Crossing over during meiotic prophase I is required for sexual reproduction in mice and contributes to genome-wide genetic diversity. Here we report on the characterization of an N-ethyl-N-nitrosourea-induced, recessive allele called mei4, which causes sterility in both sexes owing to meiotic defects. In mutant spermatocytes, chromosomes fail to congress properly at the metaphase plate, leading to arrest and apoptosis before the first meiotic division. Mutant oocytes have a similar chromosomal phenotype but in vitro can undergo meiotic divisions and fertilization before arresting. During late meiotic prophase in mei4 mutant males, absence of cyclin dependent kinase 2 and mismatch repair protein association from chromosome cores is correlated with the premature separation of bivalents at diplonema owing to lack of chiasmata. We have identified the causative mutation, a transversion in the 5′ splice donor site of exon 1 in the mouse ortholog of Human Enhancer of Invasion 10 (Hei10; also known as Gm288 in mouse and CCNB1IP1 in human), a putative B-type cyclin E3 ubiquitin ligase. Importantly, orthologs of Hei10 are found exclusively in deuterostomes and not in more ancestral protostomes such as yeast, worms, or flies. The cloning and characterization of the mei4 allele of Hei10 demonstrates a novel link between cell cycle regulation and mismatch repair during prophase I.

SUMMARYConventional soluble guanylyl cyclases form α/β heterodimers that are activated by nitric oxide (NO). Recently, atypical members of the soluble guanylyl cyclase family have been described that include the ratβ2 subunit and MsGC-β3 from Manduca sexta. Predictions from the Drosophila melanogaster genome identify three atypical guanylyl cyclase subunits: Gyc-88E (formerly CG4154), Gyc-89Da (formerly CG14885) and Gyc-89Db (formerly CG14886). Preliminary data showed that transient expression of Gyc-88E in heterologous cells generated enzyme activity in the absence of additional subunits that was slightly stimulated by the NO donor sodium nitroprusside (SNP) but not the NO donor DEA-NONOate or the NO-independent activator YC-1. Gyc-89Db was inactive when expressed alone but when co-expressed with Gyc-88E enhanced the basal and SNP-stimulated activity of Gyc-88E, suggesting that they may form heterodimers in vivo. Here,we describe the localization of Gyc-88E and Gyc-89Db and show that they are expressed in the embryonic and larval central nervous systems and are colocalized in several peripheral neurons that innervate trachea, basiconical sensilla and the sensory cones in the posterior segments of the embryo. We also show that there are two splice variants of Gyc-88E that differ by seven amino acids, although no differences in biochemical properties could be determined. We have also extended our analysis of the NO activation of Gyc-88E and Gyc-89Db, showing that several structurally unrelated NO donors activate Gyc-88E when expressed alone or when co-expressed with Gyc-89Db.

Enhancers are often located many tens of kilobases away from the promoter they regulate, sometimes residing closer to the promoter of a neighboring gene. How do they know which gene to activate? We have used homing P[en]constructs to study the enhancer-promoter communication at the engrailed locus. Here we show that engrailed enhancers can act over large distances, even skipping over other transcription units,choosing the engrailed promoter over those of neighboring genes. This specificity is achieved in at least three ways. First, early acting engrailed stripe enhancers exhibit promoter specificity. Second, a proximal promoter-tethering element is required for the action of the imaginal disc enhancer(s). Our data suggest that there are two partially redundant promoter-tethering elements. Third, the long-distance action of engrailed enhancers requires a combination of the engrailedpromoter and sequences within or closely linked to the promoter proximal Polycomb-group response elements. These data show that multiple mechanisms ensure proper enhancer-promoter communication at the Drosophila engrailed locus.

The database of Genotypes and Phenotypes (dbGaP) Data Browser (https://www.ncbi.nlm.nih.gov/gap/ddb/) was developed in response to requests from the scientific community for a resource that enable view-only access to summary-level information and individual-level genotype and sequence data associated with phenotypic features maintained in the controlled-access tier of dbGaP. Until now, the dbGaP controlled-access environment required investigators to submit a data access request, wait for Data Access Committee review, download each data set and locally examine them for potentially relevant information. Existing unrestricted-access genomic data browsing resources (e.g. http://evs.gs.washington.edu/EVS/, http://exac.broadinstitute.org/) provide only summary statistics or aggregate allele frequencies. The dbGaP Data Browser serves as a third solution, providing researchers with view-only access to a compilation of individual-level data from general research use (GRU) studies through a simplified controlled-access process. The National Institutes of Health (NIH) will continue to improve the Browser in response to user feedback and believes that this tool may decrease unnecessary download requests, while still facilitating responsible genomic data-sharing.

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The Drosophila melanogaster genome contains 5 genes that code for soluble guanylyl cyclase subunits. Two of these genes code for subunits, Gycα-99B and Gycβ-100B, which form a conventional NO-sensitive guanylyl cyclase and the other three code for atypical subunits, Gyc-88E, Gyc-89Da and Gyc-89Db. The properties and distribution of Gyc-88E and Gyc-89Db have previously been described and here Gyc-89Da is described. Gyc-89Da only forms an active guanylyl cyclase when co-expressed with Gyc-88E. The three atypical subunits probably form two different heterodimers in vivo: Gyc-88E/89Da and Gyc-88E/89Db. Both of these heterodimers were slightly stimulated by NO donors and Gyc-88E/89Da showed a greater activation by Mn2+, with an increase in Vmax and a decrease in Km, compared to Gyc-88E/89Db. Both Gyc-88E/89Da and Gyc-88E/89Db were expressed in neurons in both the peripheral and central nervous system. Although all three heterodimeric soluble guanylyl cyclases in D. melanogaster can be activated by NO and inhibited by ODQ, the atypical enzymes can be distinguished from the conventional soluble guanylyl cyclase by their sensitivity to the NO-independent activators YC-1 and BAY 41-2272, which will only activate the conventional enzyme.Abbreviation:ORFopen reading frameUTRuntranslated region

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SUMMARY Insect ecdysis is a precisely coordinated series of behavioral and hormonal events that occur at the end of each molt. A great deal is known about the hormonal events that underlie this process, although less is known about the neuronal circuitry involved. In this study we identified two populations of neurons that are required for larval and adult ecdyses in the fruit fly, Drosophila melanogaster (Meigen). These neurons were identified by using the upstream region of two genes that code for atypical soluble guanylyl cyclases to drive tetanus toxin in the neurons that express these cyclases to block their synaptic activity. Expression of tetanus toxin in neurons that express Gyc-89Da blocked adult eclosion whereas expression of tetanus toxin in neurons that express Gyc-89Db prevented the initiation of the first larval ecdysis. Expression of tetanus toxin in the Gyc-89Da neurons also resulted in about 50% lethality just prior to pupariation; however, this was probably due to suffocation in the food as lethality was prevented by stopping the larvae from burrowing deep within the food. This result is consistent with our model that the atypical soluble guanylyl cyclases can act as molecular oxygen detectors. The expression pattern of these cyclases did not overlap with any of the neurons containing peptides known to regulate ecdysis and eclosion behaviors. By using the conditional expression of tetanus toxin we were also able to demonstrate that synaptic activity in the Gyc-89Da and Gyc-89Db neurons is required during early adult development for adult eclosion.