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Fruit fly larvae occur as either 'rovers', which move a long way to find food, or 'sitters', which stay within a more restricted area. This polymorphism is determined by alleles of a cyclic GMP-dependent protein kinase gene; rovers are at an advantage in crowded populations, while sitters have the edge at low population density.
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Hypertrophic cardiomyopathy is a Mendelian disease characterized by cardiac hypertrophy. It has a prevalence of 1:500 individuals and is the most common cause of sudden death in the young. Other complications include heart failure and the need for heart transplantation. Hypertrophic cardiomyopathy is due to sarcomeric gene mutations, however, phenocopies with myocardial hypertrophy can be due to triplet-repeat syndromes (Friedreich ataxia and myotonic dystrophy), mitochondrial and metabolic diseases. In a peculiar form associated with Wolf-Parkinson-White syndrome, the disease is caused by mutations in the gamma2 regulatory subunit of the AMP-activated protein kinase gene, leading to a glycogen storage cardiomyopathy. In spite of the growing knowledge about the molecular basis of hypertrophic cardiomyopathy, very little is still known about the genotype-phenotype correlations and their clinical implications. In this review, the clinical and molecular genetics of hypertrophic cardiomyopathy are described.
Terpenes and sterols are complex molecules synthesized by equally complex biosynthetic pathways. Recent progress in using the tools of genetics, molecular genetics and genetic engineering to dissect triterpene metabolism in the cytosol, and terpene metabolism in the plastids, has opened up new strategies and avenues of investigation. Most importantly, these studies have enhanced our appreciation of the biological significance of these compounds for plants, and have revealed new secrets of this intriguing biochemistry for practical applications in agriculture and medicine.
Molecular genetics has transformed clinical concepts of Duchenne muscular dystrophy (DMD) in several different ways. (1) The disease can now be defined as a myopathy due to mutation at Xp21, a specific locus on the short arm of the X chromosome. (2) As a consequence of that discovery, any myopathy due to mutation at Xp21 should be a variant of DMD and should affect the same gene product. Moreover, any myopathy due to mutation at a location other than Xp21 should affect some other gene product. (3) For these reasons, DNA analysis is now needed for clinical diagnosis of muscle disease. (4) Xp21 myopathies may be mild or severe, may occur in females even though X-linked, and may be manifest only by high serum levels of creatine kinase. (5) Mental retardation is not consistently related to diseases that are encoded at Xp21. The association of mental retardation with DMD may be due to mutation in a separate gene near that for DMD. Concepts may soon be altered again as we learn about the affected gene product (dystrophin) and its role in these diseases.
Molecular genetic analyses of human hereditary disorders that affect cardiac atrial structure and function have recently identified several genes that regulate atrial morphogenesis. Mutations of the TBX5, NKX2.5, EVC, and PRKAR1 alpha genes all result in abnormalities of human atrial growth and development, and mutations in at least one gene results in familial atrial fibrillation and is as yet unidentified. Ongoing studies to find interactions between these transcription factors and intracellular signaling molecules and other as yet unknown genes are establishing critical pathways in human cardiogenesis. Human investigation and experimental animal models of heart development synergize to elucidate etiologies of common congenital heart disease.
PURPOSE: Since the recognition that oligodendrogliomas may be chemosensitive, their diagnosis and clinical management has become highly controversial. Histopathology diagnosis remains challenging and new tools such as molecular genetics or molecular imaging require evaluation. EXPERIMENTAL DESIGN: In a single-center, population-based prospective study, allelic imbalance in chromosomes 1p36, 19q13, 17p13, 10p12-15, and 10q22-26 has been investigated in 19 oligodendroglioma WHO grade 2 (OII), 20 oligoastrocytoma WHO grade 2 (OAII), 8 oligodendroglioma WHO grade 3 (OIII), and 12 oligoastrocytoma WHO grade 3 (OAIII), and compared with pretherapy histopathology, computed tomography and/or magnetic resonance (CT and/or MR), [fluorine-18]fluoro-2-deoxyglucose (18F-FDG), and thallium-201 single-photon emission computed tomography (201Tl SPECT). RESULTS: In 50 cases, 18F-FDG uptake correlated with 201Tl uptake; however, 8 cases had increased 201Tl uptake but were hypometabolic for 18F-FDG, and 1 case was hypermetabolic with normal 201Tl uptake. Sixteen cases enhanced on CT/MR but failed to show 201Tl uptake; and 2 low-grade non-enhancing oligodendrogliomas had increased 201Tl uptake. Increased metabolism was more likely in high-grade cases, with 201Tl uptake more strongly correlated with grade than was 18F-FDG uptake. Tumors with 1p/19q loss were more likely to show increased 201Tl uptake and, to a lesser degree, increased 18F-FDG uptake than those without these losses. Elevated metabolism in 28% of low-grade tumors was significantly more common in tumors with 1p/19q loss, and increased uptake of both 18F-FDG and 201Tl in low-grade cases was found only in those with 1p/19q loss. CONCLUSIONS: In this study, dissociation of uptake of contrast agents and radiotracers suggests independent deregulation of the blood-brain barrier breakdown and metabolism during disease progression of oligodendroglial neoplasms, and the association of elevated metabolism with 1p/19q loss, particularly in low-grade tumors, may have implications for clinical management.
Mice and humans with systemic lupus erythematosus (SLE) have been studied with regard to cellular, genetic and molecular genetic abnormalities. B cell hyperactivity and autoantibody production are the hallmarks of this illness. In humans with SLE, there is increased stem cell, B cell precursor and B cell proliferation. The same is true of NZB mice. In lpr/lpr and gld/gld mice, marked expansion of a subpopulation of T cells allows extrathymic terminal T cell maturation and secondary B cell hyperactivity. Androgens suppress these processes and polyclonal immune activators accelerate them. Three types of genes are identified: inducing genes, accelerating genes and background genes. These give rise to abnormal expression of various cellular oncogenes, T cell receptor genes and immunoglobulin genes. The data suggest that abnormal immune regulation plays a critical role in the development of SLE, with polyclonal B cell activation being common to both mice and humans with SLE. Different genetic and cellular abnormalities underlie the ultimate syndrome, the common denominator, generalized autoimmunity, that we call SLE.
The four Scottish university medical genetics centres formed a consortium in 1985 to provide a DNA based service in prenatal diagnosis, carrier detection, and predictive testing for a range of Mendelian disorders. Each centre took sole responsibility for laboratory analyses of an assigned set of disorders, while families continued to be investigated and patients counselled within their own areas. DNA was extracted from relevant tissues in the centre most convenient to the family member and then dispatched to the appropriate laboratory for analysis. Results were interpreted and risks assessed by discussion between laboratory staff and the clinical geneticist in charge of the case. In the first three years of the consortium 92 prenatal diagnoses or exclusion tests were carried out, the majority being for cystic fibrosis (35), Duchenne muscular dystrophy (21), and Huntington's disease (11). Carrier testing was carried out in 271 X linked recessive disorders, the most common indications being Duchenne and Becker muscular dystrophies (198) and haemophilias A and B (48). Predictive testing was attempted in 41 consultants at risk for Huntington's disease, 37 at risk for myotonic dystrophy, and 32 at risk for developing adult polycystic kidney disease. The total of all carrier tests, including those for autosomal recessives, was 543. A consortium or supraregional approach to molecular genetics services has a number of advantages. Constituent laboratories need hold only those probes and enzymes relevant to their assigned disorders and can gain maximum experience with these systems. Scattered families may often be linked into single kinships, thus allowing rapid confirmation of diagnosis when an urgent request is made for a prenatal diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)
The MHC is a well-characterised region of the human genome, containing a high diversity of genes and an apparent clustering of genes involved in the immune response. The genomic sequence of an 8 Mb section, containing the MHC and flanking regions and covering over 300 genes, will soon be available. Since this is a highly polymorphic region, the molecular genetics of the MHC and its relationship with disease have been studied in considerable detail.
As stated earlier, the digestion of roughly 100 short talks delivered within a few days and containing very condensed information is, even for experts, quite demanding. Sometimes one felt in danger of becoming "psyched out" by all the experiments described; perhaps smaller group discussions dealing with experiments that have not worked, as well as the elimination of redundancies in the presentations, would have added to the flavor of the meeting. But what is the "take home message" from the 1990 CSH Mouse Meeting? With all the described breakthroughs, has mouse molecular genetics and development arrived at a turning point? I am inclined to answer this question with a "yes" on the basis of the following considerations: The elegant studies of development in Drosophila and Caenorhabditis elegans were made possible by the power of genetics with the use of developmental mutations. These studies taught us that the sequential activation of a hierarchy of regulatory genes dictates the temporal and spatial patterns of expression of proteins that define cell phenotypes and the body plan, and thereby control development. With the identification of important regulatory genes responsible for many classical as well as experimentally induced mouse mutations, in conjunction with traditional transgenic studies and the power of deleting and altering genes via ES cell chimeras, the study of mouse development has now gained an important new dimension. It is feasible that the consequences of subtle but precise genetic changes, such as the modification of regulatory elements or DNA-binding domains, can be studied in the whole organism by use of ES cells.(ABSTRACT TRUNCATED AT 250 WORDS)
The availability of molecular genetic tests for the identification of mutant gene carriers, and for assessing individual genetic response to pharmacologic agents, infectious agents, and other environmental exposures, is expected to result in the increased use of the molecular genetic testing laboratory by primary care physicians. However, a number of concerns have been raised about such testing including the need for safeguards to protect patient privacy, and if the interface between genetic testing laboratories and the ordering physician facilitates the appropriate clinical use of the test result. In this study, genetic counselors were surveyed to determine their practices with regard to the clinical issues of informed consent and confidentiality in the context of genetic testing, and to assess their level of satisfaction with the reporting practices of molecular genetic testing laboratories. The results of this survey revealed that there is variability in the practices of genetic counselors with regard to obtaining informed consent, and that there are areas for improvement with regard to molecular genetic test reports, particularly in terms of interpretation of results.
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X-linked ichthyosis has been shown to be associated with the deficiency of the steroid sulfatase/arylsulfatase C. The molecular biological results are reviewed concerning the localization of the steroid sulfatase gene to the distal short arm of the X chromosome and the molecular defects of this gene in patients of X-linked ichthyosis. The conclusions are summarized for genetic counselling, carrier detection and prenatal diagnosis.
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