In the current set of experiments, the single cell profiling is likely more sensitive than the in situ methods and therefore is able to detect even low levels of these transcripts in other cell cycle phases. Through the use of the different clustering methods employed in this study, some genes were uncovered as potentially cell cycle regulated that were not previously well characterized with respect to the cell cycle. In addition, their expression patterns in the developing retina were completely unknown. One such gene was Karyopherin alpha 2. Kpna2 was observed in a subset of RPCs. ISH on retinal cryosections revealed an expression pattern in a scattered subset of ONBL cells at E12.5 that progressed to a staining pattern that was concentrated on the vitreal side of the ONBL where the S phase cells reside at P0. At E16.5,Peiminine the expression of Kpna2 was in a repeated pattern of radial stripes across the retina. The striped expression pattern is not a predicted pattern, but it may indicate a dynamic regulation of Kpna2 that is coordinated with neighboring cells. Neighboring cells might share a history of recent cell divisions and thus might be somewhat synchronized with respect to the cell cycle. DISH for Kpna2 revealed that this gene is almost exclusively expressed in S phase,Peimine as 95% of all Kpna2+ cells at P0 were also thymidine + after a 1 hour pulse. The protein product of this gene has been linked to the nuclear import of a protein important for DNA repair and checkpoint function. It is possible that this novel finding of restriction of Kpna2 expression to cells almost exclusively in S phase points to an important role in regulation of the normal cell cycle in a developing tissue. In addition to this insight into cell cycle function, this observation means that Kpna2 can be used as a marker for RPCs in S phase in future studies. One cell cycle gene that was found in the fewest RPCs and might, therefore, be tightly regulated in its cell cycle expression was Cyclin E1. Section ISH for Cyclin E1 demonstrated that while it showed weak signal in the retina, it was expressed in a small subset of cells near the vitreal surface of the ONBL. Hierarchical clustering experiments revealed that the gene Rassf1 was significantly correlated with Cyclin E1.