The clock is ticking for senescent cells Senescent cells promote their own recognition and removal through the immune system by generating a bioactive secretome called the senescence-associated secretory phenotype (SASP). Sturmlechner et al . report that the cell cycle regulator p21 directs an early form of the SASP, which they call the p21-activated secretory phenotype (PASP) (see the Perspective by Reen and Gil). As part of the PASP, the chemokine CXCL14 attracts macrophages, which monitor stressed cells expressing elevated p21. If stressed cells recuperate and p21 levels return to normal within 4 days, then macrophages disengage from their targets. Otherwise, macrophages recruit cytotoxic T cells that facilitate target cell removal. Other cell cycle regulators such as p16 can induce many factors overlapping with the PASP, but p21 uniquely drives this CXCL14-mediated “timer” mechanism of senescent cell immunosurveillance. —STS

The de novo assembly of the red fox (Vulpes vulpes) genome has facilitated the development of genomic tools for the species. Efforts to identify the population history of red foxes in North America have previously been limited by a lack of information about the red fox Y-chromosome sequence. However, a megabase of red fox Y-chromosome sequence was recently identified over 2 scaffolds in the reference genome. Here, these scaffolds were scanned for repeated motifs, revealing 194 likely microsatellites. Twenty-three of these loci were selected for primer development and, after testing, produced a panel of 11 novel markers that were analyzed alongside 2 markers previously developed for the red fox from dog Y-chromosome sequence. The markers were genotyped in 76 male red foxes from 4 populations: 7 foxes from Newfoundland (eastern Canada), 12 from Maryland (eastern United States), and 9 from the island of Great Britain, as well as 48 foxes of known North American origin maintained on an experimental farm in Novosibirsk, Russia. The full marker panel revealed 22 haplotypes among these red foxes, whereas the 2 previously known markers alone would have identified only 10 haplotypes. The haplotypes from the 4 populations clustered primarily by continent, but unidirectional gene flow from Great Britain and farm populations may influence haplotype diversity in the Maryland population. The development of new markers has increased the resolution at which red fox Y-chromosome diversity can be analyzed and provides insight into the contribution of males to red fox population diversity and patterns of phylogeography.

While the number of mammalian genome assemblies has proliferated, Y-chromosome assemblies have lagged behind. This discrepancy is caused by biological features of the Y-chromosome, such as its high repeat content, that present challenges to assembly with short-read, next-generation sequencing technologies. Partial Y-chromosome assemblies have been developed for the cat (Felis catus), dog (Canis lupus familiaris), and grey wolf (Canis lupus lupus), providing the opportunity to examine the red fox (Vulpes vulpes) Y-chromosome in the context of closely related species. Here we present a data-driven approach to identifying Y-chromosome sequence among the scaffolds that comprise the short-read assembled red fox genome. First, scaffolds containing genes found on the Y-chromosomes of cats, dogs, and wolves were identified. Next, analysis of the resequenced genomes of 15 male and 15 female foxes revealed scaffolds containing male-specific k-mers and patterns of inter-sex copy number variation consistent with the heterogametic chromosome. Analyzing variation across these two metrics revealed 171 scaffolds containing 3.37 Mbp of putative Y-chromosome sequence. The gene content of these scaffolds is consistent overall with that of the Y-chromosome in other carnivore species, though the red fox Y-chromosome carries more copies of BCORY2 and UBE1Y than has been reported in related species and fewer copies of SRY than in other canids. The assignment of these scaffolds to the Y-chromosome serves to further characterize the content of the red fox draft genome while providing resources for future analyses of canid Y-chromosome evolution.

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Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults and remains incurable. The mitochondrial coiled-coil-helix-coiled-coil-helix domain-containing protein 2 (CHCHD2) is demonstrated to mediate mitochondrial respiration, nuclear gene expression, and cell migration, but evidence of this in GBM is lacking. We hypothesized that CHCHD2 would serve a functional role in U87 GBM cells expressing the constitutively active epidermal growth factor receptor variant III (EGFRvIII). Amplification of the CHCHD2 gene was found to be associated with decreased patient overall survival and progression-free survival. CHCHD2 mRNA levels were increased in high-versus low-grade glioma, IDH-wt GBMs, and in tumor versus non-tumor tissue. Additionally, CHCHD2 protein expression was greatest in invasive, EGFRvIII-expressing patient-derived samples. CRISPR-Cas9-mediated knockout of CHCHD2 in EGFRvIII-expressing U87 cells resulted in altered mitochondrial respiration and glutathione status, decreased cell growth and invasion in both normoxia and hypoxia, and increased sensitivity to cytotoxic agents. CHCHD2 was distributed in both mitochondria and nuclei of U87 and U87vIII cells, and U87vIII displayed greater nuclear CHCHD2 compared to isogenic U87 cells. Incubation in hypoxia, serum starvation, and reductive unfolding of CHCHD2 induced nuclear accumulation of CHCHD2 in both cell lines. Collectively, these data indicate that CHCHD2 mediates a variety of GBM cell hallmark characteristics and highlights mitonuclear retrograde signaling as a pathway of interest in GBM cell biology.ImplicationsThese data demonstrate CHCHD2 as a mediator of a number of GBM cell functions representing disease hallmarks, as well as highlight its subcellular distribution in response to metabolic stressors. These results may inspire therapeutic strategies undermining mitochondrial biology to potentially improve GBM tumor management.