What information can we gain from performing adaptive radiotherapy of head and neck cancer patients from the past 10 years?

The aim of the review was to present the current literature status about replanning regarding anatomical and dosimetric changes in the target and OARs in the head and neck region during radiotherapy, to discuss and to analyze factors influencing the decision for adaptive radiotherapy of head and neck cancer patients. Significant progress has been made in head and neck patients' evaluation and qualification for adapted radiotherapy over the past ten years. Many factors leading to anatomical and dosimetric changes during treatment have been identified. Based on the literature, the most common factors triggering re-plan are weight loss, tumor and nodal changes, and parotid glands shrinkage. The fluctuations in dose distribution in the clinical area are significant predictive factors for patients' quality of life and the possibility of recovery. It has been shown that re-planning influence clinical outcomes: local control, disease free survival and overall survival. Regarding literature studies, it seems that adaptive radiotherapy would be the most beneficial for tumors of immense volume or those in the nearest proximity of the OARs. All researchers agree that the timing of re-planning is a crucial challenge, and there are still no clear consensus guidelines for time or criteria of re-planning. Nowadays, thanks to significant technological progress, the decision is mostly made based on observation and supported with IGRT verification. Although further research is still needed, adaptive strategies are evolving and now became the state of the art of modern radiotherapy.

Impact of COVID-19 on the performance of a radiation oncology department at a major comprehensive cancer centre in Poland during the first ten weeks of the epidemic

The outbreak of SARS-CoV-2 coronavirus rapidly altered radiotherapy service delivery around the world.

AIM

The main objective of this study was to assess the impact of precautionary measures implemented in response to the COVID-19 pandemic on the performance of a radiation oncology departments and on mitigation the risk of COVID-19 contagion between and among patients and staff.

METHODS

The study period was from March 15 until May 22, 2020. We evaluated total number of patients irradiated and those who initiated treatments, taking into account tumours localisations. We assessed the relationship of potential risk of contagion with patients' domiciles locations in regions with high number of COVID19 case.

RESULTS AND CONCLUSIONS

The number of patients treated with radiotherapy during the study period decreased due to precautionary measures. After five weeks, the number of radiotherapy treatments began to increase. Just over half of the radiotherapy patients (53.5%) treated at the GPCC reside in the city of Poznan or in one of the ten surrounding counties where COVID19 incidence was low and reached at the end of the study period cumulative number of cases n = 204. The precautionary measures were effective qRT-PCR tests were performed in 1545 individuals (patients and hospital staff) revealing four staff members and none patient with a positive PCR result. Immunoglobulin testing was performed in 1132 individuals (patients and hospital staff). A total of 63 individuals were positive for antibodies.

A transgenic zebrafish model for the in vivo study of the blood and choroid plexus brain barriers using claudin 5

The central nervous system (CNS) has specific barriers that protect the brain from potential threats and tightly regulate molecular transport. Despite the critical functions of the CNS barriers, the mechanisms underlying their development and function are not well understood, and there are very limited experimental models for their study. Claudin 5 is a tight junction protein required for blood brain barrier (BBB) and, probably, choroid plexus (CP) structure and function in vertebrates. Here, we show that the gene claudin 5a is the zebrafish orthologue with high fidelity expression, in the BBB and CP barriers, that demonstrates the conservation of the BBB and CP between humans and zebrafish. Expression of claudin 5a correlates with developmental tightening of the BBB and is restricted to a subset of the brain vasculature clearly delineating the BBB. We show that claudin 5a-expressing cells of the CP are ciliated ependymal cells that drive fluid flow in the brain ventricles. Finally, we find that CP development precedes BBB development and that claudin 5a expression occurs simultaneously with angiogenesis. Thus, our novel transgenic zebrafish represents an ideal model to study CNS barrier development and function, critical in understanding the mechanisms underlying CNS barrier function in health and disease.

Summary: A novel transgenic zebrafish, using claudin 5a, represents an ideal model to study blood brain barrier and choroid plexus barrier development and function in vivo.

Loss of ift122, a Retrograde Intraflagellar Transport (IFT) Complex Component, Leads to Slow, Progressive Photoreceptor Degeneration Due to Inefficient Opsin Transport

In the retina, aberrant opsin transport from cell bodies to outer segments leads to retinal degenerative diseases such as retinitis pigmentosa. Opsin transport is facilitated by the intraflagellar transport (IFT) system that mediates the bidirectional movement of proteins within cilia. In contrast to functions of the anterograde transport executed by IFT complex B (IFT-B), the precise functions of the retrograde transport mediated by IFT complex A (IFT-A) have not been well studied in photoreceptor cilia. Here, we analyzed developing zebrafish larvae carrying a null mutation in ift122 encoding a component of IFT-A. ift122 mutant larvae show unexpectedly mild phenotypes, compared with those of mutants defective in IFT-B. ift122 mutants exhibit a slow onset of progressive photoreceptor degeneration mainly after 7 days post-fertilization. ift122 mutant larvae also develop cystic kidney but not curly body, both of which are typically observed in various ciliary mutants. ift122 mutants display a loss of cilia in the inner ear hair cells and nasal pit epithelia. Loss of ift122 causes disorganization of outer segment discs. Ectopic accumulation of an IFT-B component, ift88, is observed in the ift122 mutant photoreceptor cilia. In addition, pulse-chase experiments using GFP-opsin fusion proteins revealed that ift122 is required for the efficient transport of opsin and the distal elongation of outer segments. These results show that IFT-A is essential for the efficient transport of outer segment proteins, including opsin, and for the survival of retinal photoreceptor cells, rendering the ift122 mutant a unique model for human retinal degenerative diseases.

Analysis of cilia structure and function in zebrafish

Cilia are microtubule-based protrusions on the surface of most eukaryotic cells. They are found in most, if not all, vertebrate organs. Prominent cilia form in sensory structures, the eye, the ear, and the nose, where they are crucial for the detection of environmental stimuli, such as light and odors. Cilia are also involved in developmental processes, including left-right asymmetry formation, limb morphogenesis, and the patterning of neurons in the neural tube. Some cilia, such as those found in nephric ducts, are thought to have mechanosensory roles. Zebrafish proved very useful in genetic analysis and imaging of cilia-related processes, and in the modeling of mechanisms behind human cilia abnormalities, known as ciliopathies. A number of zebrafish defects resemble those seen in human ciliopathies. Forward and reverse genetic strategies generated a wide range of cilia mutants in zebrafish, which can be studied using sophisticated genetic and imaging approaches. In this chapter, we provide a set of protocols to examine cilia morphology, motility, and cilia-related defects in a variety of organs, focusing on the embryo and early postembryonic development.

From the cytoplasm into the cilium: bon voyage

The primary cilium compartmentalizes a tiny fraction of the cell surface and volume, yet many proteins are highly enriched in this area and so efficient mechanisms are necessary to concentrate them in the ciliary compartment. Here we review mechanisms that are thought to deliver protein cargo to the base of cilia and are likely to interact with ciliary gating mechanisms. Given the immense variety of ciliary cytosolic and transmembrane proteins, it is almost certain that multiple, albeit frequently interconnected, pathways mediate this process. It is also clear that none of these pathways is fully understood at the present time. Mechanisms that are discussed below facilitate ciliary localization of structural and signaling molecules, which include receptors, G-proteins, ion channels, and enzymes. These mechanisms form a basis for every aspect of cilia function in early embryonic patterning, organ morphogenesis, sensory perception and elsewhere.

Impact of the Intra- and Inter-observer Variability in the Delineation of Parotid Glands on the Dose Calculation During Head and Neck Helical Tomotherapy

The intra- and inter-observer variability in delineation of the parotids on the kilo-voltage computed tomography (kVCT) and mega-voltage computed tomography (MVCT) were examined to establish their impact on the dose calculation during adaptive head and neck helical tomotherapy (HT). Three observers delineated left and right parotids for ten randomly selected patients with oropharynx cancer treated on HT. The pre-treatment kVCT and the MVCT from the first fraction of irradiation were selected to delineation. The delineation procedure was repeated three times by each observer. The parotids were delineated according to the institutional protocol. The analyses included intra-observer reproducibility and inter-structure, -observer and -modality variability of the volume and dose. The differences between the left and right parotid outlines were not statistically significant (p > 0.3). The reproducibility of the delineation was confirmed for each observer on the kVCT (p > 0.2) and on the MVCT (p > 0.1). The inter-observer variability of the outlines was significant (p < 0.001) as well as the inter-modality variability (p < 0.006). The parotids delineated on the MVCT were 10% smaller than on the kVCT. The inter-observer variability of the parotids delineation did not affect the average dose (p = 0.096 on the kVCT and p = 0.176 on the MVCT). The dose calculated on the MVCT was higher by 3.3% than dose from the kVCT (p = 0.009). Usage of the institutional protocols for the parotids delineation reduces intra-observer variability and increases reproducibility of the outlines. These protocols do not eliminate delineation differences between the observers, but these differences are not clinically significant and do not affect average doses in the parotids. The volumes of the parotids delineated on the MVCT are smaller than on the kVCT, which affects the differences in the calculated doses.

Who drives the ciliary highway?

Cilia are protrusions on the surface of cells. They are frequently motile and function to propel cells in an aqueous environment or to generate fluid flow. Equally important is the role of immotile cilia in detecting environmental changes or in sensing extracellular signals. The structure of cilia is supported by microtubules, and their formation requires microtubule-dependent motors, kinesins, which are thought to transport both structural and signaling ciliary proteins from the cell body into the distal portion of the ciliary shaft. In multicellular organisms, multiple kinesins are known to drive ciliary transport, and frequently cilia of a single cell type require more than one kinesin for their formation and function. In addition to kinesin-2 family motors, which function in cilia of all species investigated so far, kinesins from other families contribute to the transport of signaling proteins in a tissue-specific manner. It is becoming increasingly obvious that functional relationships between ciliary kinesins are complex, and a good understanding of these relationships is essential to comprehend the basis of biological processes as diverse as olfaction, vision, and embryonic development.

Nephrocystins and MKS proteins interact with IFT particle and facilitate transport of selected ciliary cargos

Cilia are required for the development and function of many organs. Efficient transport of protein cargo along ciliary axoneme is necessary to sustain these processes. Despite its importance, the mode of interaction between the intraflagellar ciliary transport (IFT) mechanism and its cargo proteins remains poorly understood. Our studies demonstrate that IFT particle components, and a Meckel-Gruber syndrome 1 (MKS1)-related, B9 domain protein, B9d2, bind each other and contribute to the ciliary localization of Inversin (Nephrocystin 2). B9d2, Inversin, and Nephrocystin 5 support, in turn, the transport of a cargo protein, Opsin, but not another photoreceptor ciliary transmembrane protein, Peripherin. Interestingly, the components of this mechanism also contribute to the formation of planar cell polarity in mechanosensory epithelia. These studies reveal a molecular mechanism that mediates the transport of selected ciliary cargos and is of fundamental importance for the differentiation and survival of sensory cells.

Analysis of cilia structure and function in zebrafish

The cilium, a previously little studied cell surface protrusion, has emerged as an important organelle in vertebrate cells. This tiny structure is essential for normal embryonic development, including the formation of left-right asymmetry, limb morphogenesis, and the differentiation of sensory cells. In the adult, cilia also function in a variety of processes, such as the survival of photoreceptor cells, and the homeostasis in several tissues, including the epithelia of nephric ducts. Human ciliary malfunction is associated with situs inversus, kidney cysts, polydactyly, blindness, mental retardation, obesity, and many other abnormalities. The genetic accessibility and optical transparency of the zebrafish make it an excellent vertebrate model system to study cilia biology. In this chapter, we describe the morphology and distribution of cilia in zebrafish embryonic and larval organs. We also provide essential protocols to analyze cilia formation and function.

Genetic defects of GDF6 in the zebrafish out of sight mutant and in human eye developmental anomalies

Background

The size of the vertebrate eye and the retina is likely to be controlled at several stages of embryogenesis by mechanisms that affect cell cycle length as well as cell survival. A mutation in the zebrafish out of sight (out) locus results in a particularly severe reduction of eye size. The goal of this study is to characterize the out^m233 mutant, and to determine whether mutations in the out gene cause microphthalmia in humans.

Results

In this study, we show that the severe reduction of eye size in the out^m233 mutant is caused by a mutation in the zebrafish gdf6a gene. Despite the small eye size, the overall retinal architecture appears largely intact, and immunohistochemical studies confirm that all major cell types are present in out^m233 retinae. Subtle cell fate and patterning changes are present predominantly in amacrine interneurons. Acridine orange and TUNEL staining reveal that the levels of apoptosis are abnormally high in out^m233 mutant eyes during early neurogenesis. Mutation analysis of the GDF6 gene in 200 patients with microphthalmia revealed amino acid substitutions in four of them. In two patients additional skeletal defects were observed.

Conclusions

This study confirms the essential role of GDF6 in the regulation of vertebrate eye size. The reduced eye size in the zebrafish out^m233 mutant is likely to be caused by a transient wave of apoptosis at the onset of neurogenesis. Amino acid substitutions in GDF6 were detected in 4 (2%) of 200 patients with microphthalmia. In two patients different skeletal defects were also observed, suggesting pleitrophic effects of GDF6 variants. Parents carrying these variants are asymptomatic, suggesting that GDF6 sequence alterations are likely to contribute to the phenotype, but are not the sole cause of the disease. Variable expressivity and penetrance suggest a complex non-Mendelian inheritance pattern where other genetic factors may influence the outcome of the phenotype.

A male with unilateral microphthalmia reveals a role for TMX3 in eye development

Anophthalmia and microphthalmia are important birth defects, but their pathogenesis remains incompletely understood. We studied a patient with severe unilateral microphthalmia who had a 2.7 Mb deletion at chromosome 18q22.1 that was inherited from his mother. In-situ hybridization showed that one of the deleted genes, TMX3, was expressed in the retinal neuroepithelium and lens epithelium in the developing murine eye. We re-sequenced TMX3 in 162 patients with anophthalmia or microphthalmia, and found two missense substitutions in unrelated patients: c.116G>A, predicting p.Arg39Gln, in a male with unilateral microphthalmia and retinal coloboma, and c.322G>A, predicting p.Asp108Asn, in a female with unilateral microphthalmia and severe micrognathia. We used two antisense morpholinos targeted against the zebrafish TMX3 orthologue, zgc:110025, to examine the effects of reduced gene expression in eye development. We noted that the morphant larvae resulting from both morpholinos had significantly smaller eye sizes and reduced labeling with islet-1 antibody directed against retinal ganglion cells at 2 days post fertilization. Co-injection of human wild type TMX3 mRNA rescued the small eye phenotype obtained with both morpholinos, whereas co-injection of human TMX3(p.Arg39Gln) mutant mRNA, analogous to the mutation in the patient with microphthalmia and coloboma, did not rescue the small eye phenotype. Our results show that haploinsufficiency for TMX3 results in a small eye phenotype and represents a novel genetic cause of microphthalmia and coloboma. Future experiments to determine if other thioredoxins are important in eye morphogenesis and to clarify the mechanism of function of TMX3 in eye development are warranted.

The apical complex couples cell fate and cell survival to cerebral cortical development

Cortical development depends upon tightly controlled cell fate and cell survival decisions that generate a functional neuronal population, but the coordination of these two processes is poorly understood. Here we show that conditional removal of a key apical complex protein, Pals1, causes premature withdrawal from the cell cycle, inducing excessive generation of early-born postmitotic neurons followed by surprisingly massive and rapid cell death, leading to the abrogation of virtually the entire cortical structure. Pals1 loss shows exquisite dosage sensitivity, so that heterozygote mutants show an intermediate phenotype on cell fate and cell death. Loss of Pals1 blocks essential cell survival signals, including the mammalian target of rapamycin (mTOR) pathway, while mTORC1 activation partially rescues Pals1 deficiency. These data highlight unexpected roles of the apical complex protein Pals1 in cell survival through interactions with mTOR signaling.

Analysis of the retina in the zebrafish model

The zebrafish is one of the leading models for the analysis of the vertebrate visual system. A wide assortment of molecular, genetic, and cell biological approaches is available to study zebrafish visual system development and function. As new techniques become available, genetic analysis and imaging continue to be the strengths of the zebrafish model. In particular, recent developments in the use of transposons and zinc finger nucleases to produce new generations of mutant strains enhance both forward and reverse genetic analysis. Similarly, the imaging of developmental and physiological processes benefits from a wide assortment of fluorescent proteins and the ways to express them in the embryo. The zebrafish is also highly attractive for high-throughput screening of small molecules, a promising strategy to search for compounds with therapeutic potential. Here we discuss experimental approaches used in the zebrafish model to study morphogenetic transformations, cell fate decisions, and the differentiation of fine morphological features that ultimately lead to the formation of the functional vertebrate visual system.

What drives cell morphogenesis: a look inside the vertebrate photoreceptor

Vision mediating photoreceptor cells are specialized light-sensitive neurons in the outer layer of the vertebrate retina. The human retina contains approximately 130 million of such photoreceptors, which enable images of the external environment to be captured at high resolution and high sensitivity. Rod and cone photoreceptor subtypes are further specialized for sensing light in low and high illumination, respectively. To enable visual function, these photoreceptors have developed elaborate morphological domains for the detection of light (outer segments), for changing cell shape (inner segments), and for communication with neighboring retinal neurons (synaptic terminals). Furthermore, rod and cone subtypes feature unique morphological variations of these specialized characteristics. Here, we review the major aspects of vertebrate photoreceptor morphology and key genetic mechanisms that drive their formation. These mechanisms are necessary for cell differentiation as well as function. Their defects lead to cell death.

Zebrafish ale oko, an essential determinant of sensory neuron survival and the polarity of retinal radial glia, encodes the p50 subunit of dynactin

Although microtubule-dependent motors are known to play many essential functions in eukaryotic cells, their role in the context of the developing vertebrate embryo is less well understood. Here we show that the zebrafish ale oko (ako) locus encodes the p50 component of the dynactin complex. Loss of ako function results in a degeneration of photoreceptors and mechanosensory hair cells. Additionally, mutant Müller cells lose apical processes and their perikarya translocate rapidly towards the vitreal surface of the retina. This is accompanied by the accumulation of the apical determinants Nok and Has/aPKC in their cell bodies. ako is required cell-autonomously for the maintenance of the apical process but not for cell body positioning in Müller glia. At later stages, the retinotectal projection also degenerates in ako mutants. These results indicate that the p50 component of the dynactin complex is essential for the survival of sensory neurons and the maintenance of ganglion cell axons, and functions as a major determinant of apicobasal polarity in retinal radial glia.

Lens transplantation in zebrafish and its application in the analysis of eye mutants

The lens plays an important role in the development of the optic cup. Using the zebrafish as a model organism, questions regarding lens development can be addressed. The zebrafish is useful for genetic studies due to several advantageous characteristics, including small size, high fecundity, short lifecycle, and ease of care. Lens development occurs rapidly in zebrafish. By 72 hpf, the zebrafish lens is functionally mature. Abundant genetic and molecular resources are available to support research in zebrafish. In addition, the similarity of the zebrafish eye to those of other vertebrates provides basis for its use as an excellent animal model of human defects. Several zebrafish mutants exhibit lens abnormalities, including high levels of cell death, which in some cases leads to a complete degeneration of lens tissues. To determine whether lens abnormalities are due to intrinsic causes or to defective interactions with the surrounding tissues, transplantation of a mutant lens into a wild-type eye is performed. Using fire-polished metal needles, mutant or wild-type lenses are carefully dissected from the donor animal, and transferred into the host. To distinguish wild-type and mutant tissues, a transgenic line is used as the donor. This line expresses membrane-bound GFP in all tissues, including the lens. This transplantation technique is an essential tool in the studies of zebrafish lens mutants.

CRB1 gene mutations are associated with keratoconus in patients with leber congenital amaurosis

PURPOSE

To present an association of mutations in the CRB1 gene with keratoconus in patients with Leber congenital amaurosis (LCA).

METHODS

Sixteen patients with genotyped LCA (having the CRB1, CRX, RetGC, RPE65, and AIPL1 mutations) were recruited from one ophthalmology practice and examined for the presence of keratoconus. Corneal topography, visual acuity, and slit lamp biomicroscopic examination were performed in all cases.

RESULTS

The mean age of the patients was 34.5 years (range, 13-74). Visual acuities ranged from 20/40 to light perception. Corneal topography was successfully collected in 15 of the cases. Five of the 16 cases had slit lamp and/or topographic features consistent with keratoconus. One patient had a clinical picture that was keratoglobus-like. Of these six cases, four had a CRB1 mutation and two had a CRX mutation. Of the three subjects with the CRX mutation, one had keratoconus, one had the keratoglobus-like presentation, and one was normal. Our cohort represents 14 separate, unrelated families. Only one family comprised multiple members with LCA. These were three affected brothers, one with keratoconus, all with CRB1 mutations.

CONCLUSIONS

Although the results cannot exclude other gene mutations, they suggest that LCA patients with a CRB1 mutation may have a particular susceptibility to keratoconus.

Elipsa is an early determinant of ciliogenesis that links the IFT particle to membrane-associated small GTPase Rab8

The formation and function of cilia involves the movement of intraflagellar transport (IFT) particles underneath the ciliary membrane, along axonemal microtubules. Although this process has been studied extensively, its molecular basis remains incompletely understood. For example, it is unknown how the IFT particle interacts with transmembrane proteins. To study the IFT particle further, we examined elipsa, a locus characterized by mutations that cause particularly early ciliogenesis defects in zebrafish. We show here that elipsa encodes a coiled-coil polypeptide that localizes to cilia. Elipsa protein binds to Ift20, a component of IFT particles, and Elipsa homologue in Caenorhabditis elegans, DYF-11, translocates in sensory cilia, similarly to the IFT particle. This indicates that Elipsa is an IFT particle polypeptide. In the context of zebrafish embryogenesis, Elipsa interacts genetically with Rabaptin5, a well-studied regulator of endocytosis, which in turn interacts with Rab8, a small GTPase, known to localize to cilia. We show that Rabaptin5 binds to both Elipsa and Rab8, suggesting that these proteins provide a bridging mechanism between the IFT particle and protein complexes that assemble at the ciliary membrane.

An automated method for cell detection in zebrafish

Quantification of cells is a critical step towards the assessment of cell fate in neurological disease or developmental models. Here, we present a novel cell detection method for the automatic quantification of zebrafish neuronal cells, including primary motor neurons, Rohon-Beard neurons, and retinal cells. Our method consists of four steps. First, a diffused gradient vector field is produced. Subsequently, the orientations and magnitude information of diffused gradients are accumulated, and a response image is computed. In the third step, we perform non-maximum suppression on the response image and identify the detection candidates. In the fourth and final step the detected objects are grouped into clusters based on their color information. Using five different datasets depicting zebrafish cells, we show that our method consistently displays high sensitivity and specificity of over 95%. Our results demonstrate the general applicability of this method to different data samples, including nuclear staining, immunohistochemistry, and cell death detection.

Detection of blob objects in microscopic zebrafish images based on gradient vector diffusion

The zebrafish has become an important vertebrate animal model for the study of developmental biology, functional genomics, and disease mechanisms. It is also being used for drug discovery. Computerized detection of blob objects has been one of the important tasks in quantitative phenotyping of zebrafish. We present a new automated method that is able to detect blob objects, such as nuclei or cells in microscopic zebrafish images. This method is composed of three key steps. The first step is to produce a diffused gradient vector field by a physical elastic deformable model. In the second step, the flux image is computed on the diffused gradient vector field. The third step performs thresholding and nonmaximum suppression based on the flux image. We report the validation and experimental results of this method using zebrafish image datasets from three independent research labs. Both sensitivity and specificity of this method are over 90%. This method is able to differentiate closely juxtaposed or connected blob objects, with high sensitivity and specificity in different situations. It is characterized by a good, consistent performance in blob object detection.