Modular and Distinct Plexin-A4/FARP2/Rac1 Signaling Controls Dendrite Morphogenesis

The role of semaphorin 3A in the pathogenesis and progression of Alzheimer's disease and other aging-related diseases: A comprehensive review

Aging serves as a pivotal factor in the etiology of numerous diseases, such as Alzheimer's disease (AD), Parkinson's disease, diabetes, osteoarthritis, atherosclerosis and aging-related macular degeneration. Notably, these diseases often interact with AD through various pathways, facilitating the onset or progression of one another. Semaphorin 3 A (Sema3A), a protein that is essential for axonal guidance during neural development, has recently been identified as a novel regulator in the pathogenesis and progression of multiple aging-related diseases. This article provides a comprehensive review of the expression patterns and mechanisms of action of Sema3A in these diseases. Specifically, Sema3A influences the occurrence and development of aging-related diseases by participating in oxidative stress, inflammatory responses, apoptosis, and synaptic plasticity. Therefore, therapeutic strategies targeting Sema3A present promising avenues for delaying the progression of aging-related diseases and offer novel insights and strategies for their treatment.

Semaphorin 3s signaling in the central nervous system: Mechanisms and therapeutic implication for brain diseases

Class 3 semaphorins (Sema3s), identified as secreted soluble proteins, present many therapeutic potentials. Recent evidence has suggested that Sema3s as molecular cue participate in neuroregulation, angiogenesis, and microenvironment homeostasis of the central nervous system. Moreover, Sema3s signaling pathways may be targeted for enhancing neural network connectivity, promoting neural regeneration and repair, and inhibiting pathological angiogenesis. Due to the complex co-expression patterns and crosstalk among Sema3s, new drugs targeting Sema3s-related signaling pathways are expected to be discovered to counter brain diseases. This review summarizes the specific roles of Sema3s in pathological processes of various brain diseases, and provides potential targeted strategies for the prevention and treatment.

Semaphorin 3A on Osteoporosis: An Overreview of the Literature

Semaphorin 3A (Sema3A) is a signaling protein that has attracted increasing attention in recent years for its important role in regulating bone metabolism. In this review, we searched different databases with various combinations of keywords to analyze the effects of Sema3A on osteoporosis. Sema3A promotes bone formation and inhibits bone resorption by directly affecting the osteoblast and osteoclast or indirectly targeting the nervous system. The sympathetic nervous system may be the main link between the central nervous system and bone metabolism for Sema3A. In the peripheral nervous system, Sema3A may improve bone quality via sensory nervous innervation. In addition, estrogen is found to regulate Sema3A levels to improve bone homeostasis. Lots of Sema3A agonists have been documented to exhibit anti-osteoporotic potential in preclinical investigations. Therefore, Sema3A can be considered a novel therapeutic target for preserving bone mass, highlighting an alternative strategy for the development of anti-osteoporosis drugs.

Plexins: Navigating through the neural regulation and brain pathology

Plexins are a family of transmembrane receptors known for their diverse roles in neural development, axon guidance, neuronal migration, synaptogenesis, and circuit formation. Semaphorins are a class of secreted and membrane proteins that act as primary ligands for plexin receptors. Semaphorins play a crucial role in central nervous system (CNS) development by regulating processes such as axonal growth, neuronal positioning, and synaptic connectivity. Various types of semaphorins like sema3A, sema4A, sema4C, sema4D, and many more have a crucial role in developing brain diseases. Likewise, various evidence suggests that plexin receptors are of four types: plexin A, plexin B, plexin C, and plexin D. Plexins have emerged as crucial regulators of neurogenesis and neuronal development and connectivity. When bound to semaphorins, these receptors trigger two major networking cascades, namely Rho and Ras GTPase networks. Dysregulation of plexin networking has been implicated in a myriad of brain disorders, including autism spectrum disorder (ASD), Schizophrenia, Alzheimer's disease (AD), Parkinson's disease (PD), and many more. This review synthesizes findings from molecular, cellular, and animal model studies to elucidate the mechanisms by which plexins contribute to the pathogenesis of various brain diseases.

Rho GTPase Signaling: A Molecular Switchboard for Regulating the Actin Cytoskeleton in Axon Guidance

Axon pathfinding is a highly dynamic process regulated by the interactions between cell-surface guidance receptors and guidance cues present in the extracellular environment. During development, precise axon pathfinding is crucial for the formation of functional neural circuits. The spatiotemporal expression of axon guidance receptors helps the navigating axon make correct decisions in a complex environment comprising both attractive and repulsive guidance cues. Axon guidance receptors initiate distinct signaling cascades that eventually influence the cytoskeleton at the growing tip of an axon, called the growth cone. The actin cytoskeleton is the primary target of these guidance signals and plays a key role in growth cone motility, exploration, and behavior. Of the many regulatory molecules that modulate the actin cytoskeleton in response to distinct guidance signals, Rho GTPases play central roles. Rho GTPases are molecular switchboards; their ON (GTP-bound) and OFF (GDP-bound) switches are controlled by their interactions with proteins that regulate the exchange of GDP for GTP or with the proteins that promote GTP hydrolysis. Various upstream signals, including axon guidance signals, regulate the activity of these Rho GTPase switch regulators. As cycling molecular switches, Rho GTPases interact with and control the activities of downstream effectors, which directly influence actin reorganization in a context-dependent manner. A deeper exploration of the spatiotemporal dynamics of Rho GTPase signaling and the molecular basis of their involvement in regulating growth cone actin cytoskeleton can unlock promising therapeutic strategies for neurodevelopmental disorders linked to dysregulated Rho GTPase signaling. This review not only provides a comprehensive overview of the field but also highlights recent discoveries that have considerably advanced our understanding of the complex regulatory roles of Rho GTPases in modulating actin cytoskeleton arrangement at the growth cone during axon guidance.

Genome-Wide Structural Variation Analysis and Breed Comparison of Local Domestic Ducks in Shandong Province, China

Structural variations in the duck genome significantly impact the environmental adaptability and phenotypic diversity of duck populations. Characterizing these SVs in local domestic duck breeds from Shandong province offers valuable insights for breed selection and the development of new breeds. This study aimed to profile the genomic SVs in three local duck breeds (Matahu duck, Weishan partridge duck, and Wendeng black duck) and explore their differential distributions. A total of 21,673 SVs were detected using LUMPY (v0.2.13) and DELLY (v1.0.3) software, with 46% located in intergenic regions, 33% in intronic regions, and frameshift deletions being the most prevalent in exonic regions (3%). SVs distribution showed a decreasing trend with shorter chromosome lengths. Population structure analysis revealed distinct genetic profiles, with Matahu and Weishan partridge ducks showing closer affinities and the Wendeng black duck having a more homogeneous genetic background, likely due to geographic isolation. Functional annotation identified genes related to nervous system development, mitosis, spindle assembly, and energy metabolism. Notable genes included PLXNA4, NRP2, SEMA3A, PTEN, MYBL2, ADK, and COX4I1. Additionally, genes such as PRKG1, GABRA2, and FSHR were linked to energy metabolism and reproductive activity. The study provides a comprehensive analysis of SVs, revealing significant genetic differentiation and identifying genes associated with economically important traits, offering valuable resources for the genetic improvement and breeding of local duck breeds.

Cellular and Molecular Insights into the Divergence of Neural Stem Cells on Matrigel and Poly-l-lysine Interfaces

Poly-l-lysine (PLL) and Matrigel, both classical coating materials for culture substrates in neural stem cell (NSC) research, present distinct interfaces whose effect on NSC behavior at cellular and molecular levels remains ambiguous. Our investigation reveals intriguing disparities: although both PLL and Matrigel interfaces are hydrophilic and feature amine functional groups, Matrigel stands out with lower stiffness and higher roughness. Based on this diversity, Matrigel surpasses PLL, driving NSC adhesion, migration, and proliferation. Intriguingly, PLL promotes NSC differentiation into astrocytes, whereas Matrigel favors neural differentiation and the physiological maturation of neurons. At the molecular level, Matrigel showcases a wider upregulation of genes linked to NSC behavior. Specifically, it enhances ECM-receptor interaction, activates the YAP transcription factor, and heightens glycerophospholipid metabolism, steering NSC proliferation and neural differentiation. Conversely, PLL upregulates genes associated with glial cell differentiation and amino acid metabolism and elevates various amino acid levels, potentially linked to its support for astrocyte differentiation. These distinct transcriptional and metabolic activities jointly shape the divergent NSC behavior on these substrates. This study significantly advances our understanding of substrate regulation on NSC behavior, offering novel insights into optimizing and targeting the application of these surface coating materials in NSC research.

Balancing act of small GTPases downstream of plexin-A4 signaling motifs promotes dendrite elaboration in mammalian cortical neurons

The precise development of neuronal morphologies is crucial to the establishment of synaptic circuits and, ultimately, proper brain function. Signaling by the axon guidance cue semaphorin 3A (Sema3A) and its receptor complex of neuropilin-1 and plexin-A4 has multifunctional outcomes in neuronal morphogenesis. Downstream activation of the RhoGEF FARP2 through interaction with the lysine-arginine-lysine motif of plexin-A4 and consequent activation of the small GTPase Rac1 promotes dendrite arborization, but this pathway is dispensable for axon repulsion. Here, we investigated the interplay of small GTPase signaling mechanisms underlying Sema3A-mediated dendritic elaboration in mouse layer V cortical neurons in vitro and in vivo. Sema3A promoted the binding of the small GTPase Rnd1 to the amino acid motif lysine-valine-serine (LVS) in the cytoplasmic domain of plexin-A4. Rnd1 inhibited the activity of the small GTPase RhoA and the kinase ROCK, thus supporting the activity of the GTPase Rac1, which permitted the growth and branching of dendrites. Overexpression of a dominant-negative RhoA, a constitutively active Rac1, or the pharmacological inhibition of ROCK activity rescued defects in dendritic elaboration in neurons expressing a plexin-A4 mutant lacking the LVS motif. Our findings provide insights into the previously unappreciated balancing act between Rho and Rac signaling downstream of specific motifs in plexin-A4 to mediate Sema3A-dependent dendritic elaboration in mammalian cortical neuron development.

Extracellular molecular signals shaping dendrite architecture during brain development

Proper growth and branching of dendrites are crucial for adequate central nervous system (CNS) functioning. The neuronal dendritic geometry determines the mode and quality of information processing. Any defects in dendrite development will disrupt neuronal circuit formation, affecting brain function. Besides cell-intrinsic programmes, extrinsic factors regulate various aspects of dendritic development. Among these extrinsic factors are extracellular molecular signals which can shape the dendrite architecture during early development. This review will focus on extrinsic factors regulating dendritic growth during early neuronal development, including neurotransmitters, neurotrophins, extracellular matrix proteins, contact-mediated ligands, and secreted and diffusible cues. How these extracellular molecular signals contribute to dendritic growth has been investigated in developing nervous systems using different species, different areas within the CNS, and different neuronal types. The response of the dendritic tree to these extracellular molecular signals can result in growth-promoting or growth-limiting effects, and it depends on the receptor subtype, receptor quantity, receptor efficiency, the animal model used, the developmental time windows, and finally, the targeted signal cascade. This article reviews our current understanding of the role of various extracellular signals in the establishment of the architecture of the dendrites.

DjFARP Contributes to the Regeneration and Maintenance of the Brain through Activation of DjRac1 in Dugesia japonica

FERM, RhoGEF, and Pleckstrin domain protein (FARP) mediated RhoGTPase pathways are involved in diverse biological processes, such as neuronal development and tumorigenesis. However, little is known about their role in neural regeneration. We uncovered for the first time that FARP-Rac1 signaling plays an important role in neural regeneration in Dugesia japonica, a planarian that possesses unparalleled regenerative capacities. The planarian FARP homolog DjFARP was primarily expressed in both intact and regenerating brain and pharynx tissue. Functional studies suggested that downregulation of DjFARP with dsRNA in Dugesia japonica led to smaller brain sizes, defects in brain lateral branches, and loss of cholinergic, GABAergic, and dopaminergic neurons in both intact and regenerating animals. Moreover, the Rho GTPase DjRac1 was shown to play a similar role in neural regeneration and maintenance. Rac1 activation assay showed that DjFARP acts as a guanine nucleotide exchange factor (GEF) for DjRac1. Together, these findings indicate that the brain defects seen in DjFARP knockdown animals may be attributable to DjRac1 inactivation. In conclusion, our study demonstrated that DjFARP-DjRac1 signaling was required for the maintenance and proper regeneration of the brain in Dugesia japonica.

Farnesol brain transcriptomics in CNS inflammatory demyelination

BACKGROUND

Farnesol (FOL) prevents the onset of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS).

OBJECTIVE

We examined the transcriptomic profile of the brains of EAE mice treated with daily oral FOL using next-generation sequencing (RNA-seq).

METHODS

Transcriptomics from whole brains of treated and untreated EAE mice at the peak of EAE was performed.

RESULTS

EAE-induced mice, compared to naïve, healthy mice, overall showed increased expression in pathways for immune response, as well as an increased cytokine signaling pathway, with downregulation of cellular stress proteins. FOL downregulates pro-inflammatory pathways and attenuates the immune response in EAE. FOL downregulated the expression of genes involved in misfolded protein response, MAPK activation/signaling, and pro-inflammatory response.

CONCLUSION

This study provides insight into the molecular impact of FOL in the brain and identifies potential therapeutic targets of the isoprenoid pathway in MS patients.

Palmitoylation regulates neuropilin-2 localization and function in cortical neurons and conveys specificity to semaphorin signaling via palmitoyl acyltransferases

Secreted semaphorin 3F (Sema3F) and semaphorin 3A (Sema3A) exhibit remarkably distinct effects on deep layer excitatory cortical pyramidal neurons; Sema3F mediates dendritic spine pruning, whereas Sema3A promotes the elaboration of basal dendrites. Sema3F and Sema3A signal through distinct holoreceptors that include neuropilin-2 (Nrp2)/plexinA3 (PlexA3) and neuropilin-1 (Nrp1)/PlexA4, respectively. We find that Nrp2 and Nrp1 are S-palmitoylated in cortical neurons and that palmitoylation of select Nrp2 cysteines is required for its proper subcellular localization, cell surface clustering, and also for Sema3F/Nrp2-dependent dendritic spine pruning in cortical neurons, both in vitro and in vivo. Moreover, we show that the palmitoyl acyltransferase ZDHHC15 is required for Nrp2 palmitoylation and Sema3F/Nrp2-dependent dendritic spine pruning, but it is dispensable for Nrp1 palmitoylation and Sema3A/Nrp1-dependent basal dendritic elaboration. Therefore, palmitoyl acyltransferase-substrate specificity is essential for establishing compartmentalized neuronal structure and functional responses to extrinsic guidance cues.

FOXG1 drives transcriptomic networks to specify principal neuron subtypes during the development of the medial pallium

The medial pallium (MP) is the major forebrain region underlying learning and memory, spatial navigation, and emotion; however, the mechanisms underlying the specification of its principal neuron subtypes remain largely unexplored. Here, by postmitotic deletion of FOXG1 (a transcription factor linked to autism spectrum disorders and FOXG1 syndrome) and single-cell RNA sequencing of E17.5 MP in mice, we found that FOXG1 controls the specification of upper-layer retrosplenial cortical pyramidal neurons [RSC-PyNs (UL)], subiculum PyNs (SubC-PyNs), CA1-PyNs, CA3-PyNs, and dentate gyrus granule cells (DG-GCs) in the MP. We uncovered subtype-specific and subtype-shared FOXG1-regulated transcriptomic networks orchestrating MP neuron specification. We further demonstrated that FOXG1 transcriptionally represses Zbtb20, Prox1, and Epha4 to prevent CA3-PyN and DG-GC identities during the specification of RSC-PyNs (UL) and SubC-PyNs; FOXG1 directly activates Nr4a2 to promote SubC-PyN identity. We showed that TBR1, controlled by FOXG1 during CA1-PyN specification, was down-regulated. Thus, our study illuminates MP principal neuron subtype specification and related neuropathogenesis.

Semaphorin signaling restricts neuronal regeneration in C. elegans

Extracellular signaling proteins serve as neuronal growth cone guidance molecules during development and are well positioned to be involved in neuronal regeneration and recovery from injury. Semaphorins and their receptors, the plexins, are a family of conserved proteins involved in development that, in the nervous system, are axonal guidance cues mediating axon pathfinding and synapse formation. The Caenorhabditis elegans genome encodes for three semaphorins and two plexin receptors: the transmembrane semaphorins, SMP-1 and SMP-2, signal through their receptor, PLX-1, while the secreted semaphorin, MAB-20, signals through PLX-2. Here, we evaluate the locomotion behavior of knockout animals missing each of the semaphorins and plexins and the neuronal morphology of plexin knockout animals; we described the cellular expression pattern of the promoters of all plexins in the nervous system of C. elegans; and we evaluated their effect on the regrowth and reconnection of motoneuron neurites and the recovery of locomotion behavior following precise laser microsurgery. Regrowth and reconnection were more prevalent in the absence of each plexin, while recovery of locomotion surpassed regeneration in all genotypes.

RhoB Promotes Endometrial Stromal Cells Decidualization Via Semaphorin3A/PlexinA4 Signaling in Early Pregnancy

Endometrial decidualization refers to a series of morphological changes and functional remodeling of the uterine endometrium to accept the embryo under the effect of estrogen and progesterone secreted by ovaries after ovulation. During decidualization, endometrial stromal cells (ESCs) proliferate and differentiate into decidual stromal cells, undergoing cytoskeletal rearrangement-mediated morphological changes and expressing decidualization markers, such as insulin-like growth factor-binding protein-1 and prolactin. Ras homology (Rho) proteins, a family of small G proteins, are well known as regulators of cellular morphology and involved in multiple other cellular processes. In this study, we found ras homolog family member B (RHOB) was the most significantly upregulated gene in the Rho protein family after the in vitro decidualization of human primary ESCs. RhoB expression was induced mainly by 3',5'-cyclic adenosine 5'-monophosphate (cAMP) / protein kinase A (PKA) / cyclic adenosine monophosphate-response element binding protein signaling and partly by progesterone signaling. Knockdown of RhoB in ESCs greatly inhibited actin cytoskeletal rearrangement, cell morphological transformation, and upregulation of insulin-like growth factor-binding protein-1, suggesting an indispensable role of RhoB in decidualization. Mechanistically, the downstream target of RhoB was semaphorin3A (Sema3A), which mediated its signaling via interacting with the receptor, plexinA4. More importantly, decreased expression of RhoB, Sema3A, and plexinA4 were detected in deciduas from patients with unexplained spontaneous miscarriage. Collectively, our results indicate that RhoB/Sema3A/plexinA4 signaling plays a positive role in endometrial decidualization and relates to unexplained spontaneous miscarriage, which is worthy of further exploration so as to provide new insights into therapeutic strategies for pregnancy diseases associated with poor decidualization.

Directed mechanisms for apical dendrite development during neuronal polarization

The development of the dendrite and the axon during neuronal polarization underlies the directed flow of information in the brain. Seminal studies on axon development have dominated the mechanistic analysis of neuronal polarization. These studies, many originating from examinations in cultured hippocampal and cortical neurons in vitro, have established a prevalent view that axon formation precedes and is necessary for neuronal polarization. There is also in vivo evidence supporting this view. Nevertheless, the establishment of bipolar polarity and the leading edge, and apical dendrite development in pyramidal neurons in vivo occur when axon formation is prevented. Furthermore, recent mounting evidence suggest that directed mechanisms might mediate bipolar polarity/leading process and subsequent apical dendrite development. In the presence of spatially directed extracellular cues in the developing brain, these events may operate independently of axon forming events. In this perspective we summarize evidence in support of these evolving views in neuronal polarization and highlight recent findings on dedicated mechanisms acting in apical dendrite development.

Semaphorin3A/PlexinA3 association with the Scribble scaffold for cGMP increase is required for apical dendrite development

The development of the apical dendrite from the leading process of the bipolar pyramidal neuron might be directed by spatially organized extrinsic cues acting on localized intrinsic determinants. The extracellular cues regulating apical dendrite polarization remain elusive. We show that leading process and apical dendrite development are directed by class III Semaphorins and mediated by a localized cGMP-synthesizing complex. The scaffolding protein Scribble that associates with the cGMP-synthesizing enzyme soluble guanylate cyclase (sGC) also associates with the Semaphorin3A (Sema3A) co-receptor PlexinA3. Deletion or knockdown of PlexinA3 and Sema3A or disruption of PlexinA3-Scribble association prevents Sema3A-mediated cGMP increase and causes defects in apical dendrite development. These manipulations also impair bipolar polarity and leading process establishment. Local cGMP elevation or sGC expression rescues the effects of PlexinA3 knockdown or PlexinA3-Scribble complex disruption. During neuronal polarization, leading process and apical dendrite development are directed by a scaffold that links Semaphorin cue to cGMP increase.

Szczurkowska et al. show that spatially directed Sema3A may promote development of the leading process and the apical dendrite via the co-receptor PlexinA3 by orchestrating localized cGMP increase on the scaffold protein, Scribble, at the leading edge of developing pyramidal neurons.

Semaporin3A-inhibitor ameliorates renal fibrosis through the regulation of JNK signaling

Renal fibrosis is the common pathological pathway in progressive renal diseases. In the study, we analyzed the roles of Semaphorin 3A (SEMA3A) on renal fibrosis and the effect of SEMA3A-inhibitor (SEMA3A-I) using unilateral ureteral obstruction (UUO) mouse model. The expression of SEMA3A in the proximal tubulus and neuropilin-1 (NRP1), a recepor of SEMA3A, in fibloblast and tubular cells were increased in the UUO kidneys. The increased expression of myofibroblast marker tenascin-C and fibronection as well as renal fibrosis were increased in UUO kidneys, all of which were ameliorated by SEMA3A-I. In addition, c-Jun N-terminal kinase (JNK) signaling pathway known as the target of SEMA3A signaling, was activated in proximal tubular cells and fibroblast cells after UUO surgery while SEMA3A-I significantly attenuated the activation. In vitro, treatments with SEMA3A as well as transforming growth factor-β1 (TGF-β1) in human proximal tubular cells lost epithelial cell characters while SEMA3A-I significantly ameliorated this transformation. JNK inhibitor, SP600125, partially reversed SEMA3A and TGF-β1-induced cell transformation, indicating that JNK signaling is involved in SEMA3A-induced renal fibrosis. In addition, the treatment with SEMA3A in fibroblast cells activated the expression of tenascin-C, collagen type I and fibronection, indicating that SEMA3A may accelerate renal fibrosis through the activation of fibroblast cells. The analysis of human data revealed the positive correlation between urinary SEMA3A and urinary N-acetyl-β-D-glucosaminidase, indicating the association between SEMA3A and tubular injury. In conclusion, SEMA3A signaling is involved in renal fibrosis through JNK signaling pathway and SEMA3A-I might be the therapeutic option for protecting from renal fibrosis.

Reduced hippocampal inhibition and enhanced autism-epilepsy comorbidity in mice lacking neuropilin 2

The neuropilin receptors and their secreted semaphorin ligands play key roles in brain circuit development by regulating numerous crucial neuronal processes, including the maturation of synapses and migration of GABAergic interneurons. Consistent with its developmental roles, the neuropilin 2 (Nrp2) locus contains polymorphisms in patients with autism spectrum disorder (ASD). Nrp2-deficient mice show autism-like behavioral deficits and propensity to develop seizures. In order to determine the pathophysiology in Nrp2 deficiency, we examined the hippocampal numbers of interneuron subtypes and inhibitory regulation of hippocampal CA1 pyramidal neurons in mice lacking one or both copies of Nrp2. Immunostaining for interneuron subtypes revealed that Nrp2^-/- mice have a reduced number of parvalbumin, somatostatin, and neuropeptide Y cells, mainly in CA1. Whole-cell recordings identified reduced firing and hyperpolarized shift in resting membrane potential in CA1 pyramidal neurons from Nrp2^+/- and Nrp2^-/- mice compared to age-matched wild-type controls indicating decrease in intrinsic excitability. Simultaneously, the frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs) are reduced in Nrp2-deficient mice. A convulsive dose of kainic acid evoked electrographic and behavioral seizures with significantly shorter latency, longer duration, and higher severity in Nrp2^-/- compared to Nrp2^+/+ animals. Finally, Nrp2^+/- and Nrp2^-/- but not Nrp2^+/+, mice have impaired cognitive flexibility demonstrated by reward-based reversal learning, a task associated with hippocampal circuit function. Together these data demonstrate a broad reduction in interneuron subtypes and compromised inhibition in CA1 of Nrp2^-/- mice, which could contribute to the heightened seizure susceptibility and behavioral deficits consistent with an ASD/epilepsy phenotype.

Pathogenic nsSNPs that increase the risks of cancers among the Orang Asli and Malays

Single-nucleotide polymorphisms (SNPs) are the most common genetic variations for various complex human diseases, including cancers. Genome-wide association studies (GWAS) have identified numerous SNPs that increase cancer risks, such as breast cancer, colorectal cancer, and leukemia. These SNPs were cataloged for scientific use. However, GWAS are often conducted on certain populations in which the Orang Asli and Malays were not included. Therefore, we have developed a bioinformatic pipeline to mine the whole-genome sequence databases of the Orang Asli and Malays to determine the presence of pathogenic SNPs that might increase the risks of cancers among them. Five different in silico tools, SIFT, PROVEAN, Poly-Phen-2, Condel, and PANTHER, were used to predict and assess the functional impacts of the SNPs. Out of the 80 cancer-related nsSNPs from the GWAS dataset, 52 nsSNPs were found among the Orang Asli and Malays. They were further analyzed using the bioinformatic pipeline to identify the pathogenic variants. Three nsSNPs; rs1126809 (TYR), rs10936600 (LRRC34), and rs757978 (FARP2), were found as the most damaging cancer pathogenic variants. These mutations alter the protein interface and change the allosteric sites of the respective proteins. As TYR, LRRC34, and FARP2 genes play important roles in numerous cellular processes such as cell proliferation, differentiation, growth, and cell survival; therefore, any impairment on the protein function could be involved in the development of cancer. rs1126809, rs10936600, and rs757978 are the important pathogenic variants that increase the risks of cancers among the Orang Asli and Malays. The roles and impacts of these variants in cancers will require further investigations using in vitro cancer models.

Modelling and Refining Neuronal Circuits with Guidance Cues: Involvement of Semaphorins

The establishment of neuronal circuits requires neurons to develop and maintain appropriate connections with cellular partners in and out the central nervous system. These phenomena include elaboration of dendritic arborization and formation of synaptic contacts, initially made in excess. Subsequently, refinement occurs, and pruning takes places both at axonal and synaptic level, defining a homeostatic balance maintained throughout the lifespan. All these events require genetic regulations which happens cell-autonomously and are strongly influenced by environmental factors. This review aims to discuss the involvement of guidance cues from the Semaphorin family.

Semaphorins in Adult Nervous System Plasticity and Disease

Semaphorins, originally discovered as guidance cues for developing axons, are involved in many processes that shape the nervous system during development, from neuronal proliferation and migration to neuritogenesis and synapse formation. Interestingly, the expression of many Semaphorins persists after development. For instance, Semaphorin 3A is a component of perineuronal nets, the extracellular matrix structures enwrapping certain types of neurons in the adult CNS, which contribute to the closure of the critical period for plasticity. Semaphorin 3G and 4C play a crucial role in the control of adult hippocampal connectivity and memory processes, and Semaphorin 5A and 7A regulate adult neurogenesis. This evidence points to a role of Semaphorins in the regulation of adult neuronal plasticity. In this review, we address the distribution of Semaphorins in the adult nervous system and we discuss their function in physiological and pathological processes.

Molecular mechanisms that mediate dendrite morphogenesis

Neurons develop dendritic morphologies that bear cell type-specific features in dendritic field size and geometry, branch placement and density, and the types and distributions of synaptic contacts. Dendritic patterns influence the types and numbers of inputs a neuron receives, and the ways in which neural information is processed and transmitted in the circuitry. Even subtle alterations in dendritic structures can have profound consequences on neuronal function and are implicated in neurodevelopmental disorders. In this chapter, I review how growing dendrites acquire their exquisite patterns by drawing examples from diverse neuronal cell types in vertebrate and invertebrate model systems. Dendrite morphogenesis is shaped by intrinsic and extrinsic factors such as transcriptional regulators, guidance and adhesion molecules, neighboring cells and synaptic partners. I discuss molecular mechanisms that regulate dendrite morphogenesis with a focus on five aspects of dendrite patterning: (1) Dendritic cytoskeleton and cellular machineries that build the arbor; (2) Gene regulatory mechanisms; (3) Afferent cues that regulate dendritic arbor growth; (4) Space-filling strategies that optimize dendritic coverage; and (5) Molecular cues that specify dendrite wiring. Cell type-specific implementation of these patterning mechanisms produces the diversity of dendrite morphologies that wire the nervous system.

Sculpting Dendritic Spines during Initiation and Maintenance of Neuropathic Pain

Accumulating evidence has established a firm role for synaptic plasticity in the pathogenesis of neuropathic pain. Recent advances have highlighted the importance of dendritic spine remodeling in driving synaptic plasticity within the CNS. Identifying the molecular players underlying neuropathic pain induced structural and functional maladaptation is therefore critical to understanding its pathophysiology. This process of dynamic reorganization happens in unique phases that have diverse pathologic underpinnings in the initiation and maintenance of neuropathic pain. Recent evidence suggests that pharmacological targeting of specific proteins during distinct phases of neuropathic pain development produces enhanced antinociception. These findings outline a potential new paradigm for targeted treatment and the development of novel therapies for neuropathic pain. We present a concise review of the role of dendritic spines in neuropathic pain and outline the potential for modulation of spine dynamics by targeting two proteins, srGAP3 and Rac1, critically involved in the regulation of the actin cytoskeleton.

Extrinsic Factors Regulating Dendritic Patterning

Stereotypic dendrite arborizations are key morphological features of neuronal identity, as the size, shape and location of dendritic trees determine the synaptic input fields and how information is integrated within developed neural circuits. In this review, we focus on the actions of extrinsic intercellular communication factors and their effects on intrinsic developmental processes that lead to dendrite patterning. Surrounding neurons or supporting cells express adhesion receptors and secreted proteins that respectively, act via direct contact or over short distances to shape, size, and localize dendrites during specific developmental stages. The different ligand-receptor interactions and downstream signaling events appear to direct dendrite morphogenesis by converging on two categorical mechanisms: local cytoskeletal and adhesion modulation and global transcriptional regulation of key dendritic growth components, such as lipid synthesis enzymes. Recent work has begun to uncover how the coordinated signaling of multiple extrinsic factors promotes complexity in dendritic trees and ensures robust dendritic patterning.

Recent advances in inter-cellular interactions during neural circuit assembly

Neural circuit assembly is regulated by inter-cellular interactions involving secreted and surface-tethered guidance molecules. Here, we review recent progress in our understanding of their mechanisms-of-action and biological effects. We discuss mechanisms through which the secreted cue Netrin-1 regulates neuron migration and highlight novel roles for axon-derived secreted guidance cues. We cover recent structural work at atomic resolution that provides new insights into the activation mechanisms of axon guidance receptors and into protein complexes containing cell adhesion molecules, such as Teneurin (Ten), Latrophilin (Lphn) and FLRT. Ten-Ten homophilic, Ten-Lphn heterophilic, and Ten-Lphn-FLRT tripartite complexes seem to elicit distinct context-dependent cellular responses. Seemingly opposite responses can also be triggered by the Eph/ephrin signaling system. Here, recent work provides a simple mechanism for the decision of forming a new synapse versus rejection of the pre-synaptic partner. These studies identify novel regulatory mechanisms and biological functions that will apply generally in developing neural systems.