The authors identified transcription factors specifically expressed in the kidney based on public mRNA expression data. The authors generated 55 TF candidates from this list and narrowed that to 18 based on the developmental timing of expression in embryos. 13 of these were chosen based on LOF phenotypes in mice or humans. They performed single TF overexpressions in MEFs isolated from embryonic limbs for remaining factors using Cdh16-Cre; LSL-GFP as a reporter to read-out renal identity. Cdh16 is specifically expressed in the renal tubule. Initially tried transducing all 13 factors, got 0.1% GFP+, then reduced to a minimal set Yamanaka screen style by removing factors one at a time. Combining Emx2, Hnf1b, Hnf4a, and Pax8 raised the yield to 0.6%. After 31 days of transduction, 11% of cells were GFP+.

Induced Renal Epithelial Cells (iRECs) form organoids, respond to nephronic agents, and integrate into decellularized kidneys as demonstrations of efficacy.

Interesting references

Heinaniemi, M. et al. Gene-pair expression signatures reveal lineage control. Nat. Methods 10, 577–583 (2013).

Pereira, C. F., Lemischka, I. R. & Moore, K. Reprogramming cell fates: insights from combinatorial approaches. Ann. NY Acad. Sci. 1266, 7–17 (2012).

Rackham, O. J. et al. A predictive computational framework for direct reprogramming between human cell types. Nat. Genet. 48, 331–335 (2016).