Spermatogenesis rescue in a mouse deficient for the ubiquitin ligase SCF^β-TrCP by single substrate depletion

β-TrCP, the substrate recognition subunit of a Skp1-Cul1-F-box (SCF) ubiquitin ligase, is ubiquitously expressed from two distinct paralogs, targeting many regulatory proteins for proteasomal degradation. We generated inducible β-TrCP hypomorphic mice and found that they are surprisingly healthy, yet have a severe testicular defect. We show that the two β-TrCP paralogs have a nonredundant role in spermatogenesis. The testicular defect is tightly associated with cell adhesion failure within the seminiferous tubules and is fully reversible upon β-TrCP restoration. Remarkably, testicular depletion of a single β-TrCP substrate, Snail1, rescued the adhesion defect and restored spermatogenesis. Our studies highlight an unexpected functional reserve of this central E3, as well as a bottleneck in a specific tissue: a single substrate whose stabilization is incompatible with testicular differentiation.