Olfactory Receptor Gene Family Research Articles

Conservation and selective pressures shaping baleen whale olfactory receptor genes supports their use of olfaction in the marine environment.

The relative importance of various sensory modalities can shift in response to evolutionary transitions, resulting in changes to underlying gene families encoding their reception systems. The rapid birth-and-death process underlying the evolution of the large olfactory receptor (OR) gene family has accelerated genomic-level change for the sense of smell in particular. The transition from the land to sea in marine mammals is an attractive model for understanding the influence of habitat shifts on sensory systems, with the retained OR repertoire of baleen whales contrasting with its loss in toothed whales. In this study, we examine to what extent the transition from a terrestrial to a marine environment has influenced the evolution of baleen whale OR repertoires. We developed Gene Mining Pipeline (GMPipe) (https://github.com/AprilJauhal/GMPipe), which can accurately identify large numbers of candidate OR genes. GMPipe identified 707 OR sequences from eight baleen whale species. These repertoires exhibited distinct family count distributions compared to terrestrial mammals, including signs of relative expansion in families OR10, OR11 and OR13. While many receptors have been lost or show signs of random drift in baleen whales, others exhibit signs of evolving under purifying or positive selection. Over 85% of OR genes could be sorted into orthologous groups of sequences containing at least four homologous sequences. Many of these groups, particularly from family OR10, presented signs of relative expansion and purifying selective pressure. Overall, our results suggest that the relatively small size of baleen whale OR repertoires result from specialisation to novel olfactory landscapes, as opposed to random drift.

Establishment and maintenance of random monoallelic expression.

This Review elucidates the regulatory principles of random monoallelic expression by focusing on two well-studied examples: the X-chromosome inactivation regulator Xist and the olfactory receptor gene family. Although the choice of a single X chromosome or olfactory receptor occurs in different developmental contexts, common gene regulatory principles guide monoallelic expression in both systems. In both cases, an event breaks the symmetry between genetically and epigenetically identical copies of the gene, leading to the expression of one single random allele, stabilized through negative feedback control. Although many regulatory steps that govern the establishment and maintenance of monoallelic expression have been identified, key pieces of the puzzle are still missing. We provide an overview of the current knowledge and models for the monoallelic expression of Xist and olfactory receptors. We discuss their similarities and differences, and highlight open questions and approaches that could guide the study of other monoallelically expressed genes.

Synchronized Expansion and Contraction of Olfactory, Vomeronasal, and Taste Receptor Gene Families in Hystricomorph Rodents.

Chemical senses, including olfaction, pheromones, and taste, are crucial for the survival of most animals. There has long been a debate about whether different types of senses might influence each other. For instance, primates with a strong sense of vision are thought to have weakened olfactory abilities, although the oversimplified trade-off theory is now being questioned. It is uncertain whether such interactions between different chemical senses occur during evolution. To address this question, we examined four receptor gene families related to olfaction, pheromones, and taste: olfactory receptor (OR), vomeronasal receptor type 1 and type 2 (V1R and V2R), and bitter taste receptor (T2R) genes in Hystricomorpha, which is morphologically and ecologically the most diverse group of rodents. We also sequenced and assembled the genome of the grasscutter, Thryonomys swinderianus. By examining 16 available genome assemblies alongside the grasscutter genome, we identified orthologous gene groups among hystricomorph rodents for these gene families to separate the gene gain and loss events in each phylogenetic branch of the Hystricomorpha evolutionary tree. Our analysis revealed that the expansion or contraction of the four gene families occurred synchronously, indicating that when one chemical sense develops or deteriorates, the others follow suit. The results also showed that V1R/V2R genes underwent the fastest evolution, followed by OR genes, and T2R genes were the most evolutionarily stable. This variation likely reflects the difference in ligands of V1R/V2Rs, ORs, and T2Rs: species-specific pheromones, environment-based scents, and toxic substances common to many animals, respectively.

Comparative Genomics Reveal Phylogenetic Relationship and Chromosomal Evolutionary Events of Eight Cervidae Species.

Cervidae represents a family that is not only rich in species diversity but also exhibits a wide range of karyotypes. The controversies regarding the phylogeny and classification of Cervidae still persist. The flourishing development of the genomic era has made it possible to address these issues at the genomic level. Here, the genomes of nine species were used to explore the phylogeny and chromosomal evolutionary events of Cervidae. By conducting whole-genome comparisons, we identified single-copy orthologous genes across the nine species and constructed a phylogenetic tree based on the single-copy orthologous genes sequences, providing new insights into the phylogeny of Cervidae, particularly the phylogenetic relationship among sika deer, red deer, wapiti and Tarim red deer. Gene family analysis revealed contractions in the olfactory receptor gene family and expansions in the histone gene family across eight Cervidae species. Furthermore, synteny analysis was used to explore the chromosomal evolutionary events of Cervidae species, revealing six chromosomal fissions during the evolutionary process from Bovidae to Cervidae. Notably, specific chromosomal fusion events were found in four species of Cervus, and a unique chromosomal fusion event was identified in Muntiacus reevesi. Our study further completed the phylogenetic relationship within the Cervidae and demonstrated the feasibility of inferring species phylogeny at the whole-genome level. Additionally, our findings on gene family evolution and the chromosomal evolutionary events in eight Cervidae species lay a foundation for comprehensive research of the evolution of Cervidae.

Phylogeny, Ecology, and Gene Families Covariation Shaped the Olfactory Subgenome of Rodents.

Olfactory receptor (OR) genes represent the largest multigenic family in mammalian genomes and encode proteins that bind environmental odorant molecules. The OR repertoire is extremely variable among species and is subject to many gene duplications and losses, which have been linked to ecological adaptations in mammals. Although they have been studied on a broad taxonomic scale (i.e., placental), finer sampling has rarely been explored in order to better capture the mechanisms that drove the evolution of the OR repertoire. Among placental mammals, rodents are well-suited for this task, as they exhibit diverse life history traits, and genomic data are available for most major families and a diverse array of lifestyles. In this study, 53 rodent published genomes were mined for their OR subgenomes. We retrieved more than 85,000 functional and pseudogene OR sequences that were subsequently classified into phylogenetic clusters. Copy number variation among rodents is similar to that of other mammals. Using our OR counts along with comparative phylogenetic approaches, we demonstrated that ecological niches such as diet, period of activity, and a fossorial lifestyle strongly impacted the proportion of OR pseudogenes. Within the OR subgenome, phylogenetic inertia was the main factor explaining the relative variations of the 13 OR gene families. However, a striking exception was a convergent 10-fold expansion of the OR family 14 among the phylogenetically divergent subterranean mole-rat lineages belonging to Bathyergidae and Spalacidae families. This study illustrates how the diversity of the OR repertoire has evolved among rodents, both shaped by selective forces stemming from species life history traits and neutral evolution along the rodent phylogeny.

Diverse evolutionary rates and gene duplication patterns among families of functional olfactory receptor genes in humans.

In humans, odors are detected by ~400 functional olfactory receptor (OR) genes. The superfamily of functional OR genes can be further divided into tens of families. In large part, the OR genes have experienced extensive tandem duplications, which have led to gene gains and losses. However, whether different OR gene families have experienced distinct modes of gene duplication has yet to be reported. We conducted comparative genomic and evolutionary analyses for human functional OR genes. Based on analysis of human-mouse 1-1 orthologs, we found that human functional OR genes show higher-than-average evolutionary rates, and there are significant differences among families of functional OR genes. Via comparison with seven vertebrate outgroups, families of human functional OR genes show different extents of gene synteny conservation. Although the superfamily of human functional OR genes is enriched in tandem and proximal duplications, there are particular families which are enriched in segmental duplications. These findings suggest that human functional OR genes may be governed by different evolutionary mechanisms and that large-scale gene duplications have contributed to the early evolution of human functional OR genes.

Parallel evolution of fish bi-modal breathing and expansion of olfactory receptor (OR) genes: toward a universal ORs nomenclature

Olfactory receptors (ORs) play a key role in the prime sensorial perception, being highly relevant for intra/interspecific interactions. ORs are a subgroup of G-protein coupled receptors that exhibit highly complex subgenomes in vertebrates. However, OR repertoires remain poorly studied in fish lineages, precluding finely retracing their origin, evolution, and diversification, especially in the most basal groups. Here, we conduct an exhaustive gene screening upon 43 high-quality fish genomes exhibiting varied gene repertoires (2–583 genes). While the early vertebrates performed gas exchange through gills, we hypothesize that the emergence of new breathing structures (swim bladder and paired lungs) in early osteichthyans may be associated with expansions in the ORs gene families sensitive to airborne molecules. Additionally, we verify that the OR repertoire of moderns actinopterygians has not increased as expected following a whole genome duplication, likely due to regulatory mechanisms compensating the gene load excess. Finally, we identify 25 distinct OR families, allowing us to propose an updated universal nomenclature for the fish ORs.

Genome-wide copy number variant screening of Saudi schizophrenia patients reveals larger deletions in cases versus controls.

Genome-wide association studies have discovered common polymorphisms in regions associated with schizophrenia. No genome-wide analyses have been performed in Saudi schizophrenia subjects. Genome-wide genotyping data from 136 Saudi schizophrenia cases and 97 Saudi controls in addition to 4,625 American were examined for copy number variants (CNVs). A hidden Markov model approach was used to call CNVs. CNVs in schizophrenia cases were twice as large on average than CNVs in controls (p = 0.04). The analyses focused on extremely large >250 kilobases CNVs or homozygous deletions of any size. One extremely large deletion was noted in a single case (16.5 megabases on chromosome 10). Two cases had an 814 kb duplication of chromosome 7 spanning a cluster of genes, including circadian-related loci, and two other cases had 277 kb deletions of chromosome 9 encompassing an olfactory receptors gene family. CNVs were also seen in loci previously associated with schizophrenia, namely a 16p11 proximal duplication and two 22q11.2 deletions. Runs of homozygosity (ROHs) were analyzed across the genome to investigate correlation with schizophrenia risk. While rates and sizes of these ROHs were similar in cases and controls, we identified 10 regions where multiple cases had ROHs and controls did not.

Whole-Exome Sequencing identified Olfactory Receptor genes as a key contributor to extreme obesity with progression to nonalcoholic steatohepatitis in Mexican patients: Olfactory receptor genes in obese NASH patients

Obesity is a global health problem that triggers fat liver accumulation. The prevalence of obesity and the risk of non-alcoholic steatohepatitis (NASH) among young obese Mexican is high. Furthermore, genetic predisposition is a key factor in weight gain and disrupts metabolism. Herein, we used Whole-Exome Sequencing to identify potential causal variants and the biological processes that lead to obesity with progression to NASH among Mexican patients. Whole-Exome Sequencing was performed in nine obese patients with NASH diagnosis with a BMI ≥30 kg/m2 and one control (BMI=24.2 kg/m2) by using the Ion S5TM platform. Genetic variants were determined by Ion Reporter software. Enriched GO biological set genes were identified by the WebGestalt tool. Genetic variants within ≥2 obese NASH patients and having scores of SIFT 0.0-0.05 and Polyphen 0.85-1.0 were categorized as pathogenic. A total of 1359 variants with a probable pathogenic effect were determined in obese patients with NASH diagnosis. After several filtering steps, the most frequent pathogenic variants found were rs25640-HSD17B4, rs8105737-OR1I1, rs998544-OR5R1, and rs4916685, rs10037067, and rs2366926 in ADGRV1. Notably, the primary biological processes affected by these pathogenic variants were the sensory perception and detection of chemical stimulus pathways in which the olfactory receptor gene family was the most enriched. Variants in the olfactory receptor genes were highly enriched in Mexican obese patients that progress to NASH and could be potential targets of association studies.

Identification and characterization of olfactory receptor genes and olfactory perception in rapa whelk Rapana venosa (Valenciennes, 1846) during larval settlement and metamorphosis.

The rapa whelk Rapana venosa, an economically important marine fishery resource in China but a major invader all over the world, changes from a phytophagous to a carnivorous form following settlement and metamorphosis. However, the low settlement and metamorphosis rates (<1%) of larvae limit the abundance of R. venosa. This critical step (settlement and metamorphosis) remains poorly characterized but may be related to how larvae perceive the presence of shellfish, their new source of food. Here, we report that larvae may use olfactory perception to sense shellfish. Olfactory receptor (OR) genes are involved in odor sensing in animals. We identified a total of 463 OR genes, which could be grouped into nine clades based on phylogenetic analysis. When assessing the attraction of larvae at different developmental stages to oyster odor, R. venosa showed active settlement and metamorphosis behavior only at the J4 stage (competent larva, 1000-1500 μm shell length) and in the presence of shellfish odor at the same time. Expression of OR gene family members differed between stage 2 (four-spiral whorl stage) and stage 1 (single- to three-spiral whorl stage), indicating significant changes in the olfactory system during larval development. These findings broaden our understanding of olfactory perception, settlement, and metamorphosis in gastropods and can be used to improve R. venosa harvesting, as well as the sustainable development and utilization of this resource.

Chemoreceptor co-expression in Drosophila melanogaster olfactory neurons.

Drosophila melanogaster olfactory neurons have long been thought to express only one chemosensory receptor gene family. There are two main olfactory receptor gene families in Drosophila, the odorant receptors (ORs) and the ionotropic receptors (IRs). The dozens of odorant-binding receptors in each family require at least one co-receptor gene in order to function: Orco for ORs, and Ir25a, Ir8a, and Ir76b for IRs. Using a new genetic knock-in strategy, we targeted the four co-receptors representing the main chemosensory families in D. melanogaster (Orco, Ir8a, Ir76b, Ir25a). Co-receptor knock-in expression patterns were verified as accurate representations of endogenous expression. We find extensive overlap in expression among the different co-receptors. As defined by innervation into antennal lobe glomeruli, Ir25a is broadly expressed in 88% of all olfactory sensory neuron classes and is co-expressed in 82% of Orco+ neuron classes, including all neuron classes in the maxillary palp. Orco, Ir8a, and Ir76b expression patterns are also more expansive than previously assumed. Single sensillum recordings from Orco-expressing Ir25a mutant antennal and palpal neurons identify changes in olfactory responses. We also find co-expression of Orco and Ir25a in Drosophila sechellia and Anopheles coluzzii olfactory neurons. These results suggest that co-expression of chemosensory receptors is common in insect olfactory neurons. Together, our data present the first comprehensive map of chemosensory co-receptor expression and reveal their unexpected widespread co-expression in the fly olfactory system.

Genetic variation of olfactory receptor gene family in a Japanese population

Genetic variation of olfactory receptor gene family in a Japanese population

Highly Contiguous Genomes Improve the Understanding of Avian Olfactory Receptor Repertoires

Third-generation (long-read-based) sequencing technologies are reshaping our understanding of genome structure and function. One of the most persistent challenges in genome biology has been confidently reconstructing radiations of complex gene families. Olfactory receptors (ORs) represent just such a gene family with upward of thousands of receptors in some mammalian taxa. Whereas in birds olfaction was historically an overlooked sensory modality, new studies have revealed an important role for smell. Chromosome-level assemblies for birds allow a new opportunity to characterize patterns of OR diversity among major bird lineages. Previous studies of short-read-based (second-generation) genome assemblies have associated OR gene family size with avian ecology, but such conclusions could be premature especially when new assembly methods reshape our understanding of avian OR evolution. Here we provide a fundamental characterization of OR repertoires in five recent genome assemblies, including the most recent assembly of golden-collared manakin (Manacus vitellinus). We find that short read-based assemblies systematically undercount the avian-specific gamma-c OR subfamily, a subfamily that comprises over 65% of avian OR diversity. Therefore, in contrast to previous studies, we find a high diversity of gamma-c ORs across the avian tree of life. Building on these findings, ongoing sequencing efforts and improved genome assemblies will clarify the relationship between OR diversity and avian ecology.

Investigating Olfactory Gene Variation and Odour Identification in Older Adults.

Ageing is associated with a decrease in odour identification. Additionally, deficits in olfaction have been linked to age-related disease and mortality. Heritability studies suggest genetic variation contributes to olfactory identification. The olfactory receptor (OR) gene family is the largest in the human genome and responsible for overall odour identification. In this study, we sought to find olfactory gene family variants associated with individual and overall odour identification and to examine the relationships between polygenic risk scores (PRS) for olfactory-related phenotypes and olfaction. Participants were Caucasian older adults from the Sydney Memory and Ageing Study and the Older Australian Twins Study with genome-wide genotyping data (n = 1395, mean age = 75.52 ± 6.45). The Brief-Smell Identification Test (BSIT) was administered in both cohorts. PRS were calculated from independent GWAS summary statistics for Alzheimer’s disease (AD), white matter hyperintensities (WMH), Parkinson’s disease (PD), hippocampal volume and smoking. Associations with olfactory receptor genes (n = 967), previously identified candidate olfaction-related SNPs (n = 36) and different PRS with BSIT scores (total and individual smells) were examined. All of the relationships were analysed using generalised linear mixed models (GLMM), adjusted for age and sex. Genes with suggestive evidence for odour identification were found for 8 of the 12 BSIT items. Thirteen out of 36 candidate SNPs previously identified from the literature were suggestively associated with several individual BSIT items but not total score. PRS for smoking, WMH and PD were negatively associated with chocolate identification. This is the first study to conduct genetic analyses with individual odorant identification, which found suggestive olfactory-related genes and genetic variants for multiple individual BSIT odours. Replication in independent and larger cohorts is needed.

A large genome with chromosome-scale assembly sheds light on the evolutionary success of a true toad (Bufo gargarizans).

We present a high-quality genome assembly for the Asiatic toad (Bufo gargarizans) and explore the evolution of several large gene families in amphibians. With a large genome assembly size of 4.55Gb, the chromosome-scale assembly includes 747 scaffolds with an N50 of 539.8Mb and 1.79% gaps. Long terminal repeats (LTRs) constitute a high proportion of the genome and their expansion is a key contributor to the inflated genome size in this species. This is very different from other small amphibian genomes, but similar to that of the enormous axolotl genome. The genome retains a large number of duplicated genes, with tandem (TD) and proximal duplications (PD) the predominant mode of duplication. A total of 122 gene families have undergone significant expansion and were mainly enriched in sensory perception of smell and bitter taste. The CYP2C subfamily, which plays an important role in metabolic detoxification, specifically expanded via TD and PD in the Asiatic toad and the cane toad (true toads). Most of Na+ /K+ -ATPase genes experienced accelerated evolution along Bufonid lineages and two amino acid sites involving toad-toxin resistance were found to experience positive selection. We also revealed a dynamic evolution of olfactory and vomeronasal receptor gene families which was likely driven by the water-to-land transition. The high-quality genome of the Asiatic toad will provide a solid foundation to understand the genetic basis of its many biological processes.

Evaluating the quantity, quality and size distribution of cell-free DNA by multiplex droplet digital PCR

Cell-free DNA (cfDNA) has become a comprehensive biomarker in the fields of non-invasive cancer detection and monitoring, organ transplantation, prenatal genetic testing and pathogen detection. While cfDNA samples can be obtained using a broad variety of approaches, there is an urgent need to standardize analytical tools aimed at assessing its basic properties. Typical methods to determine the yield and fragment size distribution of cfDNA samples are usually either blind to genomic DNA contamination or the presence of enzymatic inhibitors, which can confound and undermine downstream analyses. Here, we present a novel droplet digital PCR assay to identify suboptimal samples and aberrant cfDNA size distributions, the latter typically associated with high levels of circulating tumour DNA (ctDNA). Our assay was designed to promiscuously cross-amplify members of the human olfactory receptor (OR) gene family and includes a customizable diploid locus for the determination of absolute cfDNA concentrations. We demonstrate here the utility of our assay to estimate the yield and quality of cfDNA extracts and deduce fragment size distributions that correlate well with those inferred by capillary electrophoresis and high throughput sequencing. The assay described herein is a powerful tool to establish quality controls and stratify cfDNA samples based on presumed ctDNA levels, then facilitating the implementation of robust, cost-effective and standardized analytical workflows into clinical practice.

The Birth and Death of Olfactory Receptor Gene Families in Mammalian Niche Adaptation.

The olfactory receptor (OR) gene families, which govern mammalian olfaction, have undergone extensive expansion and contraction through duplication and pseudogenization. Previous studies have shown that broadly defined environmental adaptations (e.g., terrestrial vs. aquatic) are correlated with the number of functional and non-functional OR genes retained. However, to date, no study has examined species-specific gene duplications in multiple phylogenetically divergent mammals to elucidate OR evolution and adaptation. Here, we identify the OR gene families driving adaptation to different ecological niches by mapping the fate of species-specific gene duplications in the OR repertoire of 94 diverse mammalian taxa, using molecular phylogenomic methods. We analyze >70,000 OR gene sequences mined from whole genomes, generated from novel amplicon sequencing data, and collated with data from previous studies, comprising one of the largest OR studies to date. For the first time, we demonstrate statistically significant patterns of OR species-specific gene duplications associated with the presence of a functioning vomeronasal organ. With respect to dietary niche, we uncover a novel link between a large number of duplications in OR family 5/8/9 and herbivory. Our results also highlight differences between social and solitary niches, indicating that a greater OR repertoire expansion may be associated with a solitary lifestyle. This study demonstrates the utility of species-specific duplications in elucidating gene family evolution, revealing how the OR repertoire has undergone expansion and contraction with respect to a number of ecological adaptations in mammals.

Bioinformatics analysis of key genes and signaling pathways associated with myocardial infarction following telomerase activation.

The present study aimed to identify key genes and signaling pathways associated with myocardial infarction (MI) following telomerase activation, and investigate the possible underlying molecular mechanisms involved in this process. Array data of GSE62973 was downloaded, including 11 samples from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were analyzed in infarct vs. control, infarct + telomerase vs. control, and infarct + telomerase vs. infarct with the Linear Models for Microarray and RNA‑Seq Data package. Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were performed for upregulated and downregulated genes by the Database for Annotation, Visualization and Integrated Discovery. Sub network modules of 3 protein‑protein interaction (PPI) networks were analyzed by Clustering with Overlapping Neighbourhood Expansion, and genes associated with telomerase were analyzed. Proto‑oncogene tyrosine‑protein kinase Src (Src) and proto‑oncogene tyrosine‑protein kinase Fyn (Fyn) were the hub nodes of the greatest degree in the PPI network for the infarct+telomerase vs. control comparison group and infarct+telomerase vs. infarct comparison group, respectively. Olfactory receptor gene family associated genes, including olfactory receptor 10 were significantly enriched in the sub network modules of the 3 comparison groups. In addition, olfactory transduction was a significantly enriched pathway by downregulation of DEGs in the infarct vs. control comparison group, and was additionally a significantly enriched pathway by upregulated DEGs in infarct + telomerase vs. infarct comparison group. Olfactory transduction was a significant pathway enriched by genes associated with telomerase. Telomerase activation may serve an important role in MI, in part, via the regulation of Src, Fyn and olfactory receptor family associated genes.

Coordinated shift of olfactory amino acid responses and V2R expression to an amphibian water nose during metamorphosis.

All olfactory receptors identified in teleost fish are expressed in a single sensory surface, whereas mammalian olfactory receptor gene families segregate into different olfactory organs, chief among them the main olfactory epithelium expressing ORs and TAARs, and the vomeronasal organ expressing V1Rs and V2Rs. A transitional stage is embodied by amphibians, with their vomeronasal organ expressing more 'modern', later diverging V2Rs, whereas more 'ancient', earlier diverging V2Rs are expressed in the main olfactory epithelium. During metamorphosis, the main olfactory epithelium of Xenopus tadpoles transforms into an air-filled cavity (principal cavity, air nose), whereas a newly formed cavity (middle cavity) takes over the function of a water nose. We report here that larval expression of ancient V2Rs is gradually lost from the main olfactory epithelium as it transforms into the air nose. Concomitantly, ancient v2r gene expression begins to appear in the basal layers of the newly forming water nose. We observe the same transition for responses to amino acid odorants, consistent with the hypothesis that amino acid responses may be mediated by V2R receptors.

Exome Array Analyses Identify New Genes Influencing Survival Outcomes after HLA-Matched Unrelated Donor Blood and Marrow Transplantation

#the authors contributed equally to this workWhile survival outcomes after HLA-matched unrelated donor (URD) blood and marrow transplant (BMT) have significantly improved over the last two decades, about 40% of patients die before 1-year post URD BMT. Previously we performed a genome-wide association study (GWAS) named DISCOVeRY-BMT (Determining the Influence of Susceptibility COnveying Variants Related to one-Year mortality after BMT) to investigate the contributions of common genetic variants on survival outcomes. To address the specific contributions of low frequency (≤ 1%) exonic variants on survival outcomes, we used the DISCOVeRY-BMT cohorts typed with the Illumina HumanExome BeadChip containing 242,901 variants, which are mainly protein-coding variants. We used a gene-based test (the optimal sequence kernel association test (SKAT-O)) to evaluate the cumulative effects of multiple genetic variants within a gene on overall survival (OS), transplant-related mortality (TRM), and disease-related mortality (DRM) 1 year after URD BMT. SKAT-O measures the overall significance of the gene and allows the variants to have different directions and magnitude of effects. We used a 2-stage study design: SKAT-O analysis was carried out in Cohort 1 consisting of 1,972 AML, ALL or MDS patients reported to the Center for International Blood and Marrow Transplant Research from 2000 to 2008 and their 2,006 10/10 HLA-matched URD. Genes with a suggestive association with each outcome (P < 1×10-3) entered the final meta-analysis including Cohort 1 and an independent cohort (Cohort 2), consisting of 503 recipients and 520 10/10 HLA-matched URD from 2009 to 2011. The analysis included recipients and URD of European descent due to the low frequency of other populations. All association models included age at BMT, diagnosis (AML, ALL, MDS), disease status at BMT, cell source (peripheral blood, marrow), year of BMT, and principal components from EIGENSTRAT to control for population stratification. Only coding variants (missense and nonsense) with minor allele frequency ≤ 1% were included in our analysis, which resulted in > 12,000 genes tested in our gene-based analysis in recipients and donors. Exome-wide significance was set at Pmeta< 4.10×10-6 after Bonferroni correction for the total number of genes tested. The likely pathogenicity of these variants was determined in silico using SIFT and PolyPhen. In recipients, we identified OR51D1, a member of the olfactory receptor gene family, as significantly associated with both OS and TRM. The OS association with ORD51D1 is driven by TRM as the same six missense variants contribute to both TRM and OS, but not to DRM. In donors, four (ALPP, EMID1, SLC44A5, LRP1), one (HHAT), and two (LYZL4, NT5E) genes were significantly associated with OS, TRM, and DRM, respectively (Table). ALPP encodes an alkaline phosphatase. SLC44A5 is a member of the solute carrier gene family. LRP1 (low density lipoprotein receptor-related protein 1) encodes an endocytic receptor involved in several cellular processes, including intracellular signaling, lipid homeostasis, and clearance of apoptotic cells. HHAT encodes an enzyme that acts within the hedgehog secretory pathway, which is involved in hematologic malignancy. LYZL4 is a member of a family of lysozyme-like genes, which have a protective role in host defense. The encoded protein of NT5E, CD270, is used as a determinant of lymphocyte differentiation. The likely pathogenicity of several of the functional variants in all significant genes identified was predicted to be both (possibly or probably) damaging and deleterious (Table), thus indicating that the amino acid substitution of the variant may not be well tolerated. One damaging variant in LRP1 has been identified as a somatic mutation in hematopoietic and lymphoid tissue. Our study is the first analysis of the low-frequency coding variant contribution to URD BMT survival outcomes. We found that the missense variants contributing to many of these significant gene associations shows evidence of pathogenicity and thus it is biologically plausible these variants are contributing to survival outcomes. Further confirmation of these findings, and studies of the functional consequences of protein-coding changes in these genes, may provide more individualized risk prediction and prognosis as well as alternative donor selection strategies. [Display omitted] DisclosuresMcCarthy:Gamida Cell: Honoraria, Membership on an entity's Board of Directors or advisory committees; Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees; The Binding Site: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees. Hahn:Novartis: Equity Ownership; NIH: Research Funding. Sucheston-Campbell:NIH/NCI: Research Funding.