LlamaTags: A Versatile Tool to Image Transcription Factor Dynamics in Live Embryos.

Embryonic cell fates are defined by transcription factors that are rapidly deployed, yet attempts to visualize these factors in vivo often fail because of slow fluorescent protein maturation. Here, we pioneer a protein tag, LlamaTag, which circumvents this maturation limit by binding mature fluorescent proteins, making it possible to visualize transcription factor concentration dynamics in live embryos. Implementing this approach in the fruit fly Drosophila melanogaster, we discovered stochastic bursts in the concentration of transcription factors that are correlated with bursts in transcription. We further used LlamaTags to show that the concentration of protein in a given nucleus heavily depends on transcription of that gene in neighboring nuclei; we speculate that this inter-nuclear signaling is an important mechanism for coordinating gene expression to delineate straight and sharp boundaries of gene expression. Thus, LlamaTags now make it possible to visualize the flow of information along the central dogma in live embryos.

The transcription factor titration effect dictates level of gene expression.

Models of transcription are often built around a picture of RNA polymerase and transcription factors (TFs) acting on a single copy of a promoter. However, most TFs are shared between multiple genes with varying binding affinities. Beyond that, genes often exist at high copy number-in multiple identical copies on the chromosome or on plasmids or viral vectors with copy numbers in the hundreds. Using a thermodynamic model, we characterize the interplay between TF copy number and the demand for that TF. We demonstrate the parameter-free predictive power of this model as a function of the copy number of the TF and the number and affinities of the available specific binding sites; such predictive control is important for the understanding of transcription and the desire to quantitatively design the output of genetic circuits. Finally, we use these experiments to dynamically measure plasmid copy number through the cell cycle.

Building enhancers from the ground up: a synthetic biology approach.

A challenge of the synthetic biology approach is to use our understanding of a system to recreate a biological function with specific properties. We have applied this framework to bacterial enhancers, combining a driver, transcription factor binding sites, and a poised polymerase to create synthetic modular enhancers. Our findings suggest that enhancer-based transcriptional control depends critically and quantitatively on DNA looping, leading to complex regulatory effects when the enhancer cassettes contain additional transcription factor binding sites for TetR, a bacterial transcription factor. We show through a systematic interplay of experiment and thermodynamic modeling that the level of gene expression can be modulated to convert a variable inducer concentration input into discrete or step-like output expression levels. Finally, using a different DNA-binding protein (TraR), we show that the regulatory output is not a particular feature of the specific DNA-binding protein used for the enhancer but a general property of synthetic bacterial enhancers.

Competing constraints shape the nonequilibrium limits of cellular decision-making.

Gene regulation is central to cellular function. Yet, despite decades of work, we lack quantitative models that can predict how transcriptional control emerges from molecular interactions at the gene locus. Thermodynamic models of transcription, which assume that gene circuits operate at equilibrium, have previously been employed with considerable success in the context of bacterial systems. However, the presence of ATP-dependent processes within the eukaryotic transcriptional cycle suggests that equilibrium models may be insufficient to capture how eukaryotic gene circuits sense and respond to input transcription factor concentrations. Here, we employ simple kinetic models of transcription to investigate how energy dissipation within the transcriptional cycle impacts the rate at which genes transmit information and drive cellular decisions. We find that biologically plausible levels of energy input can lead to significant gains in how rapidly gene loci transmit information but discover that the regulatory mechanisms underlying these gains change depending on the level of interference from noncognate activator binding. When interference is low, information is maximized by harnessing energy to push the sensitivity of the transcriptional response to input transcription factors beyond its equilibrium limits. Conversely, when interference is high, conditions favor genes that harness energy to increase transcriptional specificity by proofreading activator identity. Our analysis further reveals that equilibrium gene regulatory mechanisms break down as transcriptional interference increases, suggesting that energy dissipation may be indispensable in systems where noncognate factor interference is sufficiently large.

Dense Bicoid hubs accentuate binding along the morphogen gradient.

Morphogen gradients direct the spatial patterning of developing embryos; however, the mechanisms by which these gradients are interpreted remain elusive. Here we used lattice light-sheet microscopy to perform in vivo single-molecule imaging in early Drosophila melanogaster embryos of the transcription factor Bicoid that forms a gradient and initiates patterning along the anteroposterior axis. In contrast to canonical models, we observed that Bicoid binds to DNA with a rapid off rate throughout the embryo such that its average occupancy at target loci is on-rate-dependent. We further observed Bicoid forming transient "hubs" of locally high density that facilitate binding as factor levels drop, including in the posterior, where we observed Bicoid binding despite vanishingly low protein levels. We propose that localized modulation of transcription factor on rates via clustering provides a general mechanism to facilitate binding to low-affinity targets and that this may be a prevalent feature of other developmental transcription factors.

Determining Factors to Understand the External Quantum Efficiency Values: Study Carried Out with Copper(I)-I and 1,2-Bis(4-pyridyl)ethane Coordination Polymers as Downshifters in Photovoltaic Modules.

Downshifters refer to compounds with the capacity to absorb UV photons and transform them into visible light. The integration of such downshifters has the potential to improve the efficiency of commercial photovoltaic modules. Initially, costly lanthanide derivatives and organic fluorescent dyes were introduced, resulting in a heightened module efficiency. In a novel research direction guided by the same physicochemical principles, the utilization of copper(I) coordination compounds is proposed. This choice is motivated by its simpler and more economical synthesis, primarily due to copper being a more abundant and less toxic element. Our proposal involves employing 1,2-bis(4-pyridyl) ethane (bpe), an economically viable commercial ligand, in conjunction with CuI to synthesize coordination polymers: [CuI(bpe)]n(1), [Cu3I3(bpe)3]n(2), and [CuI(bpe)0.5]n(3). These polymers exhibit the ability to absorb UV photons and emit light within the green and orange spectra. To conduct external quantum efficiency studies, the compounds are dispersed on glass and then encapsulated with ethylene vinyl acetate through heating to 150 °C. Interestingly, during these procedural steps, the solvents and temperatures employed induce a phase transformation, which has been thoroughly examined through both experimental analysis and theoretical calculations. The outcomes of these studies reveal an enhancement in external quantum efficiency with [Cu3I3(bpe)3]n(2), at a cost significantly lower (between 340 and 350 times) than that associated with lanthanide DS complexes.

Aging in Indigenous Communities: Perspective from Two Ancestral Communities in the Colombian Andean-Amazon Region.

The phenomenon of world aging is not foreign to indigenous communities. In the last few years, research about these communities around the world has increased, but aging in indigenous towns still has not been studied widely. The purpose of this research is to interpret the meaning of old age in two indigenous communities from the Colombian Andean-Amazon region (the Inga and Kamëntsa) to reinforce the relevance of the local sociocultural context within the configuration of the meaning of old age and to emphasize the importance of considering particular regional characteristics for the design of policies and interventions aiming to recognize and integrate indigenous populations. This is a qualitative study with an interactionism-symbolism approach. In total, six indigenous people older than 60 years from two ancestral communities from the Colombian Andean-Amazon region participated in the in-depth interviews. Data analysis was carried out in three moments: discovery, coding, and relativization of the information. The results show that old age means wisdom, "I am wise," which is supported in the cosmology and the trajectory of life, reinforces the identity and autonomy, and allows them to be agents in the dynamics of their communities from the "I do," in other words, their roles as builders of the family-society and as guards of ancestral knowledge. The loss of this knowledge and the elements that it is composed of uproot them and put them at risk of disappearing as individuals and as a collective. In conclusion, the meaning of old age in these communities is not centered on a determinate age; you are not old, you are wise, and as such, they play a central role in their communities. Moreover, wisdom is built in parallel with their cosmology and assigns them the task of safekeeping ancestral knowledge. In order to do this, they use oral tradition as a tool, words that are born in their territories, travel in a nonlinear timeline, and get strengthened by the community while also protecting it and building it. Knowing what aging means for Indigenous communities can facilitate to the development of policies and initiatives and to provide culturally appropriate and effective programs.

2D Cu(I)-I Coordination Polymer with Smart Optoelectronic Properties and Photocatalytic Activity as a Versatile Multifunctional Material.

This work presents two isostructural Cu(I)-I 2-fluoropyrazine (Fpyz) luminescent and semiconducting 2D coordination polymers (CPs). Hydrothermal synthesis allows the growth of P-1 space group single crystals, whereas solvent-free synthesis produces polycrystals. Via recrystallization in acetonitrile, P21 space group single crystals are obtained. Both show a reversible luminescent response to temperature and pressure. Structure determination by single-crystal X-ray diffraction at 200 and 100 K allows us to understand their response as a function of temperature. Applying hydrostatic/uniaxial pressure or grinding also generates significant variations in their emission. The high structural flexibility of the Cu(I)-I chain is significantly linked to the corresponding alterations in structure. Remarkably, pressure can increase the conductivity by up to 3 orders of magnitude. Variations in resistivity are consistent with changes in the band gap energy. The experimental results are in agreement with the DFT calculations. These properties may allow the use of these CPs as optical pressure or temperature sensors. In addition, their behavior as a heterogeneous photocatalyst of persistent organic dyes has also been investigated.

Multimodal transcriptional control of pattern formation in embryonic development.

Predicting how interactions between transcription factors and regulatory DNA sequence dictate rates of transcription and, ultimately, drive developmental outcomes remains an open challenge in physical biology. Using stripe 2 of the even-skipped gene in Drosophila embryos as a case study, we dissect the regulatory forces underpinning a key step along the developmental decision-making cascade: the generation of cytoplasmic mRNA patterns via the control of transcription in individual cells. Using live imaging and computational approaches, we found that the transcriptional burst frequency is modulated across the stripe to control the mRNA production rate. However, we discovered that bursting alone cannot quantitatively recapitulate the formation of the stripe and that control of the window of time over which each nucleus transcribes even-skipped plays a critical role in stripe formation. Theoretical modeling revealed that these regulatory strategies (bursting and the time window) respond in different ways to input transcription factor concentrations, suggesting that the stripe is shaped by the interplay of 2 distinct underlying molecular processes.

Real-time single-cell characterization of the eukaryotic transcription cycle reveals correlations between RNA initiation, elongation, and cleavage.

The eukaryotic transcription cycle consists of three main steps: initiation, elongation, and cleavage of the nascent RNA transcript. Although each of these steps can be regulated as well as coupled with each other, their in vivo dissection has remained challenging because available experimental readouts lack sufficient spatiotemporal resolution to separate the contributions from each of these steps. Here, we describe a novel application of Bayesian inference techniques to simultaneously infer the effective parameters of the transcription cycle in real time and at the single-cell level using a two-color MS2/PP7 reporter gene and the developing fruit fly embryo as a case study. Our method enables detailed investigations into cell-to-cell variability in transcription-cycle parameters as well as single-cell correlations between these parameters. These measurements, combined with theoretical modeling, suggest a substantial variability in the elongation rate of individual RNA polymerase molecules. We further illustrate the power of this technique by uncovering a novel mechanistic connection between RNA polymerase density and nascent RNA cleavage efficiency. Thus, our approach makes it possible to shed light on the regulatory mechanisms in play during each step of the transcription cycle in individual, living cells at high spatiotemporal resolution.

[Clinical features of Chilean patients with Fibrous Dysplasia/McCune-Albright Syndrome]. / Caracterización clínica de pacientes chilenos con displasia fibrosa/síndrome de McCune-Albright.

BACKGROUND: Fibrous Dysplasia/McCune-Albright Syndrome (FD/MAS) is characterized by a spectrum of manifestations that may include fibrous dysplasia of bone and multiple endocrinopathies. AIM: To describe the clinical spectrum, the study and follow-up of patients with FD/MAS cared at our institution. MATERIAL AND METHODS: Review of medical records of 12 pediatric and adult patients (11 women) who met the clinical and genetic diagnostic criteria for FD/ MAS. RESULTS: The patients' mean age at diagnosis was 4.9 ± 5.5 years. The most common initial clinical manifestation was peripheral precocious puberty (PPP) in 67% of patients and 75% had café-au-lait spots. Fibrous dysplasia was present in 75% of patients and the mean age at diagnosis was 7.9 ± 4.7 years. Ten patients had a bone scintigraphy, with an age at the first examination that varied between 2 and 38 years of age. The most frequent location of dysplasia was craniofacial and appendicular. No patient had a recorded history of cholestasis, hepatitis, or pancreatitis. In four patients, a genetic study was performed that was positive for the pathogenic variant of guanine nucleotide binding protein, alpha stimulating (GNAS). CONCLUSIONS: These patients demonstrate the variable nature of the clinical presentation and study of FD/MAS. It is essential to increase the index of diagnostic suspicion and adherence to international recommendations.

Mandatory notifications of type 1 diabetes incident cases in Chilean children, 2006 to 2014: A population-based study.

Type 1 diabetes mellitus (T1D) incidence in children varies across regions and countries, showing a continuous rise globally. Chile has mandatory T1D notification and guaranteed access to diagnosis and treatment since 2005, providing a strong model to evaluate T1D epidemiology. OBJECTIVE: To determine T1D incidence in Chilean population under 20 years between 2006 and 2014. METHODS: We reviewed mandatory notifications of T1D in Chile's public health system. RESULTS: A total of 4153 T1D cases in population under 20 years were notified from 2006 to 2014. Median age was 14 years and 51% were male. The average annual T1D incidence was 12 per 100 000 population, with an increase from 10.2 in 2006 to 13.8 in 2014 (ß 0.5 95% confidence interval [CI] 0.4-0.7, P < .001). A significantly increasing linear trend of T1D incidence was observed in groups of 0 to 4 years (ß 0.33, 95% CI 0.06-0.59, P = .02), 5 to 9 years (ß 0.68 95% CI 0.27-1.10, P = .006), and 10 to 14 (ß 0.94, 95% CI 0.67-1.20, P < .001), but increase was less pronounced in the oldest children aged between 15 and 19 years (ß 0.22, 95% CI -0.03 to 0.44, P = .052). The lowest regional T1D incidence was observed in the Araucanía region, which has the highest rate of indigenous population. CONCLUSION: Incidence rates of T1D in Chile, evaluated through a mandatory notification program, are rapidly increasing in children and adolescents. If increasing trends persist, Chile will reach T1D incidence rates of Western developed countries in the next decade.

[Seasonal variations in 25-hydroxy vitamin D3, parathormone and alkaline phosphatase in school-aged children]. / Variación estacional de 25-hidroxi-vitamina D3, hormona paratiroidea y fosfatasa alcalina en niños escolares.

INTRODUCTION: The main role of Vitamin D is to regulate calcium metabolism, whose main source is vitamin D3 ob tained mostly from the action of ultraviolet (UV) light on the skin. OBJECTIVE: To evaluate the seaso nal differences in the concentrations of 25-hydroxy-vitamin D3 (25OHVitD3), parathyroid hormone (PTH), alkaline phosphatase (ALP), and calcium in school-age children. SUBJECTS AND METHOD: The concentrations of 25OHVitD3, PTH, ALP, and calcium were measured in children from Santiago, Chile (latitude -33.4372), aged 5 to 8 years, without Vitamin D supplementation, in different seasons of the year. VitD status was defined as sufficient with concentrations of 25OHVitD3 >20 ng/mL (50 nmol/L), insufficient 12-20 ng/mL (30-50 nmol/L) and deficient <12 ng/mL (30 nmol/L) based on the recommendations of the expert group of the "Global Consensus for the Prevention and Mana gement of Nutritional Rickets". RESULTS: 133 children participated (89 preterms under or equal to 32 weeks), 41 during summer, 28 in fall, 35 in winter, and 29 in spring. The difference of means between summer and winter was 9.6 ng/mL for 25OHVitD3 (p <0.0001), -11.1 pg/mL for PTH (p <0.0001), and -47.5 IU/mL for ALP (p= 0.01). There were no differences in calcium concentrations. In sum mer, 97.6% of the subjects were classified with sufficiency status (> 20 ng/mL), which decreased significantly in winter to 54.3% (p <0.0001). CONCLUSIONS: In winter, 25OHVitD3 concentrations decreased in approximately half of the children, which was associated with an increase in PTH and ALP, and normal calcium concentrations. According to our results, children may need VitD supple mentation during fall and winter.

Clinical profile of children with diabetic ketoacidosis in fifteen years of management in a Critical Care Unit. / Perfil clínico de niños con cetoacidosis diabética en una Unidad de Paciente Crítico.

INTRODUCTION: Diabetic ketoacidosis (DKA) is the main cause of morbidity and mortality in children with type 1 diabetes mellitus (T1DM) due to clinical and biochemical alterations associated, cerebral edema as one of the most critical because of the high mortality rates and long-term neurological se quelae. OBJECTIVE: To analyze the clinical characteristics and complications of patients with DKA ad mitted to a pediatric intensive care unit. PATIENTS AND METHODS: Retrospective study of DKA patients treated at the Hospital Clínico, Pontificia Universidad Católica de Chile (UPCPUC) between 2000 and 2015. Demographic characteristics, clinical manifestations, biochemical alterations, treatment, complications, and prognosis were assessed. Patients with T1DM onset were compared with those patients already diagnosed with diabetes, analyzing variables according to distribution. RESULTS: 46 DKA events were identified, 67% of them were the first episode of DKA. 66% of patients already diagnosed with diabetes were admitted due to poor adherence to treatment. The main symptoms described were: 63% polydipsia, 56% polyuria, 48% vomiting, 39% weight loss and 35% abdominal pain, and mean blood sugar levels of 522 mg/dL, pH 7.17, and plasma osmolality of 305 mOsm/L. 89% of patients received insulin infusion, and 37% presented hypokalemia. No episodes of cerebral edema or deaths were registered. CONCLUSIONS: Most of the DKA admissions were due to T1DM onset. In the group of patients already diagnosed with diabetes, the poor adherence to treatment was the main cause of decompensation. There were no serious complications or deaths associated with DKA management during the studied period. Early diagnosis and proper and standardized treatment contributed to reducing morbidity and mortality in children with DKA.

The embryo as a laboratory: quantifying transcription in Drosophila.

Transcriptional regulation of gene expression is fundamental to most cellular processes, including determination of cellular fates. Quantitative studies of transcription in cultured cells have led to significant advances in identifying mechanisms underlying transcriptional control. Recent progress allowed implementation of these same quantitative methods in multicellular organisms to ask how transcriptional regulation unfolds both in vivo and at the single molecule level in the context of embryonic development. Here we review some of these advances in early Drosophila development, which bring the embryo on par with its single celled counterparts. In particular, we discuss progress in methods to measure mRNA and protein distributions in fixed and living embryos, and we highlight some initial applications that lead to fundamental new insights about molecular transcription processes. We end with an outlook on how to further exploit the unique advantages that come with investigating transcriptional control in the multicellular context of development.

Dynamic regulation of eve stripe 2 expression reveals transcriptional bursts in living Drosophila embryos.

We present the use of recently developed live imaging methods to examine the dynamic regulation of even-skipped (eve) stripe 2 expression in the precellular Drosophila embryo. Nascent transcripts were visualized via MS2 RNA stem loops. The eve stripe 2 transgene exhibits a highly dynamic pattern of de novo transcription, beginning with a broad domain of expression during nuclear cycle 12 (nc12), and progressive refinement during nc13 and nc14. The mature stripe 2 pattern is surprisingly transient, constituting just ∼15 min of the ∼90-min period of expression. Nonetheless, this dynamic transcription profile faithfully predicts the limits of the mature stripe visualized by conventional in situ detection methods. Analysis of individual transcription foci reveals intermittent bursts of de novo transcription, with duration cycles of 4-10 min. We discuss a multistate model of transcription regulation and speculate on its role in the dynamic repression of the eve stripe 2 expression pattern during development.

[Granulosa cell ovarian tumor: precocious puberty in infant less than 1 year of age. Case report]. / Tumor de las células de granulosa: pubertad precoz en lactante menor de 1 año. Caso clínico.

INTRODUCTION: Juvenile granulosa cell tumors (JGCT) are very rare, especially in infants under the age of one. The most frequent presentation is with signs of precocious puberty. OBJECTIVE: Present an in fant with peripheral precocious puberty, diagnosis of JGCT and follow up. CLINICAL CASE: 10-month-old female infant with thelarche, pubic hair and palpable abdominal mass accompanied with eleva ted levels of estradiol, very low gonadotrophins and images that show a very large ovarian mass. A sapingooforectomy was carried out with full regression of symptoms and signs and improvement of laboratory exams. The biopsy showed TCGJ so inhibin B (InB) was taken as tumoral marker after surgery. This hormone was high initially, but rapidly declined. Follow-up was based on InB, antimu-llerian Hormone (AMH) and estradiol as described in this type of tumors. CONCLUSIONS: Juvenil gra nulosa cell tumors are very infrequent in pediatric age, but should be suspected in girl with peripheral precocious puberty. The majority of cases improve with surgery, but strict surveillance of tumoral markers is needed. The most specific markers are inhibin B and anti mullerian hormone (AMH), followed by estradiol levels.

[Second Consensus of the Chilean Society of Endocrinology and Diabetes about insulin resistance]. / II Consenso de la Sociedad Chilena de Endocrinología y Diabetes sobre resistencia a la insulina.

Insulin resistance is a prevalent condition commonly associated with unhealthy lifestyles. It affects several metabolic pathways, increasing risk of abnormalities at different organ levels. Thus, diverse medical specialties should be involved in its diagnosis and treatment. With the purpose of unifying criteria about this condition, a scientific-based consensus was elaborated. A questionnaire including the most important topics such as cardio-metabolic risk, non-alcoholic fatty liver disease and polycystic ovary syndrome, was designed and sent to national experts. When no agreement among them was achieved, the Delphi methodology was applied. The main conclusions reached are that clinical findings are critical for the diagnosis of insulin resistance, not being necessary blood testing. Acquisition of a healthy lifestyle is the most important therapeutic tool. Insulin-sensitizing drugs should be prescribed to individuals at high risk of disease according to clinically validated outcomes. There are specific recommendations for pregnant women, children, adolescents and older people.

New species and notes on Microveliinae from northern South America (Hemiptera: Heteroptera: Veliidae).

Euvelia mazzucconiae sp. nov., from northern Colombia is described, illustrated, and included in an updated identification key to the species of the genus. A map with the known geographical distribution of the species of Euvelia is presented. Additionally, two species from Colombia previously placed in the genus Paravelia are transferred to Microvelia and a species of the latter genus is synonymized, such that Paravelia acantha Padilla-Gil, 2013 = Microvelia acantha (Padilla-Gil, 2013) comb. nov., Paravelia fanera Padilla-Gil, 2013 = Microvelia fanera (Padilla-Gil, 2013) comb. nov., and Microvelia amrishi Makhan 2014 = Microvelia mimula White 1879 syn. nov.

Quantitative dissection of the simple repression input-output function.

We present a quantitative case study of transcriptional regulation in which we carry out a systematic dialogue between theory and measurement for an important and ubiquitous regulatory motif in bacteria, namely, that of simple repression. This architecture is realized by a single repressor binding site overlapping the promoter. From the theory point of view, this motif is described by a single gene regulation function based upon only a few parameters that are convenient theoretically and accessible experimentally. The usual approach is turned on its side by using the mathematical description of these regulatory motifs as a predictive tool to determine the number of repressors in a collection of strains with a large variation in repressor copy number. The predictions and corresponding measurements are carried out over a large dynamic range in both expression fold change (spanning nearly four orders of magnitude) and repressor copy number (spanning about two orders of magnitude). The predictions are tested by measuring the resulting level of gene expression and are then validated by using quantitative immunoblots. The key outcomes of this study include a systematic quantitative analysis of the limits and validity of the input-output relation for simple repression, a precise determination of the in vivo binding energies for DNA-repressor interactions for several distinct repressor binding sites, and a repressor census for Lac repressor in Escherichia coli.