdTomato+ cells per mm2. Quantification of the % tdTomato+ cells that express SST (I) or PV (J). Data are represented as mean ± SEM. Scale bars in (A and G) = 100 μm. See also Figure S2.
Figure 3
Figure 3. Abnormal distribution of SST+ cells and elevated apoptosis in Nkx2.1-Cre; Pten cKOs
E15.5 coronal immunofluorescent images of Nkx2.1-Cre-lineage cells (tdTomato+) colabeled for SST and DAPI in Pten+/+ (A) and PtenFlox/Flox (E) brains. (B–D and F–H) Higher magnification fluorescent images of the lateral cortex (white boxes in A, E). (I) Quantification of the % tdTomato+ cells that express SST in the lateral cortex. (J–O) Immunofluorescent images of the neocortex (orange boxes in A, E) showing tdTomato+ cells that express SST. (P) Quantification of the % tdTomato+ cells that express SST in the neocortex. (Q–V) Immunofluorescent images of the lateral cortex at P0 showing tdTomato+ cells that express SST and cleaved-caspase-3 (cC3). (W) Quantification of the % tdTomato+ cells that express SST in the lateral cortex at P0. (X) Quantification of the % tdTomato+ cells in the MZ that are cC3+, left bars; tdTomato+/SST+, middle bars; or tdTomato+/SST, right bars. Data are represented as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001. Scale bars in (E) = 250 μm and (H, O, V) = 100 μm. Abbreviations: MZ (marginal zone), CP (cortical plate), IZ/SVZ (intermediate and subventricular zones).
Figure 4
Figure 4. Neocortical principle neurons in Nkx2.1-Cre; Pten cKOs received increased IPSC frequency
(A) Schema of neocortical recordings performed on principle neurons in somatosensory cortical layers II/III (black) from Nkx2.1-Cre+; Ai14Flox/+ ; Pten+/+, PtenFlox/+ or PtenFlox/Flox slices at P30. Nkx2.1-Cre+ interneurons were tdTomato+ (red). (B) Example traces of inhibitory postsynaptic currents (IPSCs) from Pten+/+ and PtenFlox/Flox slices. Quantification of IPSC frequency onto principle neurons (C) and IPSC amplitude (D). Data are represented as mean ± SEM. *p < 0.05. Abbreviations: (ms) milliseconds, (Hz) hertz, (pA) picoamps.
Figure 5
Figure 5. Nkx2.1-Cre; Pten cKOs showed reduced social behavior and altered EEG gamma oscillations
(A–C) Open field test: quantification of P30 Nkx2.1-Cre+; Pten+/+ (WT) and Ptenflox/flox littermates for time spent in the center of the field (A), distance traveled in the center (B) and in the perimeter (C). (D, E) Elevated plus maze: quantification of the time spent in open arms (D) and the number of entries made (E). (F) Social interaction task: quantification of the amount of social interaction time Nkx2.1-Cre+; Pten+/+ (WT) and Ptenflox/flox littermates spent with a stranger mouse. (G) Social interaction task: quantification of changes in electroencephalogram (EEG) power, log transformed, during periods of social interaction. Graph represents recordings made from prefrontal cortex; significant changes were in the high-γ range (62–90 Hz). (H) Prefrontal EEG, shown as the log transform of the averaged, normalized power spectrum. The graph was analyzed from a period before the social interaction test and the power spectrum from each mouse was normalized by the sum of all values from 0–120 Hz (excluding 58–62 Hz). Nkx2.1-Cre, Ptenflox/flox mice exhibit a decrease in the power of prefrontal baseline high-γ (62–90 Hz) oscillations compared to their WT littermates. (I) Novel object task: just after the social interaction assay, the time each mouse spent with a novel object was measured. (n = 5 mice per genotype, both groups). Data are represented as mean ± SEM. *p < 0.05, **p < 0.01.
Figure 6
Figure 6. Cortical interneurons derived from transplanted Pten cKO MGE have increased soma size and increased PV+/SST+ ratio
(A) Schema depicting the transplantation procedure. E12.5 DlxI12b-Cre+; Ai14Flox/+ MGE cells (tdTomato+) that were either Pten+/+, PtenFlox/+ or PtenFlox/Flox were transplanted into WT P1 neocortices and allowed to develop for 35 days post transplant (DPT). Coronal immunoflourescent images of neocortices transplanted with Pten+/+, PtenFlox/+ or PtenFlox/Flox MGE cells show coexpression of tdTomato and SST (B–D) or PV (E–G). Arrows point to coexpressing cells. Quantification of soma size of the tdTomato+ cells (H), and the proportion of tdTomato+ cells that express either SST (I) or PV (J). Data are represented as mean ± SD (H), ± SEM (I, J). (*p < 0.05, **p<0.01, ***p<0.001). Scale bar in (G) = 100 μm. See also Figure S4 and Table S3.
Figure 7
Figure 7. Complementation assay comparing WT and PTEN ASD alleles reveal reduced function of ASD alleles in regulating PV+ interneuron ratio
(A) Schema depicting the MGE transplantation and complementation assay. E12.5 control (Pten+/+; Ai14Flox/+) or (PtenFlox/Flox; Ai14Flox/+) MGE cells were transduced with a DlxI12b-Cre-T2a-MCS lentivirus that expresses either Cre only, or Cre with human WT PTEN, or a PTEN ASD allele, from the multiple cloning site (MCS). MGE cells were transplanted into a P1 wild type (WT) neoocortex and assessed at 35 DPT. Coronal immunoflourescent images of neocortices transplanted with transduced control (B–H) or PtenFlox/Flox (B′–H′) MGE cells show expression of tdTomato and PV at 35 DPT. Arrows point to co-expressing cells. Quantification of the % of tdTomato+ control (I) or PtenFlox/Flox (J) transduced-MGE cells that co-express PV. Data are represented as mean ± SEM. (n) = 4, all groups (**p<0.01, ***p<0.001, black asterisks = compared to Cre only lentivirus, magenta asterisks = compared to WT PTEN lentivirus). Scale bar in (H′) = 100 μm. See also Figures S5 and S6.

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