Micro-RNA Clusters Integrate Evolutionary Constraints on Expression and Target Affinities: The miR-6/5/4/286/3/309 Cluster in Drosophila.

A striking feature of micro-RNAs is that they are often clustered in the genomes of animals. The functional and evolutionary consequences of this clustering remain obscure. Here, we investigated a micro-RNA cluster miR-6/5/4/286/3/309 that is conserved across drosophilid lineages. Small RNA sequencing revealed expression of this micro-RNA cluster in Drosophila melanogaster leg discs, and conditional overexpression of the whole cluster resulted in leg appendage shortening. Transgenic overexpression lines expressing different combinations of micro-RNA cluster members were also constructed. Expression of individual micro-RNAs from the cluster resulted in a normal wild-type phenotype, but either the expression of several ancient micro-RNAs together (miR-5/4/286/3/309) or more recently evolved clustered micro-RNAs (miR-6-1/2/3) can recapitulate the phenotypes generated by the whole-cluster overexpression. Screening of transgenic fly lines revealed downregulation of leg-patterning gene cassettes in generation of the leg-shortening phenotype. Furthermore, cell transfection with different combinations of micro-RNA cluster members revealed a suite of downstream genes targeted by all cluster members, as well as complements of targets that are unique for distinct micro-RNAs. Considered together, the micro-RNA targets and the evolutionary ages of each micro-RNA in the cluster demonstrate the importance of micro-RNA clustering, where new members can reinforce and modify the selection forces on both the cluster regulation and the gene regulatory network of existing micro-RNAs. Key words: micro-RNA, cluster, evolution.

Genomic sequence and experimental tractability of a new decapod shrimp model, Neocaridina denticulata.

The speciose Crustacea is the largest subphylum of arthropods on the planet after the Insecta. To date, however, the only publically available sequenced crustacean genome is that of the water flea, Daphnia pulex, a member of the Branchiopoda. While Daphnia is a well-established ecotoxicological model, previous study showed that one-third of genes contained in its genome are lineage-specific and could not be identified in any other metazoan genomes. To better understand the genomic evolution of crustaceans and arthropods, we have sequenced the genome of a novel shrimp model, Neocaridina denticulata, and tested its experimental malleability. A library of 170-bp nominal fragment size was constructed from DNA of a starved single adult and sequenced using the Illumina HiSeq2000 platform. Core eukaryotic genes, the mitochondrial genome, developmental patterning genes (such as Hox) and microRNA processing pathway genes are all present in this animal, suggesting it has not undergone massive genomic loss. Comparison with the published genome of Daphnia pulex has allowed us to reveal 3750 genes that are indeed specific to the lineage containing malacostracans and branchiopods, rather than Daphnia-specific (E-value: 10⁻6). We also show the experimental tractability of N. denticulata, which, together with the genomic resources presented here, make it an ideal model for a wide range of further aquacultural, developmental, ecotoxicological, food safety, genetic, hormonal, physiological and reproductive research, allowing better understanding of the evolution of crustaceans and other arthropods.

[Anatomical presentation of edentulous sites in the posterior maxillary in cone beam computed tomography].

OBJECTIVE: This study aimed to analyze the bone anatomy of edentulous sites in the posterior maxillary by cone beam computed tomography (CBCT). METHODS: A total of 100 CBCT radiographs from patients with missing maxillary posterior teeth were obtained, resulting in a sample size of 217 edentulous sites. The width and height of edentulous were assessed by three-dimensional reconstruction. In addition, the angle A and morphology of the maxillary sinus walls were evaluated. RESULTS: The mean bone height was 9.53 mm, and the percentage of sites than 10 mm was 62.67% (136/217). The mean bone width was 9.30 mm, and the percentage of sites more than 6 mm was 91.71% (199/217). The bone height decreased from premolar to molar areas, but the opposite trend was observed in bone width. Regarding the morphology of the sinus floor, 64.52% exhibited an oblique configuration. In angle A, the group of less than 30° was 10.14%, 30°-60° was 42.40%, and greater than 60° was 47.47%. CONCLUSION: A high percentage of edentulous sites in the posterior maxillary requires sinus floor elevation to allow the placement of dental implants. Thus, the use of CBCT scans is recommended to evaluate the anatomical structure of the maxillary sinus for reasonable implant planning.