Comparative analyses of multi-species sequences from targeted genomic regions

The systematic comparison of genomic sequences from different organisms represents a central focus of contemporary genome analysis. Comparative analyses of vertebrate sequences can identify coding and conserved non-coding regions, including regulatory elements, and provide insight into the forces that have rendered modern-day genomes. As a complement to whole-genome sequencing efforts, we are sequencing and comparing targeted genomic regions in multiple, evolutionarily diverse vertebrates. Here we report the generation and analysis of over 12 megabases (Mb) of sequence from 12 species, all derived from the genomic region orthologous to a segment of about 1.8 Mb on human chromosome 7 containing ten genes, including the gene mutated in cystic fibrosis. These sequences show conservation reflecting both functional constraints and the neutral mutational events that shaped this genomic region. In particular, we identify substantial numbers of conserved non-coding segments beyond those previously identified experimentally, most of which are not detectable by pair-wise sequence comparisons alone. Analysis of transposable element insertions highlights the variation in genome dynamics among these species and confirms the placement of rodents as a sister group to the primates.

Effects of social experience on the corticosterone response of adult rats to pup cues

Rat mothers whose pups have been removed show greater plasma corticosterone elevations when the pups are shocked and returned in a wire-mesh basket than when only the wire basket is returned. For mothers housed with an adult male or virgin female, this differential adrenocorticoid responsiveness between the shocked-pup and empty-basket conditions was not observed unless the adult partner was removed 18 hr before testing. Nonlactating adults housed with pups and mother for up to 2 weeks exhibited corticoid elevations equivalent to the shocked-pup and empty-basket conditions whether tested with the mother or 18 hr after her removal. These results indicate that the differential pituitary-adrenal responsiveness that female rats show to pup cues during lactation cannot be accounted for by the length of the mother's exposure to pups, and, further, that this relative responsiveness during lactation appears to be largely due to the suppression of adrenocorticoid reactivity to a nonsocial environmental disturbance.