These first ant methylomes and their intra- and interspecies comparison reveal an exonic methylation pattern that points to a connection between DNA methylation and splicing. The presence of monoallelic DNA methylation and the methylation of non-CpG sites in all samples suggest roles in genome regulation in these social insects, including the intriguing possibility of parental or caste-specific genomic imprinting.

SUMMARY Two populations of Nkx2-1+ progenitors in the developing foregut endoderm give rise to the entire post-natal lung and thyroid epithelium, but little is known about these cells, as they are difficult to isolate in a pure form. We demonstrate here the purification and directed differentiation of primordial lung and thyroid progenitors derived from mouse embryonic stem cells (ESCs). Inhibition of TGFβ and BMP signaling, followed by combinatorial stimulation of BMP and FGF signaling can specify these cells efficiently from definitive endodermal precursors. When derived using Nkx2-1GFP knock-in reporter ESCs, these progenitors can be purified for expansion in culture and have a transcriptome that overlaps with developing lung epithelium. Upon induction, they can express a broad repertoire of markers indicative of lung and thyroid lineages and can recellularize a 3D lung tissue scaffold. Thus, we have derived a pure population of progenitors able to recapitulate the developmental milestones of lung/thyroid development.

EZH2 is the catalytic subunit of PRC2, a central epigenetic repressor essential for development processes in vivo and for the differentiation of embryonic stem cells (ESCs) in vitro. The biochemical function of PRC2 in depositing repressive H3K27me3 marks is well understood, but how it is regulated and directed to specific genes before and during differentiation remains unknown. Here, we report that PRC2 binds at low levels to a majority of promoters in mouse ESCs, including many that are active and devoid of H3K27me3. Using in vivo RNA–protein crosslinking, we show that EZH2 directly binds to the 5′ of nascent RNAs transcribed from a subset of these promoters and that these binding events correlate with decreased H3K27me3. Our findings suggest a molecular mechanism by which PRC2 senses the transcriptional state of the cell and translates it into epigenetic information.