Phenotype—genotype relationships in monogenic disease: lessons from the thalassaemias
TL;DR: Findings in the β-thalassaemias highlight the problems that might be encountered in defining the relationship between the genome and the environment in multifactorial disorders, in which the degree of heritability might be relatively low and several environmental agents are involved.
Abstract: The remarkable phenotypic diversity of the beta-thalassaemias reflects the heterogeneity of mutations at the beta-globin locus, the action of many secondary and tertiary modifiers, and a wide range of environmental factors. It is likely that phenotype-genotype relationships will be equally complex in the case of many monogenic diseases. These findings highlight the problems that might be encountered in defining the relationship between the genome and the environment in multifactorial disorders, in which the degree of heritability might be relatively low and several environmental agents are involved. They also emphasize the value of an understanding of phenotype-genotype relationships in designing approaches to gene therapy.
Citations
More filters
TL;DR: Meryon’s observations were neglected for many years for various reasons, and the disorder became eponymously associated with Duchenne in Paris, who detailed the clinical and muscle histology some years later.
1,494 citations
Book•
[...]
23 Apr 2021
TL;DR: Studies from past decades related to such translational research as the use of hydroxyurea in treatment, as well as the therapeutic promise of red-cell ion-channel blockers, and antiadhesion and anti-inflammatory therapy are highlighted.
Abstract: Sickle-cell disease is one of the most common severe monogenic disorders in the world. Haemoglobin polymerisation, leading to erythrocyte rigidity and vaso-occlusion, is central to the pathophysiology of this disease, although the importance of chronic anaemia, haemolysis, and vasculopathy has been established. Clinical management is basic and few treatments have a robust evidence base. One of the main problems of sickle-cell disease in children is the development of cerebrovascular disease and cognitive impairment, and the role of blood transfusion and hydroxycarbamide for prevention of these complications is starting to be understood. Recurrent episodes of vaso-occlusion and inflammation result in progressive damage to most organs, including the brain, kidneys, lungs, bones, and cardiovascular system, which becomes apparent with increasing age. Most people with sickle-cell disease live in Africa, where little is known about this disease; however, we do know that the disorder follows a more severe clinical course in Africa than for the rest of the world and that infectious diseases have a role in causing this increased severity of sickle-cell disease. More work is needed to develop effective treatments that specifically target pathophysiological changes and clinical complications of sickle-cell disease.
966 citations
TL;DR: The key to understanding the evolutionary significance of QTL is to understand the nature of inherited variation, not in the immediate mechanistic sense of how genes influence phenotype, but, rather, to know what evolutionary forces maintain genetic variability.
Abstract: Until recently, it was impracticable to identify the genes that are responsible for variation in continuous traits, or to directly observe the effects of their different alleles. Now, the abundance of genetic markers has made it possible to identify quantitative trait loci (QTL)--the regions of a chromosome or, ideally, individual sequence variants that are responsible for trait variation. What kind of QTL do we expect to find and what can our observations of QTL tell us about how organisms evolve? The key to understanding the evolutionary significance of QTL is to understand the nature of inherited variation, not in the immediate mechanistic sense of how genes influence phenotype, but, rather, to know what evolutionary forces maintain genetic variability.
716 citations
TL;DR: The results indicate that several key HIF-regulatory and targeted genes are responsible for adaptation to high altitude in Andeans and Tibetans, and several different chromosomal regions are implicated in the putative response to selection.
Abstract: High-altitude hypoxia (reduced inspired oxygen tension due to decreased barometric pressure) exerts severe physiological stress on the human body. Two high-altitude regions where humans have lived for millennia are the Andean Altiplano and the Tibetan Plateau. Populations living in these regions exhibit unique circulatory, respiratory, and hematological adaptations to life at high altitude. Although these responses have been well characterized physiologically, their underlying genetic basis remains unknown. We performed a genome scan to identify genes showing evidence of adaptation to hypoxia. We looked across each chromosome to identify genomic regions with previously unknown function with respect to altitude phenotypes. In addition, groups of genes functioning in oxygen metabolism and sensing were examined to test the hypothesis that particular pathways have been involved in genetic adaptation to altitude. Applying four population genetic statistics commonly used for detecting signatures of natural selection, we identified selection-nominated candidate genes and gene regions in these two populations (Andeans and Tibetans) separately. The Tibetan and Andean patterns of genetic adaptation are largely distinct from one another, with both populations showing evidence of positive natural selection in different genes or gene regions. Interestingly, one gene previously known to be important in cellular oxygen sensing, EGLN1 (also known as PHD2), shows evidence of positive selection in both Tibetans and Andeans. However, the pattern of variation for this gene differs between the two populations. Our results indicate that several key HIF-regulatory and targeted genes are responsible for adaptation to high altitude in Andeans and Tibetans, and several different chromosomal regions are implicated in the putative response to selection. These data suggest a genetic role in high-altitude adaption and provide a basis for future genotype/phenotype association studies necessary to confirm the role of selection-nominated candidate genes and gene regions in adaptation to altitude.
494 citations
TL;DR: Developments in genetics have allowed a more systematic study of the impact that the human genome and infectious disease have on each other, and have confirmed heritability of susceptibility to several infectious diseases.
Abstract: Before Robert Koch's work in the late nineteenth century, diseases such as tuberculosis and leprosy were widely believed to be inherited disorders. Heritability of susceptibility to several infectious diseases has been confirmed by studies in the twentieth century. Infectious diseases, old and new, continue to be an important cause of mortality worldwide. A greater understanding of disease processes is needed if more effective therapies and more useful vaccines are to be produced. As part of this effort, developments in genetics have allowed a more systematic study of the impact that the human genome and infectious disease have on each other.
456 citations
Cites background from "Phenotype—genotype relationships in..."
...Disorders of globin synthesis are found commonly in malarious regions and the disorders that give rise to the milder phenotypes are among the most common, single-gene disorders worldwid...
[...]
References
More filters
Book•
01 Jan 1995
TL;DR: In this paper, the authors present a list of disorders of MITOCHONDRIAL FUNCTION, including the following: DISORDERS OF MIOCHONDRIC FERTILITY XIX, XVI, XIX.
Abstract: I. INTRODUCTION II. PERSPECTIVES III. GENERAL THEMES IV. CANCER V. CHROMOSOMES VI. DIAGNOSTIC APPROACHES VII. CARBOHYDRATES VIII. AMINO ACIDS IX. ORGANIC ACIDS X. DISORDERS OF MITOCHONDRIAL FUNCTION XI. PURINES AND PYRIMIDINES XII. LIPIDS XIII. PORPHYRINS XIV. METALS XV. PEROXISOMES XVI. LYSOSOMAL DISORDERS XVII. VITAMINS XVIII. HORMONES XIX. BLOOD XX. IMMUNE AND DEFENSE SYSTEMS XXI. MEMBRANE TRANSPORT DISORDERS XXII. CONNECTIVE TISSUE XXIII. CARDIOVASCULAR SYSTEM XXIV. KIDNEY XXV. MUSCLE XXVI. LUNG XXVII. SKIN XXVIII. NEUROGENETICS XXIX. EYE XXX. MULTISYSTEM INBORN ERRORS OF DEVELOPMENT
10,525 citations
TL;DR: Data support the hypothesis that the extraordinary polymorphism of major histocompatibility complex genes has evolved primarily through natural selection by infectious pathogens.
Abstract: A large case-control study of malaria in West African children shows that a human leucocyte class I antigen (HLA-Bw53) and an HLA class II haplotype (DRB1*1302-DQB1*0501), common in West Africans but rare in other racial groups, are independently associated with protection from severe malaria. In this population they account for as great a reduction in disease incidence as the sickle-cell haemoglobin variant. These data support the hypothesis that the extraordinary polymorphism of major histocompatibility complex genes has evolved primarily through natural selection by infectious pathogens.
1,554 citations
TL;DR: The maintenance of the TNF2 allele at a gene frequency of 0.16 in The Gambia implies that the increased risk of cerebral malaria in homozygotes is counterbalanced by some biological advantage, suggesting that regulatory polymorphisms of cytokine genes can affect the outcome of severe infection.
Abstract: Tumour-necrosis factor-alpha (TNF-alpha) is believed to have an important role in the pathogenesis of severe infectious disease and fatal cerebral malaria is associated with high circulating levels of this cytokine. In a large case-control study in Gambian children we find that homozygotes for the TNF2 allele, a variant of the TNF-alpha gene promoter region, have a relative risk of 7 for death or severe neurological sequelae due to cerebral malaria. Although the TNF2 allele is in linkage disequilibrium with several neighbouring HLA alleles, we show that this disease association is independent of HLA class I and class II variation. These data suggest that regulatory polymorphisms of cytokine genes can affect the outcome of severe infection. The maintenance of the TNF2 allele at a gene frequency of 0.16 in The Gambia implies that the increased risk of cerebral malaria in homozygotes is counterbalanced by some biological advantage.
1,181 citations
TL;DR: A wealth of information is produced on the mechanisms by which a single base substitution in the gene encoding the human β-globin subunit, with the resulting replacement of β6 glutamic acid by valine, leads to the protean and devastating clinical manifestations of sickle cell disease.
Abstract: In 1949, the discovery that sickle hemoglobin (α2 βS2) has an abnormal electrophoretic mobility prompted Linus Pauling and his colleagues to christen sickle cell anemia “a molecular disease.”1 The ensuing five decades have produced a wealth of information on the mechanisms by which a single base substitution in the gene encoding the human β-globin subunit, with the resulting replacement of β6 glutamic acid by valine, leads to the protean and devastating clinical manifestations of sickle cell disease. Until recently there was a disappointing lag in the application of this knowledge to the design of safe and effective . . .
1,008 citations
840 citations