Heterochronic shift in gene expression leads to ontogenetic morphological divergence between two closely related polyploid species.

Heterochrony-alteration to the rate or timing of development-is an important mechanism of trait differentiation associated with speciation. Heterochrony may explain the morphological divergence between two polyploid species, June sucker () and Utah sucker (). The larvae of both species have terminal mouths; however, as adults, June sucker and Utah sucker develop subterminal and ventral mouths, respectively.

Valproic acid affects neurogenesis during early optic tectum development in zebrafish.

The mammalian superior colliculus and its non-mammalian homolog, the optic tectum (OT), are midbrain structures that integrate multimodal sensory inputs and guide non-voluntary movements in response to prevalent stimuli. Recent studies have implicated this structure as a possible site affected in autism spectrum disorder (ASD). Interestingly, fetal exposure to valproic acid (VPA) has also been associated with an increased risk of ASD in humans and animal models.

Single-Cell RNA Sequencing Characterizes the Molecular Heterogeneity of the Larval Zebrafish Optic Tectum.

The optic tectum (OT) is a multilaminated midbrain structure that acts as the primary retinorecipient in the zebrafish brain. Homologous to the mammalian superior colliculus, the OT is responsible for the reception and integration of stimuli, followed by elicitation of salient behavioral responses. While the OT has been the focus of functional experiments for decades, less is known concerning specific cell types, microcircuitry, and their individual functions within the OT.

Chimeric Claudins: A New Tool to Study Tight Junction Structure and Function.

The tight junction (TJ) is a structure composed of multiple proteins, both cytosolic and membranal, responsible for cell-cell adhesion in polarized endothelium and epithelium. The TJ is intimately connected to the cytoskeleton and plays a role in development and homeostasis. Among the TJ's membrane proteins, claudins (CLDNs) are key to establishing blood-tissue barriers that protect organismal physiology.

Genome Editing in Zebrafish Using CRISPR-Cas9: Applications for Developmental Toxicology.

Environment-gene interactions have a powerful impact on embryo development. The ability to precisely edit the genome makes it possible to address questions concerning the specific roles that genes or variants play in modulating the response to environmental challenges. In this chapter, we provide a simplified protocol using CRISPR-Cas9 ribonucleoproteins for genome editing in the zebrafish model organism.

Osteoarthritis-Like Changes in Bardet-Biedl Syndrome Mutant Ciliopathy Mice (): Evidence for a Role of Primary Cilia in Cartilage Homeostasis and Regulation of Inflammation.

Osteoarthritis (OA) is a debilitating inflammation related disease characterized by joint pain and effusion, loss of mobility, and deformity that may result in functional joint failure and significant impact on quality of life. Once thought of as a simple "wear and tear" disease, it is now widely recognized that OA has a considerable metabolic component and is related to chronic inflammation. Defects associated with primary cilia have been shown to be cause OA-like changes in Bardet-Biedl mice.

Comparative analysis of lipid-mediated CRISPR-Cas9 genome editing techniques.

CRISPR-Cas technology has revolutionized genome engineering. While Cas9 was not the first programmable endonuclease identified, its simplicity of use has driven widespread adoption in a short period of time. While CRISPR-Cas genome editing holds enormous potential for clinical applications, its use in laboratory settings for genotype-phenotype studies and genome-wide screens has led to breakthroughs in the understanding of many molecular pathways.

Innervation regulates synaptic ribbons in lateral line mechanosensory hair cells.

Failure to form proper synapses in mechanosensory hair cells, the sensory cells responsible for hearing and balance, leads to deafness and balance disorders. Ribbons are electron-dense structures that tether synaptic vesicles to the presynaptic zone of mechanosensory hair cells where they are juxtaposed with the post-synaptic endings of afferent fibers. They are initially formed throughout the cytoplasm, and, as cells mature, ribbons translocate to the basolateral membrane of hair cells to form functional synapses.

Presynaptic partner selection during retinal circuit reassembly varies with timing of neuronal regeneration in vivo.

Whether neurons can restore their original connectivity patterns during circuit repair is unclear. Taking advantage of the regenerative capacity of zebrafish retina, we show here the remarkable specificity by which surviving neurons reassemble their connectivity upon regeneration of their major input. H3 horizontal cells (HCs) normally avoid red and green cones, and prefer ultraviolet over blue cones.

A targeted gene expression system using the tryptophan repressor in zebrafish shows no silencing in subsequent generations.

The ability to visualize and manipulate cell fate and gene expression in specific cell populations has made gene expression systems valuable tools in developmental biology studies. Here, we describe a new system that uses the E. coli tryptophan repressor and its upstream activation sequence (TrpR/tUAS) to drive gene expression in stable zebrafish transgenic lines and in mammalian cells.

Postembryonic neuronal addition in zebrafish dorsal root ganglia is regulated by Notch signaling.

Background: The sensory neurons and glia of the dorsal root ganglia (DRG) arise from neural crest cells in the developing vertebrate embryo. In mouse and chick, DRG formation is completed during embryogenesis. In contrast, zebrafish continue to add neurons and glia to the DRG into adulthood, long after neural crest migration is complete.

Rheotaxis in larval zebrafish is mediated by lateral line mechanosensory hair cells.

The lateral line sensory system, found in fish and amphibians, is used in prey detection, predator avoidance and schooling behavior. This system includes cell clusters, called superficial neuromasts, located on the surface of head and trunk of developing larvae. Mechanosensory hair cells in the center of each neuromast respond to disturbances in the water and convey information to the brain via the lateral line ganglia.

Motoneurons are essential for vascular pathfinding.

The neural and vascular systems share common guidance cues that have direct and independent signaling effects on nerves and endothelial cells. Here, we show that zebrafish Netrin 1a directs Dcc-mediated axon guidance of motoneurons and that this neural guidance function is essential for lymphangiogenesis. Specifically, Netrin 1a secreted by the muscle pioneers at the horizontal myoseptum (HMS) is required for the sprouting of dcc-expressing rostral primary motoneuron (RoP) axons and neighboring axons along the HMS, adjacent to the future trajectory of the parachordal chain (PAC).

Temporal regulation of Ath5 gene expression during eye development.

During central nervous system development the timing of progenitor differentiation must be precisely controlled to generate the proper number and complement of neuronal cell types. Proneural basic helix-loop-helix (bHLH) transcription factors play a central role in regulating neurogenesis, and thus the timing of their expression must be regulated to ensure that they act at the appropriate developmental time. In the developing retina, the expression of the bHLH factor Ath5 is controlled by multiple signals in early retinal progenitors, although less is known about how these signals are coordinated to ensure correct spatial and temporal pattern of gene expression.

The netrin receptor UNC5B promotes angiogenesis in specific vascular beds.

There is emerging evidence that the canonical neural guidance factor netrin can also direct the growth of blood vessels. We deleted the gene encoding UNC5B, a receptor for the netrin family of guidance molecules, specifically within the embryonic endothelium of mice. The result is a profound structural and functional deficiency in the arterioles of the placental labyrinth, which leads first to flow reversal in the umbilical artery and ultimately to embryonic death.

Netrin/DCC signaling controls contralateral dendrites of octavolateralis efferent neurons.

The guidance molecule Netrin and its receptor DCC (deleted in colorectal cancer) attract commissural axons toward the midline en route to their final destination. To test whether these molecules can also guide dendrites, we studied the contralateral dendrites of zebrafish octavolateralis efferent (OLe) neurons, which are unusual in that they navigate toward and cross the midline. We found that, at the time of dendrite outgrowth, OLe neurons express dcc, and the hindbrain midline expresses netrin1.

Netrins promote developmental and therapeutic angiogenesis.

Axonal guidance and vascular patterning share several guidance cues, including proteins in the netrin family. We demonstrate that netrins stimulate proliferation, migration, and tube formation of human endothelial cells in vitro and that this stimulation is independent of known netrin receptors. Suppression of netrin1a messenger RNA in zebrafish inhibits vascular sprouting, implying a proangiogenic role for netrins during vertebrate development.

Comparison of two quantitative polymerase chain reaction methods for detecting HER2/neu amplification.

Two quantitative polymerase chain reaction (PCR) methods for HER2/neu gene quantification were evaluated for implementation into a clinical laboratory. Assays were developed using sequence-specific hybridization probes to detect a target (HER2/neu) and a reference gene (beta-globin) simultaneously. One method utilizes real-time quantification while the second uses internal competitors and melting curves to quantify the unknown sample.