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PubMed1998

Multivariate behavioral genetic analysis of achievement and cognitive measures in reading-disabled and control twin pairs.

In recent years behavioral genetic studies have provided conclusive evidence that reading disability and related learning disorders, such as mathematics disability, are due at least in part to heritable factors (DeFries et al. 1987; Alarcón et al. 1997). Although the observed relationship between performance in these areas also may be due substantially to genetic influences (Light and DeFries 1995; Thompson et al. 1991), relatively few studies have examined the genetic and environmental etiology of this covariation in a multivariate framework. In the present study data from 196 identical (monozygotic; MZ) and 155 same-sex fraternal (dizygotic; DZ) twin pairs in which at least one member of each pair evidenced reading problems in school (reading disabled) were subjected to a multivariate behavioral genetic analysis. Structural equation models were fitted to twin data for verbal IQ (VIQ), phonological decoding ability (PHON), reading performance (READ), and mathematics performance (MATH) to assess the extent to which VIQ and PHON mediate the observed covariation between READ and MATH. Results suggest that VIQ and PHON account for most of the covariation between READ and MATH. Moreover, approximately 82% of the observed correlation between READ and MATH was due to genetic factors that also influence VIQ and PHON. When data from 132 MZ and 91 same-sex DZ control twin pairs in which neither twin had a history of reading problems were subjected to the same analyses, the covariation between READ and MATH was found to be due to both genetic and shared environmental influences. Thus genetic factors that influence VIQ and PHON also contribute to the observed covariation between READ and MATH in both a reading-disabled and a control twin sample.

Achievement↗
PubMed2026

Molecular Determinants and Therapeutic Targeting of Stop Codon Readthrough in Eukaryotic Translation.

Accurate translation termination is essential for proteome integrity and in eukaryotes is primarily governed by the release factors eRF1 and eRF3, which ensure precise recognition of stop codons and efficient release of nascent polypeptides. However, proteome integrity is challenged by mutations that generate premature termination codons (PTCs), leading to truncated, nonfunctional proteins and degradation of the aberrant transcript via nonsense-mediated mRNA decay (NMD). Collectively, these events account for ∼1800 human genetic diseases. Translational readthrough, the process by which near-cognate tRNAs decode stop codons and allow ribosomes to continue elongation beyond the stop codon, represents a possibility to suppress PTCs and restore full-length protein synthesis. Initially discovered in viruses as a mechanism to expand coding capacity, readthrough is now recognized as a regulated feature of eukaryotic gene expression influenced by both cis-acting sequence elements and trans-acting factors. Recent evidence highlights the remarkable context dependence of readthrough, revealing variation across transcripts, tissues, and developmental stages. In this review, we examine the molecular determinants that define stop codon recognition and readthrough efficiency, with particular emphasis on nucleotide context. We further discuss the mechanisms and binding sites of small molecules that promote PTC readthrough, and summarize the clinical development landscape of readthrough-inducing compounds for the treatment of diseases caused by nonsense mutations.

Humans↗
PubMed2005

Decoding cis-regulatory systems in ascidians.

Ascidians, or sea squirts, are lower chordates, and share basic gene repertoires and many characteristics, both developmental and physiological, with vertebrates. Therefore, decoding cis-regulatory systems in ascidians will contribute toward elucidating the genetic regulatory systems underlying the developmental and physiological processes of vertebrates. cis-Regulatory DNAs can also be used for tissue-specific genetic manipulation, a powerful tool for studying ascidian development and physiology. Because the ascidian genome is compact compared with vertebrate genomes, both intergenic regions and introns are relatively small in ascidians. Short upstream intergenic regions contain a complete set of cis-regulatory elements for spatially regulated expression of a majority of ascidian genes. These features of the ascidian genome are a great advantage in identifying cis-regulatory sequences and in analyzing their functions. Function of cis-regulatory DNAs has been analyzed for a number of tissue-specific and developmentally regulated genes of ascidians by introducing promoter-reporter fusion constructs into ascidian embryos. The availability of the whole genome sequences of the two Ciona species, Ciona intestinalis and Ciona savignyi, facilitates comparative genomics approaches to identify cis-regulatory DNAs. Recent studies demonstrate that computational methods can help identify cis-regulatory elements in the ascidian genome. This review presents a comprehensive list of ascidian genes whose cis-regulatory regions have been subjected to functional analysis, and highlights the recent advances in bioinformatics and comparative genomics approaches to cis-regulatory systems in ascidians.

Animals↗
PubMed2006

Decoding errors and the involvement of the E-site.

Life depends on the faithful translation of the genetic information into proteins. Ribosomes have developed remarkable mechanisms to ensure the accurate synthesis of proteins. In the first part of this review various types of ribosomal errors and their importance for cell-life are surveyed, while in the second part two important aspects of the ribosomal E-site for the accuracy of translation are considered: (i) The fact that usually misincorporations are not harmful for the cell, since only one in about 400 misincorporations will affect the structure and/or function of a protein, is a function of the E-site. (ii) In contrast, an extremely harmful translational error is a loss of the reading frame, resulting in an immediate loss of the genetic information. Maintenance of the reading frame is one of the most remarkable achievements of the ribosome; only once in about 30,000 elongation cycles is the reading frame lost. A cognate tRNA at the E-site is an essential prerequisite for this high precision.

Anticodon↗
PubMed2002

A map of the common chimpanzee genome.

The completion of the chimpanzee genome will greatly help us determine which genetic changes are unique to humanity. Chimpanzees are our closest living relative, and a recent study has made considerable progress towards decoding the genome of our sister taxon.1 Over 75,000 common chimpanzee (Pan troglodytes) bacterial artificial chromosome end sequences were aligned and mapped to the human genome. This study shows the remarkable genetic similarity (98.77%) between humans and chimpanzees, while highlighting intriguing areas of potential difference. If we wish to understand the genetic basis of humankind, the completion of the chimpanzee genome deserves high priority.

Animals↗
PubMed2006

Biochemical characterization of the ribosomal decoding site.

Prior to the emergence of crystal structures of the ribosome, different ribosomal functions were identified with specific regions of ribosomal RNA by biochemical and genetic approaches. In particular, three universally conserved bases of 16S rRNA, G530, A1492 and A1493, were implicated in the interaction of the incoming aminoacyl-tRNA with the 30S subunit and mRNA. The conserved region surrounding A1492 and A1493 was called the "decoding site", based on the results of chemical probing experiments and antibiotic resistance mutations. Crystallographic studies from the Ramakrishnan laboratory have now shown that G530 loop, A1492 and A1493 undergo localized conformational changes to form an RNA structure that positions these three bases to inspect the accuracy of the codon-anticodon match with high stereochemical precision, using A-minor interactions. Some results from the pre-X-ray era may provide clues to further aspects of the decoding process.

Anticodon↗
PubMed2004

RNAi and HTS: exploring cancer by systematic loss-of-function.

Cancer develops through the successive accumulation and selection of genetic and epigenetic alterations, enabling cells to survive, replicate and evade homeostatic control mechanisms such as apoptosis and antiproliferative signals. This transformation process, however, may create vulnerabilities since the accumulation of mutations can expose synthetic lethal gene interactions and oncogene-driven cellular reprogramming ('addiction'), giving rise to new therapeutic avenues. With the completion of the human genome project, it is anticipated that the identification and characterization of genetic networks that regulate cell growth, differentiation, apoptosis and transformation will be fundamental to decoding the complexity of these processes, and ultimately, cancer itself. Genomic methodologies, such as large-scale mRNA profiling using microarrays, have already begun to reveal the molecular basis of cancer heterogeneity and the clinical behavior of tumors. The combination of traditional cell culture techniques with high-throughput screening approaches has given rise to new cellular-genomics methodologies that enable the simultaneous interrogation of thousands of genes in live cells, facilitating true functional profiling of biological processes. Among these, RNA interference (RNAi) has the potential to enable rapid genome-wide loss-of-function (LOF) screens in mammalian systems, which until recently has been the sole domain of lower organisms. Here, we present a broad overview of this maturing technology and explore how, within current technical constraints, large-scale LOF use of RNAi can be exploited to uncover the molecular basis of cancer--from the genetics of synthetic lethality and oncogene-dependent cellular addiction to the acquisition of cancer-associated cellular phenotypes.

False Negative Reactions↗
PubMed2026

Hidden Diversity in the Sands: Genomic Footprints of Pleistocene Refugia and Fragile Futures of the Turkestan Ground-Jay (Podoces panderi) in Central Asia.

The Turkestan ground-jay (Podoces panderi), a corvid endemic to Central Asia's deserts and steppes, exemplifies how extreme environments drive speciation. Our study provides the first comprehensive high-resolution genomic analysis of this species, using complete mitochondrial genomes (49 individuals) to decode its population structure and demographic past. Our analyses revealed three highly divergent genetic clusters with strong geographic structure. The P. p. iliensis population (Cluster_3) showed particularly pronounced genetic distinctiveness, with significant differentiation from P. p. panderi (Cluster_2 and Cluster_1) populations. This clear genetic separation supports the taxonomic validity of P. p. iliensis as a distinct evolutionary lineage. Demographic reconstruction indicated that Cluster_2 likely represents the ancestral group, with subsequent southward expansion into the Karakum region. The isolated P. p. iliensis population exhibited signatures of long-term isolation, including reduced genetic diversity and absence of recent gene flow with other clusters. These results provide strong evidence that P. p. iliensis represents a distinct evolutionary unit. The genetic structuring into three clusters reflects historical isolation in desert refugia during Pleistocene climatic fluctuations. Notably, we detected asymmetric gene flow among three clusters. These findings redefine P. panderi as a model for desert adaptation, where climatic extremes forged genetic fragmentation amid limited dispersal. Beyond taxonomy, our work highlights how aridification sculpted biodiversity in Asia's interior, urging conservation attention for these evolutionarily distinct lineages.

Animals↗
PubMed2003

The rate of peptidyl-tRNA dissociation from the ribosome during minigene expression depends on the nature of the last decoding interaction.

The expression of some very short open reading frames (ORFs) in Escherichia coli results in peptidyl-tRNA accumulation that is lethal to cells defective in peptidyl-tRNA hydrolase activity. In an attempt to understand the factors that affect this phenotype, we have surveyed the toxicity of a complete set of two-codon ORFs cloned as minigenes in inducible expression vectors. The minigenes were tested in hydrolase-defective hosts and classified according to their degree of toxicity. In general, minigenes harboring codons belonging to the same box in the standard table of the genetic code mediated similar degrees of toxicity. Moreover, the levels of peptidyl-tRNA accumulation for synonymous minigenes decoded by the same tRNA were comparable. However, two exceptions were observed: (i) expression of minigenes harboring the Arg codons CGA, CGU, and CGC, resulted in the accumulation of different levels of the unique peptidyl-tRNAArg-2 and (ii) the toxicity of minigenes containing CUG and UCU codons, each recognized by two different tRNAs, depended on peptidyl-tRNA accumulation of only one of them. Non-toxic, or partly toxic, minigenes prompted higher accumulation levels of peptidyl-tRNA upon deprivation of active RF1, implying that translation termination occurred efficiently. Our data indicate that the nature of the last decoding tRNA is crucial in the rate of peptidyl-tRNA release from the ribosome.

Blotting, Northern↗
PubMed2003

Roles of 5-substituents of tRNA wobble uridines in the recognition of purine-ending codons.

Many tRNA molecules that recognize the purine-ending codons but not the pyrimidine-ending codons have a modified uridine at the wobble position, in which a methylene carbon is attached directly to position 5 of the uracil ring. Although several models have been proposed concerning the mechanism by which the 5-substituents regulate codon-reading properties of the tRNAs, none could explain recent results of the experiments utilizing well-characterized modification-deficient strains of Escherichia coli. Here, we first summarize previous studies on the codon-reading properties of tRNA molecules with a U derivative at the wobble position. Then, we propose a hypothetical mechanism of the reading of the G-ending codons by such tRNA molecules that could explain the experimental results. The hypothesis supposes unconventional base pairs between a protonated form of the modified uridines and the G at the third position of the codon stabilized by two direct hydrogen bonds between the bases. The hypothesis also addresses differences between the prokaryotic and eukaryotic decoding systems.

Anticodon↗
PubMedDate not supplied

[Coding in molecular biology and radiation].

In work, on the basis of known base biological laws, the new natural three-dimensional designs are under construction: codonogram and aminogram. Codonogram and aminogram have revealed the new laws of coding and constructions in molecular biology. The secondary coding codonogram, at the expense of redundancy, has enabled for DNA, RNA, and mRNA to construct the hidden coding layers (HLC). HLC are constructed on a base of pirimidine and purine. In interaction with ferments HLC, should guarantee: addressation, synchronization, correction and other functional transformations of a gene. Radiation can damage a layer mRNA of synthesis protein, hidden layers of coding and structure of the ferments of the cell. In work are given: kodonogram, aminogram UGC, basis of construction HLC, the references to the literature with an example of decoding.

Base Sequence↗
PubMed2003

Genebanks: a comparison of eight proposed international genetic databases.

OBJECTIVE: To identify and compare population-based genetic databases, or "genebanks", that have been proposed in eight international locations between 1998 and 2002. A genebank can be defined as a stored collection of genetic samples in the form of blood or tissue, that can be linked with medical and genealogical or lifestyle information from a specific population, gathered using a process of generalized consent. METHODS: Genebanks were identified by searching Medline and internet search engines with key words such as "genetic database" and "biobank" and by reviewing literature on previously identified databases such as the deCode project. Collection of genebank characteristics was by an electronic and literature search, augmented by correspondence with informed individuals. The proposed genebanks are located in Iceland, the United Kingdom, Estonia, Latvia, Sweden, Singapore, the Kingdom of Tonga, and Quebec, Canada. Comparisons of the genebanks were based on the following criteria: genebank location and description of purpose, role of government, commercial involvement, consent and confidentiality procedures, opposition to the genebank, and current progress. RESULTS: All of the groups proposing the genebanks plan to search for susceptibility genes for complex diseases while attempting to improve public health and medical care in the region and, in some cases, stimulating the local economy through expansion of the biotechnology sector. While all of the identified plans share these purposes, they differ in many aspects, including funding, subject participation, and organization. The balance of government and commercial involvement in the development of each project varies. Genetic samples and health information will be collected from participants and coded in all of the genebanks, but consent procedures range from presumed consent of the entire eligible population to recruitment of volunteers with informed consent. Issues regarding confidentiality and consent have resulted in opposition to some of the more publicized projects. None of the proposed databases are currently operational and at least one project was terminated due to opposition. CONCLUSIONS: Ambitious genebank projects have been proposed in numerous countries and provinces. The characteristics of the projects vary, but all intend to map genes for common diseases and hope to improve the health of the populations involved. The impact of these projects on understanding genetic susceptibility to disease will be increasingly apparent if the projects become operational. The ethical, legal, and social implications of the projects should be carefully considered during their development.

Canada↗
PubMed2004

Multiplexed genetic analysis using an expanded genetic alphabet.

BACKGROUND: All states require some kind of testing for newborns, but the policies are far from standardized. In some states, newborn screening may include genetic tests for a wide range of targets, but the costs and complexities of the newer genetic tests inhibit expansion of newborn screening. We describe the development and technical evaluation of a multiplex platform that may foster increased newborn genetic screening. METHODS: MultiCode PLx involves three major steps: PCR, target-specific extension, and liquid chip decoding. Each step is performed in the same reaction vessel, and the test is completed in approximately 3 h. For site-specific labeling and room-temperature decoding, we use an additional base pair constructed from isoguanosine and isocytidine. We used the method to test for mutations within the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The developed test was performed manually and by automated liquid handling. Initially, 225 samples with a range of genotypes were tested retrospectively with the method. A prospective study used samples from >400 newborns. RESULTS: In the retrospective study, 99.1% of samples were correctly genotyped with no incorrect calls made. In the perspective study, 95% of the samples were correctly genotyped for all targets, and there were no incorrect calls. CONCLUSIONS: The unique genetic multiplexing platform was successfully able to test for 31 targets within the CFTR gene and provides accurate genotype assignments in a clinical setting.

Autoanalysis↗
PubMed2004

Function of genetically encoded pyrrolysine in corrinoid-dependent methylamine methyltransferases.

Methanogenesis from trimethylamine, dimethylamine or monomethylamine is initiated by a series of corrinoid-dependent methyltransferases. The non-homologous genes encoding the full-length methyltransferases each possess an in-frame UAG (amber) codon that does not terminate translation. The amber codon is decoded by a dedicated tRNA, and corresponds to the novel amino acid pyrrolysine in one of the methyltransferases, indicating pyrrolysine to be the 22nd genetically encoded amino acid. Pyrrolysine has the structure of lysine with the (epsilon)N in amide linkage with a pyrroline ring. The reactivity of the electrophilic imine bond is the basis for the proposed function of pyrrolysine in activating and optimally orienting methylamine for methyl transfer to the cobalt ion of a cognate corrinoid protein. This reaction is essential for methane formation from methylamines, and may underlie the retention of pyrrolysine in the genetic code of methanogens.

Amides↗
PubMed1993

[Current situation of dominant autosomal renal polycystosis].

Adult onset polycystic kidney disease causes 11% of all end-stage renal disease in Spain. Recent advantages in the molecular genetics of autosomal dominant polycystic kidney disease (ADPKD) point the way towards the cloning and decoding. One of the gene loci, namely PKD1, was located to the short arm of chromosome 16. Recombinants between 16p polimorphic loci and the PKD1 locus are described. The clinical consecuents of ADPKD are analyzed. Hypertension arterial are found more frequent in the those patients. Caution is therefore recommend in using ACE inhibitors who are at high risk because of compromised renal function. Our study clarifies several clinical extrarenal manifestations of ADPKD. All modalities of renal replacement therapy are appropriate therapeutics choices.

Humans↗
PubMed2026

The Tor pathway, ribosome concentration, and wobble decoding mediate inhibitory effects of the Leu-Pro CUC-CCG codon pair in Saccharomyces cerevisiae.

Translation elongation and efficiency are modulated by the genetic code, with reduced translation efficiency and slow translation caused by 17 inhibitory codon pairs in the yeast Saccharomyces cerevisiae Nine of these inhibitory pairs are functionally important as they are disproportionately strongly conserved within orthologous genes in Saccharomyces sensu stricto For three pairs, including CGA-CGA, inhibition is triggered by ribosome collisions followed by known quality control responses, but the mechanisms by which nine other pairs cause inhibition are unknown. Here, our examination of the molecular basis of inhibition by one such pair, the highly conserved Leu-Pro CUC-CCG codon pair, yielded four findings. First, inhibition is mediated by tRNALeu(UAG), which decodes CUC by a U•C wobble interaction and effectively competes with the nonessential Watson-Crick base-pairing tRNALeu(GAG) Second, despite nearly universal conservation of U33 in tRNAs, the C33 alteration in tRNALeu(GAG) does not significantly impair its function. Third, inhibition likely is mediated by ribosome collisions, as many suppressors bear mutations known or predicted to reduce ribosome concentration, and as local reduction in ribosome concentration suppresses inhibition. Thus, differences between CUC-CCG and CGA-CGA inhibition likely occur downstream from ribosome collisions. Fourth, we find a link between the metabolic state and CUC-CCG inhibition, as we find six suppressor mutations in SCH9, a downstream effector of TORC1 that mediates ribosome production. As Sch9 is inactive during starvation, causing reduced ribosome concentration, one biological function of inhibitory pairs may be to mediate a change in relative expression during starvation conditions.

Ribosomes↗