Developing microRNA screening as a functional genomics tool for disease research

Originally discovered as regulators of developmental timing in C. elegans, microRNAs (miRNAs) have emerged as modulators of nearly every cellular process, from normal development to pathogenesis. With the advent of whole genome libraries of miRNA mimics suitable for high throughput screening, it is possible to comprehensively evaluate the function of each member of the miRNAome in cell-based assays. Since the relatively few microRNAs in the genome are thought to directly regulate a large portion of the proteome, miRNAome screening, coupled with the identification of the regulated proteins, might be a powerful new approach to gaining insight into complex biological processes

Co-option of an anteroposterior head axis patterning system for proximodistal patterning of appendages in early bilaterian evolution

AbstractThe enormous diversity of extant animal forms is a testament to the power of evolution, and much of this diversity has been achieved through the emergence of novel morphological traits. The origin of novel morphological traits is an extremely important issue in biology, and a frequent source of this novelty is co-option of pre-existing genetic systems for new purposes (Carroll et al., 2008). Appendages, such as limbs, fins and antennae, are structures common to many animal body plans which must have arisen at least once, and probably multiple times, in lineages which lacked appendages. We provide evidence that appendage proximodistal patterning genes are expressed in similar registers in the anterior embryonic neurectoderm of Drosophila melanogaster and Saccoglossus kowalevskii (a hemichordate). These results, in concert with existing expression data from a variety of other animals suggest that a pre-existing genetic system for anteroposterior head patterning was co-opted for patterning of the proximodistal axis of appendages of bilaterian animals

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Three Drosophila Hox Complex microRNAs Do Not Have Major Effects on Expression of Evolutionarily Conserved Hox Gene Targets during Embryogenesis

The discovery of microRNAs has resulted in a major expansion of the number of molecules known to be involved in gene regulation. Elucidating the functions of animal microRNAs has posed a significant challenge as their target interactions with messenger RNAs do not adhere to simple rules. Of the thousands of known animal microRNAs, relatively few microRNA:messenger RNA regulatory interactions have been biologically validated in an normal organismal context. Here we present evidence that three microRNAs from the Hox complex in Drosophila (miR-10-5p, miR-10-3p, miR-iab-4-5p) do not have significant effects during embryogenesis on the expression of Hox genes that contain high confidence microRNAs target sites in the 3′ untranslated regions of their messenger RNAs. This is significant, in that it suggests that many predicted microRNA-target interactions may not be biologically relevant, or that the outcomes of these interactions may be so subtle that mutants may only show phenotypes in specific contexts, such as in environmental stress conditions, or in combinations with other microRNA mutations

<i>iab-4</i> is coexpressed with <i>Antp</i> in a subset of embryonic cells, but does not appear to play a large role in repressing translation of endogenous transcripts.

<p>(<b>A–D</b>) Fluorescent in situ hybridization was carried out using probes specific for <i>Antp</i> transcripts and for the long intron of <i>iab-4</i>, which are shown in magenta and green, respectively. (<b>A</b>) A blastoderm-stage embryo. Colored lines indicate the extents of the gap-gene-like expression patterns for each gene. (<b>B</b>) The trunk of a stage-11 embryo showing <i>Antp</i> and <i>iab-4</i> expression. (<b>C</b>) A close-up view of the dashed box indicated in (B) shows apparently spurious <i>Antp</i> expression (arrows) in the abdominal segments that occasionally appear in cells that express <i>iab-4</i>. (<b>D</b>) In a stage-14 embryo, <i>Antp</i> expression is found mainly in the ectoderm of the second and third thoracic segments, and in segments T2–A7 of the ventral nerve cord (VNC); <i>iab-4</i> expression is found mainly in the lateral ectoderm and in the VNC of abdominal segments A4–A7. (<b>E</b>) ANTP protein (magenta) and <i>iab-4</i> transcripts (green) are coexpressed in neuromeres A3–A7 in the developing VNC of a stage-14 embryo. The extent of <i>iab-4</i> expression is indicated with a green line. (<b>F</b>) A close-up view of the dashed box indicated in (E) displaying the largely complementary nature of ANTP and <i>iab-4</i> expression in the abdominal VNC. (<b>G–L</b>) ANTP expression appears largely unchanged in embryos homozygous for a <i>miR-iab-4/8</i> hairpin deletion when compared to heterozygous embryos. (<b>G</b>) ANTP expression in neuromeres A1–A4 of a stage-14 wildtype embryo (Δ<i>miR-iab4/8/TM3,Ubx-lacZ</i>). (<b>H</b>) <i>iab-4</i> expression in the same region as (G). (<b>I</b>) A merged image of (G) and (H). (<b>J</b>) ANTP expression in neuromeres A1–A4 of a stage-14 homozygous miRNA-deficient embryo (Δ<i>miR-iab-4/8</i>). (<b>K</b>) <i>iab-4</i> expression in the same region as (J). (<b>L</b>) A merged image of (J) and (K).</p

Overexpression or lack of <i>pri-miR-10</i> has no observable effect on putative target protein expression.

<p>Embryos expressing UAS-<i>pri-miR-10</i> under the control of <i>engrailed-</i>GAL4 (en><i>pri-miR-10</i>) (<b>C,D,G,H</b>) exhibit no consistent detectable decrease in either SCR protein (<b>A–D</b>) or ABD-B protein (<b>E–H</b>) in cells expressing ectopic miRNA [marked with anti-<i>en</i> antibodies (green), or circled with dotted lines] versus control cells in wild type embryos (<b>A,B,E,F</b>). No consistent detectable change in ABD-B protein levels is seen in the CNS of embryos ubiquitously expressing UAS-<i>pri-miR-10</i> under the control of <i>da</i>-GAL4 (da><i>pri-miR-10</i>) (<b>J</b>) or in embryos deficient for the <i>mir-10</i> locus ((<i>Df3R</i>)<i>CP1</i>) (<b>K</b>) compared to wild type embryos (<b>I</b>). Embryos mutant for the <i>Abd-B</i>-m specific transcripts (<i>Abd-B^D14</i>) and deficient for <i>mir-10</i> do not exhibit ectopic r-type ABD-B protein (<b>L</b>).</p