In This Issue · authors, further research is needed to uncover why the vortices formed and why...

SEPTEMBER 29, 2020

In this issue . . . IN T

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www.pnas.org/cgi/doi/10.1073/iti3920117 PNAS | September 29, 2020 | vol. 117 | no. 39 | 24005–24007

Ancestry of New Guinea singing dogs

New Guinea singing dogs (NGSD) are a rare canine population from the highlands of New Guinea that owe their name to a recognizable vocalization evoking wolf howls and whale song. Once abundant on the island, the dogs are thought to be nearly extinct in the wild, with no more than 300 captive individuals alive, bred for conservation purposes. Suriani Surbakti, Heidi Parker, et al. (pp. 24369–24376) analyzed the nuclear genomes of three puta-tive highland wild dogs (HWD), a group of 15 free-roaming dogs living near the heights of a gold mine in western Papua that share strik-ing morphological similarities with NGSDs and whose existence was uncovered by a 2016 expedition. Phylogenetic analysis suggested that the HWDs likely arose from the same stock as the captive NGSDs. Further, 72% of the HWD genome resembled that of captive NGSDs, but the HWD genome showed signs of relatively higher genetic diversity. The latter finding suggests that HWDs might play a crucial role in conservation efforts to bolster NGSD populations. According to the authors, the findings suggest that the founding population of NGSDs is not extinct and could help revitalize the compromised NGSD population. — P.N.

Stability of Jupiter’s polar vorticesThe Juno spacecraft has observed patterns of stable vortices organized in polygons at each pole of Jupiter, with eight and five cyclonic vortices around a central vortex at the north and south poles, respectively. The factors influencing the stability of the cyclones, which have been stable since August 2016, are unknown. Cheng Li et al. (pp. 24082–24087) constructed a numerical model to recreate the vortices and iden-tify factors that influence their behavior. Key to the cyclonic vortices’ stability are the depths of the vor-tices and rings of anticyclonic rotation around each vortex called shielding. Cyclones on Jupiter tend to move poleward, as they do on Earth. If the shield-ing is insufficient, however, the cyclones merge. Too much shielding can also disrupt the polygonal vor-tex pattern and drive the vortices apart. The char-acteristics of Jupiter’s polar vortices fall in between the extremes, allowing stability. According to the

Highland wild dog. Image credit: Anang Dianto (photographer).

On its 20th flyby to Jupiter, an instrument on Juno found a seventh vortex (5 o’clock direction) trying to join a family of six vortices. Later flybys did not observe the seventh vortex. Image credit: Alessandro Mura (National Institute for Astrophysics, Rome, Italy).

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authors, further research is needed to uncover why the vortices formed and why such a polygonal pat-tern persists with observed stability on Jupiter but not on other large gas giants, such as Saturn, which exhibits single polar vortices. — P.G.

Gene editing and transplantation of sperm-producing stem cellsSpermatogonial stem cell transplantation (SSCT) is a technique that involves injecting sperm- producing testicular cells from a fertile donor into the testis of an infertile recipient. For certain appli-cations, SSCT requires the elimination of the endog-enous germline in recipients to ensure that all

sperm cells produced are derived from the donor. Michela Ciccarelli, Mariana Giassetti, Deqiang Miao, et al. (pp. 24195–24204) demonstrate a method that can achieve this critical step in mice and live-stock. Using the gene-editing tool CRISPR-Cas9, the authors inactivated the NANOS2 gene to com-pletely remove the endogenous germline and ren-der recipient males sterile. Next, the authors used SSCT to achieve the production of donor-derived, mature, motile sperm cells in mice, pigs, and goats whose testes were structurally normal. The engraft-ment was successful, even though the donors and recipients were immunologically incompatible, and the recipients had a fully functional immune system. Moreover, three of the six mice that underwent SSCT before puberty mated to produce a total of 111 donor-derived offspring. According to the authors, the approach holds promise for treating male infer-tility, conserving endangered species, and improving livestock. — J.W.

Reducing resistance to a CRISPR homing gene drive CRISPR-based homing gene drives offer the poten-tial to control vector-borne diseases such as malaria. However, when the CRISPR-induced double-strand break is repaired through end-joining mechanisms rather than homology-induced repair, the target site can be mutated into a resistance allele immune to further Cas9 cleavage, limiting the gene drive’s spread. Jackson Champer, Emily Yang, et al. (pp. 24377–24383) created a CRISPR homing gene drive construct in Drosophila melanogaster that targets a haplolethal gene—where two functional copies are required for survival—so that disruption of the target gene by end-joining repair would result in a non-functional resistance allele that leads to nonviable offspring. The construct includes two guide RNAs targeting two sites in the haplolethal gene RpL35A and also provides a rescue allele to ensure that the gene drive has a functional copy of RpL35A that can-not be recognized by the guide RNAs. The authors found that the drive construct had an inheritance rate of 91% and kept functional resistance alleles to unde-tectable levels. In a large cage experiment involving thousands of flies, the drive allele successfully spread to all individuals within six generations without any apparent evolution of resistance. A CRISPR homing gene drive that targets a haplolethal gene can serve as an effective method to quickly modify entire pop-ulations, according to the authors. — S.R.

Plant community stability and biodiversityThe greater the stability of an ecological community, the more likely it is to maintain equilibrium under environmental fluctuation or perturbations from climate-driven events, such as drought, and biotic factors, such as grazing. Both species richness and synchrony—the covariation in population size among species in the same community—affect ecological stability. Enrique Valencia et al. (pp. 24345–24351)

24006 | www.pnas.org/cgi/doi/10.1073/iti3920117 In this issue

NANOS2 knockout bucks generated by somatic cell nuclear transfer of CRISPR-Cas9 gene-edited fetal goat fibroblasts.

Sampling site in Bayreuth, Germany.

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www.pnas.org/cgi/doi/10.1073/iti3920117 PNAS | September 29, 2020 | vol. 117 | no. 39 | 24007

report that the stability of plant communities depends to a greater extent on how the populations of species within the communities covary rather than on the diversity of the species themselves. The authors analyzed 79 datasets representing nearly 8,000 plant communities worldwide. In 71% of the datasets, greater synchrony significantly predicted less stability; the less fluctuations of individual pop-ulations compensate each other, the less stable the community. Higher species richness was associated with increased stability, but to a relatively smaller degree, evident in only 29% of the datasets. The authors also found that the positive effect of species richness is not necessarily due to a negative effect on synchrony. According to the authors, strategies to mitigate ecosystem damage should focus on selec-tion of species with different strategies and adapta-tions to promote low synchrony rather than solely focusing on biodiversity. — T.D.

Variation in mental health treatment of adolescentsMental illness often manifests during adolescence, but research on the determinants of variations in ado-lescent mental health care is limited. Emily Cuddy and Janet Currie (pp. 24039–24046) examined 2012–2018 data for 202,066 privately insured chil-dren with at least one mental illness claim between the ages of 11 and 18 years. Girls were more likely than boys to have claims. On average, children were 12 years of age when their first mental illness claim was filed. Following initial treatment for mental ill-ness, 70.8% of children received follow-up treatment within the next 3 months. Most children were not pre-scribed therapy for initial treatment. Almost half of children who were prescribed medication for initial treatment either received benzodiazepines, tricyclic antidepressants, or drugs that were not approved for child use by the US Food and Drug Administration. Compared with children who had preexisting neuro-developmental conditions, such as attention deficit hyperactivity disorder or autism spectrum disorder, children without such conditions were more likely to be treated with these medications. Children whose initial mental illness claim included a hospital visit were more likely than other children to receive med-ication. The findings suggest that variation in clinical practice is an important factor in the type of mental health treatment children receive, according to the authors. — M.S.

Floodwater farming in ancient Peru El Niño often induces natural disasters, but ancient farmers in Peru may have used floodwater for agri-culture. Ari Caramanica et al. (pp. 24127–24137) combined archaeological excavations of irriga-tion, water storage, and field systems with a pollen record from a prehispanic well to examine ancient use of floodwaters in the Pampa de Mocan region of Peru that is upslope of the highest active irrigation canal. The authors also compared reconstructions of ancient fields and water storage systems with modern-day vegetative communities in the region during 2016, when El Niño did not occur, and during the 2017 El Niño Costero. Analysis of Cupisnique

ceramic sherds suggested that the region was used for agriculture as early as 1100 BCE. Although the region currently has poor soil for agricultural pur-poses, ancient pollen samples indicated that veg-etation was once dynamic, and ancient farming activities continued while the area experienced runoff from El Niño flooding. Ancient farmers ben-efited from high water levels that flushed out salts; present-day local smallholders also grew crops in sedimentary buildup as 2017 floodwaters receded. Moreover, flexible irrigation systems allowed ancient farmers to alternate between runoff harvesting and river water distribution, suggesting that El Niño events may have agricultural advantages, according to the authors. — M.S.

The Peruvian Mocan desert in bloom in the months after the 2017 El Niño Costero event. Botanists collect specimens to compare the modern plants from this event to an ancient pollen record.

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