Overview of Genetic-epidemiological Studies in Ethnically and Demographically Diverse Isolates of Dagestan, Northern Caucasus, Russia

Aim: To assess genetic diversity and genetic distances among isolated populations from Dagestan. Methods: A cross-population genetic epidemiology design was applied in ethnically and demographically diverse isolates from Dagestan, some with more than 200 and some with less than 100 generations of demographical history since their founding. Results: The analysis of genetic diversity showed that Dagestan ethnic populations are clearly close to European ethnic populations. The genetic data support the view of them as ancient, highly isolated populations 85%-97% the rate of the endogamy and inbreeding coefficient F=0.010-0.015. Many Dagestan populations have very high prevalence of certain complex diseases such as cardiovascular illnesses, cancer, schizophrenia, mental retardation, and progressive muscular dystrophy. Lifetime morbid risk for schizophrenia in the isolates varied from 0 to 5%. Among the relatives, the number of men with chronic schizophrenia was at least twice as high as women. The average age of onset of schizophrenia was 21.2 years for offspring of consanguineous marriages and 17.4 years for offspring of non-consanguineous marriages (P=0.033). Conclusion: The results support the hypothesis that cross-population design provides unique opportunities for observing reliable ancestral haplotypes with disease predisposing loci, as well as population-specific linked loci

Culture creates genetic structure in the Caucasus: Autosomal, mitochondrial, and Y-chromosomal variation in Daghestan

<p>Abstract</p> <p>Background</p> <p>Near the junction of three major continents, the Caucasus region has been an important thoroughfare for human migration. While the Caucasus Mountains have diverted human traffic to the few lowland regions that provide a gateway from north to south between the Caspian and Black Seas, highland populations have been isolated by their remote geographic location and their practice of patrilocal endogamy. We investigate how these cultural and historical differences between highland and lowland populations have affected patterns of genetic diversity. We test 1) whether the highland practice of patrilocal endogamy has generated sex-specific population relationships, and 2) whether the history of migration and military conquest associated with the lowland populations has left Central Asian genes in the Caucasus, by comparing genetic diversity and pairwise population relationships between Daghestani populations and reference populations throughout Europe and Asia for autosomal, mitochondrial, and Y-chromosomal markers.</p> <p>Results</p> <p>We found that the highland Daghestani populations had contrasting histories for the mitochondrial DNA and Y-chromosome data sets. Y-chromosomal haplogroup diversity was reduced among highland Daghestani populations when compared to other populations and to highland Daghestani mitochondrial DNA haplogroup diversity. Lowland Daghestani populations showed Turkish and Central Asian affinities for both mitochondrial and Y-chromosomal data sets. Autosomal population histories are strongly correlated to the pattern observed for the mitochondrial DNA data set, while the correlation between the mitochondrial DNA and Y-chromosome distance matrices was weak and not significant.</p> <p>Conclusion</p> <p>The reduced Y-chromosomal diversity exhibited by highland Daghestani populations is consistent with genetic drift caused by patrilocal endogamy. Mitochondrial and Y-chromosomal phylogeographic comparisons indicate a common Near Eastern origin of highland populations. Lowland Daghestani populations show varying influence from Near Eastern and Central Asian populations.</p

High altitude adaptation in Daghestani populations from the Caucasus

We have surveyed 15 high-altitude adaptation candidate genes for signals of positive selection in North Caucasian highlanders using targeted re-sequencing. A total of 49 unrelated Daghestani from three ethnic groups (Avars, Kubachians, and Laks) living in ancient villages located at around 2,000 m above sea level were chosen as the study population. Caucasian (Adygei living at sea level, N = 20) and CEU (CEPH Utah residents with ancestry from northern and western Europe; N = 20) were used as controls. Candidate genes were compared with 20 putatively neutral control regions resequenced in the same individuals. The regions of interest were amplified by long-PCR, pooled according to individual, indexed by adding an eight-nucleotide tag, and sequenced using the Illumina GAII platform. 1,066 SNPs were called using false discovery and false negative thresholds of ~6%. The neutral regions provided an empirical null distribution to compare with the candidate genes for signals of selection. Two genes stood out. In Laks, a non-synonymous variant within HIF1A already known to be associated with improvement in oxygen metabolism was rediscovered, and in Kubachians a cluster of 13 SNPs located in a conserved intronic region within EGLN1 showing high population differentiation was found. These variants illustrate both the common pathways of adaptation to high altitude in different populations and features specific to the Daghestani populations, showing how even a mildly hypoxic environment can lead to genetic adaptation

Current commands for high-efficiency torque control of DC shunt motor

The current commands for a high-efficiency torque control of a DC shunt motor are described. In the proposed control method, the effect of a magnetic saturation and an armature reaction are taken into account by representing the coefficients of an electromotive force and a torque as a function of the field current, the armature current and the revolving speed. The current commands at which the loss of the motor drive system becomes a minimum are calculated as an optimal problem. The proposed control technique of a motor is implemented on the microprocessor-based control system. The effect of the consideration of the magnetic saturation and the armature reaction on the produced torque and the minimisation of the loss are discussed analytically and experimentally </p

Genetic architecture of subcortical brain structures in 38,851 individuals

Subcortical brain structures are integral to motion, consciousness, emotions and learning. We identified common genetic variation related to the volumes of the nucleus accumbens, amygdala, brainstem, caudate nucleus, globus pallidus, putamen and thalamus, using genome-wide association analyses in almost 40,000 individuals from CHARGE, ENIGMA and UK Biobank. We show that variability in subcortical volumes is heritable, and identify 48 significantly associated loci (40 novel at the time of analysis). Annotation of these loci by utilizing gene expression, methylation and neuropathological data identified 199 genes putatively implicated in neurodevelopment, synaptic signaling, axonal transport, apoptosis, inflammation/infection and susceptibility to neurological disorders. This set of genes is significantly enriched for Drosophila orthologs associated with neurodevelopmental phenotypes, suggesting evolutionarily conserved mechanisms. Our findings uncover novel biology and potential drug targets underlying brain development and disease

Novel genetic loci associated with hippocampal volume

The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness

Novel genetic loci underlying human intracranial volume identified through genome-wide association

Intracranial volume reflects the maximally attained brain size during development, and remains stable with loss of tissue in late life. It is highly heritable, but the underlying genes remain largely undetermined. In a genome-wide association study of 32,438 adults, we discovered five novel loci for intracranial volume and confirmed two known signals. Four of the loci are also associated with adult human stature, but these remained associated with intracranial volume after adjusting for height. We found a high genetic correlation with child head circumference (ρgenetic=0.748), which indicated a similar genetic background and allowed for the identification of four additional loci through meta-analysis (Ncombined = 37,345). Variants for intracranial volume were also related to childhood and adult cognitive function, Parkinson’s disease, and enriched near genes involved in growth pathways including PI3K–AKT signaling. These findings identify biological underpinnings of intracranial volume and provide genetic support for theories on brain reserve and brain overgrowth

Overview of Genetic-epidemiological Studies in Ethnically and Demographically Diverse Isolates of Dagestan, Northern Caucasus, Russia

Aim: To assess genetic diversity and genetic distances among isolated populations from Dagestan. Methods: A cross-population genetic epidemiology design was applied in ethnically and demographically diverse isolates from Dagestan, some with more than 200 and some with less than 100 generations of demographical history since their founding. Results: The analysis of genetic diversity showed that Dagestan ethnic populations are clearly close to European ethnic populations. The genetic data support the view of them as ancient, highly isolated populations 85%-97% the rate of the endogamy and inbreeding coefficient F=0.010-0.015. Many Dagestan populations have very high prevalence of certain complex diseases such as cardiovascular illnesses, cancer, schizophrenia, mental retardation, and progressive muscular dystrophy. Lifetime morbid risk for schizophrenia in the isolates varied from 0 to 5%. Among the relatives, the number of men with chronic schizophrenia was at least twice as high as women. The average age of onset of schizophrenia was 21.2 years for offspring of consanguineous marriages and 17.4 years for offspring of non-consanguineous marriages (P=0.033). Conclusion: The results support the hypothesis that cross-population design provides unique opportunities for observing reliable ancestral haplotypes with disease predisposing loci, as well as population-specific linked loci

Mapping Genes Related to Early Onset Major Depressive Disorder in Dagestan Genetic Isolates 2) who genotyped AFFX SNP 6 in selected MDD cases

SUMMARY Aim: The purpose of this study was to determine the molecular epidemiology of early onset major depressive disorder (MDD) in genetic isolates of the Caucasus Dagestan indigenous ethnic populations using molecular and statistical population-genetic approaches. Methods: Two multigenerational pedigrees from two diverse remote highland isolates with aggregation of early onset MDD were ascertained within our long-term research program titled &apos;Dagestan Genetic Heritage, DGH&apos;. The first isolate included 48 cases of MDD (19 living) with 11 suicides committed, and the second included 60 MDD cases (30 living) with 12 suicides committed. The phenotypes of the affected family members were determined using a database containing diagnoses from a regional psychiatric hospital and through our own clinical examinations, which were based on a Russian translation of DIGS software based on the DSM-IV criteria . A 10 cM genomic scan (Weber/CHLC 9.0 STRs) of the 64 affected and non-affected members of the pedigrees was performed and the data was used for multipoint parametric linkage analyses. Following this scan, selected cases were analyzed by Affymetrix 6.0 SNP arrays in order to refine the contribution of copy number variations (CNVs) to the genetic basis of MDD. Results: We found a total of 18 genomic regions with nominal (LOD&gt;1.3) linkage to MDD across the two isolates. Three genomic regions had genome-wide significant (LOD&gt;3) linkages and were found at 2p13.2-p11.2, 14q31.12-q32.13 and 22q12.3. We also confirmed previous findings for MDD at 4q25, 11p15, 12q23-24, 13q31-32, 18q21-22 and 22q11-13. Six linkage regions were observed in both genetic isolates, while 12 other linkages demonstrated population-specific heterogeneity. We detected CNV rearrangements within 12 of the 18 linkage regions. Affected subjects had the highest rate of genomic instability within the linkage regions at 2p13.2-p11.2, 4q25-q28.2, 7p14.1, 8p23, 14q31.12-q32.13, 18q22.1 and 20p13. Conclusion: The results obtained in this study suggest that mapping genes of complex diseases, including MDD, across genetically homogeneous isolates can help detect linkage signals and expedite the search for susceptibility genes when combined with methods that detect structural genomic variation in linkage regions