Endogenous retroviruses and human evolution

Humans share about 99% of their genomic DNA with chimpanzees and bonobos; thus, the differences between these species are unlikely to be in gene content but could be caused by inherited changes in regulatory systems. Endogenous retroviruses (ERVs) comprise approximately 5% of the human genome. The LTRs of ERVs contain many regulatory sequences, such as promoters, enhancers, polyadenylation signals and factor-binding sites. Thus, they can influence the expression of nearby human genes. All known human-specific LTRs belong to the HERV-K (human ERV) family, the most active family in the human genome. It is likely that some of these ERVs could have integrated into regulatory regions of the human genome, and therefore could have had an impact on the expression of adjacent genes, which have consequently contributed to human evolution. This review discusses possible functional consequences of ERV integration in active coding regions.     

Endogenous retroviruses of the chicken genome

 

We report that the positions of minor, U12 introns are conserved in orthologous genes from human and Arabidopsis to an even greater extent than the positions of the major, U2 introns. The U12 introns, especially, conserved ones are concentrated in 5'-portions of plant and animal genes, where the U12 to U2 conversions occurs preferentially in the 3'-portions of genes. These results are compatible with the hypothesis that the high level of conservation of U12 intron positions and their persistence in genomes despite the unidirectional U12 to U2 conversion are explained by the role of the slowly excised U12 introns in down-regulation of gene expression.

Reviewers

This article was reviewed by John Logsdon and Manyuan Long. For the full reviews, please go to the Reviewers' Reports section.     

Endogenous retroviruses promote homeostatic and inflammatory responses to the microbiota

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Endogenous retroviruses: potential etiologic agents in autoimmunity.

The genomes of all organisms, from yeast to humans, contain thousands of endogenous retroviruses (ERV). In most species all or almost all ERV are noninfectious, but some ERV retain open reading frames capable of encoding proteins. RNA and proteins derived from ERV are expressed in humans and other species. Until recently, there was little evidence that this ERV expression resulted in any immunologic effects. Recent studies make it increasingly clear that some ERV have important immunologic effects. The immune effects of ERV expression raise the question of a possible pathogenic role in idiopathic autoimmune diseases. Interest in this question has been heightened by the observation that some infectious retroviruses cause manifestations of autoimmunity. Nonetheless, attempts to isolate infectious retroviruses from patients with idiopathic autoimmune diseases have generally failed. The possible role of ERV in idiopathic autoimmune diseases has not yet been fully explored. This review focuses on the known and the potential immune effects of ERV, especially as they may relate to autoimmune diseases.     

Relations between animal transgenesis and reproduction

Transgenesis has become an essential tool for the study of gene expression mechanisms and functions. Transgenesis is also more and more used for biotechnological applications such as the study of human diseases, the adaptation of pig organs to humans, the production of pharmaceutical proteins in milk and likely in the future for the improvement of animal production. The use of transgenesis relies on the efficiency of gene transfer. New tools have been recently designed to improve gene transfer. The methods of gene transfer are highly dependent on the techniques of animal reproduction. Conversely, the need to improve transgenesis urges researchers to study some of the key steps in reproduction and to find new techniques for gene transfer. This paper summarises the recent data and the perspectives offered by animal transgenesis.     

Magnesium in animal and human reproduction]

The literature concerned with the amount of magnesium in genital organs and products of sexual activity is analysed in the first chapter; these data are compared with those concerning other organs and replaced in a comprehensive view of the body, related or not with the medium. It is likely that magnesium plays a role in ovule maturation, sperm viability and fecundation in Invertebrates and Fishes. In Birds and Mammals, it appears to be necessary for fecundation. In the Discoglossus (Anurian Amphibian), the deficiency and the excess in Mg2+ reduce development and influence the growth of the body and the ovary. In the Rat, the pregnancy cannot be normal, unless the food contains an adequate supply of magnesium. Severe or mild deficiencies affect the site of fetal implantation and, if they are prolonged, lead to abortion in the first instance and pathological disorders in the latter. An ionic determination of sex has been established in various animal species and in Man. In some marine Invertebrates, and in the Discoglossus, changes in ionic concentration of the breeding medium carried out immediately after fecundation induce, at will, a majority of one sex or the other; in various Mammals and in Man, variations in the composition of mineral food administered to the female before fecundation may also induce changes in the sex ratio of the progeny.     

Endogenous cannabinoids: metabolism and their role in reproduction

Over the past two decades a number of endogenous compounds that act as ligands for the cannabinoid receptors has been discovered. In analogy with the "endorphins" these compounds have been called "endocannabinoids". Endocannabinoids have been demonstrated in many mammalian tissues including humans and are widely distributed in the CNS, peripheral nerves, uterus, leukocytes, spleen and testicles. The uterus contains the highest levels of anandamide, the first discovered endocannabinoid, suggesting an important role for this substance in reproduction. Several studies have shown anandamide to be involved in the regulation of implantation and reduced activity of the enzyme that degrades anandamide has been associated with early pregnancy loss in humans. The bulk of the literature concerning endocannabinoids is based upon anandamide related studies; therefore, in this review we focus on the metabolism of anandamide and its role in reproduction.     

Endogenous viral elements in animal genomes

Integration into the nuclear genome of germ line cells can lead to vertical inheritance of retroviral genes as host alleles. For other viruses, germ line integration has only rarely been documented. Nonetheless, we identified endogenous viral elements (EVEs) derived from ten non-retroviral families by systematic in silico screening of animal genomes, including the first endogenous representatives of double-stranded RNA, reverse-transcribing DNA, and segmented RNA viruses, and the first endogenous DNA viruses in mammalian genomes. Phylogenetic and genomic analysis of EVEs across multiple host species revealed novel information about the origin and evolution of diverse virus groups. Furthermore, several of the elements identified here encode intact open reading frames or are expressed as mRNA. For one element in the primate lineage, we provide statistically robust evidence for exaptation. Our findings establish that genetic material derived from all known viral genome types and replication strategies can enter the animal germ line, greatly broadening the scope of paleovirological studies and indicating a more significant evolutionary role for gene flow from virus to animal genomes than has previously been recognized.     

Endogenous ouabain-like substances in animal tissues

Methods of purification and properties of the digitalis-like substances from different animal-origin sources are considered. Possible mechanisms of the cardiac glycoside-effect on the cardiac muscle and endogenous digitalis-like factors' effect on the smooth muscles of the blood vessels are discussed. Criteria that may be used to characterize the digitalis-like activity in samples and extracts obtained from different tissues are presented. The role of these substances in some types of pathologies, especially in the development of hypertension, is considered.     

Toll-like receptors and their role in animal reproduction

Toll-like receptors (TLRs) are evolutionarily conserved innate immune receptors that recognize pathogen specific molecular pattern (PAMPs) in an efficient, non-self-reactive manner and initiate specific immune signaling that culminates in triggering antigen-specific adaptive responses. Different TLR genes in domestic animal species have been characterized and accumulating evidence from recent studies indicates an extended role for TLR signaling in reproductive physiology. In females, TLRs have been implicated in the regulation of ovulation, fertilization, gestation and parturition, as well as in pathological conditions such as endometritis and mastitis. In males, TLRs play a role in steroidogenesis and spermatogenesis. Use of TLR agonists has also been shown to be effective in the treatment of certain reproductive tract infections. Moreover, gene polymorphisms in TLRs have been associated with mastitis providing evidence that TLRs can potentially be exploited as markers in future breeding programs. The aim of this review is to provide a comprehensive treatise on role of TLRs in male and female reproductive physiology and associated pathology in domestic livestock.     

骨形态发生蛋白家族及其受体在生殖调控中的作用

骨形态发生蛋白 (bonemorphogenelicprotein ,BMP)又称骨形成蛋白 ,属于转化生长因子超家族成员。本文从理化特性、受体种类、信号转导机制 ,以及在动物生殖调控中的作用和受体基因突变所导致的多胎机制等方面 ,详细阐述了有关BMP近年来的研究状况 ,旨在为研究绵羊或其它物种的多胎机制提供参考