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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.


Ulk4R cDNA successfully restores the normal neuronal ramification and migration.(A–C) Schematic drawing of neurite ramification of neurons electroporated with control (A), shRNA268 (B) and shRNA268+Ulk4R cDNA (C). (D) Comparable dendritic pattern for neurons electroprated with control shRNA or shRNA268+Ulk4R cDNA by Sholl analysis. Forty-one cells were included from 6 control brains and forty-three cells were analysed from 4 Ulk4R cDNA brains. Two-tailed student’s t tests were performed and no significant difference was found at any examined radial distance. (E) Control shRNA and shRNA268+Ulk4R cDNA groups show comparable percentage of GFP-tracked cells in each individual cortical sublayers.
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f8: Ulk4R cDNA successfully restores the normal neuronal ramification and migration.(A–C) Schematic drawing of neurite ramification of neurons electroporated with control (A), shRNA268 (B) and shRNA268+Ulk4R cDNA (C). (D) Comparable dendritic pattern for neurons electroprated with control shRNA or shRNA268+Ulk4R cDNA by Sholl analysis. Forty-one cells were included from 6 control brains and forty-three cells were analysed from 4 Ulk4R cDNA brains. Two-tailed student’s t tests were performed and no significant difference was found at any examined radial distance. (E) Control shRNA and shRNA268+Ulk4R cDNA groups show comparable percentage of GFP-tracked cells in each individual cortical sublayers.

Mentions: To determine the effects of Ulk4R cDNA in vivo, panels of expression plasmids including control, shRNA268 or shRNA268+Ulk4R cDNA were delivered into lateral ventricles of E15.5 mouse brains and in vivo gene transfer performed and sections of P7 brains were examined to trace the positioning of these transfected cells. Compared with the control group (Fig. 7B), almost all GFP-tracked cells in the Ulk4R cDNA group were located in layers II–III (Fig. 7D). This observation was confirmed further by statistical analysis of the percentage of cell numbers in individual sublayers (Fig. 8E; n = 3 for each group, **p < 0.01). These results suggest that this construct successfully resumed normal migration and settlement of layers II–III neurons which had been perturbed by shRNA268 (Fig. 7C). We further reconstructed and compared the arborisation pattern of apical dendrites between the two groups in subsequent electroporation using lower concentration of GFP. Sholl analysis showed that dendrite branching deficits mediated by shRNA268 have been rescued effectively by Ulk4R cDNA (Fig. 8A–D, forty-one cells were included from 6 control brains and forty-three cells were from 4 Ulk4R cDNA brains). Our results strongly indicate that the phenotypes caused by Ulk4 knockdown are specific and can be restored successfully upon Ulk4 overexpression.


Control of cortex development by ULK4, a rare risk gene for mental disorders including schizophrenia
Ulk4R cDNA successfully restores the normal neuronal ramification and migration.(A–C) Schematic drawing of neurite ramification of neurons electroporated with control (A), shRNA268 (B) and shRNA268+Ulk4R cDNA (C). (D) Comparable dendritic pattern for neurons electroprated with control shRNA or shRNA268+Ulk4R cDNA by Sholl analysis. Forty-one cells were included from 6 control brains and forty-three cells were analysed from 4 Ulk4R cDNA brains. Two-tailed student’s t tests were performed and no significant difference was found at any examined radial distance. (E) Control shRNA and shRNA268+Ulk4R cDNA groups show comparable percentage of GFP-tracked cells in each individual cortical sublayers.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037360&req=5

f8: Ulk4R cDNA successfully restores the normal neuronal ramification and migration.(A–C) Schematic drawing of neurite ramification of neurons electroporated with control (A), shRNA268 (B) and shRNA268+Ulk4R cDNA (C). (D) Comparable dendritic pattern for neurons electroprated with control shRNA or shRNA268+Ulk4R cDNA by Sholl analysis. Forty-one cells were included from 6 control brains and forty-three cells were analysed from 4 Ulk4R cDNA brains. Two-tailed student’s t tests were performed and no significant difference was found at any examined radial distance. (E) Control shRNA and shRNA268+Ulk4R cDNA groups show comparable percentage of GFP-tracked cells in each individual cortical sublayers.
Mentions: To determine the effects of Ulk4R cDNA in vivo, panels of expression plasmids including control, shRNA268 or shRNA268+Ulk4R cDNA were delivered into lateral ventricles of E15.5 mouse brains and in vivo gene transfer performed and sections of P7 brains were examined to trace the positioning of these transfected cells. Compared with the control group (Fig. 7B), almost all GFP-tracked cells in the Ulk4R cDNA group were located in layers II–III (Fig. 7D). This observation was confirmed further by statistical analysis of the percentage of cell numbers in individual sublayers (Fig. 8E; n = 3 for each group, **p < 0.01). These results suggest that this construct successfully resumed normal migration and settlement of layers II–III neurons which had been perturbed by shRNA268 (Fig. 7C). We further reconstructed and compared the arborisation pattern of apical dendrites between the two groups in subsequent electroporation using lower concentration of GFP. Sholl analysis showed that dendrite branching deficits mediated by shRNA268 have been rescued effectively by Ulk4R cDNA (Fig. 8A–D, forty-one cells were included from 6 control brains and forty-three cells were from 4 Ulk4R cDNA brains). Our results strongly indicate that the phenotypes caused by Ulk4 knockdown are specific and can be restored successfully upon Ulk4 overexpression.

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.