Heart and soul/PRKCi and nagie oko/Mpp5 regulate myocardial coherence and remodeling during cardiac morphogenesis

Abstract

Organ morphogenesis requires cellular shape changes and tissue rearrangements that occur in a precisely timed manner. Here, we show that zebrafish heart and soul (Has)/protein kinase C iota (PRKCi) is required tissue-autonomously within the myocardium for normal heart morphogenesis and that this function depends on its catalytic activity. In addition, we demonstrate that nagie oko (Nok) is the functional homolog of mammalian protein associated with Lin-seven 1 (Pals1)/MAGUK p55 subfamily member 5 (Mpp5), and we dissect its earlier and later functions during myocardial morphogenesis. Has/PRKCi and Nok/Mpp5 are required early for the polarized epithelial organization and coherence of myocardial cells during heart cone formation. Zygotic nok/mpp5 mutants have later myocardial defects, including an incomplete heart tube elongation corresponding with a failure of myocardial cells to correctly expand in size. Furthermore, we show that nok/mpp5 acts within myocardial cells during heart tube elongation.Together, these results demonstrate that cardiac morphogenesis depends on the polarized organization and coherence of the myocardium, and that the expansion of myocardial cell size contributes to the transformation of the heart cone into an elongated tube.KEY WORDS: Organ morphogenesis, prkci, Myocardium, heart and soul, nagie oko, mpp5, pals1, Zebrafish Development 133,[107][108][109][110][111][112][113][114][115]

Analysis of aPKCλ and aPKCζ reveals multiple and redundant functions during vertebrate retinogenesis

“…For aPKCλ morphants (n=241), the average RPE score was 2.2, while embryos coinjected with aPKCζ mRNA the average score was more normal at 1.6 (n=255) (p<0.01, Students t-test). Interestingly, no over-expression phenotypes were noted with injection of aPKCζ mRNA, consistent with previous experiments with aPKCλ in zebrafish (HorneBadovinac et al, 2001;Rohr et al, 2006; but compare to Chalmers et al, 2004). Overall, forced expression of aPKCζ in either has mutants or morphants partially rescued aPKCλ ocular phenotypes including RPE morphogenesis and neural retina lamination (Figure 4).…”

“…Wild-type donor cells or donor cells injected with aPKCλ MO and a dominant negative form of aPKC, in which the kinase domain is rendered non-functional (aPKCi 2A DN), were transplanted into albino host embryos. This reagent provides an efficient and complementary approach to morpholinos for the disruption of aPKC function (Rohr et al, 2006). Zebrafish with the albino mutation show no obvious ocular phenotype other than lack of pigmentation.…”

“…The zebrafish aPKCλ mutation has shows late embryonic lethality with abnormality in the polarized epithelia of the retina, heart progenitors, and digestive tract (Horne-Badovinac et al, 2001;Peterson et al, 2001;Horne-Badovinac et al, 2003;Rohr et al, 2006). Within the retina, the phenotype of has is relatively mild compared to phenotypes caused by disruptions of other genes that encode proteins essential for apicobasal polarity.…”

“…Analysis of cells lacking aPKC activity indicated that RPE morphogenesis and full cellular differentiation requires aPKC function cellautonomously. However, aspects of RPE differentiation were maintained, even in the strongest loss of function manipulations including expression of aPKCi 2A DN, a dominant negative aPKC which interferes with all aPKC function (Rohr et al, 2006). While those RPE cells did not develop a hexagonal shape, they were flattened and some showed weak pigmentation.…”

Illuminating cardiac development: Advances in imaging add new dimensions to the utility of zebrafish genetics

“…Mutations in the genes heart and soul (prcki), snakehead (atp1a1a.1), and nagie oko (mpp5) hinder heart tube extension: mutant hearts resemble arrested cardiac cones or stunted heart tubes [12,[30][31][32][33][34]. The PRKCi, Atp1a1a.…”