Spatially revealed roles for lncRNAs in Drosophila spermatogenesis, Y chromosome function and evolution.

Unlike coding genes, the number of lncRNA genes in organism genomes is relatively proportional to organism complexity. From plants to humans, the tissues with highest numbers and levels of lncRNA gene expression are the male reproductive organs. To learn why, we initiated a genome-wide analysis of Drosophila lncRNA spatial expression patterns in these tissues. The numbers of genes and levels of expression observed greatly exceed those previously reported, due largely to a preponderance of non-polyadenylated transcripts. In stark contrast to coding genes, the highest numbers of lncRNAs expressed are in post-meiotic spermatids. Correlations between expression levels, localization and previously performed genetic analyses indicate high levels of function and requirement. More focused analyses indicate that lncRNAs play major roles in evolution by controlling transposable element activities, Y chromosome gene expression and sperm construction. A new type of lncRNA-based particle found in seminal fluid may also contribute to reproductive outcomes.

Rapid genetic screening with high quality factor metasurfaces.

Genetic analysis methods are foundational to advancing personalized medicine, accelerating disease diagnostics, and monitoring the health of organisms and ecosystems. Current nucleic acid technologies such as polymerase chain reaction (PCR) and next-generation sequencing (NGS) rely on sample amplification and can suffer from inhibition. Here, we introduce a label-free genetic screening platform based on high quality (high-Q) factor silicon nanoantennas functionalized with nucleic acid fragments. Each high-Q nanoantenna exhibits average resonant quality factors of 2,200 in physiological buffer. We quantitatively detect two gene fragments, SARS-CoV-2 envelope (E) and open reading frame 1b (ORF1b), with high-specificity via DNA hybridization. We also demonstrate femtomolar sensitivity in buffer and nanomolar sensitivity in spiked nasopharyngeal eluates within 5 minutes. Nanoantennas are patterned at densities of 160,000 devices per cm2, enabling future work on highly-multiplexed detection. Combined with advances in complex sample processing, our work provides a foundation for rapid, compact, and amplification-free molecular assays.

Controlling Valley-Specific Light Emission from Monolayer MoS2 with Achiral Dielectric Metasurfaces.

Excitons in two-dimensional transition metal dichalcogenides have a valley degree of freedom that can be optically manipulated for quantum information processing. Here, we integrate MoS2 monolayers with achiral silicon disk array metasurfaces to enhance and control valley-specific absorption and emission. Through the coupling to the metasurface electric and magnetic Mie modes, the intensity and lifetime of the emission of neutral excitons, trions, and defect bound excitons can be enhanced and shortened, respectively, while the spectral shape can be modified. Additionally, the degree of polarization (DOP) of exciton and trion emission from the valley can be symmetrically enhanced at 100 K. The DOP increase is attributed to both the metasurface-enhanced chiral absorption of light and the metasurface-enhanced exciton emission from the Purcell effect. Combining Si-compatible photonic design with large-scale 2D materials integration, our work makes an important step toward on-chip valleytronic applications approaching room-temperature operation.

Universal Narrowband Wavefront Shaping with High Quality Factor Meta-Reflect-Arrays.

Optical metasurfaces offer unprecedented flexibility in light wave manipulation but suffer weak resonant enhancement. Tackling this problem, we experimentally unveil a new phase gradient metasurface platform made entirely from individually addressable high quality factor (high-Q) silicon meta-atoms. Composed of pairs of nearly identical nanoblocks, these meta-atoms support dipolar-guided-mode resonances that, due to the controlled suppression of radiation loss, serve as highly sensitive phase pixels when placed above a mirror. A key novelty of this platform lies in the vanishingly small structural perturbations needed to produce universal phase fronts. Having fabricated elements with Q-factor ∼380 and spaced by λ/1.2, we achieve strong beam steering, up to 59% efficient, to angles 32.3°, 25.3°, and 20.9°, with variations in nanoantenna volume fractions across the metasurfaces of ≤2.6%, instead of >50% required by traditional versions. Aside from extreme sensitivity, the metasurfaces exhibit near-field intensity enhancement over 1000×. Taken together, these properties represent an exciting prospect for dynamic and nonlinear wave shaping.

Evaluation of ovulation and safety outcomes in a multi-center randomized trial of three 84 day ulipristal acetate regimens.

OBJECTIVES: To describe ovulation inhibition and safety of daily oral ulipristal acetate (UPA) over 84 days. STUDY DESIGN: This multi-center phase 1 and/or 2 trial randomized participants to use oral ulipristal 10 mg or 5 mg daily or a 3 cycle regimen of 5 mg for 24 days followed by four placebo days. We stratified randomization by body mass index (BMI) <32 or 32-40 kg/m2. To estimate ovulation inhibition, the primary outcome, participants underwent transvaginal ultrasound and blood sampling twice weekly; we analyzed compliant participants who completed the 84 day study. Safety endpoints included 3 endometrial biopsies and liver chemistry tests. RESULTS: We enrolled 180 participants and included 137 in the ovulation inhibition analyses. Progesterone values that remained below 3ng/mL throughout treatment suggested consistent ovulation inhibition in 52 of 137 (38%) participants; 25 of 47(53%), 20 of 44(45%), and 7 of 46(15%) among participants randomized to the 10 mg, 5 mg, and cyclic treatments, respectively (p < 0.01). Progesterone values consistently <3 ng/mL were more frequent in participants with a BMI > 32kg/m2 (25/50(50%) vs 27/87(31%), p = 0.01). Average ulipristal concentrations were higher among participants with low progesterone concentrations (p < 0.01). Endometrial biopsies during treatment showed progesterone-receptor-modulator-associated endometrial changes in 52 of 164 participants (32%); 22 of 49(40%), 16 of 48(29%), and 14 of 51(26%) in women randomized to the 10 mg, 5 mg, and the cyclic treatments, respectively (p = 0.07, test-for-trend); these changes resolved after treatment cessation. Liver transaminase changes were rare. CONCLUSIONS: Oral ulipristal acetate over 12 weeks did not reliably suppress ovulation, particularly in the 5 mg cyclic-dose group. Ovulation inhibition and endometrial changes were dose dependent. Reversible endometrial changes occurred during treatment. IMPLICATIONS: Progesterone-receptor modulators have been suggested for daily oral contraception. Since progesterone concentrations suggest that ovulation occurred during treatment, further studies would be necessary to assess whether these were functional ovulations and to evaluate other possible mechanisms of contraception.

The use of serum segesterone acetate levels to assess adherence of trial participants with a contraceptive vaginal ring.

OBJECTIVES: To determine the incidence of out-of-range segesterone acetate (NES) concentrations in participants of a pharmacokinetic/pharmacodynamic trial of a continuous use contraceptive vaginal ring (CVR) releasing NES and estradiol (E2). We hypothesized that out-of-range concentrations reflect nonadherent ring use and predict ovulation risk. STUDY DESIGN: We conducted a secondary analysis of data from a prospective, multi-centered, randomized, Phase IIa dose-finding trial for a CVR releasing NES and E2. Our primary outcome was the risk of ovulation associated with out-of-range NES events. We calculated the 5th and 95th percentile NES concentrations of subjects at steady state to determine high and low cutoffs. We used a Fisher's exact test to determine group differences, and calculated the relative risk of ovulation for each group. RESULTS: We analyzed available serum NES data from cycles 2 (n = 172), 3 (n = 156) and 7 (n = 115) to determine the 5th and 95th percentile of all NES concentrations (64, 296 pg/mL). In the 443 cycles of observation, no ovulations occurred in participants with NES concentrations within the expected range. In contrast, we found ovulatory elevations of progesterone in 21 cycles with out-of-range values. Of these, 15 (71%) cycles had evidence of one or more nonadherent low and 6 (29%) one or more unexpected peak. The relative risk of ovulation increased with evidence of multiple non-adherent levels. CONCLUSIONS: We found out-of-range NES concentrations, suggestive of improper use of a CVR associated with an increased risk of ovulation, with a direct relationship between the number of out-of-range events and the relative risk. IMPLICATIONS: The results of this study support the use of out-of-range serum NES values as a marker of adherence in contraceptive clinical trials of continuous vaginal rings, and suggest that nonadherence occurs even in early phase clinical trials with close monitoring.

Rapid genetic screening with high quality factor metasurfaces.

Genetic analysis methods are foundational to advancing personalized and preventative medicine, accelerating disease diagnostics, and monitoring the health of organisms and ecosystems. Current nucleic acid technologies such as polymerase chain reaction (PCR), next-generation sequencing (NGS), and DNA microarrays rely on fluorescence and absorbance, necessitating sample amplification or replication and leading to increased processing time and cost. Here, we introduce a label-free genetic screening platform based on high quality (high-Q) factor silicon nanoantennas functionalized with monolayers of nucleic acid fragments. Each nanoantenna exhibits substantial electromagnetic field enhancements with sufficiently localized fields to ensure isolation from neighboring resonators, enabling dense biosensor integration. We quantitatively detect complementary target sequences using DNA hybridization simultaneously for arrays of sensing elements patterned at densities of 160,000 pixels per cm$^2$. In physiological buffer, our nanoantennas exhibit average resonant quality factors of 2,200, allowing detection of two gene fragments, SARS-CoV-2 envelope (E) and open reading frame 1b (ORF1b), down to femtomolar concentrations. We also demonstrate high specificity sensing in clinical nasopharyngeal eluates within 5 minutes of sample introduction. Combined with advances in biomarker isolation from complex samples (e.g., mucus, blood, wastewater), our work provides a foundation for rapid, compact, amplification-free and high throughput multiplexed genetic screening assays spanning medical diagnostics to environmental monitoring.

Fluorescence-Detected Circular Dichroism of a Chiral Molecular Monolayer with Dielectric Metasurfaces.

Strong enhancement of molecular circular dichroism (CD) has the potential to enable efficient asymmetric photolysis, a method of chiral separation that has conventionally been impeded by insufficient yield and low enantiomeric excess. Here, we study experimentally how predicted enhancements in optical chirality density near resonant silicon nanodisks boost CD. We use fluorescence-detected circular dichroism (FDCD) spectroscopy to measure indirectly the differential absorption of circularly polarized light by a monolayer of optically active molecules functionalized to silicon nanodisk arrays. Importantly, the molecules and nanodisk antennas have spectrally coincident resonances, and our fluorescence technique allows us to deconvolute absorption in the nanodisks from the molecules. We find that enhanced FDCD signals depend on nanophotonic resonances, in good agreement with simulated differential absorption and optical chirality density, while no signal is detected from molecules adsorbed on featureless silicon surfaces. These results verify the potential of nanophotonic platforms to be used for asymmetric photolysis with lower energy requirements.

Implementation of the Addendum Guidelines for Peanut Allergy Prevention by US allergists, a survey conducted by the NIAID, in collaboration with the AAAAI.

BACKGROUND: In 2017, the Addendum Guidelines for the Prevention of Peanut Allergy were published with recommendations on early introduction of peanut-containing foods based on infants' clinical history. OBJECTIVE: We sought to conduct a nationwide US survey to assess Guidelines implementation among allergists and immunologists who manage infants for food allergy. METHODS: Survey invitations were delivered to 3281 nonretired, US members of the American Academy of Asthma, Allergy & Immunology, board certified in allergy and immunology. The survey assessed awareness and implementation of the Guidelines and barriers to implementation. Descriptive statistics were generated. RESULTS: Twenty-nine percent (946 of 3281) of surveyed allergists/immunologists responded, and 87.1% (825 of 946) of responders met eligibility criteria. Among eligible responders, 97.1% were aware of the Guidelines. Of these, 64.5% reported full implementation of the Guidelines as published, 34.4% reported partial implementation, and 1.1% reported using none of the Guidelines. Barriers to Guidelines use included parental (47.6%) and self (21.8%) concerns about allergic reactions, lack of referrals (33.6%), parents uninterested in early feeding (28.2%), and lack of clinic time (20.9%). The 2 most common deviations from the Guidelines were considering additional factors not specified in the Guidelines such as family history (50.2%) and conducting skin prick testing in non-high-risk children (43.9%). Of respondents using the Guidelines, 45.7% indicated they needed more education or training. CONCLUSIONS: Essentially all allergists/immunologists who responded to the survey reported full or partial Guidelines implementation. Parental concerns and lack of referrals are major identifiable barriers. Improved Guidelines messaging to parents and referring physicians is warranted.

Assessment of Pediatrician Awareness and Implementation of the Addendum Guidelines for the Prevention of Peanut Allergy in the United States.

Importance: The 2017 Addendum Guidelines for the Prevention of Peanut Allergy in the United States recommend that pediatricians assess infant peanut allergy risk and introduce peanut in the diet at age 4 to 6 months. Early introduction has the potential to prevent peanut allergy development. Objectives: To measure the rates of guideline awareness and implementation and to identify barriers to and factors associated with implementation among US pediatricians. Design, Setting, and Participants: This population-based study survey used a 29-item electronic survey instrument that was administered to pediatricians practicing across the United States from June 1, 2018, to December 1, 2018. Invitations to complete a survey were emailed to all pediatricians in the American Academy of Pediatrics vendor database. Eligible participants were nonretired US-based pediatricians providing general care to infants aged 12 months or younger. Main Outcomes and Measures: The primary outcome was the prevalence of guideline implementation, which was measured by 1 survey item about awareness followed by a second item about implementation. Secondary outcomes included identification of guidelines-focused services provided by pediatricians, knowledge of the guidelines (measured with 3 clinical scenarios), barriers to guideline implementation, need for training, and facilitators of guideline implementation. Results: A total of 1781 pediatricians were eligible to participate and completed the entire survey. Most respondents self-identified as white (1287 [72.5%]) and female (1210 [67.4%]) individuals. Overall, 1725 (93.4%; 95% CI, 92.2%-94.5%) pediatricians reported being aware of the guidelines. Of those pediatricians who had knowledge of the guidelines, 497 (28.9%; 95% CI, 26.8%-31.1%) reported full implementation and 1105 (64.3%; 95% CI, 62.0%-66.6%) reported partial implementation. Common barriers to implementation included parental concerns about allergic reactions (reported by 575 respondents [36.6%; 95% CI, 34.3%-39.1%]), uncertainty in understanding and correctly applying the guidelines (reported by 521 respondents [33.2%; 95% CI, 30.9%-35.6%]), and conducting in-office supervised feedings (reported by 509 respondents [32.4%; 95% CI, 30.1%-34.8%]). Many pediatricians (1175 [68.4%; 95% CI, 66.1%-70.5%]) reported a need for further training on the guidelines. Conclusions and Relevance: This survey found that most pediatrician respondents appeared to know of the 2017 guidelines, but less than one-third of respondents reported full implementation. Results of this study may inform future efforts to eliminate barriers to guideline implementation and adherence, thereby reducing the incidence of peanut allergy in infants.

A Functional Analysis of the Drosophila Gene hindsight: Evidence for Positive Regulation of EGFR Signaling.

We have investigated the relationship between the function of the gene hindsight (hnt), which is the Drosophila homolog of Ras Responsive Element Binding protein-1 (RREB-1), and the EGFR signaling pathway. We report that hnt mutant embryos are defective in EGFR signaling dependent processes, namely chordotonal organ recruitment and oenocyte specification. We also show the temperature sensitive hypomorphic allele hntpebbled is enhanced by the hypomorphic MAPK allele rolled (rl1 ). We find that hnt overexpression results in ectopic DPax2 expression within the embryonic peripheral nervous system, and we show that this effect is EGFR-dependent. Finally, we show that the canonical U-shaped embryonic lethal phenotype of hnt, which is associated with premature degeneration of the extraembyonic amnioserosa and a failure in germ band retraction, is rescued by expression of several components of the EGFR signaling pathway (sSpi, Ras85DV12 , pntP1 ) as well as the caspase inhibitor p35 Based on this collection of corroborating evidence, we suggest that an overarching function of hnt involves the positive regulation of EGFR signaling.

Close association between vasa-positive germ plasm granules and mitochondria correlates with cytoplasmic localization of 12S and 16S mtrRNAs during zebrafish spermatogenesis.

The phenomenon of the cytoplasmic localisation of mitochondrial ribosomal subunits (12 S mitochondrial rRNA and 16 S mitochondrial rRNA) has been discovered by scientific teams working with spermatogenic cells of mice. Previous reports showed that the release of mitochondrial substance occurs during interaction of mitochondria with the germ plasm granules (GG). To determine if the interplay between the vasa-positive GG and the mitochondria is associated with cytoplasmic localisation of mtrRNAs, we studied the spermatogenic cells of zebrafish, Danio rerio. It was revealed that in type A undifferentiated spermatogonia the GG did not contact mitochondria, and the extra-mitochondrial localisation of the mtrRNAs was not found. In type A differentiated spermatogonia, the amount of GG in contact with mitochondria increased, but the extra-mitochondrial localisation of the mtrRNAs was not found either. In type B late spermatogonia, which are pre-meiotic cells, the GG/mitochondrion complexes were typically found in contact with the nucleus. This stage was associated with the intra-mitochondrial localisation of GG-originated vasa and extra-mitochondrial localisation of 12 S mtrRNA and 16 S mtrRNA. Until the onset of meiosis, which was determined by the observation of synaptonemal complexes in zygotene-pachytene spermatocytes I, the GG/mitochondrion complexes disappeared, but both types of mtrRNAs persisted in the cytoplasm of spermatids and spermatozoa.

Rhinitis in children and adolescents with asthma: Ubiquitous, difficult to control, and associated with asthma outcomes.

BACKGROUND: Rhinitis and asthma are linked, but substantial knowledge gaps in this relationship exist. OBJECTIVE: We sought to determine the prevalence of rhinitis and its phenotypes in children and adolescents with asthma, assess symptom severity and medication requirements for rhinitis control, and investigate associations between rhinitis and asthma. METHODS: Seven hundred forty-nine children with asthma participating in the Asthma Phenotypes in the Inner-City study received baseline evaluations and were managed for 1 year with algorithm-based treatments for rhinitis and asthma. Rhinitis was diagnosed by using a questionnaire focusing on individual symptoms, and predefined phenotypes were determined by combining symptom patterns with skin tests and measurement of serum specific IgE levels. RESULTS: Analyses were done on 619 children with asthma who completed at least 4 of 6 visits. Rhinitis was present in 93.5%, and phenotypes identified at baseline were confirmed during the observation/management year. Perennial allergic rhinitis with seasonal exacerbations was most common (34.2%) and severe. Nonallergic rhinitis was least common (11.3%) and least severe. The majority of children remained symptomatic despite use of nasal corticosteroids with or without oral antihistamines. Rhinitis was worse in patients with difficult-to-control versus easy-to-control asthma, and its seasonal patterns partially corresponded to those of difficult-to-control asthma. CONCLUSION: Rhinitis is almost ubiquitous in urban children with asthma, and its activity tracks that of lower airway disease. Perennial allergic rhinitis with seasonal exacerbations is the most severe phenotype and most likely to be associated with difficult-to-control asthma. This study offers strong support to the concept that rhinitis and asthma represent the manifestations of 1 disease in 2 parts of the airways.

Ankyrin repeat domain 1 regulates innate immune responses against herpes simplex virus 1: A potential role in eczema herpeticum.

BACKGROUND: Atopic dermatitis (AD) is a common inflammatory skin disease. A subset of patients with AD are susceptible to disseminated herpes simplex virus (HSV) infection, a complication termed eczema herpeticum (ADEH+). The immune mechanisms causing ADEH+ remain elusive. Using RNA sequencing, we recently found that ankyrin repeat domain 1 (ANKRD1) was significantly induced in human PBMCs upon HSV-1 stimulation, and its induction in patients with ADEH+ was significantly reduced compared with that seen in AD patients without a history of eczema herpeticum (ADEH-). OBJECTIVE: We sought to validate ANKRD1 gene expression in nonatopic (NA) subjects, patients with ADEH-, and patients with ADEH+ and to delineate the biological function of ANKRD1 and the signaling pathway or pathways involved. METHODS: Purification of human PBMCs, monocytes, B cells, dendritic cells, T cells, and natural killer cells; RNA extraction and quantitative RT-PCR; small interfering RNA technique; co-immunoprecipitation; and Western blot assays were used. RESULTS: ANKRD1 expression was significantly reduced in PBMCs from patients with ADEH+ after HSV-1 stimulation compared with PBMCs from patients with ADEH-. We found that the induction of ANKRD1 by HSV-1 and multiple pattern recognition receptor agonists are mediated by inflammatory cytokines. Silencing ANKRD1 gene expression in antigen-presenting cells led to increased viral load and reduced IFNB1 and IL29 production. Using co-immunoprecipitation methods, we demonstrated that ANKRD1 formed protein complexes with interferon regulatory factor (IRF) 3 and IRF7, which are important transcription factors regulating signaling transduction of pattern recognition receptors. Overexpression of ANKRD1 enhanced the IRF3-mediated signaling pathways. CONCLUSION: ANKRD1 is involved in IRF3-mediated antiviral innate immune signaling pathways. Its reduced expression in patients with ADEH+ might contribute to the pathogenesis of ADEH+.

High Resolution Fluorescent In Situ Hybridization in Drosophila Embryos and Tissues Using Tyramide Signal Amplification.

In our efforts to determine the patterns of expression and subcellular localization of Drosophila RNAs on a genome-wide basis, and in a variety of tissues, we have developed numerous modifications and improvements to our original fluorescent in situ hybridization (FISH) protocol. To facilitate throughput and cost effectiveness, all steps, from probe generation to signal detection, are performed using exon 96-well microtiter plates. Digoxygenin (DIG)-labelled antisense RNA probes are produced using either cDNA clones or genomic DNA as templates. After tissue fixation and permeabilization, probes are hybridized to transcripts of interest and then detected using a succession of anti-DIG antibody conjugated to biotin, streptavidin conjugated to horseradish peroxidase (HRP) and fluorescently conjugated tyramide, which in the presence of HRP, produces a highly reactive intermediate that binds to electron dense regions of immediately adjacent proteins. These amplification and localization steps produce a robust and highly localized signal that facilitates both cellular and subcellular transcript localization. The protocols provided have been optimized to produce highly specific signals in a variety of tissues and developmental stages. References are also provided for additional variations that allow the simultaneous detection of multiple transcripts, or transcripts and proteins, at the same time.

Diverse and pervasive subcellular distributions for both coding and long noncoding RNAs.

In a previous analysis of 2300 mRNAs via whole-mount fluorescent in situ hybridization in cellularizing Drosophila embryos, we found that 70% of the transcripts exhibited some form of subcellular localization. To see whether this prevalence is unique to early Drosophila embryos, we examined ∼8000 transcripts over the full course of embryogenesis and ∼800 transcripts in late third instar larval tissues. The numbers and varieties of new subcellular localization patterns are both striking and revealing. In the much larger cells of the third instar larva, virtually all transcripts observed showed subcellular localization in at least one tissue. We also examined the prevalence and variety of localization mechanisms for >100 long noncoding RNAs. All of these were also found to be expressed and subcellularly localized. Thus, subcellular RNA localization appears to be the norm rather than the exception for both coding and noncoding RNAs. These results, which have been annotated and made available on a recompiled database, provide a rich and unique resource for functional gene analyses, some examples of which are provided.

Distinct Regulation of Transmitter Release at the Drosophila NMJ by Different Isoforms of nemy.

Synaptic transmission is highly plastic and subject to regulation by a wide variety of neuromodulators and neuropeptides. In the present study, we have examined the role of isoforms of the cytochrome b561 homologue called no extended memory (nemy) in regulation of synaptic strength and plasticity at the neuromuscular junction (NMJ) of third instar larvae in Drosophila. Specifically, we generated two independent excisions of nemy that differentially affect the expression of nemy isoforms. We show that the nemy45 excision, which specifically reduces the expression of the longest splice form of nemy, leads to an increase in stimulus evoked transmitter release and altered synaptic plasticity at the NMJ. Conversely, the nemy26.2 excision, which appears to reduce the expression of all splice forms except the longest splice isoform, shows a reduction in stimulus evoked transmitter release, and enhanced synaptic plasticity. We further show that nemy45 mutants have reduced levels of amidated peptides similar to that observed in peptidyl-glycine hydryoxylating mono-oxygenase (PHM) mutants. In contrast, nemy26.2 mutants show no defects in peptide amidation but rather display a decrease in Tyramine ß hydroxylase activity (TßH). Taken together, these results show non-redundant roles for the different nemy isoforms and shed light on the complex regulation of neuromodulators.

Germ Cell Segregation from the Drosophila Soma Is Controlled by an Inhibitory Threshold Set by the Arf-GEF Steppke.

Germline cells segregate from the soma to maintain their totipotency, but the cellular mechanisms of this segregation are unclear. The Drosophila melanogaster embryo forms a posterior group of primordial germline cells (PGCs) by their division from the syncytial soma. Extended plasma membrane furrows enclose the PGCs in response to the germ plasm protein Germ cell-less (Gcl) and Rho1-actomyosin activity. Recently, we found that loss of the Arf-GEF Steppke (Step) leads to similar Rho1-dependent plasma membrane extensions but from pseudocleavage furrows of the soma. Here, we report that the loss of step also leads to premature formation of a large cell group at the anterior pole of the embryo . These anterior cells lacked germ plasm, but budded and formed at the same time as posterior PGCs, and then divided asynchronously as PGCs also do. With genetic analyses we found that Step normally activates Arf small G proteins and antagonizes Rho1-actomyosin pathways to inhibit anterior cell formation. A uniform distribution of step mRNA around the one-cell embryo cortex suggested that Step restricts cell formation through a global control mechanism. Thus, we examined the effect of Step on PGC formation at the posterior pole. Reducing Gcl or Rho1 levels decreased PGC numbers, but additional step RNAi restored their numbers. Reciprocally, GFP-Step overexpression induced dosage- and Arf-GEF-dependent loss of PGCs, an effect worsened by reducing Gcl or actomyosin pathway activity. We propose that a global distribution of Step normally sets an inhibitory threshold for Rho1 activity to restrict early cell formation to the posterior.

Spatial profiling of nuclear receptor transcription patterns over the course of Drosophila development.

Previous work has shown that many of the 18 family members of Drosophila nuclear receptor transcription factors function in a temporal hierarchy to coordinate developmental progression and growth with the rate limiting process of metabolism. To gain further insight into these interactions and processes, we have undertaken a whole-family analysis of nuclear receptor mRNA spatial expression patterns over the entire process of embryogenesis, as well as the 3rd instar wandering larva stage, by using high-resolution fluorescence in situ hybridization. Overall, the patterns of expression are remarkably consistent with previously mapped spatial activity profiles documented during the same time points, with similar hot spots and temporal profiles in endocrine and metabolically important tissues. Among the more remarkable of the findings is that the majority of mRNA expression patterns observed show striking subcellular distributions, indicating potentially critical roles in the control of protein synthesis and subsequent subcellular distributions. These patterns will serve as a useful reference for future studies on the tissue-specific roles and interactions of nuclear receptor proteins, partners, cofactors and ligands.