“…Situated just above the last Paneth cell in the crypt are the +4 position cells, which have a unique transcriptional profile including expression of Hopx (Takeda et al, 2011), Tert (Breault et al, 2008;Montgomery et al, 2011), Bmi1 (Sangiorgi and Capecchi, 2008), and Lrig1 (Powell et al, 2012) (Figure 2). These cells have previously been deemed the RSC population, which reconstitutes Lgr5 + CBCs during a state of injury (Breault et al, 2008;Sangiorgi and Capecchi, 2008;Montgomery et al, 2011;Powell et al, 2012), and have been previously shown to be radiation resistant (Tao et al, 2017;Montenegro-Miranda et al, 2020;Sheng et al, 2020), suggesting that these cells can survive acute injury in the crypt and fill in for their damaged counterparts. However, recent literature has underscored the complexity of characterizing these cells and called into question their "stemness."…”