Ultrastructural Diversity Research Articles

Discovery and characterization of a transient chaetal gland during the development of Capitella teleta (Sedentaria: Annelida).

Chaetae are among the most extensively studied structures in polychaetes, serving as a defining morphological trait for annelids. Capitella teleta stands out as one of the few established annelid models for developmental and morphological studies, thus receiving significant scholarly attention. In this study, we unveil a previously unnoticed glandular structure associated with chaetae within the larvae of C. teleta. Our investigations demonstrate the absence of comparable structures in the chaetal follicles of adults and juveniles (older than 1 week), as well as during active chaetogenesis, underscoring the transient nature of these glands. This indicates that larval chaetal follicles transform into a gland that later disappears. Utilizing histology and transmission electron microscopy, we characterized these glands. Our findings underscore the diversity of chaetal ultrastructure in annelids and show that, even in well-studied species, novel morphological details can be found. We emphasize the importance of examining various life-history stages to capture such transient morphological features. This work lays a crucial morphological foundation and deepens our understanding of chaetae and chaetogenesis in C. teleta, paving the way for more accurate interpretations of future experimental studies on chaetogenesis in this species.

Ultrastructure of the Jurassic serpulid tubes-phylogenetic and paleoecological implications.

The ultrastructural diversity of the Middle and Late Jurassic serpulid tubes from the Polish Basin has been investigated. The inspection of 12 taxa representing the two major serpulid clades allowed for the identification of three ultrastructure types-irregularly oriented prismatic structure (IOP), spherulitic prismatic structure (SPHP), and simple prismatic structure (SP). Six of the studied species are single-layered and six species possess two distinct layers. Ultrastructural diversity corresponds to certain serpulid clades. The members of Filograninae have single-layered tube walls composed of possibly plesiomorphic, irregularly oriented prismatic structure (IOP). Two-layered tubes occur solely within the clade Serpulinae, where the external, denser layer is built of either the ordered spherulitic (SPHP) or simple prismatic microstructure (SP), and the internal layer is composed of irregularly oriented prismatic structure (IOP). Apart from phylogenetic signals provided by the tube ultrastructure, it can be used in analyzing paleoecological aspects of tube-dwelling polychaetes. Compared to the more primitive, irregularly oriented microstructures of Filograninae, the regularly oriented microstructures of Serpulinae need a higher level of biological control over biomineralization. The advent of the dense outer protective layer (DOL) in serpulids, as well as the general increase in ultrastructure diversity, was likely a result of the evolutionary importance of the tubes for serpulids. Such diversity of the tube ultrastructural fabrics allowed for maximizing functionality by utilizing a variety of morphogenetic programs. The biomineralization system of serpulids remains more complex compared to other tube-dwelling polychaetes. Physiologically more expensive tube formation allows for mechanical strengthening of the tube by building robust, strongly ornamented tubes and firm attachment to the substrate. Contrary to sabellids, which perform a fugitive strategy, an increased tube durability allows serpulids a competitive advantage over other encrusters.

Ultrastructural diversity in the shell of Artemia resting eggs.

The shell of Artemia resting egg, which is a delicate multilayered envelope surrounding the inside diapause embryo, plays an important role in the survival strategy of Artemia. To date, the ultrastructure of resting eggshell has been studied for only handful populations, and knowledge about the diversity of shell structure is still limited. In this paper, resting eggs from 13 Artemia populations were studied by transmission electron microscopy. Results show that the basic configuration of resting eggshell is quite conservative, but variations are not uncommon in the fine ultrastructure of each main layer of the shell (e.g., the shape and distribution of the radially oriented pores in the cortical layer; the size, number and arrangement of chambers in the alveolar layer; and the development state of outer cuticular membrane [OCM]). The ultrastructural variation of eggshell seems not to be linked with species and reproductive mode of Artemia. Resting eggs from very high habitats (4300+ m above sea level [a.s.l.]) on Qinghai-Tibet Plateau and certain tropical salterns have a hypoplastic OCM, which may be related to the adaptation to habitat conditions such as low oxygen concentration. RESEARCH HIGHLIGHTS: Comparative study on resting eggs from 13 Artemia populations reveals high diversity in the fine structure of eggshell. Resting eggs from very high (4300+ m a.s.l.) habitats commonly have a hypoplastic OCM.

Pollen Micromorphology among Amaranthaceous Species from Desert Rangeland: Exine Stratification and their Taxonomic Significance

The aim of the study was to visualize the micromorphology of Amaranthaceous pollen using scanning electron microscopy collected from the Thal Desert. Field collection was conducted from July to September 2021. A total of 14 taxa of the family Amaranthaceae were collected which belong to nine genera. Achyranthes aspera, Aerva javanica, Aerva lanata, Amaranthus graecizans, Amaranthus retroflexus, Amaranthus viridis, Bassia indica, Chenopodium album, Chenopodium ficifolium, Chenopodium murale, Digera muricata, Haloxylon stocksii, Salsola tragus, and Suaeda fruticosa were studied in terms of pollen morphotypes. Pollen were acetolyzed and observed under optical and scanning microscopy. Qualitative and quantitative characters were measured to analyze the pollen to uncover its taxonomic significance. Qualitative characters observed were the shape of pollen in polar and equatorial views; the most frequent shape observed was spheroidal in the polar view, whereas in the equatorial view, prolate spheroidal was the dominant shape. Exine ornamentation is the key characteristic of pollen which is very helpful, and eight different types of ornamentations were observed in collected taxa: smooth sparsely granulate, scabrate‐spinulose, microspinulose perforate, microechinate scabrate to metareticulate, granulate, nanospinulate, granulate‐spinulose perforate, granulate‐perforate echinate, and microechinate perforate. Periporate‐type aperture was observed among all taxa. Mesoporia, ektexinous bodies, and tectum features also show variations among Amaranthaceous grains. In quantitative character, A. retroflexus recorded highest in polar view 26.3 μm and the lowest was of C. album 12.2 μm. Highest P/E index ratio was recorded in S. fruticosa (1.12) whereas the lowest for D. muricta (0.94). Exine thickness was highest in S. tragus 2.15 μm and lowest in A. graecizans 0.78 μm. The maximum number of pores was recorded as 32‐36 in D. muricata. Artificial taxonomic keys were constructed based on findings that reinforce the importance of the micromorphological ultrastructural diversity of pollen among Amaranthaceous taxa. It was concluded that the descriptions of pollen morphotypes presented greatly contribute to our understanding of desert species identification.

All roads lead to heterogeneity: The complex involvement of astrocytes and microglia in the pathogenesis of Alzheimer's disease.

In recent years, glial cells have been acknowledged as key players in the pathogenesis of Alzheimer’s disease (AD), a neurodegenerative condition in which an accumulation of intracellular neurofibrillary tangles and extracellular fibrillar amyloid beta is notably observed in the central nervous system. Genome-wide association studies have shown, both in microglia and astrocytes, an increase in gene variants associated with a higher risk of developing late-onset AD. Microglia, the resident innate immune cells of the brain, and astrocytes, glial cells crucial for vascular integrity and neuronal support, both agglomerate near amyloid beta plaques and dystrophic neurites where they participate in the elimination of these harmful parenchymal elements. However, their role in AD pathogenesis has been challenging to resolve due to the highly heterogeneous nature of these cell populations, i.e., their molecular, morphological, and ultrastructural diversity, together with their ever-changing responsiveness and functions throughout the pathological course of AD. With the recent expansions in the field of glial heterogeneity through innovative advances in state-of-the-art microscopy and -omics techniques, novel concepts and questions arose, notably pertaining to how the diverse microglial and astrocytic states interact with each other and with the AD hallmarks, and how their concerted efforts/actions impact the progression of the disease. In this review, we discuss the recent advances and findings on the topic of glial heterogeneity, particularly focusing on the relationships of these cells with AD hallmarks (e.g., amyloid beta plaques, neurofibrillary tangles, synaptic loss, and dystrophic neurites) in murine models of AD pathology and post-mortem brain samples of patients with AD.

Cotton genes GhMML1 and GhMML2 control trichome branching when ectopically expressed in tobacco.

Trichomes exhibit extraordinary diversity in shape, ultrastructure, distribution, secretion capability, biological functions, and morphological differences, which are strongly associated with their multifunction. Previous researches showed MIXTA-like transcription factors involved in regulating trichome initiation and patterning via forming MYB-bHLH-WD40 transcriptional activator complex to induce the expression of downstream genes. Here, we report the characteristics and role of GhMML1 and GhMML2, members of subgroup 9 of the R2R3-type MYB TFs. GhMML1 and GhMML2 were preferentially targeted to the nucleus and prominently expressed in the early stage during fiber development. Ectopic expression of GhMML1 and GhMML2 respectively in the transgenic tobacco plants changed the morphological characteristics of leaf trichomes; that is, the unbranched trichomes turned into multiple branched, and in the meantime, the density of trichomes was reduced on the surface of the leaf. Y2H and LCI assay revealed that both GhMML1 and GhMML2 could physically interact with a bZIP transcription factor family protein (GhbZIP) in vivo and in vitro. It has been reported that GhbZIP's homolog TAG3 in Arabidopsis is involved in the asymmetric growth of leaves and flowers via direct interaction with BOP1. Taken together, our results demonstrated that two MYB MIXTA-like proteins, GhMML1 and GhMML2, together with GhbZIP might form a multimeric complex to involve in trichome development. This study highlights the importance of MIXTA-like genes from TF subgroup 9 and will help to uncover the molecular mechanism underlying differential trichomes and their development.

Unique properties of dually innervated dendritic spines in pyramidal neurons of the somatosensory cortex uncovered by 3D correlative light and electron microscopy.

Pyramidal neurons (PNs) are covered by thousands of dendritic spines receiving excitatory synaptic inputs. The ultrastructure of dendritic spines shapes signal compartmentalization, but ultrastructural diversity is rarely taken into account in computational models of synaptic integration. Here, we developed a 3D correlative light–electron microscopy (3D-CLEM) approach allowing the analysis of specific populations of synapses in genetically defined neuronal types in intact brain circuits. We used it to reconstruct segments of basal dendrites of layer 2/3 PNs of adult mouse somatosensory cortex and quantify spine ultrastructural diversity. We found that 10% of spines were dually innervated and 38% of inhibitory synapses localized to spines. Using our morphometric data to constrain a model of synaptic signal compartmentalization, we assessed the impact of spinous versus dendritic shaft inhibition. Our results indicate that spinous inhibition is locally more efficient than shaft inhibition and that it can decouple voltage and calcium signaling, potentially impacting synaptic plasticity.

Effects of deoxynivalenol-contaminated diet on the composition and diversity of the intestinal microbial community and intestinal ultrastructure of juvenile largemouth bass (Micropterus salmoides)

Deoxynivalenol (DON), a trichothecene in food and feed, is a principal contaminant due to its prevalence worldwide. In order to investigate the effect of DON on the composition and diversity of intestinal microbiota and intestinal ultrastructure, an 8-week feeding trial was conducted to monitor changes in largemouth bass (Micropterus salmoides) in a control group and both a low and high DON contaminated feed group (containing 300 μg/kg and 600 μg/kg of DON respectively). The trial was conducted in 12 fibreglass tanks (500 L volume, four replications for each diet) with 30 fish (initial weight 9.85 ± 0.07 g) per tank. Our results suggested that the diversity and abundance of the intestinal microbiota were higher in the high DON experimental group than the control group at the phyla level and genera level. At the phyla level, the relative abundance of Firmicutes, Proteobacteria and Bacteroidetes in the high DON experimental group increased significantly compared with the control group, whereas the relative abundance of Fusobacteria decreased. At the genera level, the first two dominant genera in high DON treatments were different with the control and low DON groups. PIC-RUSt was used to predict the functions of intestinal microbiota among all samples, we found the high abundance of bacterial metagenomes in low and high DON groups is most likely used in metabolism and genetic information processing. TEM images suggested that DON diet could cause varying degrees of damage to the microvilli. All these results implied that DON could trigger dysregulation of intestinal microbiota taxonomic composition and cause intestine ultrastructure damage of juvenile largemouth bass (Micropterus salmoides). The results of this study will increase awareness of the toxic effects of DON on the intestine of largemouth bass and invites the discovery of new ways to combat DON toxicity.

The tubulin code specializes neuronal cilia for extracellular vesicle release.

Cilia are microtubule-based organelles that display diversity in morphology, ultrastructure, protein composition, and function. The ciliary microtubules of C. elegans sensory neurons exemplify this diversity and provide a paradigm to understand mechanisms driving ciliary specialization. Only a subset of ciliated neurons in C. elegans are specialized to make and release bioactive extracellular vesicles (EVs) into the environment. The cilia of extracellular vesicle releasing neurons have distinct axonemal features and specialized intraflagellar transport that are important for releasing EVs. In this review, we discuss the role of the tubulin code in the specialization of microtubules in cilia of EV releasing neurons.

The role of nectar traits and nectary morphoanatomy in the plant-pollinator interaction between Billbergia distachia (Bromeliaceae) and the hermit Phaethornis eurynome (Trochilidae)

Abstract Nectar production dynamics can show inter- and intraspecific variation, which can be associated with environmental and ecological factors and with the ultrastructural diversity of the floral nectary. In this context, we recorded nectar production dynamics from a morphofunctional perspective using the hummingbird-pollinated Billbergia distachia (Bromeliaceae). The scale-throated hermit Phaethornis eurynome was the only floral visitor observed, indicating a specialized pollination system. Nectar production showed significant differences between day and night, and the periods of major pollinator activity and nectar secretion were synchronous. The ultrastructural features of the nectary showed some evidence of nectar reabsorption in flowers at night, and it can be inferred that this process may be a key factor in the nocturnal pause in nectar production. In this way, nectary morphoanatomy, nectar traits and an energy-saving mechanism through nectar reabsorption contribute to the well-established relationship between B. distachia and P. eurynome.

Sub-micrometer insights into the cytoskeletal dynamics and ultrastructural diversity of butterfly wing scales.

The color patterns that adorn lepidopteran wings are ideal for studying cell type diversity using a phenomics approach. Color patterns are made of chitinous scales that are each the product of a single precursor cell, offering a 2D system where phenotypic diversity can be studied cell by cell, both within and between species. Those scales reveal complex ultrastructures in the sub-micrometer range that are often connected to a photonic function, including iridescent blues and greens, highly reflective whites, or light-trapping blacks. We found that during scale development, Fascin immunostainings reveal punctate distributions consistent with a role in the control of actin patterning. We quantified the cytoskeleton regularity as well as its relationship to chitin deposition sites, and confirmed a role in the patterning of the ultrastructures of the adults scales. Then, in an attempt to characterize the range and variation in lepidopteran scale ultrastructures, we devised a high-throughput method to quickly derive multiple morphological measurements from fluorescence images and scanning electron micrographs. We imaged a multicolor eyespot element from the butterfly Vanessa cardui (V. cardui), taking approximately 200 000 individual measurements from 1161 scales. Principal component analyses revealed that scale structural features cluster by color type, and detected the divergence of non-reflective scales characterized by tighter cross-rib distances and increased orderedness. We developed descriptive methods that advance the potential of butterfly wing scales as a model system for studying how a single cell type can differentiate into a multifaceted spectrum of complex morphologies. Our data suggest that specific color scales undergo a tight regulation of their ultrastructures, and that this involves cytoskeletal dynamics during scale growth.

Morphological and ultrastructural diversity and character evolution of the pollen in the tribe Chelidonieae (Papaveraceae)

In this paper, we examine the diversity and character transformation in pollen morphology and ultrastructure (of the pollen wall and aperture system) of the tribe Chelidonieae, the only Papaveraceae group including anemophilous species. Representatives of the nine Chelidonieae genera and three external species were studied using light, scanning-electron, and transmission-electron microscopy. A recently published phylogenetic hypothesis of Chelidonieae was used as a framework to infer the plesiomorphic character states of the tribe and to trace the evolutionary trends of pollen features, using parsimony optimisation. Chelidonieae pollen is generally medium-sized, spheroidal, microechinate-microreticulate, with a granular aperture membrane, an exine stratified in a discontinuous tectum with irregular internal face, a columellar infratectum, and foot layer, with endexine, and a uni-layer intine. Variation among taxa results mainly from: the apertural system (varying in the shape [colpi, pores]; the number [3–12] and position [zono-, panto-aperturate] of the apertures); wall ornamentation (with three more types in addition to the general type); the thickness of the layers of the interapertural exine; and, at the apertural level, the presence or not of endoapertures, and the structure of the foot layer. We have detected a general variation pattern in the thickness of the exine layers consisting of an inverse relationship between their proportions (ectexine vs. endexine, and tectum vs. infratectum). Similarly, the great development of endexine in Sanguinaria appears to have been favoured by the lack of a foot layer in the ectexine. We have found endoapertures in Bocconia pollen, which is the first report in Papaveraceae and represents the most basal lineage of Eudicots in which endoapertures have been detected. We describe for first time in angiosperms a thickening of the foot layer at the apertural level, in Bocconia and Macleaya, with a digit-shaped disruption around the pore (with white lines inside during microspore), that we call a “digit-shaped structure” and we relate to the harmomegathy process. We have inferred the plesiomorphic character states of Chelidonieae pollen and have identified 48 transformations. The evolutionary trend in the apertural system of Chelidonieae goes from many pore-shaped apertures arranged globally (pantoporate) to pollens with three equatorial colpi, contrary to the general trend in angiosperm pollen. Most of the variations in the characters occurred independently in the current taxa lineages and only 11 changes are synapomorphies supporting Chelidonieae groupings. The colpate Chelidonieae clade is supported by two character-state transitions, but no synapomorphy supports the molecular relationship of Bocconia and Macleaya with the colpate clade. According to our results, a strong pollen transformation occurred in the Bocconia-Macleaya lineage, with five of the 11 synapomorphies identified. We discuss this pollen transformation in relation to the shift in the pollination system, from zoophily to anemophily, which occurred in this Chelidonieae lineage.

Frog tendon structure and its relationship with locomotor modes

Tendon collagen fibrils are the basic force-transmitting units of the tendon. Yet, surprisingly little is known about the diversity in tendon anatomy and ultrastructure, and the possible relationships between this diversity and locomotor modes utilized. Our main objectives were to investigate: (a) the ultra-structural anatomy of the tendons in the digits of frogs; (b) the diversity of collagen fibril diameters across frogs with different locomotor modes; (c) the relationship between morphology, as expressed by the morphology of collagen fibrils and tendons, and locomotor modes. To assess the relationship between morphology and the locomotor modes of the sampled taxa we performed a principal component analysis considering body length, fibrillar cross sectional area (CSA) and tendon CSA. A MANOVA showed that differences between species with different locomotor modes were significant with collagen fibril diameter being the discriminating factor. Overall, our data related the greatest collagen fibril diameter to the most demanding locomotor modes, conversely, the smallest collagen fibril CSA and the highest tendon CSA were observed in animals showing a hopping locomotion requiring likely little absorption of landing forces given the short jump distances.

Ultrastructural diversity between centrioles of eukaryotes.

Several decades of centriole research have revealed the beautiful symmetry present in these microtubule-based organelles, which are required to form centrosomes, cilia and flagella in many eukaryotes. Centriole architecture is largely conserved across most organisms; however, individual centriolar features such as the central cartwheel or microtubule walls exhibit considerable variability when examined with finer resolution. In this paper, we review the ultrastructural characteristics of centrioles in commonly studied organisms, highlighting the subtle and not-so-subtle differences between specific structural components of these centrioles. In addition, we survey some non-canonical centriole structures that have been discovered in various species, from the coaxial bicentrioles of protists and lower land plants to the giant irregular centrioles of the fungus gnat Sciara. Finally, we speculate on the functional significance of these differences between centrioles, and the contribution of individual structural elements such as the cartwheel or microtubules towards the stability of centrioles.

Compound Heterozygous Variants in the Coiled-Coil Domain Containing 40 Gene in a Chinese Family with Primary Ciliary Dyskinesia Cause Extreme Phenotypic Diversity in Cilia Ultrastructure.

Purpose: Primary ciliary dyskinesia (PCD) is a rare genetic disorder manifested with recurrent infections of respiratory tract and infertility. Mutations in more than 20 genes including the Coiled-Coil Domain Containing 40 (CCDC40) gene are associated with PCD. A Chinese proband with a clinical diagnosis of PCD was analyzed for mutations in these genes to identify the genetic basis of the disease in the family. The proband showed altered mucociliary clearance of the airways, various degree of hyperemia and edema of the mucous membrane, left/right body asymmetry, infertility and ultrastructural abnormality of cilia in both sperm and bronchioles.Methods: The DNA from the proband was analyzed for genetic variation in a subset of genes known to cause PCD using targeted next generation sequencing in order to understand the molecular and genetic basis of the PCD in present family. The result of targeted next generation sequencing has been validated by Sanger sequencing and q-PCR.Results: Targeted next-generation sequencing identified two novel mutations (c.1259delA and EX17_20 deletion) in CCDC40 gene that causes abnormal CCDC40 mRNA expression. These two novel variants cause disorganization of axoneme filaments, which resulted in reduction of sperm motility and phenotypic diversity in ultrastructure of cilia in the proband.Conclusion: These findings highlight the significance of the mutations in CCDC40 as novel candidates for genetic testing in PCD patients as well as the key role of ICSI treatment for the families affected by this ciliary dysmotility. Our findings showed that our work enriched the performance of cilia ultrastructure which were not previously reported in PCD patients.

Intraspecific variation in seed morphology of tribe vicieae (Papilionoidae) using scanning electron microscopy techniques.

Seed micromorphology of 12 species of tribe Vicieae (Papilionoidae) representing five genera were examined using Scanning Electron Microscope (SEM). The different seed types were described, illustrated, compared, and their taxonomic importance is discussed. Seeds exhibit great diversity in ultrastructure and a variety of novel morphological features have been determined among and within genera of the tribe. Seeds were characterized by oval to round shape, ovate to oblong outline and striate to papillate ornamentation. Radiate and wavy cell pattern has been observed as a characteristic exomorphological feature. In Vicia sativa, testa cells superficially seem to form peltate hairs. As a result, seed micromorphology with few exceptions showed variation and its taxonomic value was significant in distinguishing taxa at species level. The disparity in shape and density of papillae or protuberances and alignment of testa cells, may possibly give further insight at intraspecific level within tribe. The findings also illustrated that the use of SEM in seed morphology can reveal hidden morphological affinities among species and showed potential in delimitation of Vicieae members generally at tribe, genus, and particularly at species level.

Molecular, morphological and ultrastructural characteristics of Prasiola crispa (Lightfoot) Kützing (Chlorophyta) from Spitsbergen (Arctic)

It is commonly known that seabirds, along with cyanobacteria, play a key role in the enrichment of nutrient-poor polar terrestrial ecosystems. In habitats particularly enriched with nitrogen and phosphate ions, ornithogenic vegetation with Prasiola crispa and unique species composition develops. However, no studies have examined the potentially different impacts associated with seabirds on the morphological, ultrastructural and molecular diversity of P. crispa. For that purpose, the present study analyzed four populations from the Hornsund Fjord area (West Spitsbergen) collected in the vicinity of planktivorous or piscivorous colonies and individual nests of seabirds. The morphological variability of P. crispa was studied using fresh samples, and it was documented with light microscopy as well as transmission and scanning electron microscopy. Populations were investigated by molecular analyses based on rbcL and 18S rRNA sequences. The differences in features measured were subjected to statistical analysis. This study provides new data concerning the macro- and submicroscopic structure and molecular diversity of P. crispa with regard to differences in humidity and the quantity of biogenic nutrients deposited by seabirds. Molecular research provided the first data about P. crispa from Spitsbergen. Birds’ diet is relevant for the quantity and quality of the provided nutrients, especially nitrogen compounds (planktivorous species) and phosphorus (piscivorous birds). Climate changes influence the quantitative structure of the colony, clearly favoring piscivorous birds. This, in turn, causes changes in the environment and vegetation. The obtained data on the P. crispa population may be compared with potential changes in the future.

A new type of 3-D peripheral ultrastructure in Glaucocystis (Glaucocystales, Glaucophyta) as revealed by ultra-high voltage electron microscopy.

The coccoid glaucophyte genus Glaucocystis is characterized by having a thick cell wall, which has to date prohibited examination of the native ultrastructural features of the protoplast periphery. Recently, however, the three-dimensional (3-D) ultrastructure of the protoplast periphery was revealed in two divergent Glaucocystis species, with the world's most powerful ultra-high voltage electron microscope (UHVEM). The two species exhibit morphological diversity in terms of their 3-D ultrastructural features. However, these two types do not seem to encompass actual ultrastructural diversity in the genetically diverse genus Glaucocystis. Here, we report a new type of peripheral 3-D ultrastructure resolved in "G.incrassata" SAG 229-2 cells by 3-D modeling based on UHVEM tomography using high-pressure freezing and freeze-substitution fixation. The plasma membrane and underlying flattened vesicles in "G.incrassata" SAG 229-2 exhibited grooves at intervals of 200-600nm, and the flattened vesicles often overlapped one another at the protoplast periphery. This 3-D ultrastructure differs from those of the two types previously reported in other species of Glaucocystis. The possibility of classification of Glaucocystis species based on the 3-D ultrastructure of the protoplast periphery is discussed.

PSD95 nanoclusters are postsynaptic building blocks in hippocampus circuits.

The molecular features of synapses in the hippocampus underpin current models of learning and cognition. Although synapse ultra-structural diversity has been described in the canonical hippocampal circuitry, our knowledge of sub-synaptic organisation of synaptic molecules remains largely unknown. To address this, mice were engineered to express Post Synaptic Density 95 protein (PSD95) fused to either eGFP or mEos2 and imaged with two orthogonal super-resolution methods: gated stimulated emission depletion (g-STED) microscopy and photoactivated localisation microscopy (PALM). Large-scale analysis of ~100,000 synapses in 7 hippocampal sub-regions revealed they comprised discrete PSD95 nanoclusters that were spatially organised into single and multi-nanocluster PSDs. Synapses in different sub-regions, cell-types and locations along the dendritic tree of CA1 pyramidal neurons, showed diversity characterised by the number of nanoclusters per synapse. Multi-nanocluster synapses were frequently found in the CA3 and dentate gyrus sub-regions, corresponding to large thorny excrescence synapses. Although the structure of individual nanoclusters remained relatively conserved across all sub-regions, PSD95 packing into nanoclusters also varied between sub-regions determined from nanocluster fluorescence intensity. These data identify PSD95 nanoclusters as a basic structural unit, or building block, of excitatory synapses and their number characterizes synapse size and structural diversity.

Atypical teratoid/rhabdoid tumor with ganglioglioma-like differentiation: case report and review of the literature

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly aggressive embryonal tumor of the central nervous system, which typically affects young children. A characteristic feature of AT/RT is a polyphenotypic immunoprofile and ultrastructural diversity. The morphologic and antigenic heterogeneity of AT/RT give it the potential to mimic other embryonal central nervous system tumors, epithelial neoplasms or mesenchymal tumors. Alternatively, "collision-type" tumors have been published, in which AT/RT coexists with a separate low-grade central nervous system tumor. Here, we report a case of AT/RT with morphologic and immunohistochemical evidence of extensive ganglioglioma-like differentiation with only a small focal primitive component and minimal rhabdoid cytology. Fluorescence in situ hybridization and immunohistochemistry demonstrated INI1/BAF47 gene/protein losses in both histologic components. To the best of our knowledge, this is the first reported case of AT/RT with extensive ganglioglioma-like differentiation. This unique case supports the notion that routine application of INI1 stains/in situ hybridization can capture AT/RT with unexpected patterns of differentiation.