PHD2 regulates arteriogenic macrophages through TIE2 signalling

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Macrophage skewing by Phd2 haplodeficiency prevents ischemia by inducing arteriogenesis

The authors are thankful to Dr. P. Carmeliet for scientific discussion and support. VE-Cadherin:CreERT and PDGFRB:Cre transgenic mice were generated at the Cancer Research UK (London, UK) and kindly donated by Dr. R. Adams. The IKKβ floxed mice are a generous gift of Dr. M. Karin (UCSD, La Jolla, CA). The hydroxylase-deficient PHD2 construct was given by Dr. P. Ratcliffe (Oxford, UK).PHD2 serves as an oxygen sensor that rescues blood supply by regulating vessel formation and shape in case of oxygen shortage. However, it is unknown whether PHD2 can influence arteriogenesis. Here we studied the role of PHD2 in collateral artery growth by using hindlimb ischaemia as a model, a process that compensates for the lack of blood flow in case of major arterial occlusion. We show that Phd2 (also known as Egln1) haplodeficient (Phd2(+/-)) mice displayed preformed collateral arteries that preserved limb perfusion and prevented tissue necrosis in ischaemia. Improved arteriogenesis in Phd2(+/-) mice was due to an expansion of tissue-resident, M2-like macrophages and their increased release of arteriogenic factors, leading to enhanced smooth muscle cell (SMC) recruitment and growth. Both chronic and acute deletion of one Phd2 allele in macrophages was sufficient to skew their polarization towards a pro-arteriogenic phenotype. Mechanistically, collateral vessel preconditioning relied on the activation of canonical NF-κB pathway in Phd2(+/-) macrophages. These results unravel how PHD2 regulates arteriogenesis and artery homeostasis by controlling a specific differentiation state in macrophages and suggest new treatment options for ischaemic disorders.This work was supported by grants from FWO (G.0726.10), Belgium, and from VIB. ED was granted by ARC, SC by FCT, RLO and VF by FWO, AH by DFG. CR was supported by COST action TD0901. MDP was supported by an ERC starting grant

A cryptic cytoplasmic male sterility unveils a possible gynodioecious past for Arabidopsis thaliana.

Gynodioecy, the coexistence of hermaphrodites and females (i.e. male-sterile plants) in natural plant populations, most often results from polymorphism at genetic loci involved in a particular interaction between the nuclear and cytoplasmic genetic compartments (cytonuclear epistasis): cytoplasmic male sterility (CMS). Although CMS clearly contributes to the coevolution of involved nuclear loci and cytoplasmic genomes in gynodioecious species, the occurrence of CMS genetic factors in the absence of sexual polymorphism (cryptic CMS) is not easily detected and rarely taken in consideration. We found cryptic CMS in the model plant Arabidopsis thaliana after crossing distantly related accessions, Sha and Mr-0. Male sterility resulted from an interaction between the Sha cytoplasm and two Mr-0 genomic regions located on chromosome 1 and chromosome 3. Additional accessions with either nuclear sterility maintainers or sterilizing cytoplasms were identified from crosses with either Sha or Mr-0. By comparing two very closely related cytoplasms with different male-sterility inducing abilities, we identified a novel mitochondrial ORF, named orf117Sha, that is most likely the sterilizing factor of the Sha cytoplasm. The presence of orf117Sha was investigated in worldwide natural accessions. It was found mainly associated with a single chlorotype in accessions belonging to a clade predominantly originating from Central Asia. More than one-third of accessions from this clade carried orf117Sha, indicating that the sterilizing-inducing cytoplasm had spread in this lineage. We also report the coexistence of the sterilizing cytoplasm with a non-sterilizing cytoplasm at a small, local scale in a natural population; in addition a correlation between cytotype and nuclear haplotype was detected in this population. Our results suggest that this CMS system induced sexual polymorphism in A. thaliana populations, at the time when the species was mainly outcrossing

Cytonuclear interactions affect adaptive traits of the annual plant Arabidopsis thaliana in the field

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Distribution of nuclear diversity groups and of <i>orf117Sha</i> in a simplified chloroplast phylogeny.

<p>Chlorotypes or groups of chlorotypes are organized according to their phylogeny <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062450#pone.0062450-Moison1" target="_blank">[27]</a>. The vertical thick dashed arrow indicates the root of the network (according to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062450#pone.0062450-Moison1" target="_blank">[27]</a>). Each small square represents an accession, colored according to its nuclear diversity group (pink: group 1, green: group 2, blue: group 3, orange: group 4) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062450#pone.0062450-Simon1" target="_blank">[24]</a>. The red dotted line gathers accessions carrying the <i>orf117Sha</i> gene (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062450#pone.0062450.s013" target="_blank">Table S5</a>).</p

Phenotypes of reciprocal F1s from Sha and Mr-0 parents.

<p>Reciprocal F1s are shown at the flowering stage. The Mr-0 x Sha F1 (right panel) is fully fertile as shown by the elongated siliques containing developing seeds (arrows). The Sha x Mr-0 F1 (left panel) is sterile as shown by short remnants of pistils, producing no seeds (arrowheads). The boxed area highlights elongated siliques with developing seeds (arrows) resulting from hand-pollination of the flowers with pollen from a fertile plant.</p

Genotyping of the (Sha x Mr-0) x Sha backcross population.

<p>The five Arabidopsis chromosomes are represented as vertical black bars, with centromeres indicated as dots. Markers used for genotyping are indicated as thin black cross-bars, according to their physical position on the chromosomes (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062450#pone.0062450.s009" target="_blank">Table S1</a>). At each marker position, the gray and black sectors in the small bar graphs indicate proportions of heterozygotes found in the fertile (top) and sterile (bottom) plant subpopulations, respectively. These proportions are given as percentages on the right. Asterisks indicate proportions that significantly differ from the expected 50% of heterozygotes (* 0.05>P>0.01; **0.01>P>0.001; *** P<0.001).</p

Alexander staining of anthers on plants from the fourth backcross.

<p>Anthers were dissected from buds just before opening, stained with Alexander’s staining, mounted on glass slides and observed under a light microscope. A: typical anthers from a sterile plant. B: typical anther from a fertile plant. Red-colored pollen is viable, whereas blue-green pollen has aborted.</p

Geographical distribution of accessions tested for the presence of <i>orf117Sha.</i>

<p>Accessions are mapped to their geographical origin (information available on the Versailles Arabidopsis Stock Centre website <a href="http://dbsgap.versailles.inra.fr/vnat/" target="_blank">http://dbsgap.versailles.inra.fr/vnat/</a>). Accessions with <i>orf117Sha</i> are represented with red crosses, other accessions with black open circles.</p