Phylomedicine

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Phylomedicine is an emerging discipline at the intersection of medicine, genomics, and evolution. It focuses on the use of evolutionary knowledge to predict functional consequences of mutations found in personal genomes and populations. [1] [2]

History

Modern technologies have made genome sequencing accessible, and biomedical scientists have profiled genomic variation in apparently healthy individuals and individuals diagnosed with a variety of diseases. This work has led to the discovery of thousands of disease-associated genes and genetic variants, elucidating a more robust picture of the amount and types of variations found within and between humans. [3] [4]

Proteins are encoded in genomic DNA by exons, and these comprise only ~1% of the human genomic sequence (aka the exome). The exome of an individual carries about 6,000–10,000 amino-acid-altering nSNVs, and many of these variants are already known to be associated with more than 1000 diseases. [5] Although only a small fraction of these personal variants are likely to impact health, the sheer volume of known genomic and exomic variants is too large to apply traditional laboratory or experimental techniques to explore their functional consequences. Translating a personal genome into useful phenotypic information (e.g. relating to predisposition to disease, differential drug response, or other health concerns), is therefore a grand challenge in the field of genomic medicine.

Fortunately, results from the natural experiment of molecular evolution are recorded in the genomes of humans and other living species. All genomic variation is subjected to the process of natural selection which generally reduces mutations with negative effects on phenotype over time. With the availability of a large number of genomes from the tree of life, evolutionary conservation of individual genomic positions and the sets of mutations permitted among species informs the functional and health consequences of these mutations.

Consequently, phylomedicine has emerged as an important discipline at the intersection of molecular evolution and genomic medicine with a focus on understanding the inherited component of human disease and health. Examples include studies of retinal disease, auditory diseases, and common diseases more generally. [6] [7] [8] Phylomedicine expands the purview of contemporary evolutionary medicine to use evolutionary patterns beyond short-term history (e.g. populations within a species) to the long-term evolutionary history of multispecies genomics.

Related Research Articles

<span class="mw-page-title-main">Phenotype</span> Composite of the organisms observable characteristics or traits

In genetics, the phenotype is the set of observable characteristics or traits of an organism. The term covers the organism's morphology, its developmental processes, its biochemical and physiological properties, its behavior, and the products of behavior. An organism's phenotype results from two basic factors: the expression of an organism's genetic code and the influence of environmental factors. Both factors may interact, further affecting the phenotype. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented example of polymorphism is Labrador Retriever coloring; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black, and brown. Richard Dawkins in 1978 and then again in his 1982 book The Extended Phenotype suggested that one can regard bird nests and other built structures such as caddisfly larva cases and beaver dams as "extended phenotypes".

<span class="mw-page-title-main">Human genome</span> Complete set of nucleic acid sequences for humans

The human genome is a complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual mitochondria. These are usually treated separately as the nuclear genome and the mitochondrial genome. Human genomes include both protein-coding DNA sequences and various types of DNA that does not encode proteins. The latter is a diverse category that includes DNA coding for non-translated RNA, such as that for ribosomal RNA, transfer RNA, ribozymes, small nuclear RNAs, and several types of regulatory RNAs. It also includes promoters and their associated gene-regulatory elements, DNA playing structural and replicatory roles, such as scaffolding regions, telomeres, centromeres, and origins of replication, plus large numbers of transposable elements, inserted viral DNA, non-functional pseudogenes and simple, highly repetitive sequences. Introns make up a large percentage of non-coding DNA. Some of this non-coding DNA is non-functional junk DNA, such as pseudogenes, but there is no firm consensus on the total amount of junk DNA.

A microsatellite is a tract of repetitive DNA in which certain DNA motifs are repeated, typically 5–50 times. Microsatellites occur at thousands of locations within an organism's genome. They have a higher mutation rate than other areas of DNA leading to high genetic diversity. Microsatellites are often referred to as short tandem repeats (STRs) by forensic geneticists and in genetic genealogy, or as simple sequence repeats (SSRs) by plant geneticists.

Gene duplication is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. Gene duplications can arise as products of several types of errors in DNA replication and repair machinery as well as through fortuitous capture by selfish genetic elements. Common sources of gene duplications include ectopic recombination, retrotransposition event, aneuploidy, polyploidy, and replication slippage.

<span class="mw-page-title-main">Single-nucleotide polymorphism</span> Single nucleotide in genomic DNA at which different sequence alternatives exist

In genetics and bioinformatics, a single-nucleotide polymorphism is a germline substitution of a single nucleotide at a specific position in the genome that is present in a sufficiently large fraction of the population.

<span class="mw-page-title-main">Human genetic variation</span> Genetic diversity in human populations

Human genetic variation is the genetic differences in and among populations. There may be multiple variants of any given gene in the human population (alleles), a situation called polymorphism.

<span class="mw-page-title-main">1000 Genomes Project</span> International research effort on genetic variation

The 1000 Genomes Project, launched in January 2008, was an international research effort to establish by far the most detailed catalogue of human genetic variation. Scientists planned to sequence the genomes of at least one thousand anonymous participants from a number of different ethnic groups within the following three years, using newly developed technologies which were faster and less expensive. In 2010, the project finished its pilot phase, which was described in detail in a publication in the journal Nature. In 2012, the sequencing of 1092 genomes was announced in a Nature publication. In 2015, two papers in Nature reported results and the completion of the project and opportunities for future research.

<span class="mw-page-title-main">Gene redundancy</span>

Gene redundancy is the existence of multiple genes in the genome of an organism that perform the same function. Gene redundancy can result from gene duplication. Such duplication events are responsible for many sets of paralogous genes. When an individual gene in such a set is disrupted by mutation or targeted knockout, there can be little effect on phenotype as a result of gene redundancy, whereas the effect is large for the knockout of a gene with only one copy. Gene knockout is a method utilized in some studies aiming to characterize the maintenance and fitness effects functional overlap.

<span class="mw-page-title-main">Whole genome sequencing</span> Determining nearly the entirety of the DNA sequence of an organisms genome at a single time

Whole genome sequencing (WGS), also known as full genome sequencing, complete genome sequencing, or entire genome sequencing, is the process of determining the entirety, or nearly the entirety, of the DNA sequence of an organism's genome at a single time. This entails sequencing all of an organism's chromosomal DNA as well as DNA contained in the mitochondria and, for plants, in the chloroplast.

The exome is composed of all of the exons within the genome, the sequences which, when transcribed, remain within the mature RNA after introns are removed by RNA splicing. This includes untranslated regions of messenger RNA (mRNA), and coding regions. Exome sequencing has proven to be an efficient method of determining the genetic basis of more than two dozen Mendelian or single gene disorders.

<span class="mw-page-title-main">Institute of Genomics and Integrative Biology</span> Indian scientific research institute

CSIR Institute of Genomics and Integrative Biology (CSIR-IGIB) is a scientific research institute devoted primarily to biological research. It is a part of Council of Scientific and Industrial Research (CSIR), India.

<span class="mw-page-title-main">Exome sequencing</span> Sequencing of all the exons of a genome

Exome sequencing, also known as whole exome sequencing (WES), is a genomic technique for sequencing all of the protein-coding regions of genes in a genome. It consists of two steps: the first step is to select only the subset of DNA that encodes proteins. These regions are known as exons—humans have about 180,000 exons, constituting about 1% of the human genome, or approximately 30 million base pairs. The second step is to sequence the exonic DNA using any high-throughput DNA sequencing technology.

Philip Awadalla is a professor of medical and population genetics at the Ontario Institute for Cancer Research, and the Department of Molecular Genetics, Faculty of Medicine, University of Toronto. He is the National Scientific Director of the Canadian Partnership for Tomorrow's Health (CanPath), formerly the Canadian Partnership for Tomorrow Project (CPTP), and Executive Director of the Ontario Health Study. He is also the Executive Scientific Director of the Genome Canada Genome Technology Platform, the Canadian Data Integration Centre. Professor Awadalla was the Executive Scientific Director of the CARTaGENE biobank, a regional cohort member of the CPTP, from 2009 to 2015, and is currently a scientific advisor for this and other scientific and industry platforms. At the OICR, he is Director of Computational Biology.

Predictive genomics is at the intersection of multiple disciplines: predictive medicine, personal genomics and translational bioinformatics. Specifically, predictive genomics deals with the future phenotypic outcomes via prediction in areas such as complex multifactorial diseases in humans. To date, the success of predictive genomics has been dependent on the genetic framework underlying these applications, typically explored in genome-wide association (GWA) studies. The identification of associated single-nucleotide polymorphisms underpin GWA studies in complex diseases that have ranged from Type 2 Diabetes (T2D), Age-related macular degeneration (AMD) and Crohn's disease.

Single nucleotide polymorphism annotation is the process of predicting the effect or function of an individual SNP using SNP annotation tools. In SNP annotation the biological information is extracted, collected and displayed in a clear form amenable to query. SNP functional annotation is typically performed based on the available information on nucleic acid and protein sequences.

A variant of uncertainsignificance (VUS) is a genetic variant that has been identified through genetic testing but whose significance to the function or health of an organism is not known. Two related terms are "gene of uncertain significance" (GUS), which refers to a gene that has been identified through genome sequencing but whose connection to a human disease has not been established, and "insignificant mutation", referring to a gene variant that has no impact on the health or function of an organism. The term "variant' is favored in clinical practice over "mutation" because it can be used to describe an allele more precisely. When the variant has no impact on health, it is called a "benign variant". When it is associated with a disease, it is called a "pathogenic variant". A "pharmacogenomic variant" has an effect only when an individual takes a particular drug and therefore is neither benign nor pathogenic.

A human disease modifier gene is a modifier gene that alters expression of a human gene at another locus that in turn causes a genetic disease. Whereas medical genetics has tended to distinguish between monogenic traits, governed by simple, Mendelian inheritance, and quantitative traits, with cumulative, multifactorial causes, increasing evidence suggests that human diseases exist on a continuous spectrum between the two.

ANNOVAR is a bioinformatics software tool for the interpretation and prioritization of single nucleotide variants (SNVs), insertions, deletions, and copy number variants (CNVs) of a given genome.

Personalized onco-genomics (POG) is the field of oncology and genomics that is focused on using whole genome analysis to make personalized clinical treatment decisions. The program was devised at British Columbia's BC Cancer Agency and is currently being led by Marco Marra and Janessa Laskin. Genome instability has been identified as one of the underlying hallmarks of cancer. The genetic diversity of cancer cells promotes multiple other cancer hallmark functions that help them survive in their microenvironment and eventually metastasise. The pronounced genomic heterogeneity of tumours has led researchers to develop an approach that assesses each individual's cancer to identify targeted therapies that can halt cancer growth. Identification of these "drivers" and corresponding medications used to possibly halt these pathways are important in cancer treatment.

Personalized genomics is the human genetics-derived study of analyzing and interpreting individualized genetic information by genome sequencing to identify genetic variations compared to the library of known sequences. International genetics communities have spared no effort from the past and have gradually cooperated to prosecute research projects to determine DNA sequences of the human genome using DNA sequencing techniques. The methods that are the most commonly used are whole exome sequencing and whole genome sequencing. Both approaches are used to identify genetic variations. Genome sequencing became more cost-effective over time, and made it applicable in the medical field, allowing scientists to understand which genes are attributed to specific diseases.

References

  1. ↑ Kumar, Sudhir; Dudley, Joel T.; Filipski, Alan; Liu, Li (2011-09-01). "Phylomedicine: An evolutionary telescope to explore and diagnose the universe of disease mutations". Trends in Genetics. 27 (9): 377–386. doi:10.1016/j.tig.2011.06.004. PMC   3272884 . PMID   21764165.
  2. ↑ "Institute for Genomics and Evolutionary Medicine at Temple University". igem.temple.edu. Retrieved 2016-06-29.
  3. ↑ McCarthy, Mark I.; Abecasis, Gonçalo R.; et al. (2008-05-01). "Genome-wide association studies for complex traits: consensus, uncertainty and challenges". Nature Reviews. Genetics. 9 (5): 356–369. doi:10.1038/nrg2344. PMID   18398418. S2CID   15032294.
  4. ↑ Hindorff, L.A.; MacArthur, J.; Morales, J.; Junkins, H.A.; Hall, P.N.; Klemm, A.K.; Manolio, T.A. (2015-05-12). "A Catalog of Published Genome-Wide Association Studies". National Human Genome Research Institute. Retrieved 2016-06-29.
  5. ↑ Stenson, Peter D.; et al. (2014-01-01). "The Human Gene Mutation Database: building a comprehensive mutation repository for clinical and molecular genetics, diagnostic testing and personalized genomic medicine". Human Genetics. 133 (1): 1–9. doi:10.1007/s00439-013-1358-4. PMC   3898141 . PMID   24077912.
  6. ↑ Hauser, Frances E.; et al. (2016-01-01). "Comparative sequence analyses of rhodopsin and RPE65 reveal patterns of selective constraint across hereditary retinal disease mutations". Visual Neuroscience. 33: e002. doi:10.1017/S0952523815000322. PMID   26750628. S2CID   206288497.
  7. ↑ Kirwan, John D.; et al. (2013-04-01). "A phylomedicine approach to understanding the evolution of auditory sensory perception and disease in mammals". Evolutionary Applications. 6 (3): 412–422. doi:10.1111/eva.12047. PMC   3673470 . PMID   23745134.
  8. ↑ Dudley, Joel T.; et al. (2012-09-01). "Evolutionary meta-analysis of association studies reveals ancient constraints affecting disease marker discovery". Molecular Biology and Evolution. 29 (9): 2087–2094. doi:10.1093/molbev/mss079. PMC   3424407 . PMID   22389448.
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