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Rac-GTPases Regulate Microtubule Stability and Axon Growth of Cortical GABAergic Interneurons.

Tivodar S, Kalemaki K, Kounoupa Z, Vidaki M, Theodorakis K, Denaxa M, Kessaris N, de Curtis I, Pachnis V, Karagogeos D - Cereb. Cortex (2014)

Bottom Line: We show that in the absence of both Rac proteins, the embryonic migration of medial ganglionic eminence-derived interneurons is further impaired.In addition, Rac1/Rac3-deficient interneurons show gross cytoskeletal defects in vitro, with the length of their leading processes significantly reduced and a clear multipolar morphology.We propose that in the absence of Rac1/Rac3, cortical interneurons fail to migrate tangentially towards the pallium due to defects in actin and microtubule cytoskeletal dynamics.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece.

No MeSH data available.


Related in: MedlinePlus

The number of different MGE-derived cortical interneuron subtypes in the Rac1 and Rac3 mutant postnatal barrel cortex is severely reduced. Distribution of different interneuron subtypes in P5 and P15 brains was analyzed using specific markers for GABAergic interneurons. The distribution (A, A′) and number of YFP+ (C), Lhx6+;YFP+ (D), GABA+;YFP+ (E), PVA+;YFP+ (F) and Sst+ (G) interneurons was reduced to almost 80% in the double mutants compared with the control animals. The number of CR+ cells was not affected in the absence of Rac1/Rac3 proteins (H). The percentage of double positive Lhx6;YFP (I), GABA;YFP (J) and PVA;YFP (K) over the total number of YFP+ cells is not different between control and mutant in the barrel cortex. Coronal sections from P5 brains with Nissl staining were taken within the range of bregmata from 0.86 to −1.46 mm (B, B′). These brain sections were used for counting and the boxed regions represent the area of the barrel cortex where the countings were performed. Statistical significance was assessed, using Student's t-test (P value < 0.05). Error bars represent the standard error of mean. Scale bars: 150 μm.
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BHU037F3: The number of different MGE-derived cortical interneuron subtypes in the Rac1 and Rac3 mutant postnatal barrel cortex is severely reduced. Distribution of different interneuron subtypes in P5 and P15 brains was analyzed using specific markers for GABAergic interneurons. The distribution (A, A′) and number of YFP+ (C), Lhx6+;YFP+ (D), GABA+;YFP+ (E), PVA+;YFP+ (F) and Sst+ (G) interneurons was reduced to almost 80% in the double mutants compared with the control animals. The number of CR+ cells was not affected in the absence of Rac1/Rac3 proteins (H). The percentage of double positive Lhx6;YFP (I), GABA;YFP (J) and PVA;YFP (K) over the total number of YFP+ cells is not different between control and mutant in the barrel cortex. Coronal sections from P5 brains with Nissl staining were taken within the range of bregmata from 0.86 to −1.46 mm (B, B′). These brain sections were used for counting and the boxed regions represent the area of the barrel cortex where the countings were performed. Statistical significance was assessed, using Student's t-test (P value < 0.05). Error bars represent the standard error of mean. Scale bars: 150 μm.

Mentions: From the embryonic analysis we observed that the majority of MGE-derived interneurons, missing both Rac1 and Rac3, did not manage to migrate and populate the cortex on time (Fig. 1). Instead, they were found accumulated in the ventral telencephalon even postnatally (data not shown). Given the great reduction in migrating interneurons during embryogenesis, we analyzed the distribution (Supplementary Fig. 2) and numbers of interneuron subpopulations with specific markers at P5, after they reached their final position in the cortex (Fig. 3). For comparison we used equivalent cryosections from the double-mutant cortex and from the control cortex at different anterior–posterior levels (Fig. 3B,B′). A striking 80% of YFP+ cells were absent in the double-mutant barrel cortex compared with the control barrel cortex (Fig. 3A,A′,C). Comparisons between control and Rac3 mutant for YFP+ cells in the P15 cortex showed no statistically significant differences (data not shown). By using specific interneuron markers (Lhx6, GABA, PV) and quantifying the double-positive cells we demonstrated that in all cases, only 20% of double-labeled interneurons were found in the cortex of double-mutant mice (Fig. 3D,E,F and Supplementary Fig. 2). The same 80% reduction was observed after quantification of cells positive for Sst mRNA (Fig. 3G). The percentages of YFP+ cells that co-express GABA, Lhx6, and PV over the total number of YFP+ cells were not significantly different between control and mutants deficient in Rac1/Rac3 (Fig. 3I–K), indicating that the ability of the double-mutant precursors to differentiate into the various mature interneuron subtypes is not affected despite the great reduction in absolute numbers.Figure 3.


Rac-GTPases Regulate Microtubule Stability and Axon Growth of Cortical GABAergic Interneurons.

Tivodar S, Kalemaki K, Kounoupa Z, Vidaki M, Theodorakis K, Denaxa M, Kessaris N, de Curtis I, Pachnis V, Karagogeos D - Cereb. Cortex (2014)

The number of different MGE-derived cortical interneuron subtypes in the Rac1 and Rac3 mutant postnatal barrel cortex is severely reduced. Distribution of different interneuron subtypes in P5 and P15 brains was analyzed using specific markers for GABAergic interneurons. The distribution (A, A′) and number of YFP+ (C), Lhx6+;YFP+ (D), GABA+;YFP+ (E), PVA+;YFP+ (F) and Sst+ (G) interneurons was reduced to almost 80% in the double mutants compared with the control animals. The number of CR+ cells was not affected in the absence of Rac1/Rac3 proteins (H). The percentage of double positive Lhx6;YFP (I), GABA;YFP (J) and PVA;YFP (K) over the total number of YFP+ cells is not different between control and mutant in the barrel cortex. Coronal sections from P5 brains with Nissl staining were taken within the range of bregmata from 0.86 to −1.46 mm (B, B′). These brain sections were used for counting and the boxed regions represent the area of the barrel cortex where the countings were performed. Statistical significance was assessed, using Student's t-test (P value < 0.05). Error bars represent the standard error of mean. Scale bars: 150 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4537417&req=5

BHU037F3: The number of different MGE-derived cortical interneuron subtypes in the Rac1 and Rac3 mutant postnatal barrel cortex is severely reduced. Distribution of different interneuron subtypes in P5 and P15 brains was analyzed using specific markers for GABAergic interneurons. The distribution (A, A′) and number of YFP+ (C), Lhx6+;YFP+ (D), GABA+;YFP+ (E), PVA+;YFP+ (F) and Sst+ (G) interneurons was reduced to almost 80% in the double mutants compared with the control animals. The number of CR+ cells was not affected in the absence of Rac1/Rac3 proteins (H). The percentage of double positive Lhx6;YFP (I), GABA;YFP (J) and PVA;YFP (K) over the total number of YFP+ cells is not different between control and mutant in the barrel cortex. Coronal sections from P5 brains with Nissl staining were taken within the range of bregmata from 0.86 to −1.46 mm (B, B′). These brain sections were used for counting and the boxed regions represent the area of the barrel cortex where the countings were performed. Statistical significance was assessed, using Student's t-test (P value < 0.05). Error bars represent the standard error of mean. Scale bars: 150 μm.
Mentions: From the embryonic analysis we observed that the majority of MGE-derived interneurons, missing both Rac1 and Rac3, did not manage to migrate and populate the cortex on time (Fig. 1). Instead, they were found accumulated in the ventral telencephalon even postnatally (data not shown). Given the great reduction in migrating interneurons during embryogenesis, we analyzed the distribution (Supplementary Fig. 2) and numbers of interneuron subpopulations with specific markers at P5, after they reached their final position in the cortex (Fig. 3). For comparison we used equivalent cryosections from the double-mutant cortex and from the control cortex at different anterior–posterior levels (Fig. 3B,B′). A striking 80% of YFP+ cells were absent in the double-mutant barrel cortex compared with the control barrel cortex (Fig. 3A,A′,C). Comparisons between control and Rac3 mutant for YFP+ cells in the P15 cortex showed no statistically significant differences (data not shown). By using specific interneuron markers (Lhx6, GABA, PV) and quantifying the double-positive cells we demonstrated that in all cases, only 20% of double-labeled interneurons were found in the cortex of double-mutant mice (Fig. 3D,E,F and Supplementary Fig. 2). The same 80% reduction was observed after quantification of cells positive for Sst mRNA (Fig. 3G). The percentages of YFP+ cells that co-express GABA, Lhx6, and PV over the total number of YFP+ cells were not significantly different between control and mutants deficient in Rac1/Rac3 (Fig. 3I–K), indicating that the ability of the double-mutant precursors to differentiate into the various mature interneuron subtypes is not affected despite the great reduction in absolute numbers.Figure 3.

Bottom Line: We show that in the absence of both Rac proteins, the embryonic migration of medial ganglionic eminence-derived interneurons is further impaired.In addition, Rac1/Rac3-deficient interneurons show gross cytoskeletal defects in vitro, with the length of their leading processes significantly reduced and a clear multipolar morphology.We propose that in the absence of Rac1/Rac3, cortical interneurons fail to migrate tangentially towards the pallium due to defects in actin and microtubule cytoskeletal dynamics.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Biology and Biotechnology (IMBB, FORTH), Heraklion, Greece Department of Basic Science, Faculty of Medicine, University of Crete, Heraklion, Greece.

No MeSH data available.


Related in: MedlinePlus