Exocyst-mediated membrane trafficking of the lissencephaly-associated ECM receptor dystroglycan is required for proper brain compartmentalization

To assemble a brain, differentiating neurons must make proper connections and establish specialized brain compartments. Abnormal levels of cell adhesion molecules disrupt these processes. Dystroglycan (Dg) is a major non-integrin cell adhesion receptor, deregulation of which is associated with dramatic neuroanatomical defects such as lissencephaly type II or cobblestone brain. The previously established Drosophila model for cobblestone lissencephaly was used to understand how Dg is regulated in the brain. During development, Dg has a spatiotemporally dynamic expression pattern, fine-tuning of which is crucial for accurate brain assembly. In addition, mass spectrometry analyses identified numerous components associated with Dg in neurons, including several proteins of the exocyst complex. Data show that exocyst-based membrane trafficking of Dg allows its distinct expression pattern, essential for proper brain morphogenesis. Further studies of the Dg neuronal interactome will allow identification of new factors involved in the development of dystroglycanopathies and advance disease diagnostics in humans

Notch-dependent Fizzy-related/Hec1/Cdh1 expression is required for the mitotic-to-endocycle transition in Drosophila follicle cells.

AbstractDuring Drosophila oogenesis, Notch function regulates the transition from mitotic cell cycle to endocycle in follicle cells at stage 6 [1, 2]. Loss of either Notch function or its ligand Delta (Dl) disrupts the normal transition; this disruption causes mitotic cycling to continue and leads to an overproliferation phenotype [1, 2]. In this context, the only known cell cycle component that responds to the Notch pathway is String/Cdc25 (Stg), a G2/M cell cycle regulator [1]. We found that prolonged expression of string is not sufficient to keep cells efficiently in mitotic cell cycle past stage 6, suggesting that Notch also regulates other cell cycle components in the transition. By using an expression screen, we found such a component: Fizzy-related/Hec1/Cdh1 (Fzr), a WD40 repeat protein. Fzr regulates the anaphase-promoting complex/cyclosome (APC/C) and is expressed at the mitotic-to-endocycle transition in a Notch-dependent manner. Mutant clones of Fzr revealed that Fzr is dispensable for mitosis but essential for endocycles. Unlike in Notch clones, in Fzr mutant cells mitotic markers are absent past stage 6. Only a combined reduction of Fzr and ectopic Stg expression prolongs mitotic cycles in follicle cells, suggesting that these two cell cycle regulators, Fzr and Stg, are important mediators of the Notch pathway in the mitotic-to-endocycle transition

TfAP-2 is required for night sleep in Drosophila.

BACKGROUND: The AP-2 transcription factor APTF-1 is crucially required for developmentally controlled sleep behavior in Caenorhabditis elegans larvae. Its human ortholog, TFAP-2beta, causes Char disease and has also been linked to sleep disorders. These data suggest that AP-2 transcription factors may be highly conserved regulators of various types of sleep behavior. Here, we tested the idea that AP-2 controls adult sleep in Drosophila. RESULTS: Drosophila has one AP-2 ortholog called TfAP-2, which is essential for viability. To investigate its potential role in sleep behavior and neural development, we specifically downregulated TfAP-2 in the nervous system. We found that neuronal TfAP-2 knockdown almost completely abolished night sleep but did not affect day sleep. TfAP-2 insufficiency affected nervous system development. Conditional TfAP-2 knockdown in the adult also produced a modest sleep phenotype, suggesting that TfAP-2 acts both in larval as well as in differentiated neurons. CONCLUSIONS: Thus, our results show that AP-2 transcription factors are highly conserved regulators of development and sleep

Stem cells signal to the niche through the notch pathway in the Drosophila ovary.

SummaryStem cells are maintained and retain their capacity to continue dividing because of the influence of a niche. Although niches are important to maintain “stemness” in a wide variety of tissues, control of these niches is poorly understood. The Drosophila germline stem cells (GSCs) reside in a somatic cell niche [1, 2]. We show that Notch activation can induce the expression of niche-cell markers even in an adult fly; overexpression of Delta in the germline, or activated Notch in the somatic cells, results in extra niche cells, up to 10-fold over the normal number. In turn, these ectopic niche cells induce ectopic GSCs. Conversely, when GCSs do not produce functional Notch ligands, Delta and Serrate, the TGF-β pathway is not activated in the GSCs, and they differentiate and subsequently leave the niche. Importantly, clonal analysis reveals that the receiving end of the Notch pathway is required in the somatic cells. These data show that a feedback loop exists between the stem cells and niche cells. Demonstration that stem cells can contribute to niche function has far-reaching consequences for stem cell therapies and may provide insight into how cancer can spread throughout an organism via populations of cancer stem cells

Optimization of infectious disease processes modelled by nonlinear delay differential equations

In this paper the numerical approach to the solution of optimization problems of processes which are modelled by nonlinear delay differential equations (DDEs) with constant delays is presented. Based on DDEs solution the different characteristics of the modelled process are calculated. One of them is selected as the objective functional. Other characteristics can play a role of constraints. The control is made by the functions, which define the coefficients of DDEs. As a result of piecewise-linear approximation of control function the non-linear mathematical programming problems are obtained. The efficiency of the software developed for solution of nonlinear DDEs and optimization of DDE systems is illustrated on the infectious disease process model.У роботі запропоновано числовий підхід до розв’язування задач оптимізації процесів, поведінка яких моделюється нелінійними диференціальними рівняннями із запізненням (ДРЗ) з постійним кроком запізнення. На основі отриманого розв’язку для ДРЗ обчислюються відповідні характеристики процесу, що розглядається. Одна з цих характеристик вибирається за критерій оптимізації, а інші виконують роль обмежень. За керуючі вибрано функції, від яких залежать коефіцієнти ДРЗ. У результаті апроксимації функцій керування кусково-лінійними функціями отримуємо задачі нелінійного математичного програмування. Ефективність створеного програмного забезпечення для розв’язування нелінійних ДРЗ і задач оптимізації систем, поведінка яких моделюється ДРЗ, проілюстровано на прикладі моделі інфекційного захворювання.В работе предложен численный подход к решению задач оптимизации процессов, поведение которых моделируется нелинейными дифференциальными уравнениями с запаздывающим аргументом (ДУЗ) с постоянным шагом запаздывания. На основе полученного решения для ДУЗ исчисляются соответствующие характеристики рассматриваемого процесса. Одна из этих характеристик выбирается критерием оптимизации, а другие выполняют роль ограничений. В качестве управляющих выбрано функции, от которых зависят коэффициенты ДУЗ. В результате аппроксимации функций управления кусочно-линейными функциями получаем задачи нелинейного математического программирования. Эффективность созданного программного обеспечения для решения нелинейных ДУЗ и задач оптимизации систем, поведение которых моделируется ДУЗ, проиллюстрировано на примере модели инфекционного заболевания

Tissue-specific regulation of translational readthrough tunes functions of the traffic jam transcription factor

Translational readthrough (TR) occurs when the ribosome decodes a stop codon as a sense codon, resulting in two protein isoforms synthesized from the same mRNA. TR has been identified in several eukaryotic organisms; however, its biological significance and mechanism remain unclear. Here, we quantify TR of several candidate genes in Drosophila melanogaster and characterize the regulation of TR in the large Maf transcription factor Traffic jam (Tj). Using CRISPR/Cas9-generated mutant flies, we show that the TR-generated Tj isoform is expressed in a subset of neural cells of the central nervous system and is excluded from the somatic cells of gonads. Control of TR in Tj is critical for preservation of neuronal integrity and maintenance of reproductive health. The tissue-specific distribution of a release factor splice variant, eRF1H, plays a critical role in modulating differential TR of leaky stop codon contexts. Finetuning of gene regulatory functions of transcription factors by TR provides a potential mechanism for cell-specific regulation of gene ex-pression

Profiling of the muscle-specific dystroglycan interactome reveals the role of Hippo signaling in muscular dystrophy and age-dependent muscle atrophy.

Dystroglycanopathies are a group of inherited disorders characterized by vast clinical and genetic heterogeneity and caused by abnormal functioning of the ECM receptor dystroglycan (Dg). Remarkably, among many cases of diagnosed dystroglycanopathies, only a small fraction can be linked directly to mutations in Dg or its regulatory enzymes, implying the involvement of other, not-yet-characterized, Dg-regulating factors. To advance disease diagnostics and develop new treatment strategies, new approaches to find dystroglycanopathy-related factors should be considered. The Dg complex is highly evolutionarily conserved; therefore, model genetic organisms provide excellent systems to address this challenge. In particular, Drosophila is amenable to experiments not feasible in any other system, allowing original insights about the functional interactors of the Dg complex. METHODS: To identify new players contributing to dystroglycanopathies, we used Drosophila as a genetic muscular dystrophy model. Using mass spectrometry, we searched for muscle-specific Dg interactors. Next, in silico analyses allowed us to determine their association with diseases and pathological conditions in humans. Using immunohistochemical, biochemical, and genetic interaction approaches followed by the detailed analysis of the muscle tissue architecture, we verified Dg interaction with some of the discovered factors. Analyses of mouse muscles and myocytes were used to test if interactions are conserved in vertebrates. RESULTS: The muscle-specific Dg complexome revealed novel components that influence the efficiency of Dg function in the muscles. We identified the closest human homologs for Dg-interacting partners, determined their significant enrichment in disease-associations, and verified some of the newly identified Dg interactions. We found that Dg associates with two components of the mechanosignaling Hippo pathway: the WW domain-containing proteins Kibra and Yorkie. Importantly, this conserved interaction manages adult muscle size and integrity. CONCLUSIONS: The results presented in this study provide a new list of muscle-specific Dg interactors, further analysis of which could aid not only in the diagnosis of muscular dystrophies, but also in the development of new therapeutics. To regulate muscle fitness during aging and disease, Dg associates with Kibra and Yorkie and acts as a transmembrane Hippo signaling receptor that transmits extracellular information to intracellular signaling cascades, regulating muscle gene expression