Constitutive expression of ciliary neurotrophic factor in mouse hypothalamus

Ciliary neurotrophic factor (CNTF) is a potent survival molecule for a large number of neuronal and glial cells in culture; its expression in glial cells is strongly upregulated after a variety of nerve tissue injuries. Exogenously administered CNTF produces an anorectic effect via activation of hypothalamic neurons and stimulates neurogenesis in mouse hypothalamus. To determine whether CNTF is produced endogenously in the hypothalamus, we sought cellular sources and examined their distribution in adult mouse hypothalamus by immunohistochemistry. CNTF immunoreactivity (IR) was predominantly detected in the ependymal layer throughout the rostrocaudal extension of the third ventricle, where numerous ependymocytes and tanycytes exhibited specific staining. Some astrocytes in the grey matter of the anterior hypothalamus and in the median eminence of the hypothalamic tuberal region were also positive. Stimulation of cells bearing CNTF receptor α (CNTFRα) induces specific activation of the signal transducer and activator of transcription 3 (STAT3) signalling system. Treatment with recombinant CNTF and detection of the nuclear expression of phospho-STAT3 (P-STAT3) showed that CNTF-producing ependymal cells and tanycytes were intermingled with, or very close to, P-STAT3-positive, CNTFRα-bearing cells. A fraction of CNTF-producing ependymal cells and tanycytes and some median eminence astrocytes also exhibited P-STAT3 IR. Thus, in normal adult mice the ependyma of the third ventricle is both a source of and a target for CNTF, which may play hitherto unknown roles in hypothalamic function in physiological conditions.

Genome size, GC percentage and 5mC level in the Indonesian coelacanth Latimeria menadoensis

The living fossil Latimeria menadoensis is important to understand sarcopterygian evolution. To gain further insights into this fish species we studied its genome size, GC% and 5mC level. The genome size and the GC% of the Indonesian coelacanth seem to be very similar to those of the African coelacanth. Moreover the GC%, the CpG frequency and the 5mC level of L. menadoensis are more similar to those of fish and amphibians than to those of mammals, birds and reptiles and this is in line with the hypothesis that two different DNA methylation and CpG shortage equilibria arose during vertebrate evolution. Our results suggest that the genome of L. menadoensis has remained unchanged for several million years, maybe since the origin of the lineage which from lobe-finned fish led to tetrapods. These data fit a conservative evolutionary landscape and suggest that the genome of the extant crossopterygians may be a sort of evolutionarily frozen genome.