On ${\mathbf{\Sigma }}_3^1$- and ${\mathrm{\Sigma }}_4^1$-uniformization

Assuming the consistency of $\mathsf{Z}\mathsf{F}\mathsf{C}$, we construct a model of set theory in which the boldface ${\mathbf{\Sigma }}_3^1$-uniformization property holds, yet the lightface ${\mathrm{\Sigma }}_4^1$-uniformization property fails, separating these two principles for the first time. We also indicate how to create a universe where ${\mathrm{\Sigma }}_3^1$-uniformization holds, but ${\mathrm{\Sigma }}_4^1$-uniformization fails using inner models with large cardinals.