👤 Takumi Mikawa

Senescent cells are characterized by a stable proliferation arrest and a senescence-associated secretory phenotype or SASP. Although these cells can have some beneficial effects, including protecting from tumor formation, their accumulation is deleterious during aging as it promotes age-related diseases, including cancer initiation and progression. Although the SASP has a critical role, its composition, regulation and dual role in cancer remain largely misunderstood. Here, we show that ANGPTL4 is one of the rare secreted factors induced in many different types of senescent cells. Importantly, ANGPTL4 knockdown during senescence or its constitutive expression, respectively inhibits or induces classical proinflammatory SASP factors, such as IL1A, IL6 and IL8. The latter effect is mediated upstream of IL1A, an early SASP factor, suggesting an upstream role of ANGPTL4 in SASP induction. This ANGPTL4-dependent proinflammatory SASP can promote human neutrophil activation in ex vivo assays, or tumor initiation in a KRAS-dependent lung tumorigenesis model in mice. This upstream activity of ANGPTL4 in regulating the proinflammatory SASP depends on its upregulation following a hypoxia-like response and HIF2A activation, and its proteolytic processing by the FURIN proprotein convertase. Altogether these findings shed light on a two-step activation of ANGPTL4 by HIF2A and FURIN in senescent cells and its upstream role in promoting the proinflammatory SASP, cancer and potentially other senescence-associated diseases. Show less

Fatty acid composition is an economically important trait in meat-producing livestock. To gain insight into the molecular genetics of fatty acid desaturase (FADS) genes in pigs, we investigated the genomic structure of the porcine FADS gene family on chromosome 2. We also examined the tissue distribution of FADS gene expression. The genomic structure of FADS family in mammals consists of three isoforms FADS1, FADS2 and FADS3. However, porcine FADS cluster in the latest pig genome assembly (Sscrofa 10.2) containing some gaps is distinct from that in other mammals. We therefore sought to determine the genomic structure, including the FADS cluster in a 200-kbp range by sequencing gap regions. The structure we obtained was similar to that in other mammals. We then investigated the porcine FADS1 transcription start site and identified a novel isoform named FADS1b. Phylogenetic analysis revealed that the three members of the FADS cluster were orthologous among mammals, whereas the various FADS1 isoforms identified in pigs, mice and cattle might be attributable to species-specific transcriptional regulation with alternative promoters. Porcine FADS1b and FADS3 isoforms were predominantly expressed in the inner layer of the subcutaneous adipose tissue. Additional analyses will reveal the effects of these functionally unknown isoforms on fatty acid composition in pig fat tissues. Show less

We evaluated multiple effects of genetic variations of five candidate loci (LEP, LEPR, MC4R, PIK3C3 and VRTN) on four production traits (average daily weight gain (ADG); backfat thickness (BFT); loin eye muscle area (EMA); and intramuscular fat content (IMF)) in a closed nucleus herd of pure Duroc pigs. Polymorphisms in LEPR, MC4R and PIK3C3 had significant single gene effects on ADG and BFT. The additive genetic variance in ADG and BFT (16.99% and 22.51%, respectively) was explained by genetic effects of these three loci. No correlations were observed between the LEP genotype and production traits in this study. Although we detected marginally epistatic interactions between LEPR and PIK3C3 on the eye muscle area, there were no significant epistatic effects on any traits among all loci pairs. These results suggest that LEPR, MC4R, PIK3C3 and VRTN may independently influence growth rate and fat deposition. Furthermore, the statistical models for predicting the breeding values of each trait had the lowest Akaike's information criterion values when considering the effect of the MC4R, LEPR, PIK3C3 and VRTN genotype simultaneously. These results suggest that LEPR, MC4R, PIK3C3 and VRTN are useful markers for accurately predicting breeding values in Duroc pigs. Show less