Reply to Emv2, the only endogenous ecotropic murine leukemia virus of C57BL/6J mice

The authors of the paper by Lee et al [1]. appreciate the interest shown and comments by Young et al [2].Young et al. contend that Emv2 is the only endogenous ecotropic murine leukemia virus in C57BL/6J mice, although not annotated on the current NCBI reference genome assembly, Build 37.2, and maps to the distal region of chromosome 8 based on previous genetic studies.As stated in the paper by Lee et al., the Emv2 locus was annotated in the NCBI database Build 37.1 when analyzed around November 2010. At that time, the annotated Emv2 locus did not contain any sequences similar to mouse endogenous retroviruses. Interestingly, a survey of the latest NCBI database (Build 37.2) for the Emv2 locus on December 08, 2011, in response to the correspondence by Young et al., yielded no annotated information about the Emv2 locus, and it appears that the previous annotations may have been removed. During the course of our analysis regarding the Emv2 locus in the C57BL/6J mouse genome, screenshots of the data were captured and recorded, and revealed the annotation of the Emv2 locus on chromosome 8, which is distantly located from the ERVmch8 locus (Figure 1). Although the paper by Lee et al. uses Build 37.1 to show the annotation for Emv2, this annotation for Emv2 appears as far back as 2006 (NCBI, when reverting to the previous build version 36.1).This was cited in the paper by Lee et al.:In addition, Emv2 is located/annotated at 67.0 cM, ~11.4 cM upstream of the ERVmch8 locus (~78.4 cM), according to a survey of the NCBI map viewer (http://www.ncbi.nlm.nih.gov/projects/mapview webcite)... Unexpectedly, we were unable to retrieve the nucleotide sequence, which is presumed to be the Emv2 provirus, from the Emv2 locus annotated in the ... However, it is still a possibility that ERVmch8 shares the same locus on chromosome 8-qE1 region with Emv2 with an assumption that the NCBI annotation information regarding the Emv2 locus needs to be revised.As indicated in the paper by Lee et al.