Zebrafish nampt-a mutants are viable despite perturbed primitive hematopoiesis.

Background: Nicotinamide phosphoribosyltransferase (Nampt) is required for recycling NAD in numerous cellular contexts. Morpholino-based knockdown of zebrafish nampt-a has been shown to cause abnormal development and defective hematopoiesis concomitant with decreased NAD levels. However, surprisingly, nampt-a mutant zebrafish were recently found to be viable, suggesting a discrepancy between the phenotypes in knockdown and knockout conditions.

Analysis of SMAD1/5 target genes in a sea anemone reveals ZSWIM4-6 as a novel BMP signaling modulator.

BMP signaling has a conserved function in patterning the dorsal-ventral body axis in Bilateria and the directive axis in anthozoan cnidarians. So far, cnidarian studies have focused on the role of different BMP signaling network components in regulating pSMAD1/5 gradient formation. Much less is known about the target genes downstream of BMP signaling.

Integration of Nodal and BMP Signaling by Mutual Signaling Effector Antagonism.

Opposing sources of bone morphogenetic protein (BMP) and Nodal signaling molecules are sufficient to induce the formation of a full axis in zebrafish embryos. To address how these signals orchestrate patterning, we transplant sources of fluorescently tagged Nodal and BMP into zebrafish embryos, robustly inducing the formation of secondary axes. Nodal and BMP signal non-cell-autonomously and form similar protein gradients in this context, but the signaling range of Nodal (pSmad2) is shorter than the BMP range (pSmad5).

Dynamics of BMP signaling and distribution during zebrafish dorsal-ventral patterning.

During vertebrate embryogenesis, dorsal-ventral patterning is controlled by the BMP/Chordin activator/inhibitor system. BMP induces ventral fates, whereas Chordin inhibits BMP signaling on the dorsal side. Several theories can explain how the distributions of BMP and Chordin are regulated to achieve patterning, but the assumptions regarding activator/inhibitor diffusion and stability differ between models.