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At least 163 records · Page 9Linked to original sources

Chemical suppression of a genetic mutation in a zebrafish model of aortic coarctation.

Conventional drug discovery approaches require a priori selection of an appropriate molecular target, but it is often not obvious which biological pathways must be targeted to reverse a disease phenotype. Phenotype-based screens offer the potential to identify pathways and potential therapies that influence disease processes. The zebrafish mutation gridlock (grl, affecting the gene hey2) disrupts aortic blood flow in a region and physiological manner akin to aortic coarctation in humans. Here we use a whole-organism, phenotype-based, small-molecule screen to discover a class of compounds that suppress the coarctation phenotype and permit survival to adulthood. These compounds function during the specification and migration of angioblasts. They act to upregulate expression of vascular endothelial growth factor (VEGF), and the activation of the VEGF pathway is sufficient to suppress the gridlock phenotype. Thus, organism-based screens allow the discovery of small molecules that ameliorate complex dysmorphic syndromes even without targeting the affected gene directly.

Animals↗

Genetic mutations influencing ovulation rate in sheep.

Ovulation rate in mammals is determined by a complex exchange of endocrine signals between the pituitary gland and the ovary, and by paracrine signals within ovarian follicles between the oocyte and its adjacent somatic cells. One approach to identifying factors regulating ovulation rate is to find mutations that influence the target phenotype and, in this context, sheep are proving to be remarkable experimental models. Recently, in three sheep families, namely Inverdale, Hanna and Booroola, the inherited mutation was mapped to a specific region of the sheep X chromosome (Inverdale, Hanna) or sheep chromosome 6 (Booroola) and in each, a point mutation was identified in genes from the bone morphogenetic protein (BMP) relatives of the transforming growth factor beta superfamily or their receptors. In Inverdale (I) and Hanna (H) sheep, separate point mutations were identified in the BMP15 gene corresponding to sites in the mature peptide coding region of the BMP15 growth factor (also known as growth differentiation factor 9B; GDF9B). Expression of the BMP15 gene was located exclusively in oocytes from the primary stage of follicular growth. There is a complete block of normal follicular development in females carrying two copies of the Inverdale mutation (II), two copies of the Hanna mutation (HH), or one copy of each mutation (HI). Increased ovulation rates are found in females with only one copy of either mutation (I+ or H+). In Booroola sheep, a point mutation was identified in the highly conserved intracellular serine threonine kinase signalling domain of the BMP-1B receptor. Within the ovary, this gene is expressed in oocytes in primordial and pre-antral follicles and in granulosa cells from the primary stage of growth as well as in corpora lutea. The effect of the Booroola mutation is additive for ovulation rate: animals with one copy of the mutation have an ovulation rate of 3 or 4, whereas those with two copies have an ovulation rate of between 5 and 14. Physiological studies of the above mutations demonstrate that the oocyte plays an active role with respect to its adjacent somatic cells during follicular development and support the hypothesis that the oocyte has a significant influence on the number of follicles that proceed to ovulation.

Animals↗

Huntington's disease: prospects for neuroprotective therapy 10 years after the discovery of the causative genetic mutation.

PURPOSE OF REVIEW: Ten years of intensive research are now beginning to bring candidate neuroprotective therapies to clinical trials. This review describes recent progress in basic, preclinical, and clinical research that underlies current and potential neuroprotective trials. RECENT FINDINGS: Basic research continues to elucidate the proteolytic processing of huntingtin into toxic fragments and has examined the toxic potential of huntingtin monomers versus oligomers versus insoluble aggregates. Energy depletion has been reinvigorated as a therapeutic target by studies identifying very early mitochondrial alterations. Toxic interactions between mutant huntingtin and a variety of transcription factors have emerged as a major focus with a variety of studies suggesting transcriptional dysfunction to be a central mechanism in Huntington's disease. Progress in preclinical research included therapeutic leads identified by compound library screens, by designing polypeptides that can interact with huntingtin, and by testing compounds in transgenic mice with the potential for affecting some of the mechanisms thought to underlie neurodegeneration. While early results of neurotransplantation are generating increasing controversy, a variety of compounds discovered to benefit transgenic mice are working their way into clinical trials in symptomatic patients. Studies in presymptomatic individuals at risk for developing Huntington's disease are underway to enable the testing of agents with the potential for delaying or preventing onset of symptoms. SUMMARY: While laboratory research continues to advance and provide therapeutic leads, clinical trials are needed to test existing leads and guide further progress. With any luck, some of these tests will begin to identify treatments that make a difference for families with the disease.

Amantadine↗

Digital detection of genetic mutations using SPC-sequencing.

Deletion or insertion mutations lead to a frameshift that causes misalignment between wild-type and mutated allele sequences, making it difficult to identify such mutations unambiguously by using electrophoresis-based DNA sequencing. We have previously established the feasibility of an accurate DNA sequencing method using solid-phase capturable (SPC) dideoxynucleotides and MALDI-TOF mass spectrometry on synthetic templates, an approach we refer to as SPC-sequencing. Here, we report the application of SPC-sequencing in characterizing frameshift mutations by using the detection of the BRCA1 gene mutations 185delAG and 5382insC as examples. In this method, Sanger DNA sequencing fragments are generated in one tube by using biotinylated dideoxynucleotides. The sequencing fragments carrying a biotin moiety at the 3' end are captured on a streptavidin-coated solid phase to eliminate excess primer, primer dimers, and false stops. Only correctly terminated DNA fragments are captured, subsequently released, and analyzed by mass spectrometry to obtain digital DNA sequencing data. This method produces distinct doublet mass peaks at each point in the mass spectrum beyond the mutation site, facilitating the accurate characterization of the mutation. We have compared SPC-sequencing with electrophoresis-based sequencing in characterizing the above BRCA1 mutations, demonstrating the significant advantage offered by SPC-sequencing for the accurate identification of frameshift mutations.

DNA↗

No genetic mutation in type II 3 beta-hydroxysteroid dehydrogenase gene in patients with biochemical evidence of enzyme deficiency.

Nonclassic or the mild form of 3 beta-hydroxysteroid dehydrogenase (NC3 beta-HSD) deficiency is an entity which is identified with typical features of premature pubarche, hirsutism, or oligomenorrhea. In this study, type II 3 beta-HSD gene from 4 girls who were diagnosed as NC3 beta-HSD deficient, base on the adrenal steroidogenic responses to ACTH, was analyzed to determine whether NC3 beta-HSD deficiency was an allelic variant of classical 3 beta-HSD deficiency by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP). We could not detect any alterations of type II 3 beta-HSD gene from these patients. Our result strongly suggests that unlike classical 3 beta-HSD deficiency, NC3 beta-HSD deficiency may be secondary adrenal biosynthetic defects, rather than dual inherited deficiencies.

Adolescent↗