Site-specific X-chromosome rearrangements from hybrid dysgenesis in Drosophila melanogaster

When the germ line of Drosophila males is destabilized by a syndrome known as hybrid dysgenesis, X-chromosome rearrangements are found in up to 10 percent of the gametes produced. Some of these aberrations are simple inversions, but many are complex multibreak rearrangements. Furthermore, most of the breakpoints fall into a few highly localized positions on the chromosome. These positions are mostly at points of intercalary heterochromatin and may vary from one strain to the next. the results suggest that they may represent points of insertion of mobile DNA sequences.     

Mutations in the pericentrin (PCNT) gene cause primordial dwarfism

Fundamental processes influencing human growth can be revealed by studying extreme short stature. Using genetic linkage analysis, we find that biallelic loss-of-function mutations in the centrosomal pericentrin (PCNT) gene on chromosome 21q22.3 cause microcephalic osteodysplastic primordial dwarfism type II (MOPD II) in 25 patients. Adults with this rare inherited condition have an average height of 100 centimeters and a brain size comparable to that of a 3-month-old baby, but are of near-normal intelligence. Absence of PCNT results in disorganized mitotic spindles and missegregation of chromosomes. Mutations in related genes are known to cause primary microcephaly (MCPH1, CDK5RAP2, ASPM, and CENPJ).     

Compositional relatedness between histocompatibility antigens and human serum lipoproteins

Human histocompatibility antigens and the protein part of Lp(a) lipoprotein and low density lipoprotein of human serum appear to be related when the amino acid compositions are compared. The Lp(a) lipoprotein appears to be closely related also to murine H-2(d) antigen. The results support the concept of a relation between serum lipoproteins and histocompatibility antigens on cell membranes.     

Erythrocyte membrane: chemical modification

Erythrocytes treated with 1-fluoro-2,4-dinitrobenzene become permeable to Na(+) and K(+), but not to small water-soluble nonelectrolytes hemoglobin, and eventually lyse inisotonic buffer. Erythrocytes treated with 1,5-difluoro-2,4-dinitrobenzene become permeable to Na(+) and K(+) but do not lyse in buffer or in water, even after extraction with lipid solvents. The difluoro compound crosslinks the membrane and increases its strength. Both reagents appear to remove the positive fixed charge responsible for the cation impermeability of the normal cell.     

Evidence for ectopic neurotransmission at a neuronal synapse

Neurotransmitter release is well known to occur at specialized synaptic regions that include presynaptic active zones and postsynaptic densities. At cholinergic synapses in the chick ciliary ganglion, however, membrane formations and physiological measurements suggest that release distant from postsynaptic densities can activate the predominantly extrasynaptic alpha7 nicotinic receptor subtype. We explored such ectopic neurotransmission with a novel model synapse that combines Monte Carlo simulations with high-resolution serial electron microscopic tomography. Simulated synaptic activity is consistent with experimental recordings of miniature excitatory postsynaptic currents only when ectopic transmission is included in the model, broadening the possibilities for mechanisms of neuronal communication.     

The mutational landscape of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a common, morbid, and frequently lethal malignancy. To uncover its mutational spectrum, we analyzed whole-exome sequencing data from 74 tumor-normal pairs. The majority exhibited a mutational profile consistent with tobacco exposure; human papillomavirus was detectable by sequencing DNA from infected tumors. In addition to identifying previously known HNSCC genes (TP53, CDKN2A, PTEN, PIK3CA, and HRAS), our analysis revealed many genes not previously implicated in this malignancy. At least 30% of cases harbored mutations in genes that regulate squamous differentiation (for example, NOTCH1, IRF6, and TP63), implicating its dysregulation as a major driver of HNSCC carcinogenesis. More generally, the results indicate the ability of large-scale sequencing to reveal fundamental tumorigenic mechanisms.     

Utilization of durum wheat landraces in East Shewa,central Ethiopia: Are home uses an incentive for on-farm conservation?

The study was conducted in East Shewa, central Ethiopia, where durum wheat landraces were once popular, but were displaced and re-introduced. Combinations of survey techniques are employed to document the different home uses of durum wheat landraces and to assess whether these serve as an incentive to on-farm conservation. The findings reveal that wheat landraces have multiple dietary and sociocultural uses that contribute to the maintenance of landraces on-farm. Temporal analysis of historical information showed that (1) richness in food traditions is associated with a high level of landrace diversity on-farm; (2) food traditions in East Shewa did not change radically as a result of the integration of farmers into the market economy; and (3) farm households still have an appreciation of, and a preference for, the home-use related qualities of the landraces, this despite their long term disappearance and the subsequent availability of several improved wheat varieties. The study illustrates the relationship between the local availability of landrace wheats and their on-farm survival. The home uses of landraces plays an instrumental role in the promotion of on-farm (in situ) conservation. Augmenting conservation activities with non-breeding approaches (e.g., awareness-creation) would support the survival of wheat landraces for the foreseeable future. Bayush Tsegaye (PhD) is a graduate from Noragric – the Department of International Environment and Development Studies, of the Norwegian University of Life Sciences. Prior to joining the University, she was engaged in various development programs in Ethiopia affiliated with government institutions as well as national and international non-governmental organizations. Her research interests include community management of plant genetic resources, food security, and gender issues. Trygve Berg is an Associate Professor at Noragric – the Department of International Environment and Development Studies, of the Norwegian University of Life Sciences. His research interests focus on the management of plant genetic resources and participatory plant breeding.