The Role of Gene Duplication and Unconstrained Selective Pressures in the Melanopsin Gene Family Evolution and Vertebrate Circadian Rhythm Regulation

Melanopsin is a photosensitive cell protein involved in regulating circadian rhythms and other non-visual responses to light. The melanopsin gene family is represented by two paralogs, OPN4x and OPN4m, which originated through gene duplication early in the emergence of vertebrates. Here we studied the melanopsin gene family using an integrated gene/protein evolutionary approach, which revealed that the rhabdomeric urbilaterian ancestor had the same amino acid patterns (DRY motif and the Y and E conterions) as extant vertebrate species, suggesting that the mechanism for light detection and regulation is similar to rhabdomeric rhodopsins. Both OPN4m and OPN4x paralogs are found in vertebrate genomic paralogons, suggesting that they diverged following this duplication event about 600 million years ago, when the complex eye emerged in the vertebrate ancestor. Melanopsins generally evolved under negative selection (ω = 0.171) with some minor episodes of positive selection (proportion of sites = 25%) and functional divergence (θ_I = 0.349 and θ_II = 0.126). The OPN4m and OPN4x melanopsin paralogs show evidence of spectral divergence at sites likely involved in melanopsin light absorbance (200F, 273S and 276A). Also, following the teleost lineage-specific whole genome duplication (3R) that prompted the teleost fish radiation, type I divergence (θ_I = 0.181) and positive selection (affecting 11% of sites) contributed to amino acid variability that we related with the photo-activation stability of melanopsin. The melanopsin intracellular regions had unexpectedly high variability in their coupling specificity of G-proteins and we propose that Gq/11 and Gi/o are the two G-proteins most-likely to mediate the melanopsin phototransduction pathway. The selection signatures were mainly observed on retinal-related sites and the third and second intracellular loops, demonstrating the physiological plasticity of the melanopsin protein group. Our results provide new insights on the phototransduction process and additional tools for disentangling and understanding the links between melanopsin gene evolution and the specializations observed in vertebrates, especially in teleost fish.     

Reconstructing the Evolution of Brachypodium Genomes Using Comparative Chromosome Painting

Brachypodium distachyon is a model for the temperate cereals and grasses and has a biology, genomics infrastructure and cytogenetic platform fit for purpose. It is a member of a genus with fewer than 20 species, which have different genome sizes, basic chromosome numbers and ploidy levels. The phylogeny and interspecific relationships of this group have not to date been resolved by sequence comparisons and karyotypical studies. The aims of this study are not only to reconstruct the evolution of Brachypodium karyotypes to resolve the phylogeny, but also to highlight the mechanisms that shape the evolution of grass genomes. This was achieved through the use of comparative chromosome painting (CCP) which hybridises fluorescent, chromosome-specific probes derived from B. distachyon to homoeologous meiotic chromosomes of its close relatives. The study included five diploids (B. distachyon 2n = 10, B. sylvaticum 2n = 18, B. pinnatum 2n = 16; 2n = 18, B. arbuscula 2n = 18 and B. stacei 2n = 20) three allotetraploids (B. pinnatum 2n = 28, B. phoenicoides 2n = 28 and B. hybridum 2n = 30), and two species of unknown ploidy (B. retusum 2n = 38 and B. mexicanum 2n = 40). On the basis of the patterns of hybridisation and incorporating published data, we propose two alternative, but similar, models of karyotype evolution in the genus Brachypodium. According to the first model, the extant genome of B. distachyon derives from B. mexicanum or B. stacei by several rounds of descending dysploidy, and the other diploids evolve from B. distachyon via ascending dysploidy. The allotetraploids arise by interspecific hybridisation and chromosome doubling between B. distachyon and other diploids. The second model differs from the first insofar as it incorporates an intermediate 2n = 18 species between the B. mexicanum or B. stacei progenitors and the dysploidic B. distachyon.     

Distinct Gene Number-Genome Size Relationships for Eukaryotes and Non-Eukaryotes: Gene Content Estimation for Dinoflagellate Genomes

The ability to predict gene content is highly desirable for characterization of not-yet sequenced genomes like those of dinoflagellates. Using data from completely sequenced and annotated genomes from phylogenetically diverse lineages, we investigated the relationship between gene content and genome size using regression analyses. Distinct relationships between log₁₀-transformed protein-coding gene number (Y′) versus log₁₀-transformed genome size (X′, genome size in kbp) were found for eukaryotes and non-eukaryotes. Eukaryotes best fit a logarithmic model, Y′ = ln(-46.200+22.678X′, whereas non-eukaryotes a linear model, Y′ = 0.045+0.977X′, both with high significance (p<0.001, R²>0.91). Total gene number shows similar trends in both groups to their respective protein coding regressions. The distinct correlations reflect lower and decreasing gene-coding percentages as genome size increases in eukaryotes (82%–1%) compared to higher and relatively stable percentages in prokaryotes and viruses (97%–47%). The eukaryotic regression models project that the smallest dinoflagellate genome (3×10⁶ kbp) contains 38,188 protein-coding (40,086 total) genes and the largest (245×10⁶ kbp) 87,688 protein-coding (92,013 total) genes, corresponding to 1.8% and 0.05% gene-coding percentages. These estimates do not likely represent extraordinarily high functional diversity of the encoded proteome but rather highly redundant genomes as evidenced by high gene copy numbers documented for various dinoflagellate species.     

Genetic and Phenotypic Correlations between Performance Traits with Meat Quality and Carcass Characteristics in Commercial Crossbred Pigs

Genetic correlations between performance traits with meat quality and carcass traits were estimated on 6,408 commercial crossbred pigs with performance traits recorded in production systems with 2,100 of them having meat quality and carcass measurements. Significant fixed effects (company, sex and batch), covariates (birth weight, cold carcass weight, and age), random effects (additive, litter and maternal) were fitted in the statistical models. A series of pairwise bivariate analyses were implemented in ASREML to estimate heritability, phenotypic, and genetic correlations between performance traits (n = 9) with meat quality (n = 25) and carcass (n = 19) traits. The animals had a pedigree compromised of 9,439 animals over 15 generations. Performance traits had low-to-moderate heritabilities (±SE), ranged from 0.07±0.13 to 0.45±0.07 for weaning weight, and ultrasound backfat depth, respectively. Genetic correlations between performance and carcass traits were moderate to high. The results indicate that: (a) selection for birth weight may increase drip loss, lightness of longissimus dorsi, and gluteus medius muscles but may reduce fat depth; (b) selection for nursery weight can be valuable for increasing both quantity and quality traits; (c) selection for increased daily gain may increase the carcass weight and most of the primal cuts. These findings suggest that deterioration of pork quality may have occurred over many generations through the selection for less backfat thickness, and feed efficiency, but selection for growth had no adverse effects on pork quality. Low-to-moderate heritabilities for performance traits indicate that they could be improved using traditional selection or genomic selection. The estimated genetic parameters for performance, carcass and meat quality traits may be incorporated into the breeding programs that emphasize product quality in these Canadian swine populations.     

Male-Biased Autosomal Effect of 16p13.11 Copy Number Variation in Neurodevelopmental Disorders

Copy number variants (CNVs) at chromosome 16p13.11 have been associated with a range of neurodevelopmental disorders including autism, ADHD, intellectual disability and schizophrenia. Significant sex differences in prevalence, course and severity have been described for a number of these conditions but the biological and environmental factors underlying such sex-specific features remain unclear. We tested the burden and the possible sex-biased effect of CNVs at 16p13.11 in a sample of 10,397 individuals with a range of neurodevelopmental conditions, clinically referred for array comparative genomic hybridisation (aCGH); cases were compared with 11,277 controls. In order to identify candidate phenotype-associated genes, we performed an interval-based analysis and investigated the presence of ohnologs at 16p13.11; finally, we searched the DECIPHER database for previously identified 16p13.11 copy number variants. In the clinical referral series, we identified 46 cases with CNVs of variable size at 16p13.11, including 28 duplications and 18 deletions. Patients were referred for various phenotypes, including developmental delay, autism, speech delay, learning difficulties, behavioural problems, epilepsy, microcephaly and physical dysmorphisms. CNVs at 16p13.11 were also present in 17 controls. Association analysis revealed an excess of CNVs in cases compared with controls (OR = 2.59; p = 0.0005), and a sex-biased effect, with a significant enrichment of CNVs only in the male subgroup of cases (OR = 5.62; p = 0.0002), but not in females (OR = 1.19, p = 0.673). The same pattern of results was also observed in the DECIPHER sample. Interval-based analysis showed a significant enrichment of case CNVs containing interval II (OR = 2.59; p = 0.0005), located in the 0.83 Mb genomic region between 15.49–16.32 Mb, and encompassing the four ohnologs NDE1, MYH11, ABCC1 and ABCC6. Our data confirm that duplications and deletions at 16p13.11 represent incompletely penetrant pathogenic mutations that predispose to a range of neurodevelopmental disorders, and suggest a sex-limited effect on the penetrance of the pathological phenotypes at the 16p13.11 locus.     

Fine Characterisation of a Recombination Hotspot at the DPY19L2 Locus and Resolution of the Paradoxical Excess of Duplications over Deletions in the General Population

We demonstrated previously that 75% of infertile men with round, acrosomeless spermatozoa (globozoospermia) had a homozygous 200-Kb deletion removing the totality of DPY19L2. We showed that this deletion occurred by Non-Allelic Homologous Recombination (NAHR) between two homologous 28-Kb Low Copy Repeats (LCRs) located on each side of the gene. The accepted NAHR model predicts that inter-chromatid and inter-chromosome NAHR create a deleted and a duplicated recombined allele, while intra-chromatid events only generate deletions. Therefore more deletions are expected to be produced de novo. Surprisingly, array CGH data show that, in the general population, DPY19L2 duplicated alleles are approximately three times as frequent as deleted alleles. In order to shed light on this paradox, we developed a sperm-based assay to measure the de novo rates of deletions and duplications at this locus. As predicted by the NAHR model, we identified an excess of de novo deletions over duplications. We calculated that the excess of de novo deletion was compensated by evolutionary loss, whereas duplications, not subjected to selection, increased gradually. Purifying selection against sterile, homozygous deleted men may be sufficient for this compensation, but heterozygously deleted men might also suffer a small fitness penalty. The recombined alleles were sequenced to pinpoint the localisation of the breakpoints. We analysed a total of 15 homozygous deleted patients and 17 heterozygous individuals carrying either a deletion (n = 4) or a duplication (n = 13). All but two alleles fell within a 1.2-Kb region central to the 28-Kb LCR, indicating that >90% of the NAHR took place in that region. We showed that a PRDM9 13-mer recognition sequence is located right in the centre of that region. Our results therefore strengthen the link between this consensus sequence and the occurrence of NAHR.     

Global Genetic Variations Predict Brain Response to Faces

Face expressions are a rich source of social signals. Here we estimated the proportion of phenotypic variance in the brain response to facial expressions explained by common genetic variance captured by ∼500,000 single nucleotide polymorphisms. Using genomic-relationship-matrix restricted maximum likelihood (GREML), we related this global genetic variance to that in the brain response to facial expressions, as assessed with functional magnetic resonance imaging (fMRI) in a community-based sample of adolescents (n = 1,620). Brain response to facial expressions was measured in 25 regions constituting a face network, as defined previously. In 9 out of these 25 regions, common genetic variance explained a significant proportion of phenotypic variance (40–50%) in their response to ambiguous facial expressions; this was not the case for angry facial expressions. Across the network, the strength of the genotype-phenotype relationship varied as a function of the inter-individual variability in the number of functional connections possessed by a given region (R² = 0.38, p<0.001). Furthermore, this variability showed an inverted U relationship with both the number of observed connections (R² = 0.48, p<0.001) and the magnitude of brain response (R² = 0.32, p<0.001). Thus, a significant proportion of the brain response to facial expressions is predicted by common genetic variance in a subset of regions constituting the face network. These regions show the highest inter-individual variability in the number of connections with other network nodes, suggesting that the genetic model captures variations across the adolescent brains in co-opting these regions into the face network.     

Promoter Variation and Transcript Divergence in Brassicaceae Lineages of FLOWERING LOCUS T

Brassica napus (AACC, 2n = 38), an oil crop of world-wide importance, originated from interspecific hybridization of B. rapa (AA, 2n = 20) and B. oleracea (CC, 2n = 18), and has six FLOWERING LOCUS T (FT) paralogues. Two located on the homeologous chromosomes A2 and C2 arose from a lineage distinct from four located on A7 and C6. A set of three conserved blocks A, B and C, which were found to be essential for FT activation by CONSTANS (CO) in Arabidopsis, was identified within the FT upstream region in B. napus and its progenitor diploids. However, on chromosome C2, insertion of a DNA transposable element (TE) and a retro-element in FT upstream blocks A and B contributed to significant structural divergence between the A and C genome orthologues. Phylogenetic analysis of upstream block A indicated the conserved evolutionary relationships of distinct FT genes within Brassicaceae. We conclude that the ancient At-α whole genome duplication contributed to distinct ancestral lineages for this key adaptive gene, which co-exist within the same genus. FT-A2 was found to be transcribed in all leaf samples from different developmental stages in both B. rapa and B. napus, whereas FT-C2 was not transcribed in either B. napus or B. oleracea. Silencing of FT-C2 appeared to result from TE insertion and consequent high levels of cytosine methylation in TE sequences within upstream block A. Interestingly, FT-A7/C6 paralogues were specifically silenced in winter type B. napus but abundantly expressed in spring type cultivars under vernalization-free conditions. Motif prediction indicated the presence of two CO protein binding sites within all Brassica block A and additional sites for FT activation in block C. We propose that the ancestral whole genome duplications have contributed to more complex mechanisms of floral regulation and niche adaptation in Brassica compared to Arabidopsis.     

Network Topologies and Convergent Aetiologies Arising from Deletions and Duplications Observed in Individuals with Autism

Autism Spectrum Disorders (ASD) are highly heritable and characterised by impairments in social interaction and communication, and restricted and repetitive behaviours. Considering four sets of de novo copy number variants (CNVs) identified in 181 individuals with autism and exploiting mouse functional genomics and known protein-protein interactions, we identified a large and significantly interconnected interaction network. This network contains 187 genes affected by CNVs drawn from 45% of the patients we considered and 22 genes previously implicated in ASD, of which 192 form a single interconnected cluster. On average, those patients with copy number changed genes from this network possess changes in 3 network genes, suggesting that epistasis mediated through the network is extensive. Correspondingly, genes that are highly connected within the network, and thus whose copy number change is predicted by the network to be more phenotypically consequential, are significantly enriched among patients that possess only a single ASD-associated network copy number changed gene (p = 0.002). Strikingly, deleted or disrupted genes from the network are significantly enriched in GO-annotated positive regulators (2.3-fold enrichment, corrected p = 2×10⁻⁵), whereas duplicated genes are significantly enriched in GO-annotated negative regulators (2.2-fold enrichment, corrected p = 0.005). The direction of copy change is highly informative in the context of the network, providing the means through which perturbations arising from distinct deletions or duplications can yield a common outcome. These findings reveal an extensive ASD-associated molecular network, whose topology indicates ASD-relevant mutational deleteriousness and that mechanistically details how convergent aetiologies can result extensively from CNVs affecting pathways causally implicated in ASD.     

A high-resolution map of segmental DNA copy number variation in the mouse genome

Submicroscopic (less than 2 Mb) segmental DNA copy number changes are a recently recognized source of genetic variability between individuals. The biological consequences of copy number variants (CNVs) are largely undefined. In some cases, CNVs that cause gene dosage effects have been implicated in phenotypic variation. CNVs have been detected in diverse species, including mice and humans. Published studies in mice have been limited by resolution and strain selection. We chose to study 21 well-characterized inbred mouse strains that are the focus of an international effort to measure, catalog, and disseminate phenotype data. We performed comparative genomic hybridization using long oligomer arrays to characterize CNVs in these strains. This technique increased the resolution of CNV detection by more than an order of magnitude over previous methodologies. The CNVs range in size from 21 to 2,002 kb. Clustering strains by CNV profile recapitulates aspects of the known ancestry of these strains. Most of the CNVs (77.5%) contain annotated genes, and many (47.5%) colocalize with previously mapped segmental duplications in the mouse genome. We demonstrate that this technique can identify copy number differences associated with known polymorphic traits. The phenotype of previously uncharacterized strains can be predicted based on their copy number at these loci. Annotation of CNVs in the mouse genome combined with sequence-based analysis provides an important resource that will help define the genetic basis of complex traits.     

Ultra High-Resolution Gene Centric Genomic Structural Analysis of a Non-Syndromic Congenital Heart Defect,Tetralogy of Fallot

Tetralogy of Fallot (TOF) is one of the most common severe congenital heart malformations. Great progress has been made in identifying key genes that regulate heart development, yet approximately 70% of TOF cases are sporadic and nonsyndromic with no known genetic cause. We created an ultra high-resolution gene centric comparative genomic hybridization (gcCGH) microarray based on 591 genes with a validated association with cardiovascular development or function. We used our gcCGH array to analyze the genomic structure of 34 infants with sporadic TOF without a deletion on chromosome 22q11.2 (n _male = 20; n _female = 14; age range of 2 to 10 months). Using our custom-made gcCGH microarray platform, we identified a total of 613 copy number variations (CNVs) ranging in size from 78 base pairs to 19.5 Mb. We identified 16 subjects with 33 CNVs that contained 13 different genes which are known to be directly associated with heart development. Additionally, there were 79 genes from the broader list of genes that were partially or completely contained in a CNV. All 34 individuals examined had at least one CNV involving these 79 genes. Furthermore, we had available whole genome exon arrays from right ventricular tissue in 13 of our subjects. We analyzed these for correlations between copy number and gene expression level. Surprisingly, we could detect only one clear association between CNVs and expression (GSTT1) for any of the 591 focal genes on the gcCGH array. The expression levels of GSTT1 were correlated with copy number in all cases examined (r = 0.95, p = 0.001). We identified a large number of small CNVs in genes with varying associations with heart development. Our results illustrate the complexity of human genome structural variation and underscore the need for multifactorial assessment of potential genetic/genomic factors that contribute to congenital heart defects.     

Molecular evolution of glycinin and β-conglycinin gene families in soybean (Glycine max L. Merr.)

There are two main classes of multi-subunit seed storage proteins, glycinin (11S) and β-conglycinin (7S), which account for approximately 70% of the total protein in a typical soybean seed. The subunits of these two protein classes are encoded by a number of genes. The genomic organization of these genes follows a complex evolutionary history. This research was designed to describe the origin and maintenance of genes in each of these gene families by analyzing the synteny, phylogenies, selection pressure and duplications of the genes in each gene family. The ancestral glycinin gene initially experienced a tandem duplication event; then, the genome underwent two subsequent rounds of whole-genome duplication, thereby resulting in duplication of the glycinin genes, and finally a tandem duplication likely gave rise to the Gy1 and Gy2 genes. The β-conglycinin genes primarily originated through the more recent whole-genome duplication and several tandem duplications. Purifying selection has had a key role in the maintenance of genes in both gene families. In addition, positive selection in the glycinin genes and a large deletion in a β-conglycinin exon contribute to the diversity of the duplicate genes. In summary, our results suggest that the duplicated genes in both gene families prefer to retain similar function throughout evolution and therefore may contribute to phenotypic robustness.     

Recent genome duplications facilitate the phenotypic diversity of Hb repertoire in the Cyprinidae

Whole-genome duplications(WGDs) are an important contributor to phenotypic innovations in evolutionary history. The diversity of blood oxygen transport traits is the perfect reflection of physiological versatility for evolutionary success among vertebrates. In this study, the evolutionary changes of hemoglobin(Hb) repertoire driven by the recent genome duplications were detected in representative Cyprinidae fish, including eight diploid and four tetraploid species. Comparative genomic analysis revealed a substantial variation in both membership composition and intragenomic organization of Hb genes in these species.Phylogenetic reconstruction analyses were conducted to characterize the evolutionary history of these genes. Data were integrated with the expression profiles of the genes during ontogeny. Our results indicated that genome duplications facilitated the phenotypic diversity of the Hb gene family; each was associated with species-specific changes in gene content via gene loss and fusion after genome duplications. This led to repeated evolutionary transitions in the ontogenic regulation of Hb gene expression.Our results revealed that genome duplications helped to generate phenotypic changes in Cyprinidae Hb systems.     

8.2% of the Human Genome Is Constrained: Variation in Rates of Turnover across Functional Element Classes in the Human Lineage

Ten years on from the finishing of the human reference genome sequence, it remains unclear what fraction of the human genome confers function, where this sequence resides, and how much is shared with other mammalian species. When addressing these questions, functional sequence has often been equated with pan-mammalian conserved sequence. However, functional elements that are short-lived, including those contributing to species-specific biology, will not leave a footprint of long-lasting negative selection. Here, we address these issues by identifying and characterising sequence that has been constrained with respect to insertions and deletions for pairs of eutherian genomes over a range of divergences. Within noncoding sequence, we find increasing amounts of mutually constrained sequence as species pairs become more closely related, indicating that noncoding constrained sequence turns over rapidly. We estimate that half of present-day noncoding constrained sequence has been gained or lost in approximately the last 130 million years (half-life in units of divergence time, d_1/2 = 0.25–0.31). While enriched with ENCODE biochemical annotations, much of the short-lived constrained sequences we identify are not detected by models optimized for wider pan-mammalian conservation. Constrained DNase 1 hypersensitivity sites, promoters and untranslated regions have been more evolutionarily stable than long noncoding RNA loci which have turned over especially rapidly. By contrast, protein coding sequence has been highly stable, with an estimated half-life of over a billion years (d_1/2 = 2.1–5.0). From extrapolations we estimate that 8.2% (7.1–9.2%) of the human genome is presently subject to negative selection and thus is likely to be functional, while only 2.2% has maintained constraint in both human and mouse since these species diverged. These results reveal that the evolutionary history of the human genome has been highly dynamic, particularly for its noncoding yet biologically functional fraction.     

Loss of Heterozygosity and Copy Number Alterations in Flow-Sorted Bulky Cervical Cancer

Treatment choices for cervical cancer are primarily based on clinical FIGO stage and the post-operative evaluation of prognostic parameters including tumor diameter, parametrial and lymph node involvement, vaso-invasion, infiltration depth, and histological type. The aim of this study was to evaluate genomic changes in bulky cervical tumors and their relation to clinical parameters, using single nucleotide polymorphism (SNP)-analysis.Flow-sorted tumor cells and patient-matched normal cells were extracted from 81 bulky cervical tumors. DNA-index (DI) measurement and whole genome SNP-analysis were performed. Data were analyzed to detect copy number alterations (CNA) and allelic balance state: balanced, imbalanced or pure LOH, and their relation to clinical parameters.The DI varied from 0.92–2.56. Pure LOH was found in ≥40% of samples on chromosome-arms 3p, 4p, 6p, 6q, and 11q, CN gains in >20% on 1q, 3q, 5p, 8q, and 20q, and losses on 2q, 3p, 4p, 11q, and 13q. Over 40% showed gain on 3q. The only significant differences were found between histological types (squamous, adeno and adenosquamous) in the lesser allele intensity ratio (LAIR) (p = 0.035) and in the CNA analysis (p = 0.011). More losses were found on chromosome-arm 2q (FDR = 0.004) in squamous tumors and more gains on 7p, 7q, and 9p in adenosquamous tumors (FDR = 0.006, FDR = 0.004, and FDR = 0.029).Whole genome analysis of bulky cervical cancer shows widespread changes in allelic balance and CN. The overall genetic changes and CNA on specific chromosome-arms differed between histological types. No relation was found with the clinical parameters that currently dictate treatment choice.     

Hypoxia Adaptations in the Grey Wolf (Canis lupus chanco) from Qinghai-Tibet Plateau

The Tibetan grey wolf (Canis lupus chanco) occupies habitats on the Qinghai-Tibet Plateau, a high altitude (>3000 m) environment where low oxygen tension exerts unique selection pressure on individuals to adapt to hypoxic conditions. To identify genes involved in hypoxia adaptation, we generated complete genome sequences of nine Chinese wolves from high and low altitude populations at an average coverage of 25× coverage. We found that, beginning about 55,000 years ago, the highland Tibetan grey wolf suffered a more substantial population decline than lowland wolves. Positively selected hypoxia-related genes in highland wolves are enriched in the HIF signaling pathway (P = 1.57E-6), ATP binding (P = 5.62E-5), and response to an oxygen-containing compound (P≤5.30E-4). Of these positively selected hypoxia-related genes, three genes (EPAS1, ANGPT1, and RYR2) had at least one specific fixed non-synonymous SNP in highland wolves based on the nine genome data. Our re-sequencing studies on a large panel of individuals showed a frequency difference greater than 58% between highland and lowland wolves for these specific fixed non-synonymous SNPs and a high degree of LD surrounding the three genes, which imply strong selection. Past studies have shown that EPAS1 and ANGPT1 are important in the response to hypoxic stress, and RYR2 is involved in heart function. These three genes also exhibited significant signals of natural selection in high altitude human populations, which suggest similar evolutionary constraints on natural selection in wolves and humans of the Qinghai-Tibet Plateau.     

Bioinformatics Analysis Identify Novel OB Fold Protein Coding Genes in C. elegans

Background

The C. elegans genome has been extensively annotated by the WormBase consortium that uses state of the art bioinformatics pipelines, functional genomics and manual curation approaches. As a result, the identification of novel genes in silico in this model organism is becoming more challenging requiring new approaches. The Oligonucleotide-oligosaccharide binding (OB) fold is a highly divergent protein family, in which protein sequences, in spite of having the same fold, share very little sequence identity (5–25%). Therefore, evidence from sequence-based annotation may not be sufficient to identify all the members of this family. In C. elegans, the number of OB-fold proteins reported is remarkably low (n = 46) compared to other evolutionary-related eukaryotes, such as yeast S. cerevisiae (n = 344) or fruit fly D. melanogaster (n = 84). Gene loss during evolution or differences in the level of annotation for this protein family, may explain these discrepancies.

Methodology/Principal Findings

This study examines the possibility that novel OB-fold coding genes exist in the worm. We developed a bioinformatics approach that uses the most sensitive sequence-sequence, sequence-profile and profile-profile similarity search methods followed by 3D-structure prediction as a filtering step to eliminate false positive candidate sequences. We have predicted 18 coding genes containing the OB-fold that have remarkably partially been characterized in C. elegans.

Conclusions/Significance

This study raises the possibility that the annotation of highly divergent protein fold families can be improved in C. elegans. Similar strategies could be implemented for large scale analysis by the WormBase consortium when novel versions of the genome sequence of C. elegans, or other evolutionary related species are being released. This approach is of general interest to the scientific community since it can be used to annotate any genome.     

Human Induced Rotation and Reorganization of the Brain of Domestic Dogs

Domestic dogs exhibit an extraordinary degree of morphological diversity. Such breed-to-breed variability applies equally to the canine skull, however little is known about whether this translates to systematic differences in cerebral organization. By looking at the paramedian sagittal magnetic resonance image slice of canine brains across a range of animals with different skull shapes (N = 13), we found that the relative reduction in skull length compared to width (measured by Cephalic Index) was significantly correlated to a progressive ventral pitching of the primary longitudinal brain axis (r = 0.83), as well as with a ventral shift in the position of the olfactory lobe (r = 0.81). Furthermore, these findings were independent of estimated brain size or body weight. Since brachycephaly has arisen from generations of highly selective breeding, this study suggests that the remarkable diversity in domesticated dogs'' body shape and size appears to also have led to human-induced adaptations in the organization of the canine brain.     

Determining the Population Frequency of the CFHR3/CFHR1 Deletion at 1q32

In this study we have used multiplex ligation-dependent probe amplification (MLPA) to measure the copy number of CFHR3 and CFHR1 in DNA samples from 238 individuals from the UK and 439 individuals from the HGDP-CEPH Human Genome Diversity Cell Line Panel. We have then calculated the allele frequency and frequency of homozygosity for the copy number polymorphism represented by the CFHR3/CFHR1 deletion. There was a highly significant difference between geographical locations in both the allele frequency (X² = 127.7, DF = 11, P-value = 4.97x10^-22) and frequency of homozygosity (X² = 142.3, DF = 22, P-value = 1.33x10^-19). The highest frequency for the deleted allele (54.7%) was seen in DNA samples from Nigeria and the lowest (0%) in samples from South America and Japan. The observed frequencies in conjunction with the known association of the deletion with AMD, SLE and IgA nephropathy is in keeping with differences in the prevalence of these diseases in African and European Americans. This emphasises the importance of identifying copy number polymorphism in disease.