Advances in genome sequencing reveal changes in gene content that contribute to arthropod macroevolution.

Current sequencing technology allows for the relatively affordable generation of highly contiguous genomes. Technological advances have made it possible for researchers to investigate the consequences of diverse sorts of genomic variants, such as gene gain and loss. With the extraordinary number of high-quality genomes now available, we take stock of how these genomic variants impact phenotypic evolution.

Anterior-posterior patterning of segments in Anopheles stephensi offers insights into the transition from sequential to simultaneous segmentation in holometabolous insects.

The gene regulatory network for segmentation in arthropods offers valuable insights into how networks evolve owing to the breadth of species examined and the extremely detailed knowledge gained in the model organism Drosophila melanogaster. These studies have shown that Drosophila's network represents a derived state that acquired changes to accelerate segment patterning, whereas most insects specify segments gradually as the embryo elongates. Such heterochronic shifts in segmentation have potentially emerged multiple times within holometabolous insects, resulting in many mechanistic variants and difficulties in isolating underlying commonalities that permit such shifts.

Regulatory gene function handoff allows essential gene loss in mosquitoes.

Regulatory genes are often multifunctional and constrained, which results in evolutionary conservation. It is difficult to understand how a regulatory gene could be lost from one species' genome when it is essential for viability in closely related species. The gene paired is a classic Drosophila pair-rule gene, required for formation of alternate body segments in diverse insect species.

Brown marmorated stink bug, Halyomorpha halys (Stål), genome: putative underpinnings of polyphagy, insecticide resistance potential and biology of a top worldwide pest.

Background: Halyomorpha halys (Stål), the brown marmorated stink bug, is a highly invasive insect species due in part to its exceptionally high levels of polyphagy. This species is also a nuisance due to overwintering in human-made structures. It has caused significant agricultural losses in recent years along the Atlantic seaboard of North America and in continental Europe.

Shifting roles of pair-rule gene orthologs: segmental expression and function in the milkweed bug .

The discovery of pair-rule genes (PRGs) in revealed the existence of an underlying two-segment-wide prepattern directing embryogenesis. The milkweed bug , a hemimetabolous insect, is a more representative arthropod: most of its segments form sequentially after gastrulation. Here, we report the expression and function of orthologs of the complete set of nine PRGs in Seven -PRG-orthologs are expressed in stripes in the primordia of every segment, rather than every other segment; is PR-like and several orthologs are also expressed in the segment addition zone.

The genome of the water strider Gerris buenoi reveals expansions of gene repertoires associated with adaptations to life on the water.

Background: Having conquered water surfaces worldwide, the semi-aquatic bugs occupy ponds, streams, lakes, mangroves, and even open oceans. The diversity of this group has inspired a range of scientific studies from ecology and evolution to developmental genetics and hydrodynamics of fluid locomotion. However, the lack of a representative water strider genome hinders our ability to more thoroughly investigate the molecular mechanisms underlying the processes of adaptation and diversification within this group.

Effect of Genetic Diagnosis on Patients with Previously Undiagnosed Disease.

Background: Many patients remain without a diagnosis despite extensive medical evaluation. The Undiagnosed Diseases Network (UDN) was established to apply a multidisciplinary model in the evaluation of the most challenging cases and to identify the biologic characteristics of newly discovered diseases. The UDN, which is funded by the National Institutes of Health, was formed in 2014 as a network of seven clinical sites, two sequencing cores, and a coordinating center.

Genome-wide use of high- and low-affinity Tbrain transcription factor binding sites during echinoderm development.

Sea stars and sea urchins are model systems for interrogating the types of deep evolutionary changes that have restructured developmental gene regulatory networks (GRNs). Although -regulatory DNA evolution is likely the predominant mechanism of change, it was recently shown that Tbrain, a Tbox transcription factor protein, has evolved a changed preference for a low-affinity, secondary binding motif. The primary, high-affinity motif is conserved.

The Function and Evolution of Nuclear Receptors in Insect Embryonic Development.

Nuclear receptors are a family of transcription factors that are often responsive to small ligands, allowing for efficient gene expression-level responses to a stimulus. The average insect has 21 genes encoding nuclear receptors, whose functions are especially well studied in developmental transitions during the insect life cycle, such as metamorphosis and molting. However, their utility as well-controlled transcriptional regulators also lends them to important roles in embryogenesis, neurogenesis, metabolism, and organogenesis.

A gene regulatory network for apical organ neurogenesis and its spatial control in sea star embryos.

How neural stem cells generate the correct number and type of differentiated neurons in appropriate places remains an important question. Although nervous systems are diverse across phyla, in many taxa the larva forms an anterior concentration of serotonergic neurons, or apical organ. The sea star embryo initially has a pan-neurogenic ectoderm, but the genetic mechanism that directs a subset of these cells to generate serotonergic neurons in a particular location is unresolved.

Evo-Devo: Discovery of Diverse Mechanisms Regulating Development.

Evo-devo is a relatively new field focusing on how mechanisms controlling development have changed during evolution. To date, studies of highly conserved members of an animal genetic toolkit have predominated in this field. These toolkit genes were originally identified in a small number of model organisms that do not represent the extant diversity of metazoans.

Evolution of transcription factor function as a mechanism for changing metazoan developmental gene regulatory networks.

The form that an animal takes during development is directed by gene regulatory networks (GRNs). Developmental GRNs interpret maternally deposited molecules and externally supplied signals to direct cell-fate decisions, which ultimately leads to the arrangements of organs and tissues in the organism. Genetically encoded modifications to these networks have generated the wide range of metazoan diversity that exists today.

A method for microinjection of Patiria miniata zygotes.

Echinoderms have long been a favorite model system for studies of reproduction and development, and more recently for the study of gene regulation and evolution of developmental processes. The sea star, Patiria miniata, is gaining prevalence as a model system for these types of studies which were previously performed almost exclusively in the sea urchins, Strongylocentrotus purpuratus and Lytechinus variegatus. An advantage of these model systems is the ease of producing modified embryos in which a particular gene is up or downregulated, labeling a group of cells, or introducing a reporter gene.

Modular evolution of DNA-binding preference of a Tbrain transcription factor provides a mechanism for modifying gene regulatory networks.

Gene regulatory networks (GRNs) describe the progression of transcriptional states that take a single-celled zygote to a multicellular organism. It is well documented that GRNs can evolve extensively through mutations to cis-regulatory modules (CRMs). Transcription factor proteins that bind these CRMs may also evolve to produce novelty.

Developmental gene regulatory network evolution: insights from comparative studies in echinoderms.

One of the central concerns of Evolutionary Developmental biology is to understand how the specification of cell types can change during evolution. In the last decade, developmental biology has progressed toward a systems level understanding of cell specification processes. In particular, the focus has been on determining the regulatory interactions of the repertoire of genes that make up gene regulatory networks (GRNs).