Zebrafish cardiac development requires a conserved secondary heart field.

The secondary heart field is a conserved developmental domain in avian and mammalian embryos that contributes myocardium and smooth muscle to the definitive cardiac arterial pole. This field is part of the overall heart field and its myocardial component has been fate mapped from the epiblast to the heart in both mammals and birds. In this study we show that the population that gives rise to the arterial pole of the zebrafish can be traced from the epiblast, is a discrete part of the mesodermal heart field, and contributes myocardium after initial heart tube formation, giving rise to both smooth muscle and myocardium.

Phylogeny informs ontogeny: a proposed common theme in the arterial pole of the vertebrate heart.

In chick and mouse embryogenesis, a population of cells described as the secondary heart field (SHF) adds both myocardium and smooth muscle to the developing cardiac outflow tract (OFT). Following this addition, at approximately HH stage 22 in chick embryos, for example, the SHF can be identified architecturally by an overlapping seam at the arterial pole, where beating myocardium forms a junction with the smooth muscle of the arterial system. Previously, using either immunohistochemistry or nitric oxide indicators such as diaminofluorescein 2-diacetate, we have shown that a similar overlapping architecture also exists in the arterial pole of zebrafish and some shark species.

Ras controls melanocyte expansion during zebrafish fin stripe regeneration.

Regenerative medicine for complex tissues like limbs will require the provision or activation of precursors for different cell types, in the correct number, and with the appropriate instructions. These strategies can be guided by what is learned from spectacular events of natural limb or fin regeneration in urodele amphibians and teleost fish. Following zebrafish fin amputation, melanocyte stripes faithfully regenerate in tandem with complex fin structures.

Maintenance of blastemal proliferation by functionally diverse epidermis in regenerating zebrafish fins.

Appendage regeneration in salamanders and fish occurs through formation and maintenance of a mass of progenitor tissue called the blastema. A dedicated epidermis overlays the blastema and is required for its proliferation and patterning, yet this interaction is poorly understood. Here, we identified molecularly and functionally distinct compartments within the basal epidermal layer during zebrafish fin regeneration.

Intragenic suppressors of temperature-sensitive rne mutations lead to the dissociation of RNase E activity on mRNA and tRNA substrates in Escherichia coli.

RNase E of Escherichia coli is an essential endoribonuclease that is involved in many aspects of RNA metabolism. Point mutations in the S1 RNA-binding domain of RNase E (rne-1 and rne-3071) lead to temperature-sensitive growth along with defects in 5S rRNA processing, mRNA decay and tRNA maturation. However, it is not clear whether RNase E acts similarly on all kinds of RNA substrates.