Ghost admixture in eastern gorillas

Archaic admixture has had a substantial impact on human evolution with multiple events across different clades, including from extinct hominins such as Neanderthals and Denisovans into modern humans. In great apes, archaic admixture has been identified in chimpanzees and bonobos but the possibility of such events has not been explored in other species. Here, we address this question using high-coverage whole-genome sequences from all four extant gorilla subspecies, including six newly sequenced eastern gorillas from previously unsampled geographic regions. Using approximate Bayesian computation with neural networks to model the demographic history of gorillas, we find a signature of admixture from an archaic 'ghost' lineage into the common ancestor of eastern gorillas but not western gorillas. We infer that up to 3% of the genome of these individuals is introgressed from an archaic lineage that diverged more than 3 million years ago from the common ancestor of all extant gorillas. This introgression event took place before the split of mountain and eastern lowland gorillas, probably more than 40 thousand years ago and may have influenced perception of bitter taste in eastern gorillas. When comparing the introgression landscapes of gorillas, humans and bonobos, we find a consistent depletion of introgressed fragments on the X chromosome across these species. However, depletion in protein-coding content is not detectable in eastern gorillas, possibly as a consequence of stronger genetic drift in this species.

Genomic and phenotypic characterization of Acinetobacter colistiniresistens isolated from the feces of a healthy member of the community

Acinetobacter species are widely known opportunistic pathogens causing severe community and healthcare-associated infections. One such emerging pathogen, Acinetobacter colistiniresistens, is known to exhibit intrinsic resistance to colistin. We investigated the molecular characteristics of A. colistiniresistens strain C-214, isolated from the fecal sample of a healthy community member, as part of a cohort study being conducted in Segamat, Malaysia. Comparison of the whole genome sequence of C-214 with other A. colistiniresistens sequences retrieved from the NCBI database showed 95% sequence identity or more with many of the genome sequences representing that species. Use of the Galleria mellonella killing assay showed that C-214 was pathogenic in this model infection system. The strain C-214 had a colistin and polymyxin B MIC of 32 and 16 mg/L, respectively. Besides, it was resistant to cefotaxime, amikacin, and tetracycline and showed moderate biofilm-producing ability. Different genes associated with virulence or resistance to major classes of antibiotics were detected. We observed mutations in lpxA/C/D in C-214 and other A. colistiniresistens strains as probable causes of colistin resistance, but the biological effects of these mutations require further investigation. This study provides genomic insights into A. colistiniresistens, a potentially pathogenic bacterium isolated from a community member and notes the public health threat it may pose.

Identification of Prominent Genes between 3D Glioblastoma Models and Clinical Samples via GEO/TCGA/CGGA Data Analysis

A paradigm shift in preclinical evaluations of new anticancer GBM drugs should occur in favour of 3D cultures. This study leveraged the vast genomic data banks to investigate the suitability of 3D cultures as cell-based models for GBM. We hypothesised that correlating genes that are highly upregulated in 3D GBM models will have an impact in GBM patients, which will support 3D cultures as more reliable preclinical models for GBM. Using clinical samples of brain tissue from healthy individuals and GBM patients from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), Chinese Glioma Genome Atlas (CGGA), and Genotype-Tissue Expression (GTEx) databases, several genes related to pathways such as epithelial-to-mesenchymal transition (EMT)-related genes (CD44, TWIST1, SNAI1, CDH2, FN1, VIM), angiogenesis/migration-related genes (MMP1, MMP2, MMP9, VEGFA), hypoxia-related genes (HIF1A, PLAT), stemness-related genes (SOX2, PROM1, NES, FOS), and genes involved in the Wnt signalling pathway (DKK1, FZD7) were found to be upregulated in brain samples from GBM patients, and the expression of these genes were also enhanced in 3D GBM cells. Additionally, EMT-related genes were upregulated in GBM archetypes (wild-type IDH1^R132 ) that historically have poorer treatment responses, with said genes being significant predictors of poorer survival in the TCGA cohort. These findings reinforced the hypothesis that 3D GBM cultures can be used as reliable models to study increased epithelial-to-mesenchymal transitions in clinical GBM samples.

Molecular characterization and comparative genomic analysis of Acinetobacter baumannii isolated from the community and the hospital: an epidemiological study in Segamat, Malaysia

Acinetobacter baumannii is a common cause of multidrug-resistant (MDR) nosocomial infections around the world. However, little is known about the persistence and dynamics of A. baumannii in a healthy community. This study investigated the role of the community as a prospective reservoir for A. baumannii and explored possible links between hospital and community isolates. A total of 12 independent A. baumannii strains were isolated from human faecal samples from the community in Segamat, Malaysia, in 2018 and 2019. Another 15 were obtained in 2020 from patients at the co-located tertiary public hospital. The antimicrobial resistance profile and biofilm formation ability were analysed, and the relatedness of community and hospital isolates was determined using whole-genome sequencing (WGS). Antibiotic profile analysis revealed that 12 out of 15 hospital isolates were MDR, but none of the community isolates were MDR. However, phylogenetic analysis based on single-nucleotide polymorphisms (SNPs) and a pangenome analysis of core genes showed clustering between four community and two hospital strains. Such clustering of strains from two different settings based on their genomes suggests that these strains could persist in both. WGS revealed 41 potential resistance genes on average in the hospital strains, but fewer (n=32) were detected in the community strains. In contrast, 68 virulence genes were commonly seen in strains from both sources. This study highlights the possible transmission threat to public health posed by virulent A. baumannii present in the gut of asymptomatic individuals in the community.

Complete Genome Sequence and Analysis of a ST573 Multidrug-Resistant Methicillin-Resistant Staphylococcus aureus SauR3 Clinical Isolate from Terengganu, Malaysia

Methicillin-resistant Staphylococcus aureus (MRSA) is a World Health Organization-listed priority pathogen. Scarce genomic data are available for MRSA isolates from Malaysia. Here, we present the complete genome sequence of a multidrug-resistant MRSA strain SauR3, isolated from the blood of a 6-year-old patient hospitalized in Terengganu, Malaysia, in 2016. S. aureus SauR3 was resistant to five antimicrobial classes comprising nine antibiotics. The genome was sequenced on the Illumina and Oxford Nanopore platforms and hybrid assembly was performed to obtain its complete genome sequence. The SauR3 genome consists of a circular chromosome of 2,800,017 bp and three plasmids designated pSauR3-1 (42,928 bp), pSauR3-2 (3011 bp), and pSauR3-3 (2473 bp). SauR3 belongs to sequence type 573 (ST573), a rarely reported sequence type of the staphylococcal clonal complex 1 (CC1) lineage, and harbors a variant of the staphylococcal cassette chromosome mec (SCCmec) type V (5C2&5) element which also contains the aac(6')-aph(2″) aminoglycoside-resistance genes. pSauR3-1 harbors several antibiotic resistance genes in a 14,095 bp genomic island (GI), previously reported in the chromosome of other staphylococci. pSauR3-2 is cryptic, whereas pSauR3-3 encodes the ermC gene that mediates inducible resistance to macrolide-lincosamide-streptogramin B (iMLS_B). The SauR3 genome can potentially be used as a reference genome for other ST573 isolates.

Biomonitoring of heavy metals in the feathers of House crow (Corvus splendens) from some metropolitans of Asia and Africa

Urban-dwelling birds can be useful biomonitors to assess the impact of the urbanisation on both public and wildlife health. Widely distributed urban bird species, the House crow, was studied for heavy metal accumulation levels from nine cities of South Asia, Southeast Asia and Africa that border the Indian Ocean. Feathers were spectroscopically investigated for the deposition of ten heavy metals, i.e. As, Zn, Pb, Cd, Ni, iron Fe, Mn, Cr, Cu and Li. Fe and Zn were found to be the most prevalent metals in all sites. Measured concentrations of Pb (4.38-14.77 mg kg^-1) overall, and Fe (935.66 mg kg^-1) and Cu (67.17 mg kg^-1) at some studied sites were above the toxicity levels reported lethal in avian toxicological studies. Multivariate analysis and linear models supported geographical location as a significant predictor for the level of most of the metals. Zn and Cu, generally and Pb, Cd, Mn, Cr at some sites exhibited potential bioaccumulation from surrounding environments. Inter-species comparisons strengthen the inference that the House crow is a reliable bioindicator species for the qualitative assessment of local urban environmental pollution and could be a useful tool for inter-regional monitoring programs.

Sequence analyses of Malaysian Indigenous communities reveal historical admixture between Hoabinhian hunter-gatherers and Neolithic farmers

Southeast Asia comprises 11 countries that span mainland Asia across to numerous islands that stretch from the Andaman Sea to the South China Sea and Indian Ocean. This region harbors an impressive diversity of history, culture, religion and biology. Indigenous people of Malaysia display substantial phenotypic, linguistic, and anthropological diversity. Despite this remarkable diversity which has been documented for centuries, the genetic history and structure of indigenous Malaysians remain under-studied. To have a better understanding about the genetic history of these people, especially Malaysian Negritos, we sequenced whole genomes of 15 individuals belonging to five indigenous groups from Peninsular Malaysia and one from North Borneo to high coverage (30X). Our results demonstrate that indigenous populations of Malaysia are genetically close to East Asian populations. We show that present-day Malaysian Negritos can be modeled as an admixture of ancient Hoabinhian hunter-gatherers and Neolithic farmers. We observe gene flow from South Asian populations into the Malaysian indigenous groups, but not into Dusun of North Borneo. Our study proposes that Malaysian indigenous people originated from at least three distinct ancestral populations related to the Hoabinhian hunter-gatherers, Neolithic farmers and Austronesian speakers.

The Oral, Gut Microbiota and Cardiometabolic Health of Indigenous Orang Asli Communities

The Orang Asli (OA) of Malaysia have been relatively understudied where little is known about their oral and gut microbiomes. As human health is closely intertwined with the human microbiome, this study first assessed the cardiometabolic health in four OA communities ranging from urban, rural to semi-nomadic hunter-gatherers. The urban Temuan suffered from poorer cardiometabolic health while rural OA communities were undergoing epidemiological transition. The oral microbiota of the OA were characterised by sequencing the V4 region of the 16S rRNA gene. The OA oral microbiota were unexpectedly homogenous, with comparably low alpha diversity across all four communities. The rural Jehai and Temiar PP oral microbiota were enriched for uncharacterised bacteria, exhibiting potential for discoveries. This finding also highlights the importance of including under-represented populations in large cohort studies. The Temuan oral microbiota were also elevated in opportunistic pathogens such as Corynebacterium, Prevotella, and Mogibacterium, suggesting possible oral dysbiosis in these urban settlers. The semi-nomadic Jehai gut microbiota had the highest alpha diversity, while urban Temuan exhibited the lowest. Rural OA gut microbiota were distinct from urban-like microbiota and were elevated in bacteria genera such as Prevotella 2, Prevotella 9, Lachnospiraceae ND3007, and Solobacterium. Urban Temuan microbiota were enriched in Odoribacter, Blautia, Parabacetroides, Bacteroides and Ruminococcacecae UCG-013. This study brings to light the current health trend of these indigenous people who have minimal access to healthcare and lays the groundwork for future, in-depth studies in these populations.

Prioritization of putatively detrimental variants in euploid miscarriages

Miscarriage is the spontaneous termination of a pregnancy before 24 weeks of gestation. We studied the genome of euploid miscarried embryos from mothers in the range of healthy adult individuals to understand genetic susceptibility to miscarriage not caused by chromosomal aneuploidies. We developed GP , a pipeline that we used to prioritize 439 unique variants in 399 genes, including genes known to be associated with miscarriages. Among the prioritized genes we found STAG2 coding for the cohesin complex subunit, for which inactivation in mouse is lethal, and TLE4 a target of Notch and Wnt, physically interacting with a region on chromosome 9 associated to miscarriages.

The gut virome in two indigenous populations from Malaysia

The human gut contains a complex microbiota dominated by bacteriophages but also containing other viruses and bacteria and fungi. There are a growing number of techniques for the extraction, sequencing, and analysis of the virome but currently no standardized protocols. This study established an effective workflow for virome analysis to investigate the virome of stool samples from two understudied ethnic groups from Malaysia: the Jakun and Jehai Orang Asli. By using the virome extraction and analysis workflow with the Oxford Nanopore Technology, long-read sequencing successfully captured close to full-length viral genomes. The virome composition of the two indigenous Malaysian communities were remarkably different from those found in other parts of the world. Additionally, plant viruses found in the viromes of these individuals were attributed to traditional food-seeking methods. This study establishes a human gut virome workflow and extends insights into the healthy human gut virome, laying the groundwork for comparative studies.

Prioritising positively selected variants in whole-genome sequencing data using FineMAV

Background

In population genomics, polymorphisms that are highly differentiated between geographically separated populations are often suggestive of Darwinian positive selection. Genomic scans have highlighted several such regions in African and non-African populations, but only a handful of these have functional data that clearly associates candidate variations driving the selection process. Fine-Mapping of Adaptive Variation (FineMAV) was developed to address this in a high-throughput manner using population based whole-genome sequences generated by the 1000 Genomes Project. It pinpoints positively selected genetic variants in sequencing data by prioritizing high frequency, population-specific and functional derived alleles.

Results

We developed a stand-alone software that implements the FineMAV statistic. To graphically visualise the FineMAV scores, it outputs the statistics as bigWig files, which is a common file format supported by many genome browsers. It is available as a command-line and graphical user interface. The software was tested by replicating the FineMAV scores obtained using 1000 Genomes Project African, European, East and South Asian populations and subsequently applied to whole-genome sequencing datasets from Singapore and China to highlight population specific variants that can be subsequently modelled. The software tool is publicly available at https://github.com/fadilla-wahyudi/finemav.

Conclusions

The software tool described here determines genome-wide FineMAV scores, using low or high-coverage whole-genome sequencing datasets, that can be used to prioritize a list of population specific, highly differentiated candidate variants for in vitro or in vivo functional screens. The tool displays these scores on the human genome browsers for easy visualisation, annotation and comparison between different genomic regions in worldwide human populations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04506-9.

A Positively Selected MAGEE2 LoF Allele Is Associated with Sexual Dimorphism in Human Brain Size and Shows Similar Phenotypes in Magee2 Null Mice

A nonsense allele at rs1343879 in human MAGEE2 on chromosome X has previously been reported as a strong candidate for positive selection in East Asia. This premature stop codon causing ∼80% protein truncation is characterized by a striking geographical pattern of high population differentiation: common in Asia and the Americas (up to 84% in the 1000 Genomes Project East Asians) but rare elsewhere. Here, we generated a Magee2 mouse knockout mimicking the human loss-of-function mutation to study its functional consequences. The Magee2 null mice did not exhibit gross abnormalities apart from enlarged brain structures (13% increased total brain area, P = 0.0022) in hemizygous males. The area of the granular retrosplenial cortex responsible for memory, navigation, and spatial information processing was the most severely affected, exhibiting an enlargement of 34% (P = 3.4×10-6). The brain size in homozygous females showed the opposite trend of reduced brain size, although this did not reach statistical significance. With these insights, we performed human association analyses between brain size measurements and rs1343879 genotypes in 141 Chinese volunteers with brain MRI scans, replicating the sexual dimorphism seen in the knockout mouse model. The derived stop gain allele was significantly associated with a larger volume of gray matter in males (P = 0.00094), and smaller volumes of gray (P = 0.00021) and white (P = 0.0015) matter in females. It is unclear whether or not the observed neuroanatomical phenotypes affect behavior or cognition, but it might have been the driving force underlying the positive selection in humans.

Geographical separation and ethnic origin influence the human gut microbial composition: a meta-analysis from a Malaysian perspective

Ethnicity is consistently reported as a strong determinant of human gut microbiota. However, the bulk of these studies are from Western countries, where microbiota variations are mainly driven by relatively recent migration events. Malaysia is a multicultural society, but differences in gut microbiota persist across ethnicities. We hypothesized that migrant ethnic groups continue to share fundamental gut traits with the population in the country of origin due to shared cultural practices despite subsequent geographical separation. To test this hypothesis, the 16S rRNA gene amplicons from 16 studies comprising three major ethnic groups in Malaysia were analysed, covering 636 Chinese, 248 Indian and 123 Malay individuals from four countries (China, India, Indonesia and Malaysia). A confounder-adjusted permutational multivariate analysis of variance (PERMANOVA) detected a significant association between ethnicity and the gut microbiota (PERMANOVA R2=0.005, pseudo-F=2.643, P=0.001). A sparse partial least squares - discriminant analysis model trained using the gut microbiota of individuals from China, India and Indonesia (representation of Chinese, Indian and Malay ethnic group, respectively) showed a better-than-random performance in classifying Malaysian of Chinese descent, although the performance for Indian and Malay were modest (true prediction rate, Chinese=0.60, Indian=0.49, Malay=0.44). Separately, differential abundance analysis singled out Ligilactobacillus as being elevated in Indians. We postulate that despite the strong influence of geographical factors on the gut microbiota, cultural similarity due to a shared ethnic origin drives the presence of a shared gut microbiota composition. The interplay of these factors will likely depend on the circumstances of particular groups of migrants.

Investigation of culturable human gut mycobiota from the segamat community in Johor, Malaysia

Although several studies have already been carried out in investigating the general profile of the gut mycobiome across several countries, there has yet to be an officially established baseline of a healthy human gut mycobiome, to the best of our knowledge. Microbial composition within the gastrointestinal tract differ across individuals worldwide, and most human gut fungi studies concentrate specifically on individuals from developed countries or diseased cohorts. The present study is the first culture-dependent community study assessing the prevalence and diversity of gut fungi among different ethnic groups from South East Asia. Samples were obtained from a multi-ethnic semi-rural community from Segamat in southern Malaysia. Faecal samples were screened for culturable fungi and questionnaire data analysis was performed. Culturable fungi were present in 45% of the participants' stool samples. Ethnicity had an impact on fungal prevalence and density in stool samples. The prevalence of resistance to fluconazole, itraconazole, voriconazole and 5-fluorocytosine, from the Segamat community, were 14%, 14%, 11% and 7% respectively. It was found that Jakun individuals had lower levels of antifungal resistance irrespective of the drug tested, and male participants had more fluconazole resistant yeast in their stool samples. Two novel point mutations were identified in the ERG11 gene from one azole resistant Candida glabrata, suggesting a possible cause of the occurrence of antifungal resistant isolates in the participant's faecal sample.

Monitoring of heavy metal pollution in urban and rural environments across Pakistan using House crows (Corvus splendens) as bioindicator

A widely distributed urban bird, the house crow (Corvus splendens), was used to assess bioavailable heavy metals in urban and rural environments across Pakistan. Bioaccumulation of arsenic (As), zinc (Zn), lead (Pb), cadmium (Cd), nickel (Ni), iron (Fe), manganese (Mn), chromium (Cr), and copper (Cu) was investigated in wing feathers of 96 crows collected from eight locations and categorized into four groups pertaining to their geographical and environmental similarities. Results revealed that the concentrations of Pb, Ni, Mn, Cu, and Cr were positively correlated and varied significantly among the four groups. Zn, Fe, Cr, and Cu regarded as industrial outputs, were observed in birds both in industrialized cities and in adjoining rural agricultural areas irrigated through the Indus Basin Irrigation System. Birds in both urban regions accrued Pb more than the metal toxicity thresholds for birds. The house crow was ranked in the middle on the metal accumulation levels in feathers between highly accumulating raptor and piscivore and less contaminated insectivore and granivore species in the studied areas,. This study suggests that the house crow is an efficient bioindicator and supports the feasibility of using feathers to discriminate the local pollution differences among terrestrial environments having different levels and kinds of anthropogenic activities.

Characterization of multidrug-resistant Acinetobacter baumannii strain ATCC BAA1605 using whole-genome sequencing

Objective

The nosocomial pathogen, Acinetobacter baumannii, has acquired clinical significance due to its ability to persist in hospital settings and survive antibiotic treatment, which eventually resulted in the rapid spread of this bacterium with antimicrobial resistance (AMR) phenotypes. This study used a multidrug-resistant A. baumannii (strain ATCC BAA1605) as a model to study the genomic features of this pathogen.

Results

One circular chromosome and one circular plasmid were discovered in the complete genome of A. baumannii ATCC BAA1605 using whole-genome sequencing. The chromosome is 4,039,171 bp long with a GC content of 39.24%. Many AMR genes, which confer resistance to major classes of antibiotics (beta-lactams, aminoglycosides, tetracycline, sulphonamides), were found on the chromosome. Two genomic islands were predicted on the chromosome, one of which (Genomic Island 1) contains a cluster of AMR genes and mobile elements, suggesting the possibility of horizontal gene transfer. A subtype I-F CRISPR-Cas system was also identified on the chromosome of A. baumannii ATCC BAA1605.

This study provides valuable genome data that can be used as a reference for future studies on A. baumannii. The genome of A. baumannii ATCC BAA1605 has been deposited at GenBank under accession no. CP058625 and CP058626.

Transcriptome analysis of Escherichia coli K1 after therapy with hesperidin conjugated with silver nanoparticles

Backgrounds

Escherichia coli K1 causes neonatal meningitis. Transcriptome studies are indispensable to comprehend the pathology and biology of these bacteria. Recently, we showed that nanoparticles loaded with Hesperidin are potential novel antibacterial agents against E. coli K1. Here, bacteria were treated with and without Hesperidin conjugated with silver nanoparticles, and silver alone, and 50% minimum inhibitory concentration was determined. Differential gene expression analysis using RNA-seq, was performed using Degust software and a set of genes involved in cell stress response and metabolism were selected for the study.

Results

50% minimum inhibitory concentration with silver-conjugated Hesperidin was achieved with 0.5 μg/ml of Hesperidin conjugated with silver nanoparticles at 1 h. Differential genetic analysis revealed the expression of 122 genes (≥ 2-log FC, P< 0.01) in both E. coli K1 treated with Hesperidin conjugated silver nanoparticles and E. coli K1 treated with silver alone, compared to untreated E. coli K1. Of note, the expression levels of cation efflux genes (cusA and copA) and translocation of ions, across the membrane genes (rsxB) were found to increase 2.6, 3.1, and 3.3- log FC, respectively. Significant regulation was observed for metabolic genes and several genes involved in the coordination of flagella.

Conclusions

The antibacterial mechanism of nanoparticles maybe due to disruption of the cell membrane, oxidative stress, and metabolism in E. coli K1. Further studies will lead to a better understanding of the genetic mechanisms underlying treatment with nanoparticles and identification of much needed novel antimicrobial drug candidates.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02097-2.

Mitochondrial DNA Profiling Reveals Two Lineages of Sun Bears in East and West Malaysia

Sun bear populations are fragmented and at risk from habitat loss and exploitation for body parts. These threats are made worse by significant gaps in knowledge of sun bear population genetic diversity, population connectivity, and taxonomically significant management units. Using a complete sun bear mitochondrial genome, we developed a set of mitochondrial markers to assess haplotype variation and the evolutionary history of sun bears from Peninsular (West) Malaysia and Sabah (East Malaysia). Genetic samples from 28 sun bears from Peninsular Malaysia, 36 from Sabah, and 18 from Thailand were amplified with primers targeting a 1800 bp region of the mitochondrial genome including the complete mitochondrial control region and adjacent genes. Sequences were analyzed using phylogenetic methods. We identified 51 mitochondrial haplotypes among 82 sun bears. Phylogenetic and network analyses provided strong support for a deep split between Malaysian sun bears and sun bears in East Thailand and Yunnan province in China. The Malaysian lineage was further subdivided into two clades: Peninsular Malaysian and Malaysian Borneo (Sabah). Sun bears from Thailand occurred in both Sabah and Peninsular Malaysian clades. Our study supports recent findings that sun bears from Sundaland form a distinct clade from those in China and Indochina with Thailand possessing lineages from the three clades. Importantly, we demonstrate a more recent and clear genetic delineation between sun bears from the Malay Peninsula and Sabah indicating historical barriers to gene flow within the Sundaic region.

Genomic characterization of Vibrio parahaemolyticus from Pacific white shrimp and rearing water in Malaysia reveals novel sequence types and structural variation in genomic regions containing the Photorhabdus insect-related (Pir) toxin-like genes

The Malaysian and global shrimp aquaculture production has been significantly impacted by acute hepatopancreatic necrosis disease (AHPND) typically caused by Vibrio parahaemolyticus harboring the pVA plasmid containing the pirAVp and pirBVp genes, which code for Photorhabdus insect-related (Pir) toxin. The limited genomic resource for V. parahaemolyticus strains from Malaysian aquaculture farms precludes an in-depth understanding of their diversity and evolutionary relationships. In this study, we isolated shrimp-associated and environmental (rearing water) V. parahaemolyticus from three aquaculture farms located in Northern and Central Malaysia followed by whole-genome sequencing of 40 randomly selected isolates on the Illumina MiSeq. Phylogenomic analysis and multilocus sequence typing (MLST) reveal distinct lineages of V. parahaemolyticus that harbor the pirABVp genes. The recovery of pVA plasmid backbone devoid of pirAVp or pirABVp in some V. parahaemolyticus isolates suggests that the toxin genes are prone to deletion. The new insight gained from phylogenomic analysis of Asian V. parahaemolyticus, in addition to the observed genomic instability of pVa plasmid, will have implications for improvements in aquaculture practices to diagnose, treat or limit the impacts of this disease.

Naegleria fowleri: differential genetic expression following treatment with Hesperidin conjugated with silver nanoparticles using RNA-Seq

Naegleria fowleri causes a deadly infection known as primary amoebic meningoencephalitis (PAM). To our knowledge, there are very few transcriptome studies conducted on these brain-eating amoebae, despite rise in the number of cases. Although the Naegleria genome has been sequenced, currently, it is not well annotated. Transcriptome level studies are needed to help understand the pathology and biology of this fatal parasitic infection. Recently, we showed that nanoparticles loaded with the flavonoid Hesperidin (HDN) are potential novel antimicrobial agents. N. fowleri trophozoites were treated with and without HDN-conjugated with silver nanoparticles (AgNPs) and silver only, and then, 50% minimum inhibitory concentration (MIC) was determined. The results revealed that the MIC of HDN-conjugated AgNPs was 12.5 microg/mL when treated for 3 h. As no reference genome exists for N. fowleri, de novo RNA transcriptome analysis using RNA-Seq and differential gene expression analysis was performed using the Trinity software. Analysis revealed that more than 2000 genes were differentially expressed in response to N. fowleri treatment with HDN-conjugated AgNPs. Some of the genes were linked to oxidative stress response, DNA repair, cell division, cell signalling and protein synthesis. The downregulated genes were linked with processes such as protein modification, synthesis of aromatic amino acids, when compared with untreated N. fowleri. Further transcriptome studies will lead to understanding of genetic mechanisms of the biology and pathogenesis and/or the identification of much needed drug candidates.

Insights into human genetic variation and population history from 929 diverse genomes

Genome sequences from diverse human groups are needed to understand the structure of genetic variation in our species and the history of, and relationships between, different populations. We present 929 high-coverage genome sequences from 54 diverse human populations, 26 of which are physically phased using linked-read sequencing. Analyses of these genomes reveal an excess of previously undocumented common genetic variation private to southern Africa, central Africa, Oceania, and the Americas, but an absence of such variants fixed between major geographical regions. We also find deep and gradual population separations within Africa, contrasting population size histories between hunter-gatherer and agriculturalist groups in the past 10,000 years, and a contrast between single Neanderthal but multiple Denisovan source populations contributing to present-day human populations.

Selected neuropeptide genes show genetic differentiation between Africans and non-Africans

Background

Publicly available genome data provides valuable information on the genetic variation patterns across different modern human populations. Neuropeptide genes are crucial to the nervous, immune, endocrine system, and physiological homeostasis as they play an essential role in communicating information in neuronal functions. It remains unclear how evolutionary forces, such as natural selection and random genetic drift, have affected neuropeptide genes among human populations. To date, there are over 100 known human neuropeptides from the over 1000 predicted peptides encoded in the genome. The purpose of this study is to analyze and explore the genetic variation in continental human populations across all known neuropeptide genes by examining highly differentiated SNPs between African and non-African populations.

Results

We identified a total of 644,225 SNPs in 131 neuropeptide genes in 6 worldwide population groups from a public database. Of these, 5163 SNPs that had ΔDAF |(African - non-African)| ≥ 0.20 were identified and fully annotated. A total of 20 outlier SNPs that included 19 missense SNPs with a moderate impact and one stop lost SNP with high impact, were identified in 16 neuropeptide genes. Our results indicate that an overall strong population differentiation was observed in the non-African populations that had a higher derived allele frequency for 15/20 of those SNPs. Highly differentiated SNPs in four genes were particularly striking: NPPA (rs5065) with high impact stop lost variant; CHGB (rs6085324, rs236150, rs236152, rs742710 and rs742711) with multiple moderate impact missense variants; IGF2 (rs10770125) and INS (rs3842753) with moderate impact missense variants that are in linkage disequilibrium. Phenotype and disease associations of these differentiated SNPs indicated their association with hypertension and diabetes and highlighted the pleiotropic effects of these neuropeptides and their role in maintaining physiological homeostasis in humans.

Conclusions

We compiled a list of 131 human neuropeptide genes from multiple databases and literature survey. We detect significant population differentiation in the derived allele frequencies of variants in several neuropeptide genes in African and non-African populations. The results highlights SNPs in these genes that may also contribute to population disparities in prevalence of diseases such as hypertension and diabetes.

Cytosine methylation of rice mitochondrial DNA from grain and leaf tissues

The rice leaf mitochondrial DNA is  more methylated compared to the rice grain mitochondrial DNA. The old rice leaf mitochondrial DNA has also a higher methylation level than the young rice leaf mitochondrial DNA. The presence of DNA methylation in rice organelles has not been well characterized. We have previously shown that cytosine methylation of chloroplast DNA is different between leaf and grain, and varies between young and old leaves in rice. However, the variation in cytosine methylation of mitochondrial DNA is still poorly characterized. In this study, we have investigated cytosine methylation of mitochondrial DNA in the rice grain and leaf. Based on CpG, CHG, and CHH methylation analyses, the leaf mitochondrial DNA was found to be  more methylated compared to the grain mitochondrial DNA. The methylation of the leaf mitochondrial DNA was also higher in old compared to young leaves. Differences in methylation were observed at different cytosine positions of the mitochondrial DNA between grain and leaf, although there were also positions with a similar level of high methylation in all the tissues examined. The differentially methylated cytosine positions in rice mitochondrial DNA were observed mostly in the intergenic region and in some mitochondrial-specific genes involved in ATP production, transcription, and translation. The functional importance of cytosine methylation in the life cycle of rice mitochondria is still to be determined.

Sequence and phylogeny of the complete mitochondrial genome of the Himalayan jungle crow (Corvidae: Corvus macrorhynchos intermedius) from Pakistan

Corvus macrorhynchos formerly referred to as the jungle crow or the large-billed crow is a polytypic species with unresolved taxonomy, comprising various subspecies widespread across South, Southeast, and East Asia. In this study, we report the complete mitogenome of one of these subspecies, Corvus macrorhynchos intermedius (Himalaya crow), from Pakistan. The mitochondrial genome is circular, 16,927 bp and contains typical animal mitochondrial genes (13 protein-coding genes, 2 ribosomal RNA, and 22 transfer RNA) and one non-coding region (D-loop) with a nucleotide content of A (30.6%), T (24.8%), G (14.8%), and C (29.8%). Phylogenetic analysis using the whole mitochondrial genome showed that C. m. intermedius and only reported subspecies Corvus macrorhynchos culminatus (Indian Jungle crow) are genetically distinct and it supports the recognition of the latter as a separate biospecies.

Evolutionary and functional analysis of RBMY1 gene copy number variation on the human Y chromosome

Human RBMY1 genes are located in four variable-sized clusters on the Y chromosome, expressed in male germ cells and possibly associated with sperm motility. We have re-investigated the mutational background and evolutionary history of the RBMY1 copy number distribution in worldwide samples and its relevance to sperm parameters in an Estonian cohort of idiopathic male factor infertility subjects. We estimated approximate RBMY1 copy numbers in 1218 1000 Genomes Project phase 3 males from sequencing read-depth, then chose 14 for valid ation by multicolour fibre-FISH. These fibre-FISH samples provided accurate calibration standards for the entire panel and led to detailed insights into population variation and mutational mechanisms. RBMY1 copy number worldwide ranged from 3 to 13 with a mode of 8. The two larger proximal clusters were the most variable, and additional duplications, deletions and inversions were detected. Placing the copy number estimates onto the published Y-SNP-based phylogeny of the same samples suggested a minimum of 562 mutational changes, translating to a mutation rate of 2.20 × 10-3 (95% CI 1.94 × 10-3 to 2.48 × 10-3) per father-to-son Y-transmission, higher than many short tandem repeat (Y-STRs), and showed no evidence for selection for increased or decreased copy number, but possible copy number stabilizing selection. An analysis of RBMY1 copy numbers among 376 infertility subjects failed to replicate a previously reported association with sperm motility and showed no significant effect on sperm count and concentration, serum follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone levels or testicular and semen volume. These results provide the first in-depth insights into the structural rearrangements underlying RBMY1 copy number variation across diverse human lineages.

Comparative sequence and methylation analysis of chloroplast and amyloplast genomes from rice

Grain amyloplast and leaf chloroplast DNA sequences are identical in rice plants but are differentially methylated. The leaf chloroplast DNA becomes more methylated as the rice plant ages. Rice is an important crop worldwide. Chloroplasts and amyloplasts are critical organelles but the amyloplast genome is poorly studied. We have characterised the sequence and methylation of grain amyloplast DNA and leaf chloroplast DNA in rice. We have also analysed the changes in methylation patterns in the chloroplast DNA as the rice plant ages. Total genomic DNA from grain, old leaf and young leaf tissues were extracted from the Oryza sativa ssp. indica cv. MR219 and sequenced using Illumina Miseq. Sequence variant analysis revealed that the amyloplast and chloroplast DNA of MR219 were identical to each other. However, comparison of CpG and CHG methylation between the identical amyloplast and chloroplast DNA sequences indicated that the chloroplast DNA from rice leaves collected at early ripening stage was more methylated than the amyloplast DNA from the grains of the same plant. The chloroplast DNA became more methylated as the plant ages so that chloroplast DNA from young leaves was less methylated overall than amyloplast DNA. These differential methylation patterns were primarily observed in organelle-encoded genes related to photosynthesis followed by those involved in transcription and translation.

Y Chromosome Sequences Reveal a Short Beringian Standstill, Rapid Expansion, and early Population structure of Native American Founders

The Americas were the last inhabitable continents to be occupied by humans, with a growing multidisciplinary consensus for entry 15-25 thousand years ago (kya) from northeast Asia via the former Beringia land bridge [1-4]. Autosomal DNA analyses have dated the separation of Native American ancestors from the Asian gene pool to 23 kya or later [5, 6] and mtDNA analyses to ∼25 kya [7], followed by isolation ("Beringian Standstill" [8, 9]) for 2.4-9 ky and then a rapid expansion throughout the Americas. Here, we present a calibrated sequence-based analysis of 222 Native American and relevant Eurasian Y chromosomes (24 new) from haplogroups Q and C [10], with four major conclusions. First, we identify three to four independent lineages as autochthonous and likely founders: the major Q-M3 and rarer Q-CTS1780 present throughout the Americas, the very rare C3-MPB373 in South America, and possibly the C3-P39/Z30536 in North America. Second, from the divergence times and Eurasian/American distribution of lineages, we estimate a Beringian Standstill duration of 2.7 ky or 4.6 ky, according to alternative models, and entry south of the ice sheet after 19.5 kya. Third, we describe the star-like expansion of Q-M848 (within Q-M3) starting at 15 kya [11] in the Americas, followed by establishment of substantial spatial structure in South America by 12 kya. Fourth, the deep branches of the Q-CTS1780 lineage present at low frequencies throughout the Americas today [12] may reflect a separate out-of-Beringia dispersal after the melting of the glaciers at the end of the Pleistocene.

Demographic History and Genetic Adaptation in the Himalayan Region Inferred from Genome-Wide SNP Genotypes of 49 Populations

We genotyped 738 individuals belonging to 49 populations from Nepal, Bhutan, North India, or Tibet at over 500,000 SNPs, and analyzed the genotypes in the context of available worldwide population data in order to investigate the demographic history of the region and the genetic adaptations to the harsh environment. The Himalayan populations resembled other South and East Asians, but in addition displayed their own specific ancestral component and showed strong population structure and genetic drift. We also found evidence for multiple admixture events involving Himalayan populations and South/East Asians between 200 and 2,000 years ago. In comparisons with available ancient genomes, the Himalayans, like other East and South Asian populations, showed similar genetic affinity to Eurasian hunter-gatherers (a 24,000-year-old Upper Palaeolithic Siberian), and the related Bronze Age Yamnaya. The high-altitude Himalayan populations all shared a specific ancestral component, suggesting that genetic adaptation to life at high altitude originated only once in this region and subsequently spread. Combining four approaches to identifying specific positively selected loci, we confirmed that the strongest signals of high-altitude adaptation were located near the Endothelial PAS domain-containing protein 1 and Egl-9 Family Hypoxia Inducible Factor 1 loci, and discovered eight additional robust signals of high-altitude adaptation, five of which have strong biological functional links to such adaptation. In conclusion, the demographic history of Himalayan populations is complex, with strong local differentiation, reflecting both genetic and cultural factors; these populations also display evidence of multiple genetic adaptations to high-altitude environments.

FineMAV: prioritizing candidate genetic variants driving local adaptations in human populations

We present a new method, Fine-Mapping of Adaptive Variation (FineMAV), which combines population differentiation, derived allele frequency, and molecular functionality to prioritize positively selected candidate variants for functional follow-up. We calibrate and test FineMAV using eight experimentally validated "gold standard" positively selected variants and simulations. FineMAV has good sensitivity and a low false discovery rate. Applying FineMAV to the 1000 Genomes Project Phase 3 SNP dataset, we report many novel selected variants, including ones in TGM3 and PRSS53 associated with hair phenotypes that we validate using available independent data. FineMAV is widely applicable to sequence data from both human and other species.

The Genetic Legacy of the Indian Ocean Slave Trade: Recent Admixture and Post-admixture Selection in the Makranis of Pakistan

From the eighth century onward, the Indian Ocean was the scene of extensive trade of sub-Saharan African slaves via sea routes controlled by Muslim Arab and Swahili traders. Several populations in present-day Pakistan and India are thought to be the descendants of such slaves, yet their history of admixture and natural selection remains largely undefined. Here, we studied the genome-wide diversity of the African-descent Makranis, who reside on the Arabian Sea coast of Pakistan, as well that of four neighboring Pakistani populations, to investigate the genetic legacy, population dynamics, and tempo of the Indian Ocean slave trade. We show that the Makranis are the result of an admixture event between local Baluch tribes and Bantu-speaking populations from eastern or southeastern Africa; we dated this event to ∼300 years ago during the Omani Empire domination. Levels of parental relatedness, measured through runs of homozygosity, were found to be similar across Pakistani populations, suggesting that the Makranis rapidly adopted the traditional practice of endogamous marriages. Finally, we searched for signatures of post-admixture selection at traits evolving under positive selection, including skin color, lactase persistence, and resistance to malaria. We demonstrate that the African-specific Duffy-null blood group-believed to confer resistance against Plasmodium vivax infection-was recently introduced to Pakistan through the slave trade and evolved adaptively in this P. vivax malaria-endemic region. Our study reconstructs the genetic and adaptive history of a neglected episode of the African Diaspora and illustrates the impact of recent admixture on the diffusion of adaptive traits across human populations.

Copy number variation arising from gene conversion on the human Y chromosome

We describe the variation in copy number of a ~ 10 kb region overlapping the long intergenic noncoding RNA (lincRNA) gene, TTTY22, within the IR3 inverted repeat on the short arm of the human Y chromosome, leading to individuals with 0-3 copies of this region in the general population. Variation of this CNV is common, with 266 individuals having 0 copies, 943 (including the reference sequence) having 1, 23 having 2 copies, and two having 3 copies, and was validated by breakpoint PCR, fibre-FISH, and 10× Genomics Chromium linked-read sequencing in subsets of 1234 individuals from the 1000 Genomes Project. Mapping the changes in copy number to the phylogeny of these Y chromosomes previously established by the Project identified at least 20 mutational events, and investigation of flanking paralogous sequence variants showed that the mutations involved flanking sequences in 18 of these, and could extend over > 30 kb of DNA. While either gene conversion or double crossover between misaligned sister chromatids could formally explain the 0-2 copy events, gene conversion is the more likely mechanism, and these events include the longest non-allelic gene conversion reported thus far. Chromosomes with three copies of this CNV have arisen just once in our data set via another mechanism: duplication of 420 kb that places the third copy 230 kb proximal to the existing proximal copy. Our results establish gene conversion as a previously under-appreciated mechanism of generating copy number changes in humans and reveal the exceptionally large size of the conversion events that can occur.

"Like sugar in milk": reconstructing the genetic history of the Parsi population

BACKGROUND

The Parsis are one of the smallest religious communities in the world. To understand the population structure and demographic history of this group in detail, we analyzed Indian and Pakistani Parsi populations using high-resolution genetic variation data on autosomal and uniparental loci (Y-chromosomal and mitochondrial DNA). Additionally, we also assayed mitochondrial DNA polymorphisms among ancient Parsi DNA samples excavated from Sanjan, in present day Gujarat, the place of their original settlement in India.

RESULTS

Among present-day populations, the Parsis are genetically closest to Iranian and the Caucasus populations rather than their South Asian neighbors. They also share the highest number of haplotypes with present-day Iranians and we estimate that the admixture of the Parsis with Indian populations occurred ~1,200 years ago. Enriched homozygosity in the Parsi reflects their recent isolation and inbreeding. We also observed 48% South-Asian-specific mitochondrial lineages among the ancient samples, which might have resulted from the assimilation of local females during the initial settlement. Finally, we show that Parsis are genetically closer to Neolithic Iranians than to modern Iranians, who have witnessed a more recent wave of admixture from the Near East.

CONCLUSIONS

Our results are consistent with the historically-recorded migration of the Parsi populations to South Asia in the 7th century and in agreement with their assimilation into the Indian sub-continent's population and cultural milieu "like sugar in milk". Moreover, in a wider context our results support a major demographic transition in West Asia due to the Islamic conquest.

An Ethnolinguistic and Genetic Perspective on the Origins of the Dravidian-Speaking Brahui in Pakistan

Pakistan is a part of South Asia that modern humans encountered soon after they left Africa ~50 - 70,000 years ago. Approximately 9,000 years ago they began establishing cities that eventually expanded to represent the Harappan culture, rivalling the early city states of Mesopotamia. The modern state constitutes the north western land mass of the Indian sub-continent and is now the abode of almost 200 million humans representing many ethnicities and linguistic groups. Studies utilising autosomal, Y chromosomal and mitochondrial DNA markers in selected Pakistani populations revealed a mixture of Western Eurasian-, South- and East Asian-specific lineages, some of which were unequivocally associated with past migrations. Overall in Pakistan, genetic relationships are generally predicted more accurately by geographic proximity than linguistic origin. The Dravidian-speaking Brahui population are a prime example of this. They currently reside in south-western Pakistan, surrounded by Indo-Europeans speakers with whom they share a common genetic origin. In contrast, the Hazara share the highest affinity with East Asians, despite their Indo-European linguistic affiliation. In this report we reexamine the genetic origins of the Brahuis, and compare them with diverse populations from India, including several Dravidian-speaking groups, and present a genetic perspective on ethnolinguistic groups in present-day Pakistan. Given the high affinity of Brahui to the other Indo-European Pakistani populations and the absence of population admixture with any of the examined Indian Dravidian groups, we conclude that Brahui are an example of cultural (linguistic) retention following a major population replacement.

Deep Roots for Aboriginal Australian Y Chromosomes

Australia was one of the earliest regions outside Africa to be colonized by fully modern humans, with archaeological evidence for human presence by 47,000 years ago (47 kya) widely accepted [1, 2]. However, the extent of subsequent human entry before the European colonial age is less clear. The dingo reached Australia about 4 kya, indirectly implying human contact, which some have linked to changes in language and stone tool technology to suggest substantial cultural changes at the same time [3]. Genetic data of two kinds have been proposed to support gene flow from the Indian subcontinent to Australia at this time, as well: first, signs of South Asian admixture in Aboriginal Australian genomes have been reported on the basis of genome-wide SNP data [4]; and second, a Y chromosome lineage designated haplogroup C^∗, present in both India and Australia, was estimated to have a most recent common ancestor around 5 kya and to have entered Australia from India [5]. Here, we sequence 13 Aboriginal Australian Y chromosomes to re-investigate their divergence times from Y chromosomes in other continents, including a comparison of Aboriginal Australian and South Asian haplogroup C chromosomes. We find divergence times dating back to ∼50 kya, thus excluding the Y chromosome as providing evidence for recent gene flow from India into Australia.

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We have sequenced 13 Aboriginal Australian Y chromosomes

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These diverged from Y chromosomes in other continents around 50,000 years ago

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They diverged from Papua New Guinean Y chromosomes soon after this

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We find no evidence for Holocene male gene flow to Australia from South Asia

Wide distribution and altitude correlation of an archaic high-altitude-adaptive EPAS1 haplotype in the Himalayas

High-altitude adaptation in Tibetans is influenced by introgression of a 32.7-kb haplotype from the Denisovans, an extinct branch of archaic humans, lying within the endothelial PAS domain protein 1 (EPAS1), and has also been reported in Sherpa. We genotyped 19 variants in this genomic region in 1507 Eurasian individuals, including 1188 from Bhutan and Nepal residing at altitudes between 86 and 4550 m above sea level. Derived alleles for five SNPs characterizing the core Denisovan haplotype (AGGAA) were present at high frequency not only in Tibetans and Sherpa, but also among many populations from the Himalayas, showing a significant correlation with altitude (Spearman’s correlation coefficient = 0.75, p value 3.9 × 10⁻¹¹). Seven East- and South-Asian 1000 Genomes Project individuals shared the Denisovan haplotype extending beyond the 32-kb region, enabling us to refine the haplotype structure and identify a candidate regulatory variant (rs370299814) that might be interacting in an additive manner with the derived G allele of rs150877473, the variant previously associated with high-altitude adaptation in Tibetans. Denisovan-derived alleles were also observed at frequencies of 3–14 % in the 1000 Genomes Project African samples. The closest African haplotype is, however, separated from the Asian high-altitude haplotype by 22 mutations whereas only three mutations, including rs150877473, separate the Asians from the Denisovan, consistent with distant shared ancestry for African and Asian haplotypes and Denisovan adaptive introgression.

Genes Regulated by Vitamin D in Bone Cells Are Positively Selected in East Asians

Vitamin D and folate are activated and degraded by sunlight, respectively, and the physiological processes they control are likely to have been targets of selection as humans expanded from Africa into Eurasia. We investigated signals of positive selection in gene sets involved in the metabolism, regulation and action of these two vitamins in worldwide populations sequenced by Phase I of the 1000 Genomes Project. Comparing allele frequency-spectrum-based summary statistics between these gene sets and matched control genes, we observed a selection signal specific to East Asians for a gene set associated with vitamin D action in bones. The selection signal was mainly driven by three genes CXXC finger protein 1 (CXXC1), low density lipoprotein receptor-related protein 5 (LRP5) and runt-related transcription factor 2 (RUNX2). Examination of population differentiation and haplotypes allowed us to identify several candidate causal regulatory variants in each gene. Four of these candidate variants (one each in CXXC1 and RUNX2 and two in LRP5) had a >70% derived allele frequency in East Asians, but were present at lower (20-60%) frequency in Europeans as well, suggesting that the adaptation might have been part of a common response to climatic and dietary changes as humans expanded out of Africa, with implications for their role in vitamin D-dependent bone mineralization and osteoporosis insurgence. We also observed haplotype sharing between East Asians, Finns and an extinct archaic human (Denisovan) sample at the CXXC1 locus, which is best explained by incomplete lineage sorting.

Monoamine Oxidase A gene polymorphisms and self reported aggressive behaviour in a Pakistani ethnic group

OBJECTIVE

To investigate the association of monoamine oxidase Agene polymorphisms with aggression.

METHODS

The study was conducted in an ethnic community in Lahore, Pakistan, from August 2008 to December 2009 on the basis of data that was collected through a questionnaire between August 2004 and September 2005. It analysed 10 single nucleotide polymorphisms of monoamine oxidase A in unrelated males from the same ethnic background who were administered a Punjabi translation of the Buss and Perry aggression questionnaire. SPSS 13 was used for statistical analysis.

RESULTS

Of the total 133 haplotypes studied, 52(39%) were Haplotype A, 58(43.6%) B, 8(6%) C, 3(2.3%) D, 9(6.8%) E and 3(2.3%) F. The six haplotypes were analysed for association with scores of the four subscales of the aggression questionnaire and multivariate analysis of variance showed no significant differences (p>0.05 each) in the error variances of the total scores and scores for three of the sub-scales across the haplotypes. The variance was significantly different only for the anger sub-scale (p<0.05).

CONCLUSIONS

The association of an extended haplotype with low levels of self-reported aggression in this study should assist in characterisation of functional variants responsible for non-aggressive behaviour in male subjects.

Structural variation on the human Y chromosome from population-scale resequencing

AIM

To investigate the information about Y-structural variants (SVs) in the general population that could be obtained by low-coverage whole-genome sequencing.

METHODS

We investigated SVs on the male-specific portion of the Y chromosome in the 70 individuals from Africa, Europe, or East Asia sequenced as part of the 1000 Genomes Pilot project, using data from this project and from additional studies on the same samples. We applied a combination of read-depth and read-pair methods to discover candidate Y-SVs, followed by validation using information from the literature, independent sequence and single nucleotide polymorphism-chip data sets, and polymerase chain reaction experiments.

RESULTS

We validated 19 Y-SVs, 2 of which were novel. Non-reference allele counts ranged from 1 to 64. The regions richest in variation were the heterochromatic segments near the centromere or the DYZ19 locus, followed by the ampliconic regions, but some Y-SVs were also present in the X-transposed and X-degenerate regions. In all, 5 of the 27 protein-coding gene families on the Y chromosome varied in copy number.

CONCLUSIONS

We confirmed that Y-SVs were readily detected from low-coverage sequence data and were abundant on the chromosome. We also reported both common and rare Y-SVs that are novel.

Copy number variation in the human Y chromosome in the UK population

We have assessed copy number variation (CNV) in the male-specific part of the human Y chromosome discovered by array comparative genomic hybridization (array-CGH) in 411 apparently healthy UK males, and validated the findings using SNP genotype intensity data available for 149 of them. After manual curation taking account of the complex duplicated structure of Y-chromosomal sequences, we discovered 22 curated CNV events considered validated or likely, mean 0.93 (range 0–4) per individual. 16 of these were novel. Curated CNV events ranged in size from <1 kb to >3 Mb, and in frequency from 1/411 to 107/411. Of the 24 protein-coding genes or gene families tested, nine showed CNV. These included a large duplication encompassing the AMELY and TBL1Y genes that probably has no phenotypic effect, partial deletions of the TSPY cluster and AZFc region that may influence spermatogenesis, and other variants with unknown functional implications, including abundant variation in the number of RBMY genes and/or pseudogenes, and a novel complex duplication of two segments overlapping the AZFa region and including the 3′ end of the UTY gene.

Mountain gorilla genomes reveal the impact of long-term population decline and inbreeding

Mountain gorillas are an endangered great ape subspecies and a prominent focus for conservation, yet we know little about their genomic diversity and evolutionary past. We sequenced whole genomes from multiple wild individuals and compared the genomes of all four Gorilla subspecies. We found that the two eastern subspecies have experienced a prolonged population decline over the past 100,000 years, resulting in very low genetic diversity and an increased overall burden of deleterious variation. A further recent decline in the mountain gorilla population has led to extensive inbreeding, such that individuals are typically homozygous at 34% of their sequence, leading to the purging of severely deleterious recessive mutations from the population. We discuss the causes of their decline and the consequences for their future survival.

A recent bottleneck of Y chromosome diversity coincides with a global change in culture

It is commonly thought that human genetic diversity in non-African populations was shaped primarily by an out-of-Africa dispersal 50–100 thousand yr ago (kya). Here, we present a study of 456 geographically diverse high-coverage Y chromosome sequences, including 299 newly reported samples. Applying ancient DNA calibration, we date the Y-chromosomal most recent common ancestor (MRCA) in Africa at 254 (95% CI 192–307) kya and detect a cluster of major non-African founder haplogroups in a narrow time interval at 47–52 kya, consistent with a rapid initial colonization model of Eurasia and Oceania after the out-of-Africa bottleneck. In contrast to demographic reconstructions based on mtDNA, we infer a second strong bottleneck in Y-chromosome lineages dating to the last 10 ky. We hypothesize that this bottleneck is caused by cultural changes affecting variance of reproductive success among males.