Referee Comments: Referee 2

Reviewer 2's Review

“The manuscript titled "Extinction of Xist RNA Expression and Reprogramming of the Inactive X Chromosome Initiates in Migrating XX female Primordial Germ Cells." by de Napoles contains a study of Xist expression and related histone modifications on the inactive X chromosome in female primordial germ cells (PGCs). The authors use cell sorting and immunological staining to infer that Xist RNA expression is lost at an earlier timepoint during the development of PGCs than previously observed. They imply in the discussion that a minor problem in antibody specificity had led them to estimate a slightly later timepoint of Xist extinction in an earlier study.
The report is of interest to the field and contains observations to understanding the process of Xi reactivation and genome reprogramming in the germline.”

N.B. These are the general comments made by the reviewer when reviewing this paper in light of which the manuscript was revised. Specific points addressed during revision of the paper are not shown.