The zebrafishnodal-related genesouthpawis required for visceral and diencephalic left-right asymmetry

Abstract

We have identified and characterized a new zebrafish gene, southpaw, that is required for visceral and diencephalic left-right asymmetry. southpaw encodes a new member of the nodal-related class of proteins, a subfamily within the transforming growth factor β superfamily of secreted factors. southpaw is expressed bilaterally in paraxial mesoderm precursors and then within the left lateral plate mesoderm. At late somite stages, left-sided southpaw expression transiently overlaps the left-sided expression domains of other genes that mark the developing heart, such as lefty2. We have injected morpholinos to block the translation of the southpaw mRNA or to block splicing of the southpaw pre-mRNA. These morpholinos cause a severe disruption of early (cardiac jogging) and late (cardiac looping) aspects of cardiac left-right asymmetry. As the left-right asymmetry of the pancreas is also affected, southpaw appears to regulate left-right asymmetry throughout a large part of the embryo. Consistent with the morphological changes, the left-sided expression domains of downstream genes (cyclops, pitx2, lefty1 and lefty2) are severely downregulated or abolished within the lateral plate mesoderm of Southpaw-deficient embryos. Surprisingly, despite the absence of southpaw expression in the brain, we find that early diencephalic left-right asymmetry also requires Southpaw activity. These observations lead to a model of how visceral organ and brain left-right asymmetry are coordinated during embryogenesis.

Early, H+-V-ATPase-dependent proton flux is necessary for consistent left-right patterning of non-mammalian vertebrates

“…Similarly staged embryos treated early with the H + -V-ATPase inhibitor lobatomide A16 exhibited reversed (K, red arrow) and bilateral (L, green and red arrows) Spaw expression (Long et al, 2003). See Table 5 for statistical analysis.…”

A mutation in the zebrafish Na,K‐ATPase subunit atp1a1a.1 provides genetic evidence that the sodium potassium pump contributes to left‐right asymmetry downstream or in parallel to nodal flow

“…Probes used were preproinsulin, ipf1 (Milewski et al, 1998), glucagon, preprosomatostatin2 (called somatostatin2 in this study) (Argenton et al, 1999), trypsin (Biemar et al, 2001), islet-1 (Korzh et al, 1993), nkx2.2 (Barth and Wilson, 1995;Kudoh et al, 2001), pax6.2 (Nornes et al, 1998), foxa2 (Strahle et al, 1993;Odenthal and Nusslein-Volhard, 1998), sox32 (Dickmeis et al, 2001;Kikuchi et al, 2001), sox17 (Al-exander and Stainier, 1999), foxA2 (Strahle et al, 1993;Odenthal and Nusslein-Volhard, 1998), foxa1 (Odenthal and Nusslein-Volhard, 1998), prox1 (Glasgow and Tomarev, 1998), cha (Hashimoto et al, 2004), lefty1 (Bisgrove et al, 1999;Thisse and Thisse, 1999), spaw (Long et al, 2003), and pitx2 (Essner et al, 2000).…”

“…The earliest gene of the nodal pathway expressed asymmetrically in the lateral plate mesoderm is southpaw (Long et al, 2003). The left-sided expression domain starts at about 10 -12 somite stage, and fades away around 24 somite stage.…”

“…A conserved feature in all vertebrates is the expression of Nodal in the left lateral plate mesoderm, and the establishment of a feedback loop with Lefty proteins, which together maintain stable Nodal expression, and limit the expansion of the Nodal signals across the midline. In zebrafish, the Nodal gene acting in the LPM is southpaw (Long et al, 2003).…”

Modeling human hematopoietic and cardiovascular diseases in zebrafish

“…Recently, another Nodal-related gene, southpaw (spaw), was identified in zebrafish and demonstrated by means of morpholino knockdown to be crucial for the expression of left-specific genes and the processes of cardiac jogging and looping (Long et al, 2003).…”