Project description:The genetic structure of the indigenous hunter-gatherer peoples of Southern Africa, the oldest known lineage of modern man, holds an important key to understanding humanity's early history. Previously sequenced human genomes have been limited to recently diverged populations. Here we present the first complete genome sequences of an indigenous hunter-gatherer from the Kalahari Desert and of a Bantu from Southern Africa, as well as protein-coding regions from an additional three hunter-gatherers from disparate regions of the Kalahari. We characterize the extent of whole-genome and exome diversity among the five men, reporting 1.3 million novel DNA differences genome-wide, and 13,146 novel amino-acid variants. These data allow genetic relationships among Southern African foragers and neighboring agriculturalists to be traced more accurately than was previously possible. Adding the described variants to current databases will facilitate inclusion of Southern Africans in medical research efforts.
Project description:The genetic structure of the indigenous hunter-gatherer peoples of Southern Africa, the oldest known lineage of modern man, holds an important key to understanding humanity's early history. Previously sequenced human genomes have been limited to recently diverged populations. Here we present the first complete genome sequences of an indigenous hunter-gatherer from the Kalahari Desert and of a Bantu from Southern Africa, as well as protein-coding regions from an additional three hunter-gatherers from disparate regions of the Kalahari. We characterize the extent of whole-genome and exome diversity among the five men, reporting 1.3 million novel DNA differences genome-wide, and 13,146 novel amino-acid variants. These data allow genetic relationships among Southern African foragers and neighboring agriculturalists to be traced more accurately than was previously possible. Adding the described variants to current databases will facilitate inclusion of Southern Africans in medical research efforts. Copy number differences between NA18507 and KB1 were predicted from the depth of whole-genome shotgun sequence reads. These predictions were then validated using array-CGH using a a genome-wide design as well as a custom design targeted at specific regions of copy number difference
Project description:Only a few scattered groups with oral traditions of Khoe-San hunter-gatherer ancestry remain in southeastern Africa. We investigate genomic variation of remaining individuals from two South African groups with oral histories connecting them to eastern San groups, i.e., the San from Lake Chrissie and the Duma San of the uKhahlamba-Drakensberg. Using ~2.2 million genetic markers, combined with comparative published datasets, we show that the Lake Chrissie San have genetic ancestry from both Khoe-San (likely the ||Xegwi San) and Bantu-speakers. Specifically, we found that the Lake Chrissie San are closely related to current southern San groups (i.e. the Karretjie People). Duma San individuals, on the other hand, were genetically similar to southeastern Bantu speakers from South Africa. Samples were genotyped on the Illumina Omni2.5M (HumanOmni25-8v1-2_A1) SNP chip. Results were analyzed using the software GenomeStudio 2011.1 and the data were exported to Plink format, aligned to Human Genome build version 37.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.
Project description:Bantu languages are spoken by ~310 million Africans, yet the genetic history of Bantu-speaking populations remains largely unexplored. We generated genomic data for 1,318 individuals from 35 populations in western central Africa, where Bantu languages originated. We found that early Bantu speakers first moved southward, through the equatorial rainforest, before spreading toward eastern and southern Africa. We also found that genetic adaptation of Bantu speakers was facilitated by admixture with autochthonous populations, particularly for the HLA and LCT loci. Finally, we identified a major contribution of western central African Bantu speakers to the ancestry of African Americans, whose genomes present no strong signals of natural selection. Together, these results highlight the contribution of Bantu-speaking peoples to the complex genetic history of Africans and African Americans.
Project description:As the evolution of miRNA genes has been found to be one of the important factors in formation of the modern type of man, we performed a comparative analysis of the evolution of miRNA genes in two archaic hominines, Homo sapiens neanderthalensis and Homo sapiens denisova, and elucidated the expression of their target mRNAs in bain.A comparative analysis of the genomes of primates, including species in the genus Homo, identified a group of miRNA genes having fixed substitutions with important implications for the evolution of Homo sapiens neanderthalensis and Homo sapiens denisova. The mRNAs targeted by miRNAs with mutations specific for Homo sapiens denisova exhibited enhanced expression during postnatal brain development in modern humans. By contrast, the expression of mRNAs targeted by miRNAs bearing variations specific for Homo sapiens neanderthalensis was shown to be enhanced in prenatal brain development.Our results highlight the importance of changes in miRNA gene sequences in the course of Homo sapiens denisova and Homo sapiens neanderthalensis evolution. The genetic alterations of miRNAs regulating the spatiotemporal expression of multiple genes in the prenatal and postnatal brain may contribute to the progressive evolution of brain function, which is consistent with the observations of fine technical and typological properties of tools and decorative items reported from archaeological Denisovan sites. The data also suggest that differential spatial-temporal regulation of gene products promoted by the subspecies-specific mutations in the miRNA genes might have occurred in the brains of Homo sapiens denisova and Homo sapiens neanderthalensis, potentially contributing to the cultural differences between these two archaic hominines.
Project description:PurposeWe investigated the evidence of recent positive selection in the human phototransduction system at single nucleotide polymorphism (SNP) and gene level.MethodsSNP genotyping data from the International HapMap Project for European, Eastern Asian, and African populations was used to discover differences in haplotype length and allele frequency between these populations. Numeric selection metrics were computed for each SNP and aggregated into gene-level metrics to measure evidence of recent positive selection. The level of recent positive selection in phototransduction genes was evaluated and compared to a set of genes shown previously to be under recent selection, and a set of highly conserved genes as positive and negative controls, respectively.ResultsSix of 20 phototransduction genes evaluated had gene-level selection metrics above the 90th percentile: RGS9, GNB1, RHO, PDE6G, GNAT1, and SLC24A1. The selection signal across these genes was found to be of similar magnitude to the positive control genes and much greater than the negative control genes.ConclusionsThere is evidence for selective pressure in the genes involved in retinal phototransduction, and traces of this selective pressure can be demonstrated using SNP-level and gene-level metrics of allelic variation. We hypothesize that the selective pressure on these genes was related to their role in low light vision and retinal adaptation to ambient light changes. Uncovering the underlying genetics of evolutionary adaptations in phototransduction not only allows greater understanding of vision and visual diseases, but also the development of patient-specific diagnostic and intervention strategies.