We began investigating the relationship between the four cell sub-fractions (CD90+CD49f+, CD90−CD49f+, CD90+CD49f−, and CD90−CD49f−) by determining their repopulating capacity and frequencies (commonly denoted as SCID-repopulating cell or SRC) in NSG (non-obese diabetic/severe combined immunodeficiency, gamma chain null) mice using stringent gating, double flow-sorting and purity-checked protocols (Supplementary Fig. 1a–c). This evidence concerns the gene ITGA6 and immune system disorder.