Conserved chromatin and repetitive patterns reveal slow genome evolution in frogs.

Frogs are an ecologically diverse and phylogenetically ancient group of anuran amphibians that include important vertebrate cell and developmental model systems, notably the genus Xenopus. Here we report a high-quality reference genome sequence for the western clawed frog, Xenopus tropicalis, along with draft chromosome-scale sequences of three distantly related emerging model frog species, Eleutherodactylus coqui, Engystomops pustulosus, and Hymenochirus boettgeri. Frog chromosomes have remained remarkably stable since the Mesozoic Era, with limited Robertsonian (i.

Microinjection of Embryos.

Microinjection is an important technique used to study development in the oocyte and early embryo. In , substances such as DNA, mRNA, and morpholino oligonucleotides have traditionally been injected into , because of their large embryo size and the relatively long time from their fertilization to first division. In the past few decades, has become an important model in developmental biology; it is particularly useful in genetic studies.

Obtaining Embryos by Natural Mating.

is a powerful model system for cell and developmental biology in part because frogs produce thousands of eggs and embryos year-round. Natural matings are a simple and common method to obtain embryos for injection or other experimental use or to raise to adulthood. This method does not require sacrificing a male as in vitro fertilization (IVF) does.

Obtaining Embryos by In Vitro Fertilization.

is a powerful model system for cell and developmental biology in part because frogs produce thousands of eggs and embryos year-round. In vitro fertilization (IVF) is ideal for obtaining developmentally synchronized embryos for microinjection or when natural mating has failed to produce a fertilization. In IVF, females are induced to ovulate, and then eggs are collected by manual expression.

Tadpole Craniocardiac Imaging Using Optical Coherence Tomography.

Optical coherence tomography (OCT) imaging can be used to visualize craniocardiac structures in the model system. OCT is analogous to ultrasound, utilizing light instead of sound to create a gray-scale image from the echo time delay of infrared light reflected from the specimen. OCT is a high-speed, cross-sectional, label-free imaging modality, which can outline dynamic in vivo morphology at resolutions approaching histological detail.

Raising and Maintaining from Tadpole to Adult.

is a powerful model organism for cell and developmental biology research. Recently, precise gene-editing methods such as CRISPR-Cas9 have allowed facile creation of mutants. The ability to raise and maintain lines of wild-type and mutant animals through all life stages is thus critical for researchers using this model organism.

Obtaining Eggs.

is a powerful model system for cell and developmental biology in part because frogs produce thousands of eggs and embryos year-round. For cell biological studies, egg extracts can mimic many processes in a cell-free system. For developmental biology, embryos are a premier system, combining cut-and-paste embryology with modern gene manipulation tools.

A chromosome-scale genome assembly and dense genetic map for Xenopus tropicalis.

The Western clawed frog Xenopus tropicalis is a diploid model system for both frog genetics and developmental biology, complementary to the paleotetraploid X. laevis. Here we report a chromosome-scale assembly of the X.

CRISPR/Cas9 F0 Screening of Congenital Heart Disease Genes in Xenopus tropicalis.

In the US and Europe, birth defects are the leading cause of infant mortality. Among birth defects, Congenital Heart Disease (CHD) occurs in approximately 8 out of 1000 live births, affects 1.3 million newborns per year worldwide, and has the highest mortality rate.

CRISPR-Cpf1 mediates efficient homology-directed repair and temperature-controlled genome editing.

Cpf1 is a novel class of CRISPR-Cas DNA endonucleases, with a wide range of activity across different eukaryotic systems. Yet, the underlying determinants of this variability are poorly understood. Here, we demonstrate that LbCpf1, but not AsCpf1, ribonucleoprotein complexes allow efficient mutagenesis in zebrafish and Xenopus.

Measuring Absolute RNA Copy Numbers at High Temporal Resolution Reveals Transcriptome Kinetics in Development.

Transcript regulation is essential for cell function, and misregulation can lead to disease. Despite technologies to survey the transcriptome, we lack a comprehensive understanding of transcript kinetics, which limits quantitative biology. This is an acute challenge in embryonic development, where rapid changes in gene expression dictate cell fate decisions.

CRISPR/Cas9: An inexpensive, efficient loss of function tool to screen human disease genes in Xenopus.

Congenital malformations are the major cause of infant mortality in the US and Europe. Due to rapid advances in human genomics, we can now efficiently identify sequence variants that may cause disease in these patients. However, establishing disease causality remains a challenge.

Breeding based remobilization of Tol2 transposon in Xenopus tropicalis.

Xenopus is a powerful model for studying a diverse array of biological processes. However, despite multiple methods for transgenesis, relatively few transgenic reporter lines are available and commonly used. Previous work has demonstrated that transposon based strategies are effective for generating transgenic lines in both invertebrate and vertebrate systems.

A novel domain in translational GTPase BipA mediates interaction with the 70S ribosome and influences GTP hydrolysis.

BipA is a universally conserved prokaryotic GTPase that exhibits differential ribosome association in response to stress-related events. It is a member of the translation factor family of GTPases along with EF-G and LepA. BipA has five domains.

Identification of mutants in inbred Xenopus tropicalis.

Xenopus tropicalis offers the potential for genetic analysis in an amphibian. In order to take advantage of this potential, we have been inbreeding strains of frogs for future mutagenesis. While inbreeding a population of Nigerian frogs, we identified three mutations in the genetic background of this strain.

Development of interlimb movement synchrony in the rat fetus.

In the fetal rat, interlimb synchrony is a prominent form of temporally organized spontaneous motor activity in which movement of different limbs occurs at nearly the same instant. In the present study, synchrony profiles were created for different pairwise combinations of limbs over the last 5 days of gestation. Observed rates of synchrony differentiated from randomized time series from Gestational Day 19 to Day 21 (E19-E21), with forelimb synchrony emerging earlier than that of other limb pairs.