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Control of cortex development by ULK4, a rare risk gene for mental disorders including schizophrenia

View Article: PubMed Central - PubMed

ABSTRACT

Schizophrenia is a debilitating familial neuropsychiatric disorder which affects 1% of people worldwide. Although the heritability for schizophrenia approaches 80% only a small proportion of the overall genetic risk has been accounted for, and to date only a limited number of genetic loci have been definitively implicated. We have identified recently through genetic and in vitro functional studies, a novel serine/threonine kinase gene, unc-51-like kinase 4 (ULK4), as a rare risk factor for major mental disorders including schizophrenia. Now using the approach of in utero gene transfer we have discovered that Ulk4 plays a key modulatory role in corticogenesis. Knockdown of Ulk4 leads to significantly decreased cell proliferation in germinal zones and profound deficits in radial migration and neurite ramification. These abnormalities can be reversed successfully by Ulk4 gene supplementation. Ulk4 also regulated acetylation of α-tubulin, an important post-translational modification of microtubules. We conclude that Ulk4 plays an essential role in normal brain development and when defective, the risk of neurodevelopmental disorders such as schizophrenia is increased.

No MeSH data available.


Ulk4 knockdown leads to decreased acetylation of α-tubulin both in vitro and in vivo.(A,B) Primary cultured neurons transfected with shRNA268 display less α-acetylated tubulin (n = 3). Two-tailed student’s t tests. *p < 0.05. (C–H) Compared with neurons transfected with control shRNA (C,E,G), cortical neurons incorporated with shRNA268 (D,F,H) displayed reduced expression of α-acetylated tubulin (in red) in vivo. Bars = 25 μm in (C–H).
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f6: Ulk4 knockdown leads to decreased acetylation of α-tubulin both in vitro and in vivo.(A,B) Primary cultured neurons transfected with shRNA268 display less α-acetylated tubulin (n = 3). Two-tailed student’s t tests. *p < 0.05. (C–H) Compared with neurons transfected with control shRNA (C,E,G), cortical neurons incorporated with shRNA268 (D,F,H) displayed reduced expression of α-acetylated tubulin (in red) in vivo. Bars = 25 μm in (C–H).

Mentions: How Ulk4 silencing leads to abnormal corticogenesis remains unclear. In our previous study, depletion of ULK4 in SHSY-5Y cells remarkably decreased acetylation of α-tubulin12. Intriguingly, reduced tubulin acetylation could result in profound deficits in radial migration and neurite ramification during brain development2526 and disrupt hippocampal formation27. We therefore postulate that acetylated α-tubulin could be a component molecule of Ulk4 signalling which modulates corticogenesis. To test this hypothesis, we transfected primary cultured mouse cortical neurons with control and shRNA268 plasmids. The transfection efficiency was 76% and 74% respectively with no statistically significant difference (p > 0.05). We then determined the expression of acetylated α-tubulin by western blotting. Our results indeed showed that shRNA268 significantly reduced the expression of acetylated α-tubulin in the cultured neurons (n = 3, p < 0.05, Fig. 6A,B). In P7 brains, Ulk4 knockdown resulted in consistently diminished expression of acetylated α-tubulin (Fig. 6C–H). The reduction of acetylated α-tubulin also was confirmed by imaging analysis in both primary cultured neurons and brain sections (Supplementary Fig. S6). Similarly, shRNA269 also led to reduced expression of acetylated α-tubulin in P7 mouse brains (Supplementary Fig. S7). These results suggest that acetylated α-tubulin may contribute at least partially, to the altered corticogenesis caused by Ulk4 knockdown.


Control of cortex development by ULK4, a rare risk gene for mental disorders including schizophrenia
Ulk4 knockdown leads to decreased acetylation of α-tubulin both in vitro and in vivo.(A,B) Primary cultured neurons transfected with shRNA268 display less α-acetylated tubulin (n = 3). Two-tailed student’s t tests. *p < 0.05. (C–H) Compared with neurons transfected with control shRNA (C,E,G), cortical neurons incorporated with shRNA268 (D,F,H) displayed reduced expression of α-acetylated tubulin (in red) in vivo. Bars = 25 μm in (C–H).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037360&req=5

f6: Ulk4 knockdown leads to decreased acetylation of α-tubulin both in vitro and in vivo.(A,B) Primary cultured neurons transfected with shRNA268 display less α-acetylated tubulin (n = 3). Two-tailed student’s t tests. *p < 0.05. (C–H) Compared with neurons transfected with control shRNA (C,E,G), cortical neurons incorporated with shRNA268 (D,F,H) displayed reduced expression of α-acetylated tubulin (in red) in vivo. Bars = 25 μm in (C–H).
Mentions: How Ulk4 silencing leads to abnormal corticogenesis remains unclear. In our previous study, depletion of ULK4 in SHSY-5Y cells remarkably decreased acetylation of α-tubulin12. Intriguingly, reduced tubulin acetylation could result in profound deficits in radial migration and neurite ramification during brain development2526 and disrupt hippocampal formation27. We therefore postulate that acetylated α-tubulin could be a component molecule of Ulk4 signalling which modulates corticogenesis. To test this hypothesis, we transfected primary cultured mouse cortical neurons with control and shRNA268 plasmids. The transfection efficiency was 76% and 74% respectively with no statistically significant difference (p > 0.05). We then determined the expression of acetylated α-tubulin by western blotting. Our results indeed showed that shRNA268 significantly reduced the expression of acetylated α-tubulin in the cultured neurons (n = 3, p < 0.05, Fig. 6A,B). In P7 brains, Ulk4 knockdown resulted in consistently diminished expression of acetylated α-tubulin (Fig. 6C–H). The reduction of acetylated α-tubulin also was confirmed by imaging analysis in both primary cultured neurons and brain sections (Supplementary Fig. S6). Similarly, shRNA269 also led to reduced expression of acetylated α-tubulin in P7 mouse brains (Supplementary Fig. S7). These results suggest that acetylated α-tubulin may contribute at least partially, to the altered corticogenesis caused by Ulk4 knockdown.

View Article: PubMed Central - PubMed

ABSTRACT

Schizophrenia is a debilitating familial neuropsychiatric disorder which affects 1% of people worldwide. Although the heritability for schizophrenia approaches 80% only a small proportion of the overall genetic risk has been accounted for, and to date only a limited number of genetic loci have been definitively implicated. We have identified recently through genetic and in vitro functional studies, a novel serine/threonine kinase gene, unc-51-like kinase 4 (ULK4), as a rare risk factor for major mental disorders including schizophrenia. Now using the approach of in utero gene transfer we have discovered that Ulk4 plays a key modulatory role in corticogenesis. Knockdown of Ulk4 leads to significantly decreased cell proliferation in germinal zones and profound deficits in radial migration and neurite ramification. These abnormalities can be reversed successfully by Ulk4 gene supplementation. Ulk4 also regulated acetylation of &alpha;-tubulin, an important post-translational modification of microtubules. We conclude that Ulk4 plays an essential role in normal brain development and when defective, the risk of neurodevelopmental disorders such as schizophrenia is increased.

No MeSH data available.