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Epoxyeicosatrienoic acids (EETs) are lipid-derived signaling molecules with cardioprotective and vasodilatory actions. We recently showed that 11,12-EET enhances hematopoietic induction and engraftment in mice and zebrafish. EETs are known to signal via G protein-coupled receptors, with evidence supporting the existence of a specific high-affinity receptor. Identification of a hematopoietic-specific EET receptor would enable genetic interrogation of EET signaling pathways, and perhaps clinical use of this molecule. We developed a bioinformatic approach to identify an EET receptor based on the expression of G protein-coupled receptors in cell lines with differential responses to EETs. We found 10 candidate EET receptors that are expressed in three EET-responsive cell lines, but not expressed in an EET-unresponsive line. Of these, only recombinant GPR132 showed EET-responsiveness in vitro, using a luminescence-based β-arrestin recruitment assay. Knockdown of zebrafish gpr132b prevented EET-induced hematopoiesis, and marrow from GPR132 knockout mice showed decreased long-term engraftment capability. In contrast to high-affinity EET receptors, GPR132 is reported to respond to additional hydroxy-fatty acids in vitro, and we found that these same hydroxy-fatty acids enhance hematopoiesis in the zebrafish. We conducted structure–activity relationship analyses using both cell culture and zebrafish assays on diverse medium-chain fatty acids. Certain oxygenated, unsaturated free fatty acids showed high activation of GPR132, whereas unoxygenated or saturated fatty acids had lower activity. Absence of the carbon-1 position carboxylic acid prevented activity, suggesting that this moiety is required for receptor activation. GPR132 responds to a select panel of oxygenated polyunsaturated fatty acids to enhance both embryonic and adult hematopoiesis.

Epoxyeicosatrienoic acids (EETs) are endogenous lipid signaling molecules with cardioprotective and vasodilatory actions. We recently showed that exogenous addition of 11,12-EET enhances hematopoietic induction and engraftment in mice and zebrafish. EETs are known to signal via a G-protein coupled receptor(s), and significant research supports the existence of a specific high-affinity receptor. Identification of a hematopoietic specific EET receptor would enable genetic interrogation of the EET signaling pathway and perhaps clinical use of this molecule. We developed a bioinformatic approach to identify the EET receptor based on the expression of GPCRs in cell lines with differential responses to EETs. We found 10 candidate EET receptors that are commonly expressed in three EET-responsive human cell lines, but not expressed in an EET-unresponsive line. Of these candidates, only GPR132 showed EET-responsivenessin vitrousing a luminescence-based assay for β-arrestin recruitment. Knockdown of zebrafishgpr132bprevented EET-induced hematopoiesis, and marrow from GPR132 knockout mice showed decreased long-term engraftment capability. In contrast to the putative high-affinity EET receptor, GPR132 is reported to have affinity for additional fatty acidsin vitro,and we found that these same fatty acids enhance hematopoietic stem cell specification in the zebrafish. We conducted structure-activity relationship analyses using bothin vitroandin vivoassays on diverse medium chain fatty acids. Certain oxygenated, unsaturated free fatty acids showed high activation of GPR132, while unoxygenated or saturated fatty acids had lower activity. Absence of the carboxylic acid moiety prevented activity, suggesting that this moiety is required for receptor activation. GPR132 responds to a select panel of polyunsaturated, oxygenated fatty acids to enhance both embryonic and adult hematopoiesis.

In different locations of Croatia (Nova Gradiška, Koprivnica, Gospić and Jastrebarsko) adults and developmental stages of Ips cembrae, the large larch bark beetle, and Ips typographus, the European spruce bark beetle, were collected from Picea abies, Larix decidua und Pinus sylvestris together with substrate from their breeding galleries and examined for phoretic mites. Four different mite species were identified by collecting specimens directly from the beetles:Iponemus gaebleri (Tarsenomidae), Histiostoma piceae (Astigmata, Histiostomatoidea), Dendrolaelaps quadrisetus (Gamasina) and Urobovella sp. (Uropodidae). I. gaebleri was the most abundant mite on both beetle species.Three other mite species have been collected directly from bark beetle galleries.We also studied the attachment-areas of phoretic mites on their beetle carriers. I gaebleri and D. quadrisetus preferred the elytral declivity, while the phoretic deutonymphs of the Histiostomatidae commonly were found on the ventral side of the thorax.We discovered statistically significant differences concerning the total of attached mites and a clear preference of I. gaebleri for I. cembrae.Young callow adults of Ips cembrae, emerging from their maternal galleries carried significantly more phoretic mites than parental beetles, which were picked out of their breeding galleries.Females of an another species of genus Histiostoma were found in galleries of I. typographus. They all were largely covered by great numbers of two-chamber spores of a fungus belonging to the Ascomycota (Hypocreales).A dichotomous key to identify larvae and protonymphs of the Histiostomatidae is provided., Na nekoliko lokacija u Hrvatskoj (Nova Gradiška, Koprivnica, Gospić i Jastrebarsko) sa različitih vrsta drveća (Picea abies, Larix decidua i Pinus sylvestris) sakupljani su različiti stadiji ariševog potkornjaka, Ips cembrae i smrekinog pisara, Ips typographus te supstrat iz njihovih hodnika u svrhu sakupljana i identifikacije foretičkih grinja. Izravno sa tijela potkornjaka determinirano je 4 vrsta grinja: Iponemus gaebleri (Tarsenomidae), Histiostoma piceae (Astigmata, Histiostomatoidea), Dendrolaelaps quadrisetus (Gamasina) i Urobovella sp. (Uropodidae). Iponemus gaebleri bila je najčešća nađena vrsta kod obiju vrsta potkornjaka.Tri druge vtrste sakupljene su izravno iz hodničkih sustava. Istraživana su i mjesta spajanja foretičkih grinja s potkornjacima. Iponemus gaebleri i D. quadrisetus tako se najčešće nalaze na obronku zadka, dok se foretičke deutonimfe porodice Histiostomatidae obično nalaze na ventralnoj strani prsišta. Statističkom anlizom potvrđen je jasna preferencija I. gaebleri na I. cembrae. Mladi još nezreli kukci Ips cembrae, koji izlaze iz materinjih hodnika nose signifikantno više foretičkih grinja nego roditeljski. Ženke neidentifcirane vrste roda Histiostoma nađene su u hodnicima I. typographus. Grinje su uglavnom bile pokrivene s većim brojem neidentificiranim sporama gljiva iz skupine Ascomycota (Hypocreales).U radu se daje dihotomski ključ za identifikaciju larvi i protonimfi za porodicu Histiostomatidae.

Na nekoliko lokacija u Hrvatskoj (Nova Gradiška, Koprivnica, Gospić i Jastrebarsko) sa različitih vrsta drveća (Picea abies, Larix decidua i Pinus sylvestris) sakupljani su različiti stadiji ariševog potkornjaka, Ips cembrae i smrekinog pisara, Ips typographus te supstrat iz njihovih hodnika u svrhu sakupljana i identifikacije foretičkih grinja. Izravno sa tijela potkornjaka determinirano je 4 vrsta grinja: Iponemus gaebleri (Tarsenomidae), Histiostoma piceae (Astigmata, Histiostomatoidea), Dendrolaelaps quadrisetus (Gamasina) i Urobovella sp. (Uropodidae). Iponemus gaebleri bila je najčešća nađena vrsta kod obiju vrsta potkornjaka. Tri druge vtrste sakupljene su izravno iz hodničkih sustava. Istraživana su i mjesta spajanja foretičkih grinja s potkornjacima. Iponemus gaebleri i D. quadrisetus tako se najčešće nalaze na obronku zadka, dok se foretičke deutonimfe porodice Histiostomatidae obično nalaze na ventralnoj strani prsišta. Statističkom anlizom potvrđen je jasna preferencija I. gaebleri na I. cembrae. Mladi još nezreli kukci Ips cembrae, koji izlaze iz materinjih hodnika nose signifikantno više foretičkih grinja nego roditeljski. Ženke neidentifcirane vrste roda Histiostoma nađene su u hodnicima I. typographus. Grinje su uglavnom bile pokrivene s većim brojem neidentificiranim sporama gljiva iz skupine Ascomycota (Hypocreales). U radu se daje dihotomski ključ za identifikaciju larvi i protonimfi za porodicu Histiostomatidae.

Small molecule treatment of hematopoietic stem cells ex vivo has the potential to expand these cells or increase their engraftability. Previously, we discovered that ex vivo treatment of marrow with 11,12-epoxyeicosatrienoic acid (EET) enhances the engraftment of hematopoietic stem and progenitor cells in both zebrafish and mammals. Additionally, EET treatment promotes specification of HSPC from the hemogenic endothelium, suggesting a broad pro-hematopoietic role of this molecule. Indeed, bioactive lipids play an important role as signaling molecules both during embryo development and adult tissue homeostasis. However, due to their small-molecule nature, identifying their receptors biochemically has been a long-standing challenge which impedes the understanding of the biological processes they regulate. The identity of the EET receptor remains unknown despite more than a decade of research. Here, we utilized a novel bioinformatic approach to identify candidate EET receptors and identified a candidate functional in cell culture, zebrafish and mouse assays. EET signaling is known to be G-protein dependent, suggesting its receptor is a G-protein coupled receptor (GPCR). We performed RNAseq on U937 monocytes, EaHy endothelial cells, and PC3M-LN4 prostate cancer cells, three human cell lines with clear EET-responsive phenotypes. These three cell lines expressed 37 GPCR in common at a basal level of greater than or equal to 0.3 fragments per kilobase per million reads (FPKM). 27 of these GPCR were also expressed in a non-EET-responsive cell line, HEK293, leaving only 10 candidate EET receptors. We screened 7 of these candidates for EET-responsiveness using a cell-culture based β-arrestin recruitment assay. Of these, only GPR132 exhibited EET-dependent recruitment of β-arrestin to the cell membrane, indicating GPCR activation. GPR132 was previously identified as a receptor for a variety of small oxygenated fatty acids, and we confirmed that these related molecules induce GPR132-dependent β-arrestin recruitment. We additionally treated developing zebrafish embryos with these molecules. Like EET, these GPR132 ligands increased HSPC numbers in the zebrafish aorta-gonad-mesonephros (AGM) and caused ectopic expression of the HSPC marker runx1 in the zebrafish tail, a phenotype that was previously seen only with EET treatment. To test the requirement of GPR132 for EET signaling, we knocked down the zebrafish ortholog of GPR132 by morpholino injection, which prevented the EET-induced increase of runx1in both the AGM and tail. Finally, we performed competitive whole bone marrow transplant using wildtype and GPR132-/- mice as donors and found that while treatment with EET increases engraftment of WT donor cells, no such improvement is seen in GPR132-/- cells. GPR132 is thus required in both zebrafish and mice for EET phenotypes. Combining bioinformatic, biochemical, and genetic approaches, we identified GPR132 as a receptor for EET involved in regulating hematopoiesis and marrow transplant. GPR132 thus represents a therapeutic target for the enhancement of hematopoietic stem cell transplant, and genetic manipulation of GPR132 could help illuminate the endogenous roles of its fatty acid ligands. Disclosures Zon: Fate, Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Founder; Marauder Therapeutics: Equity Ownership, Other: Founder; Scholar Rock: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Founder.