Comparative cytogenetics of three species of Dichotomius (Coleoptera, Scarabaeidae)

Meiotic and mitotic chromosomes of Dichotomius nisus, D. semisquamosus and D. sericeus were analyzed after conventional staining, C-banding and silver nitrate staining. In addition, Dichotomius nisus and D. semisquamosus chromosomes were also analyzed after fluorescent in situ hybridization (FISH) with an rDNA probe. The species analyzed had an asymmetrical karyotype with 2n = 18 and meta-submetacentric chromosomes. The sex determination mechanism was of the Xyp type in D. nisus and D. semisquamosus and of the Xy r type in D. sericeus. C-banding revealed the presence of pericentromeric blocks of constitutive heterochromatin (CH) in all the chromosomes of the three species. After silver staining, the nucleolar organizer regions (NORs) were located in autosomes of D. semisquamosus and D. sericeus and in the sexual bivalent of D. nisus. FISH with an rDNA probe confirmed NORs location in D. semisquamosus and in D. nisus. Our results suggest that chromosome inversions and fusions occurred during the evolution of the group

A novel X-linked gene, G4.5. is responsible for Barth Syndrome

Barth syndrome is a severe inherited disorder, often fatal in childhood, characterized by cardiac and skeletal myopathy, short stature and neutropenia. The disease has been mapped to a very gene-rich region in distal portion of Xq28. We now report the identification of unique mutations in one of the genes in this region, termed G4.5, expressed at high level in cardiac and skeletal muscle. Different mRNAs can be produced by alternative splicing of the primary G4.5 transcript, encoding novel proteins that differ at the N terminus and in the central region. The mutations introduce stop codons in the open reading frame interrupting translation of most of the putative proteins (which we term 'tafazzins'). Our results suggest that G4.5 is the genetic locus responsible for the Barth syndrome

Heritability of young- and old-onset ischaemic stroke

© 2015 European Academy of Neurology. Background and purpose: Although the genetic contribution to stroke risk is well known, it remains unclear if young-onset stroke has a stronger genetic contribution than old-onset stroke. This study aims to compare the heritability of ischaemic stroke risk between young and old, using common genetic variants from whole-genome array data in population-based samples. Methods: This analysis included 4050 ischaemic stroke cases and 5765 controls from six study populations of European ancestry; 47% of cases were young-onset stroke (age < 55 years). To quantify the heritability for stroke risk in these unrelated individuals, the pairwise genetic relatedness was estimated between individuals based on their whole-genome array data using a mixed linear model. Heritability was estimated separately for young-onset stroke and old-onset stroke (age ≥ 55 years). Results: Heritabilities for young-onset stroke and old-onset stroke were estimated at 42% (±8%, P < 0.001) and 34% (±10%, P < 0.001), respectively. Conclusions: Our data suggest that the genetic contribution to the risk of stroke may be higher in young-onset ischaemic stroke, although the difference was not statistically significant