The genomic echoes of the last Green Sahara on the Fulani and Sahelian people.

The population history of the Sahara/Sahelian belt is understudied, despite previous work highlighting complex dynamics.1,2,3,4,5,6,7 The Sahelian Fulani, i.e., the largest nomadic pastoral population in the world,8 represent an interesting case because they show a non-negligible proportion of an Eurasian genetic component, usually explained by recent admixture with northern Africans.1,2,5,6,7,9,10,11,12 Nevertheless, their origins are largely unknown, although several hypotheses have been proposed, including a possible link to ancient peoples settled in the Sahara during its last humid phase (Green Sahara, 12,000-5,000 years before present [BP]).13,14,15 To shed light about the Fulani ancient genetic roots, we produced 23 high-coverage (30×) whole genomes from Fulani individuals from 8 Sahelian countries, plus 17 samples from other African groups and 3 from Europeans as controls, for a total of 43 new whole genomes. These data have been compared with 814 published modern whole genomes2,16,17,18 and with relevant published ancient sequences (> 1,800 samples).19 These analyses showed some evidence that the non-sub-Saharan genetic ancestry component of the Fulani might have also been shaped by older events,1,5,6 possibly tracing the Fulani origins to unsampled ancient Green Saharan population(s). The joint analysis of modern and ancient samples allowed us to shed light on the genetic ancestry composition of such ancient Saharans, suggesting a similarity with Late Neolithic Moroccans and possibly pointing to a link with the spread of cattle herding. We also identified two different Fulani clusters whose admixture pattern may be informative about the historical Fulani movements and their later involvement in the western African empires.

Sequence Read Depth Analysis of a Monophyletic Cluster of Y Chromosomes Characterized by Structural Rearrangements in the AZFc Region Resulting in DYS448 Deletion and DYF387S1 Duplication.

The azoospermia factor c region (AZFc), located in the long arm of the human Y chromosome, is frequently involved in chromosome rearrangements, mainly due to non-allelic homologous recombination events that occur between the nearly identical sequences (amplicon) that comprises it. These rearrangements may have major phenotypic effects like spermatogenic failure or other pathologies linked to male infertility. Moreover, they may also be relevant in forensic genetics, since some of the Y chromosome short tandem repeats (Y-STRs) commonly used in forensic analysis are located in amplicons or in inter-amplicon sequences of the AZFc. In a previous study, we identified four phylogenetically related samples with a null allele at DYS448 and a tetrallelic pattern at DYF387S1, two Y-STRs located in the AZFc. Through NGS read depth analysis, we found that the unusual Y-STR pattern may be due to a 1.6 Mb deletion arising concurrently or after a 3.5 Mb duplication event. The observed large genomic rearrangement results in copy number reduction for the RBMY gene family as well as duplication of other AZFc genes. Based on the diversity of 16 additional Y-STRs, we estimated that the duplication/deletion event occurred at least twenty generations ago, suggesting that it has not been affected by negative selection.