Project description:Nuclear remodeling to an extreme condensed state is a hallmark of spermatogenesis. This is achieved by varied degrees of replacement of histones with protamines. Regions retaining nucleosomes may be of functional significance. To determine potential roles for somatic-like chromatin in the paternal gamete, sperm from wild type and transgenic mice harboring a single copy insert of the human protamine cluster were subjected to Micrococcal Nuclease (MNase)-seq. Nuclease footprints linked robust endogenous protamine transcription and transgene suppression to its chromatin environment. Murine footprints were enriched within regulatory regions and sequences expressed in the early embryo. These were highlighted by Ctcf footprints that were enriched within chromatin domain boundaries and sites bound in testes and ESCs. In contrast, Ctcf footprints were absent in human and bull sperm. The continuity of Ctcf binding through the murine germline may permit rapid reconstitution of chromatin organization following fertilization. This likely reflects its preparation for early zygotic genome activation and comparatively accelerated preimplantation embryonic development program observed in mouse as compared to human.
Project description:Animals traversing different environments encounter both stable background stimuli and novel cues, which are thought to be detected by primary sensory neurons and then distinguished by downstream brain circuits. Here we show that each of the ~1000 olfactory sensory neuron (OSN) subtypes in the mouse harbors a distinct transcriptome whose content is precisely determined by interactions between its odorant receptor and the environment. This transcriptional variation is systematically organized to support sensory adaptation: expression levels of more than 70 genes relevant to transforming odors into spikes continuously vary across OSN subtypes, dynamically adjust to new environments over hours, and accurately predict acute OSN-specific odor responses. The sensory periphery therefore separates salient signals from predictable background via a transcriptional rheostat whose moment-to-moment state reflects the past and constrains the future; these findings suggest a general model in which structured transcriptional variation within a cell type reflects individual experience.