Gene expansions contributing to human brain evolution.

Genomic drivers of human-specific neurological traits remain largely undiscovered. Duplicated genes expanded uniquely in the human lineage likely contributed to brain evolution, including the increased complexity of synaptic connections between neurons and the dramatic expansion of the neocortex. Discovering duplicate genes is challenging because the similarity of paralogs makes them prone to sequence-assembly errors. To mitigate this issue, we analyzed a complete telomere-to-telomere human genome sequence (T2T-CHM13) and identified 213 duplicated gene families likely containing human-specific paralogs (>98% identity). Positing that genes important in universal human brain features should exist with at least one copy in all modern humans and exhibit expression in the brain, we narrowed in on 362 paralogs with at least one copy across thousands of ancestrally diverse genomes and present in human brain transcriptomes. Of these, 38 paralogs co-express in gene modules enriched for autism-associated genes and potentially contribute to human language and cognition. We narrowed in on 13 duplicate gene families with human-specific paralogs that are fixed among modern humans and show convincing brain expression patterns. Using long-read DNA sequencing revealed hidden variation across 200 modern humans of diverse ancestries, uncovering signatures of selection not previously identified, including possible balancing selection of CD8B. To understand the roles of duplicated genes in brain development, we generated zebrafish CRISPR "knockout" models of nine orthologs and transiently introduced mRNA-encoding paralogs, effectively "humanizing" the larvae. Morphometric, behavioral, and single-cell RNA-seq screening highlighted, for the first time, a possible role for GPR89B in dosage-mediated brain expansion and FRMPD2B function in altered synaptic signaling, both hallmark features of the human brain. Our holistic approach provides important insights into human brain evolution as well as a resource to the community for studying additional gene expansion drivers of human brain evolution.

Zebrafish models of human-duplicated SRGAP2 reveal novel functions in microglia and visual system development.

The expansion of the human SRGAP2 family, resulting in a human-specific paralog SRGAP2C, likely contributed to altered evolutionary brain features. The introduction of SRGAP2C in mouse models is associated with changes in cortical neuronal migration, axon guidance, synaptogenesis, and sensory-task performance. Truncated SRGAP2C heterodimerizes with the full-length ancestral gene product SRGAP2A and antagonizes its functions. However, the significance of SRGAP2 duplication beyond neocortex development has not been elucidated due to the embryonic lethality of complete Srgap2 knockout in mice. Using zebrafish, we show that srgap2 knockout results in viable offspring and that these larvae phenocopy "humanized" SRGAP2C larvae, including altered morphometric features (i.e., reduced body length and inter-eye distance) and differential expression of synapse-, axonogenesis-, and vision-related genes. Through single-cell transcriptome analysis, we demonstrate a skewed balance of excitatory and inhibitory neurons that likely contribute to increased susceptibility to seizures displayed by Srgap2 mutant larvae, a phenotype resembling SRGAP2 loss-of-function in a child with early infantile epileptic encephalopathy. Single-cell data also shows strong endogenous expression of srgap2 in microglia with mutants exhibiting altered membrane dynamics and likely delayed maturation of microglial cells. Microglia cells expressing srgap2 were also detected in the developing eye together with altered expression of genes related to axonogenesis in mutant retinal cells. Consistent with the perturbed gene expression in the retina, we found that SRGAP2 mutant larvae exhibited increased sensitivity to broad and fine visual cues. Finally, comparing the transcriptomes of relevant cell types between human (+SRGAP2C) and non-human primates (-SRGAP2C) revealed significant overlaps of gene alterations with mutant cells in our zebrafish models; this suggests that SRGAP2C plays a similar role altering microglia and the visual system in modern humans. Together, our functional characterization of conserved ortholog Srgap2 and human SRGAP2C in zebrafish uncovered novel gene functions and highlights the strength of cross-species analysis in understanding the development of human-specific features.

Regulation of young-adult neurogenesis and neuronal differentiation by neural cell adhesion molecule 2 (NCAM2).

Adult neurogenesis persists in mammals in the neurogenic zones, where newborn neurons are incorporated into preexisting circuits to preserve and improve learning and memory tasks. Relevant structural elements of the neurogenic niches include the family of cell adhesion molecules (CAMs), which participate in signal transduction and regulate the survival, division, and differentiation of radial glial progenitors (RGPs). Here we analyzed the functions of neural cell adhesion molecule 2 (NCAM2) in the regulation of RGPs in adult neurogenesis and during corticogenesis. We characterized the presence of NCAM2 across the main cell types of the neurogenic process in the dentate gyrus, revealing different levels of NCAM2 amid the progression of RGPs and the formation of neurons. We showed that Ncam2 overexpression in adult mice arrested progenitors in an RGP-like state, affecting the normal course of young-adult neurogenesis. Furthermore, changes in Ncam2 levels during corticogenesis led to transient migratory deficits but did not affect the survival and proliferation of RGPs, suggesting a differential role of NCAM2 in adult and embryonic stages. Our data reinforce the relevance of CAMs in the neurogenic process by revealing a significant role of Ncam2 levels in the regulation of RGPs during young-adult neurogenesis in the hippocampus.

NPC1-dependent alterations in KV2.1-CaV1.2 nanodomains drive neuronal death in models of Niemann-Pick Type C disease.

Lysosomes communicate through cholesterol transfer at endoplasmic reticulum (ER) contact sites. At these sites, the Niemann Pick C1 cholesterol transporter (NPC1) facilitates the removal of cholesterol from lysosomes, which is then transferred to the ER for distribution to other cell membranes. Mutations in NPC1 result in cholesterol buildup within lysosomes, leading to Niemann-Pick Type C (NPC) disease, a progressive and fatal neurodegenerative disorder. The molecular mechanisms connecting NPC1 loss to NPC-associated neuropathology remain unknown. Here we show both in vitro and in an animal model of NPC disease that the loss of NPC1 function alters the distribution and activity of voltage-gated calcium channels (CaV). Underlying alterations in calcium channel localization and function are KV2.1 channels whose interactions drive calcium channel clustering to enhance calcium entry and fuel neurotoxic elevations in mitochondrial calcium. Targeted disruption of KV2-CaV interactions rescues aberrant CaV1.2 clustering, elevated mitochondrial calcium, and neurotoxicity in vitro. Our findings provide evidence that NPC is a nanostructural ion channel clustering disease, characterized by altered distribution and activity of ion channels at membrane contacts, which contribute to neurodegeneration.

Notch directs telencephalic development and controls neocortical neuron fate determination by regulating microRNA levels.

The central nervous system contains a myriad of different cell types produced from multipotent neural progenitors. Neural progenitors acquire distinct cell identities depending on their spatial position, but they are also influenced by temporal cues to give rise to different cell populations over time. For instance, the progenitors of the cerebral neocortex generate different populations of excitatory projection neurons following a well-known sequence. The Notch signaling pathway plays crucial roles during this process, but the molecular mechanisms by which Notch impacts progenitor fate decisions have not been fully resolved. Here, we show that Notch signaling is essential for neocortical and hippocampal morphogenesis, and for the development of the corpus callosum and choroid plexus. Our data also indicate that, in the neocortex, Notch controls projection neuron fate determination through the regulation of two microRNA clusters that include let-7, miR-99a/100 and miR-125b. Our findings collectively suggest that balanced Notch signaling is crucial for telencephalic development and that the interplay between Notch and miRNAs is essential for the control of neocortical progenitor behaviors and neuron cell fate decisions.

The E3 Ubiquitin Ligase CRL5 Regulates Dentate Gyrus Morphogenesis, Adult Neurogenesis, and Animal Behavior.

The dentate gyrus (DG) is an essential part of the hippocampal formation and participates in the majority of hippocampal functions. The DG is also one of the few structures in the mammalian central nervous system that produces adult-born neurons and, in humans, alterations in adult neurogenesis are associated with stress and depression. Given the importance of DG in hippocampal function, it is imperative to understand the molecular mechanisms driving DG development and homeostasis. The E3 ubiquitin ligase Cullin-5/RBX2 (CRL5) is a multiprotein complex involved in neuron migration and localization in the nervous system, but its role during development and in the adult DG remain elusive. Here, we show that CRL5 participates in mossy fiber pruning, DG layering, adult neurogenesis, and overall physical activity in mice. During DG development, RBX2 depletion causes an overextension of the DG mossy fiber infrapyramidal bundle (IPB). We further demonstrate that the increased activity in Reelin/DAB1 or ARF6 signaling, observed in RBX2 knockout mice, is not responsible for the lack of IPB pruning. Knocking out RBX2 also affects granule cell and neural progenitor localization and these defects were rescued by downregulating the Reelin/DAB1 signaling. Finally, we show that absence of RBX2 increases the number neural progenitors and adult neurogenesis. Importantly, RBX2 knockout mice exhibit higher levels of physical activity, uncovering a potential mechanism responsible for the increased adult neurogenesis in the RBX2 mutant DG. Overall, we present evidence of CRL5 regulating mossy fiber pruning and layering during development and opposing adult neurogenesis in the adult DG.

RapID Cell Counter: Semi-Automated and Mid-Throughput Estimation of Cell Density within Diverse Cortical Layers.

Tracking and quantifying the abundance and location of cells in the developing brain is essential in neuroscience research, enabling a greater understanding of mechanisms underlying nervous system morphogenesis. Widely used experimental methods to quantify cells labeled with fluorescent markers, such as immunohistochemistry (IHC), in situ hybridization, and expression of transgenes via stable lines or transient in utero electroporations (IUEs), depend on accurate and consistent quantification of images. Current methods to quantify fluorescently-labeled cells rely on labor-intensive manual counting approaches, such as the Fiji plugin Cell Counter, which requires custom macros to enable higher-throughput analyses. Here, we present RapID Cell Counter, a semi-automated cell-counting tool with an easy-to-implement graphical user interface (GUI), which facilitates quick and consistent quantifications of cell density within user-defined boundaries that can be divided into equally-partitioned segments. Compared with the standard manual counting approach, we show that RapID matched accuracy and consistency and only required ∼10% of user time relative to manual counting methods, when quantifying the distribution of fluorescently-labeled neurons in mouse IUE experiments. Using RapID, we recapitulated previously published work focusing on two genes, SRGAP2 and CUL5, important for projection neuron (PN) migration in the neocortex and used it to quantify PN displacement in a mouse knock-out model of RBX2 Moreover, RapID is capable of quantifying other cell types in the brain with complex cell morphologies, including astrocytes and dopaminergic neurons. We propose RapID as an efficient method for neuroscience researchers to process fluorescently-labeled brain images in a consistent, accurate, and mid-throughput manner.

IP3R-driven increases in mitochondrial Ca2+ promote neuronal death in NPC disease.

Ca2+ is the most ubiquitous second messenger in neurons whose spatial and temporal elevations are tightly controlled to initiate and orchestrate diverse intracellular signaling cascades. Numerous neuropathologies result from mutations or alterations in Ca2+ handling proteins; thus, elucidating molecular pathways that shape Ca2+ signaling is imperative. Here, we report that loss-of-function, knockout, or neurodegenerative disease-causing mutations in the lysosomal cholesterol transporter, Niemann-Pick Type C1 (NPC1), initiate a damaging signaling cascade that alters the expression and nanoscale distribution of IP3R type 1 (IP3R1) in endoplasmic reticulum membranes. These alterations detrimentally increase Gq-protein coupled receptor-stimulated Ca2+ release and spontaneous IP3R1 Ca2+ activity, leading to mitochondrial Ca2+ cytotoxicity. Mechanistically, we find that SREBP-dependent increases in Presenilin 1 (PS1) underlie functional and expressional changes in IP3R1. Accordingly, expression of PS1 mutants recapitulate, while PS1 knockout abrogates Ca2+ phenotypes. These data present a signaling axis that links the NPC1 lysosomal cholesterol transporter to the damaging redistribution and activity of IP3R1 that precipitates cell death in NPC1 disease and suggests that NPC1 is a nanostructural disease.

CRL5-dependent regulation of the small GTPases ARL4C and ARF6 controls hippocampal morphogenesis.

The small GTPase ARL4C participates in the regulation of cell migration, cytoskeletal rearrangements, and vesicular trafficking in epithelial cells. The ARL4C signaling cascade starts by the recruitment of the ARF-GEF cytohesins to the plasma membrane, which, in turn, bind and activate the small GTPase ARF6. However, the role of ARL4C-cytohesin-ARF6 signaling during hippocampal development remains elusive. Here, we report that the E3 ubiquitin ligase Cullin 5/RBX2 (CRL5) controls the stability of ARL4C and its signaling effectors to regulate hippocampal morphogenesis. Both RBX2 knockout and Cullin 5 knockdown cause hippocampal pyramidal neuron mislocalization and development of multiple apical dendrites. We used quantitative mass spectrometry to show that ARL4C, Cytohesin-1/3, and ARF6 accumulate in the RBX2 mutant telencephalon. Furthermore, we show that depletion of ARL4C rescues the phenotypes caused by Cullin 5 knockdown, whereas depletion of CYTH1 or ARF6 exacerbates overmigration. Finally, we show that ARL4C, CYTH1, and ARF6 are necessary for the dendritic outgrowth of pyramidal neurons to the superficial strata of the hippocampus. Overall, we identified CRL5 as a key regulator of hippocampal development and uncovered ARL4C, CYTH1, and ARF6 as CRL5-regulated signaling effectors that control pyramidal neuron migration and dendritogenesis.

NCAM2 Regulates Dendritic and Axonal Differentiation through the Cytoskeletal Proteins MAP2 and 14-3-3.

Neural cell adhesion molecule 2 (NCAM2) is involved in the development and plasticity of the olfactory system. Genetic data have implicated the NCAM2 gene in neurodevelopmental disorders including Down syndrome and autism, although its role in cortical development is unknown. Here, we show that while overexpression of NCAM2 in hippocampal neurons leads to minor alterations, its downregulation severely compromises dendritic architecture, leading to an aberrant phenotype including shorter dendritic trees, retraction of dendrites, and emergence of numerous somatic neurites. Further, our data reveal alterations in the axonal tree and deficits in neuronal polarization. In vivo studies confirm the phenotype and reveal an unexpected role for NCAM2 in cortical migration. Proteomic and cell biology experiments show that NCAM2 molecules exert their functions through a protein complex with the cytoskeletal-associated proteins MAP2 and 14-3-3γ and ζ. We provide evidence that NCAM2 depletion results in destabilization of the microtubular network and reduced MAP2 signal. Our results demonstrate a role for NCAM2 in dendritic formation and maintenance, and in neural polarization and migration, through interaction of NCAM2 with microtubule-associated proteins.

Let-7 regulates cell cycle dynamics in the developing cerebral cortex and retina.

In the neural progenitors of the developing central nervous system (CNS), cell proliferation is tightly controlled and coordinated with cell fate decisions. Progenitors divide rapidly during early development and their cell cycle lengthens progressively as development advances to eventually give rise to a tissue of the correct size and cellular composition. However, our understanding of the molecules linking cell cycle progression to developmental time is incomplete. Here, we show that the microRNA (miRNA) let-7 accumulates in neural progenitors over time throughout the developing CNS. Intriguingly, we find that the level and activity of let-7 oscillate as neural progenitors progress through the cell cycle by in situ hybridization and fluorescent miRNA sensor analyses. We also show that let-7 mediates cell cycle dynamics: increasing the level of let-7 promotes cell cycle exit and lengthens the S/G2 phase of the cell cycle, while let-7 knock down shortens the cell cycle in neural progenitors. Together, our findings suggest that let-7 may link cell proliferation to developmental time and regulate the progressive cell cycle lengthening that occurs during development.

Comparative Analysis of cul5 and rbx2 Expression in the Developing and Adult Murine Brain and Their Essentiality During Mouse Embryogenesis.

BACKGROUND: The E3 Cullin 5-RING ubiquitin ligase (CRL5) is a multiprotein complex that has recently been highlighted as a major regulator of central nervous system development. Cullin 5 (Cul5) and the RING finger protein Rbx2 are two CRL5 core components required for CRL5 function in the brain, but their full expression patterns and developmental functions have not been described in detail. RESULTS: Using a gene-trap mouse model for Cul5 and a knock-in-knockout mouse model for Rbx2, we show that lack of Cul5, but not Rbx2, disrupts blastocyst formation. However, Rbx2 is required for embryo survival at later embryonic stages. We also show that cul5 is expressed in the embryo proper as early as E7.5 and its expression is mostly restricted to the central nervous system and limbs at later time points. Finally, we show that rbx2 and cul5 are co-expressed in most areas of the brain during development and in the adult. CONCLUSIONS: Our results show that Cul5, but not Rbx2, is required during early embryogenesis and suggests that Cul5 has Rbx2-independent functions in early development. In the brain, Cul5 and Rbx2 are expressed in a similar fashion, allowing the nucleation of an active CRL5 complex. Developmental Dynamics 247:1227-1236, 2018. © 2018 Wiley Periodicals, Inc.

RBX2 maintains final retinal cell position in a DAB1-dependent and -independent fashion.

The laminated structure of the retina is fundamental for the organization of the synaptic circuitry that translates light input into patterns of action potentials. However, the molecular mechanisms underlying cell migration and layering of the retina are poorly understood. Here, we show that RBX2, a core component of the E3 ubiquitin ligase CRL5, is essential for retinal layering and function. RBX2 regulates the final cell position of rod bipolar cells, cone photoreceptors and Muller glia. Our data indicate that sustained RELN/DAB1 signaling, triggered by depletion of RBX2 or SOCS7 - a CRL5 substrate adaptor known to recruit DAB1 - causes rod bipolar cell misposition. Moreover, whereas SOCS7 also controls Muller glia cell lamination, it is not responsible for cone photoreceptor positioning, suggesting that RBX2, most likely through CRL5 activity, controls other signaling pathways required for proper cone localization. Furthermore, RBX2 depletion reduces the number of ribbon synapses and disrupts cone photoreceptor function. Together, these results uncover RBX2 as a crucial molecular regulator of retina morphogenesis and cone photoreceptor function.

Positron emission tomography with α-[11C]methyl-L-tryptophan in tuberous sclerosis complex-related epilepsy.

OBJECTIVE: Tuberous sclerosis complex (TSC) is often associated with cerebral tubers and medically intractable epilepsy. We reevaluated whether increased uptake of α-[(11) C]methyl-l-tryptophan (AMT) in cerebral tubers is associated with tuber epileptogenicity. METHODS: We included 12 patients (six male, 4-53 years old) with TSC and refractory seizures who were evaluated for epilepsy surgery in our center, including video-electroencephalographic (EEG) monitoring, fluid-attenuated inversion recovery magnetic resonance imaging (FLAIR MRI), and positron emission tomography (PET) with α-[(11) C]methyl-l-tryptophan (AMT-PET). Nine of these 12 patients also underwent intracerebral EEG recording. AMT uptake in each tuber was visually evaluated on PET coregistered with MRI. An AMT uptake index based on lesional/healthy cortex ratio was also calculated. Sensitivity and specificity values of AMT-PET in the detection of epileptogenic lesions were obtained, using the available electroclinical and neuroimaging evidence as the gold standard for epileptogenicity. RESULTS: A total of 126 tubers were identified. Two of 12 patients demonstrated a tuber with clearly increased AMT uptake, one of whom also showed a subtle increased AMT uptake in another contralateral tuber. Four other patients showed only subtle increased AMT uptake. The only two tubers with clearly increased AMT uptake proved to be epileptogenic based on intracerebral EEG data, whereas none of the tubers associated with subtle increased AMT uptake were involved at ictal onset. In a per-patient approach, this yielded a sensitivity of clearly increased AMT uptake in detecting tuber epileptogenicity of 17% (2/12 patients), whereas the per-lesion sensitivity and specificity were 12% (95% confidence interval [CI]: 3-34%) and 100% (95% CI: 97-100%), respectively. SIGNIFICANCE: AMT-PET is a specific neuroimaging technique in the identification of epileptogenic tubers in TSC. Despite its low sensitivity, the clinical usefulness of AMT-PET still deserves to be considered according to the challenging complexity of epilepsy surgery in tuberous sclerosis.

[The position of nursing at the beginning of the Meiji Era: the elucidation of the original source of "Kango-Kokoroe," translated by Dr. Yunei Ota, and a comparative study of the original and translated versions].

In this paper, through a detailed comparison between a translated book on nursing and its original American source, I examine the position of nursing in the mentality of a Japanese doctor at the beginning of the Meiji Era. In 1877, Dr. Yunei Ota published a translated version of a book on nursing titled "Kango-Kokoroe." The original book, titled "A Universal Formulary, 3rd. Edition," was written by R. E. Griffith and published in 1873. Further, I show that Yunei Ota translated a part of its introduction. These two books differ in terms of their target audiences and purposes for publication. From the viewpoint of the doctor-nurse relationship, Yunei Ota described his unique mentality in his translation; that is, he stressed the importance of nursing by stating that nurses were for doctors as wings were for birds. This mentality was rarely found in the original American book. Moreover, Yunei Ota did not make a literal translation; instead, he selected, added, and deleted contents from the book in keeping with a practical standpoint. Yunei Ota recognized that nursing was an indispensable part of medical treatment and he advocated the necessity of nursing education before systematic nursing education had been established in Japan.

Effect of dietary cyclic nigerosylnigerose on intestinal immune functions in mice.

We examined the dietary effects of cyclic nigerosylnigerose (CNN), a dietary indigestible oligosaccharide with four D-glucopyranosyl residues linked by alternating alpha-(1-->3)- and alpha-(1-->6) glucosidic linkages, on the intestinal immune function of mice, and the effects were compared with those of alpha-(1-->3)-linked oligosaccharide (nigerooligosaccharides, NOS) or alpha-(1-->6)-linked oligosaccharide (isomaltooligosaccharides, IMO). BALB/c mice were fed with 1-5% CNN, 5% IMO, or 12.5% NOS for 4 weeks, and the intestinal mucosal immune responses were determined. In the 1-5% CNN fed groups, the amounts of IgA in feces increased significantly. In addition, IgA, transforming growth factor-beta1 (TGF-beta1), and interleukin-6 (IL-6) secretion by Peyer's patch (PP) cells were enhanced in CNN fed mice. In the 5% CNN group, pH in the cecum decreased, and the amounts of lactic acid and butyric acid increased. These findings were not observed in the NOS- or IMO-fed group of mice. They suggest that CNN supplementation changes the intestinal environment of microflora and indirectly enhances the immune function in the gut.

[A case of severe glaucoma with pseudopemphigoid successfully treated by filtration surgery using amniotic membrane].

BACKGROUND: It is necessary to decrease topical anti-glaucoma medication for severe glaucoma with pseudopemphigoid caused by anti-glaucoma eye drops. Glaucoma filtrating surgery is often needed instead of medication, but the prognosis is poor because it induces scar fomation and makes the filtrating bleb vanish. CASE: An 85-year-old male patient with exfoliation syndrome had twice undergone glaucoma surgery about ten years previously. His intra-ocular pressure (IOP) was high despite topical anti-glaucoma medication. At the first examination in our hospital, he had severe superficial punctate keratopathy, blephariticshortening and symblepharon, and we therefore diagnosed severe pseudopemphigoid induced by anti-glaucoma eye drops. Because his IOP could not be controlled by topical and general medication, we conducted a glaucoma filtrating operation using amniotic membrane. CONCLUSION: The administration of oral anti-inflammatory drugs before and after surgery and the use of amniotic membrane prevented post-operative scar formation and the progress of symblepharon, resulting in the successful control of IOP after surgery.

Inhibition of chlamydia trachomatis growth by human interferon-alpha: mechanisms and synergistic effect with interferon-gamma and tumor necrosis factor-alpha.

We have evaluated the effect of natural human interferon (IFN)-alpha on the growth of chlamydia trachomatis in human epithelial cells in vitro and revealed that IFN-alpha has reduced both growth and infectivity of C. trachomatis. The effect of IFN-alpha was reversed by the addition of exogenous L-tryptophan and iron to the culture medium, suggesting that antichlamydial effect of IFN-alpha was caused by depletion of intracellular tryptophan and iron, both of which are essential for chlamydial growth. When IFN-alpha was combined with another antichlamydial cytokines, IFN-gamma and tumor necrosis factor (TNF)-alpha, the effect was synergistically enhanced. Therefore, IFN-alpha would act coordinately with other cytokines such as IFN-gamma and TNF-alpha, and play an important role in host defense against infection and in the establishment of persistent chlamydial infection of host, in which the organism remains viable, but in a culture-negative state.