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PNAS Papers on Central African Hunter-Gatherers, Myopia Development, Ancient Microtia Allele

A team from the University of Zurich, University of Oslo, and other centers in Europe and the US explore population patterns in hunter-gatherer groups in Central Africa. Based on a machine learning-based analysis of genetic, archeological, and ethnographic data for hundreds of hunter-gatherer camps spanning 11 groups, the researchers attributed present-day Central African hunter-gatherer distribution and density patterns to ecological and environmental shifts. Those results were backed up by paleoclimatic modeling of historical ranges reaching back roughly 120,000 years, and by population divergence estimates performed with published genomic data. "[T]he fact that our modeled relationship between ecology and [Central African hunter-gatherer] presence is consistent with the location of past archaeological assemblages and human remains suggests that as well as having remained genetically distinct for a very long time, contemporary African hunter-gatherers occupy similar habitats to their ancestors," they write, noting that the results point to structured, semi-isolated population groups.

Investigators at the University College London, King's College London, Moorfields Eye Hospital, and the University of Cambridge consider the consequences of a myopia-associated genetic variant, particularly on the way retinal cone cells respond to electrical signals. With electroretinogram-based measurements of retinal neuron light responses in 186 adult twin participants, coupled with targeted genotyping data and follow-up single-cell RNA sequencing experiments, the team saw changes in light-adapted and cone-driven responses in the retina in the presence of a myopia-linked variant near the retinal gap junction-coding gene GJD2. "Our findings support a potential role for altered signaling in cone-driven OFF pathways in myopia development," the authors write, noting that cone photoreceptors appear to have the most pronounced GJD2 expression.

A team from Harvard Medical School, Boston Children's Hospital, and elsewhere describe a founder mutation that appears to contribute to a congenital outer ear condition called microtia in Indigenous American populations. The investigators narrowed in on a microtia-linked locus between the ROBO1 and ROBO2 genes with the help of transmission disequilibrium, parent-child trio-based association, and single-nucleus RNA sequencing analyses, subsequently demonstrating that the risk site affects the expression of the genes in multiple cell types found in the human ear. "Because the microtia allele is enriched in [Indigenous American] populations and is shared by some East Asian subjects with craniofacial malformations," they write, "we propose that both populations share a mutation that arose in a common ancestor prior to the ancient migration of Eurasian populations into the Americas, and that the high incidence of microtia among [Indigenous American] populations reflects the population bottleneck that occurred during the migration out of Eurasia."