Crumbs 2 prevents cortical abnormalities in mouse dorsal telencephalon

AbstractThe formation of a functionally integrated nervous system is dependent on a highly organized sequence of events that includes timely division and differentiation of progenitors. Several apical polarity proteins have been shown to play crucial roles during neurogenesis, however, the role of Crumbs 2 (CRB2) in cortical development has not previously been reported.Here, we show that conditional ablation of Crb2 in the murine dorsal telencephalon leads to defects in the maintenance of the apical complex. Furthermore, within the mutant dorsal telencephalon there is premature expression of differentiation proteins. We examined the physiological function of Crb2 on wild type genetic background as well as on background lacking Crb1. Telencephalon lacking CRB2 resulted in reduced levels of PALS1 and CRB3 from the apical complex, an increased number of mitotic cells and expanded neuronal domain. These defects are transient and therefore only result in rather mild cortical abnormalities. We show that CRB2 is required for maintenance of the apical polarity complex during development of the cortex and regulation of cell division, and that loss of CRB2 results in cortical abnormalities

Deletion of Munc18-1 in 5-HT Neurons Results in Rapid Degeneration of the 5-HT System and Early Postnatal Lethality

The serotonin (5-HT) system densely innervates many brain areas and is important for proper brain development. To specifically ablate the 5-HT system we generated mutant mice carrying a floxed Munc18-1 gene and Cre recombinase driven by the 5-HT-specific serotonin reuptake transporter (SERT) promoter. The majority of mutant mice died within a few days after birth. Immunohistochemical analysis of brains of these mice showed that initially 5-HT neurons are formed and the cortex is innervated with 5-HT projections. From embryonic day 16 onwards, however, 5-HT neurons started to degenerate and at postnatal day 2 hardly any 5-HT projections were present in the cortex. The 5-HT system of mice heterozygous for the floxed Munc18-1 allele was indistinguishable from control mice. These data show that deletion of Munc18-1 in 5-HT neurons results in rapid degeneration of the 5-HT system and suggests that the 5-HT system is important for postnatal survival

Keep off the grass?:Cannabis, cognition and addiction

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.In an increasing number of states and countries, cannabis now stands poised to join alcohol and tobacco as a legal drug. Quantifying the relative adverse and beneficial effects of cannabis and its constituent cannabinoids should therefore be prioritized. Whereas newspaper headlines have focused on links between cannabis and psychosis, less attention has been paid to the much more common problem of cannabis addiction. Certain cognitive changes have also been attributed to cannabis use, although their causality and longevity are fiercely debated. Identifying why some individuals are more vulnerable than others to the adverse effects of cannabis is now of paramount importance to public health. Here, we review the current state of knowledge about such vulnerability factors, the variations in types of cannabis, and the relationship between these and cognition and addiction.This work was supported by grants from the US National Institutes of Health to L.H.P. (AA020404, AA006420, AA022249 and AA017447) and by grants from the UK Medical Research Council to H.V.C. and C.J.A.M. (G0800268; MR/K015524/1)

Genetic and Molecular Approaches to Study Neuronal Migration in the Developing Cerebral Cortex

The migration of neuronal cells in the developing cerebral cortex is essential for proper development of the brain and brain networks. Disturbances in this process, due to genetic abnormalities or exogenous factors, leads to aberrant brain formation, brain network formation, and brain function. In the last decade, there has been extensive research in the field of neuronal migration. In this review, we describe different methods and approaches to assess and study neuronal migration in the developing cerebral cortex. First, we discuss several genetic methods, techniques and genetic models that have been used to study neuronal migration in the developing cortex. Second, we describe several molecular approaches to study aberrant neuronal migration in the cortex which can be used to elucidate the underlying mechanisms of neuronal migration. Finally, we describe model systems to investigate and assess the potential toxicity effect of prenatal exposure to environmental chemicals on proper brain formation and neuronal migration

Deletion of Munc18-1 in 5-HT Neurons Results in Rapid Degeneration of the 5-HT System and Early Postnatal

The serotonin (5-HT) system densely innervates many brain areas and is important for proper brain development. To specifically ablate the 5-HT system we generated mutant mice carrying a floxed Munc18-1 gene and Cre recombinase driven by the 5-HT-specific serotonin reuptake transporter (SERT) promoter. The majority of mutant mice died within a few days after birth. Immunohistochemical analysis of brains of these mice showed that initially 5-HT neurons are formed and the cortex is innervated with 5-HT projections. From embryonic day 16 onwards, however, 5-HT neurons started to degenerate and at postnatal day 2 hardly any 5-HT projections were present in the cortex. The 5-HT system of mice heterozygous for the floxed Munc18-1 allele was indistinguishable from control mice. These data show that deletion of Munc18-1 in 5-HT neurons results in rapid degeneration of the 5-HT system and suggests that the 5-HT system is important for postnatal survival

Degeneration of 5-HT projections in DRN and cortex.

<p>(A<b>–</b>F) At E16 in the midbrain containing the DRN, there was no difference in 5-HT projection density between control (A) and SERT-Cre^cre/wt Munc18-1^lox/lox (lox/lox) (B) mice. In control sections at E18 (C) and P2 (E) several 5-HT projections were present. However, in SERT-Cre^cre/wt Munc18-1^lox/lox sections at E18 (D) and P2 (F) only very few 5-HT projections are left. (G–L) In the cortex already at E16 there is a reduction in 5-HT projection density in sections from SERT-Cre^cre/wt Munc18-1^lox/lox (H) mice compared to control (G). At E18 (J) and P2 (L), in cortical sections from SERT-Cre^cre/wt Munc18-1^lox/lox mice only very few remaining 5-HT projections are present, in contrast to E18 (I) and P2 (K) control cortical sections. (M) Quantification of the 5-HT projection density in the DRN revealed that at E16 there is no difference, but at E18 and P2 5-HT projection density is reduced to ∼20%. (N) In cortical sections, at E16 and E18 the 5-HT projection density is reduced to ∼20% and at P2 the 5-HT projection density is reduced to ∼10%. Scale bar 50 µm in L. Data shown are mean±SEM * p<0.05.</p

In SERT-Cre^cre/wt Munc18-1^lox/wt mice number of 5-HT cell bodies and 5-HT innervations are not affected.

<p>(A-D) Midbrain sections containing the DRN from control (A) and hz (B) mice shows that 5-HT neurons are distributed in the characteristic DRN topology. Zooming in on 5-HT cell bodies show that both in control (C) and hz sections (D) these neurons have a fusiform or ovoid morphology and grow out several neurites. (E–H) 5-HT projection density is not different between control and hz mice in the midbrain containing the DRN (E and F respectively) or in cortical sections from control and hz mice (G and H respectively). (I) Number of 5-HT cell bodies per section does not differ between control and hz. (J) 5-HT projection density in midbrain containing DRN and cortical sections is not different between control and hz. Scale bars: 200 µm in B, 50 µm in D and H.</p

Postnatal lethality in SERT-Cre^cre/wt Munc18-1^lox/lox mice.

<p>(A) Genotype of the conditional knockout mice. Crossing SERT-Cre with Munc18-1^lox/lox mice results in deletion of Munc18-1 only and specifically in SERT expressing neurons, whereas all other neurons still express Munc18-1. (B) Genotyping mice after weaning at three weeks of age revealed that only few SERT-Cre^cre/wt Munc18-1^lox/lox mice survived up to three weeks.</p

Rapid degeneration of 5-HT neurons in SERT-Cre^cre/wt Munc18-1^lox/lox mice.

<p>We compared the number of 5-HT cell bodies in the DRN in control and SERT-Cre^cre/wt Munc18-1^lox/lox mice at E16, E18 and P2. (A-F) At E16, in both control mice (A) and SERT-Cre^cre/wt Munc18-1^lox/lox (lox/lox) mice (B) the 5-HT cell bodies are distributed in the DRN topology. At E18 and P2, however, in midbrain sections from SERT-Cre^cre/wt Munc18-1^lox/lox brains (D, F respectively) only few 5-HT neurons are present compared to control sections (C, E respectively). (G-L) Zooming in on 5-HT cell bodies shows that in control sections at E16 (G), E18 (I) and P2 (K) the cell bodies grow out several neurites and have a fusiform or ovoid morphology. However, remaining 5-HT cell bodies in SERT-Cre^cre/wt Munc18-1^lox/lox sections at E16 (H), E18 (J) and P2 (L) have a round morphology with hardly any neurites. (M,N) Blow up of some 5-HT cell bodies in control and SERT-Cre^cre/wt Munc18-1^lox/lox mice sections shows the differences in 5-HT cell body morphology. (O) Analysis of the number of 5-HT cell bodies in the sections showed that there is no difference at E16, but at E18 and P2 there is a decrease of 80% to 90% in the number of 5-HT cell bodies in SERT-Cre^cre/wt Munc18-1^lox/lox sections. Scale bars: 200 µm in F, 50 µm in L and 20 µm in N. Data shown are mean ± standard error of the mean (SEM). * p<0.05.</p

恐ろしい「第二の誕生」 : W. B. イェイツ"The Second Coming"を読む

<div><p>Development in the central nervous system is highly dependent on the regulation of the switch from progenitor cell proliferation to differentiation, but the molecular and cellular events controlling this process remain poorly understood. Here, we report that ablation of <i>Crb1</i> and <i>Crb2</i> genes results in severe impairment of retinal function, abnormal lamination and thickening of the retina mimicking human Leber congenital amaurosis due to loss of <i>CRB1</i> function. We show that the levels of CRB1 and CRB2 proteins are crucial for mouse retinal development, as they restrain the proliferation of retinal progenitor cells. The lack of these apical proteins results in altered cell cycle progression and increased number of mitotic cells leading to an increased number of late-born cell types such as rod photoreceptors, bipolar and Müller glia cells in postmitotic retinas. Loss of CRB1 and CRB2 in the retina results in dysregulation of target genes for the Notch1 and YAP/Hippo signaling pathways and increased levels of P120-catenin. Loss of CRB1 and CRB2 result in altered progenitor cell cycle distribution with a decrease in number of late progenitors in G1 and an increase in S and G2/M phase. These findings suggest that CRB1 and CRB2 suppress late progenitor pool expansion by regulating multiple proliferative signaling pathways.</p></div