Building Blocks of Functioning Brain: Cytoskeletal Dynamics in Neuronal Development

Neural connectivity requires proper polarization of neurons, guidance to appropriate target locations, and establishment of synaptic connections. From when neurons are born to when they finally reach their synaptic partners, neurons undergo constant rearrangment of the cytoskeleton to achieve appropriate shape and polarity. Of particular importance to neuronal guidance to target locations is the growth cone at the tip of the axon. Growth-cone steering is also dictated by the underlying cytoskeleton. All these changes require spatiotemporal control of the cytoskeletal machinery. This review summarizes the proteins that are involved in modulating the actin and microtubule cytoskeleton during the various stages of neuronal development

Biophysical and biochemical factors in the cellular microenvironment; effects on cell migration and invasion

Cellular migration is a vital process central to many physiological events including development, immune surveillance and wound healing. However, migration and invasion are not unique to normal physiology, they are also key determinants in the progression of disease states such as cancer. Given the significance of migration it is important that we understand how the process is regulated intracellularly and the various stimuli that can promote it. Even though the role of biochemical factors in mediating migration has been studied extensively, the role of biophysical factors in modulating migration and invasion is less appreciation. The biochemical and biophysical components of cell and tissue microenvironments influence cellular behavior. This is true for both normal and disease conditions. For example, the role of substrate stiffness and extracellular matrix (ECM) composition in cell proliferation, spreading, preferential migration and even stem cell differentiation has been observed. However, a number of questions remain unanswered, such as the ability of cells to sense locally applied mechanical stimuli and how this mechanosensing is regulated. Would the regulation be different if cancer cells were to sense the applied stimulus? Studies have shown that as cells migrate they produce contractile forces called traction forces that are generated by the cellular cytoskeleton and transmitted onto the substrate. Yet the signaling mechanism that promotes this force production or how is it regulated is not well characterized. In attempt at address these questions, we have identified the importance of locally applied mechanical stimuli in cancer cell invasion and we have also identified a major link in the traction force production pathway. Our study on the influence of local mechanical stimuli on cancer cell invasion suggests that the stimuli produced as a result of ECM remodeling by and migration of non-cancerous cells present in the tumor microenvironment could enhance tumor cell invasion. This enhanced invasion is dependent on actin and cofilin, and the ECM protein, fibronectin. In gaining understanding of the mechanisms and interplay between traction force and mechanosensing we have focused on the Calpain protease. We previously identified that the calpain small subunit, calpain 4 (Capn4), influences force production independent of the proteolytic activity of the catalytic subunits calpain 1 and 2, yet their mechanosensing mechanism overlaps. To further explore the relationship, we asked how Capn4 could regulate force production. We have found that Capn4 indirectly mediates tyrosine phosphorylation of a lectin binding protein, galectin-3. Upon phosphorylation, galectin-3 is secreted into the ECM from where it is able to modulate traction force and associated events involving focal adhesion maturation and adhesion strength. It however, does not influence mechanosensing. Together these results further emphasize the point that cell migration and invasion is significantly influenced by the biochemical and biophysical components and properties on the microenvironment. Further studies will elucidate these pathways and provide greater insight for bioengineering and medical advances

PRIMARY ECTOPIC PAPILLARY CARCINOMA OF THYROID IN THE LARYNX: AN UNUSUAL PRESENTATION

 Ectopic thyroid is the result of the failure of migration of thyroid along its tract from the floor of the primitive foregut to its final pretracheal position. The incidence of an ectopic lesion in adults is 7%. Most common location is the base of tongue (lingual). Other diverse sites are larynx, trachea, mediastinum, and pericardium. These ectopic tissues may develop the same diseases as the thyroid gland. Here, we report a case of a young female presenting with a foreign body sensation in the throat and on examination revealed a smooth submucosal swelling involving the supraglottis. The entire cyst was excised in toto by KTP 532 laser via an endolaryngeal approach and it was reported as papillary carcinoma of the thyroid. Literature search reported only a few cases of intralaryngeal ectopic thyroid and none with a papillary carcinoma of the larynx. This is the first reported case of papillary carcinoma of thyroid in the larynx

Recent advances in branching mechanisms underlying neuronal morphogenesis [version 1; referees: 2 approved]

Proper neuronal wiring is central to all bodily functions, sensory perception, cognition, memory, and learning. Establishment of a functional neuronal circuit is a highly regulated and dynamic process involving axonal and dendritic branching and navigation toward appropriate targets and connection partners. This intricate circuitry includes axo-dendritic synapse formation, synaptic connections formed with effector cells, and extensive dendritic arborization that function to receive and transmit mechanical and chemical sensory inputs. Such complexity is primarily achieved by extensive axonal and dendritic branch formation and pruning. Fundamental to neuronal branching are cytoskeletal dynamics and plasma membrane expansion, both of which are regulated via numerous extracellular and intracellular signaling mechanisms and molecules. This review focuses on recent advances in understanding the biology of neuronal branching

TRIM67 regulates exocytic mode and neuronal morphogenesis via SNAP47

Neuronal morphogenesis involves dramatic plasma membrane expansion, fueled by soluble N-ethylmaleimide-sensitive factor attachment protein eceptors (SNARE)-mediated exocytosis. Distinct fusion modes described at synapses include full-vesicle fusion (FVF) and kiss-and-run fusion (KNR). During FVF, lumenal cargo is secreted and vesicle membrane incorporates into the plasma membrane. During KNR, a transient fusion pore secretes cargo but closes without membrane addition. In contrast, fusion modes are not described in developing neurons. Here, we resolve individual exocytic events in developing murine cortical neurons and use classification tools to identify four distinguishable fusion modes: two FVF-like modes that insert membrane material and two KNR-like modes that do not. Discrete fluorescence profiles suggest distinct behavior of the fusion pore. Simulations and experiments agree that FVF-like exocytosis provides sufficient membrane material for morphogenesis. We find the E3 ubiquitin ligase TRIM67 promotes FVF-like exocytosis in part by limiting incorporation of the Qb/Qc SNARE SNAP47 into SNARE complexes and, thus, SNAP47 involvement in exocytosis

TRIM9-dependent ubiquitination of DCC constrains kinase signaling, exocytosis, and axon branching

Extracellular netrin-1 and its receptor deleted in colorectal cancer (DCC) promote axon branching in developing cortical neurons. Netrin-dependent morphogenesis is preceded by multimerization of DCC, activation of FAK and Src family kinases, and increases in exocytic vesicle fusion, yet how these occurrences are linked is unknown. Here we demonstrate that tripartite motif protein 9 (TRIM9)-dependent ubiquitination of DCC blocks the interaction with and phosphorylation of FAK. Upon netrin-1 stimulation TRIM9 promotes DCC multimerization, but TRIM9-dependent ubiquitination of DCC is reduced, which promotes an interaction with FAK and subsequent FAK activation. We found that inhibition of FAK activity blocks elevated frequencies of exocytosis in vitro and elevated axon branching in vitro and in vivo. Although FAK inhibition decreased soluble N-ethylmaleimide attachment protein receptor (SNARE)-mediated exocytosis, assembled SNARE complexes and vesicles adjacent to the plasma membrane increased, suggesting a novel role for FAK in the progression from assembled SNARE complexes to vesicle fusion in developing murine neurons

Noctiluca scintillans bloom and measures to protect marine hatcheries

During the third week of November 2022, bloom of Noctiluca scintillans (Macartney, 1810) was observed in multiple locations along the coastal waters off Thiruvananthapuram. Noctiluca bloom is commonly called as 'sea sparkles, as it produces blue bioluminescence at nigh

Comparing delivery channels to promote nutrition-sensitive agriculture: A cluster-randomized controlled trial in Bangladesh

We use a randomized controlled trial in rural Bangladesh to compare two models of delivering nutrition content jointly to husbands and wives: deploying female nutrition workers versus mostly male agriculture extension workers. Both approaches increased nutrition knowledge of men and women, household and individual diet quality, and women’s empowerment. Intervention effects on agriculture and nutrition knowledge, agricultural production diversity, dietary diversity, women’s empowerment, and gender parity do not significantly differ between models where nutrition workers versus agriculture extension workers provide the training. The exception is in an attitudes score, where results indicate same-sex agents may affect scores differently than opposite-sex agents. Our results suggest opposite-sex agents may not necessarily be less effective in providing training. In South Asia, where agricultural extension systems and the pipeline to those systems are male-dominated, training men to deliver nutrition messages may offer a temporary solution to the shortage of female extension workers and offer opportunities to scale promote nutrition-sensitive agriculture

Increasing production diversity and diet quality through agriculture, gender, and nutrition linkages: A cluster-randomized controlled trial in Bangladesh

A growing body of evidence indicates that agricultural development programs can potentially improve production diversity and diet quality of poor rural households; however, less is known about which aspects of program design are effective in diverse contexts and feasible to implement at scale. We address this issue through an evaluation of the Agriculture, Gender, and Nutrition Linkages (ANGeL) project. ANGeL is a randomized controlled trial testing what combination of trainings focused on agricultural production, nutrition behavior change communication, and gender sensitization were most effective in improving production diversity and diet quality among rural farm households in Bangladesh. We find that trainings focused on agriculture improved production diversity in terms of greater production of fruits and vegetables grown on the homestead, eggs, dairy, and fish; adding trainings on nutrition and gender did not significantly change these impacts. Trainings focused on both agriculture and nutrition showed the largest impacts on diet quality, with evidence indicating that households in this arm also significantly increased consumption out of homestead production for fruits and vegetables, eggs, dairy, and fish. Findings indicate that agricultural training that promotes production of diverse, high-value, nutrient-rich foods can increase production diversity, and this can improve diet quality, but diet quality impacts are larger when agricultural training is combined with nutrition training. Relative to treatments combining agriculture and nutrition training, we find no significant impact of adding the gender sensitization on our measures of production diversity or diet quality

The E3 Ubiquitin Ligase TRIM9 Is a Filopodia Off Switch Required for Netrin-Dependent Axon Guidance

Neuronal growth cone filopodia contain guidance receptors and contribute to axon guidance; however, the mechanism by which the guidance cue netrin increases filopodia density is unknown. Here, we demonstrate that TRIM9, an E3 ubiquitin ligase that localizes to filopodia tips and binds the netrin receptor DCC, interacts with and ubiquitinates the barbed-end polymerase VASP to modulate filopodial stability during netrin-dependent axon guidance. Studies with murine Trim9(+/+) and Trim9(-/-) cortical neurons, along with a non-ubiquitinatable VASP mutant, demonstrate that TRIM9-mediated ubiquitination of VASP reduces VASP filopodial tip localization, VASP dynamics at tips, and filopodial stability. Upon netrin treatment, VASP is deubiquitinated, which promotes VASP tip localization and filopodial stability. Trim9 deletion induces axon guidance defects in vitro and in vivo, whereas a gradient of deubiquitinase inhibition promotes axon turning in vitro. We conclude that a gradient of TRIM9-mediated ubiquitination of VASP creates a filopodial stability gradient during axon turning