C4B and fragile X syndrome: This protocol was developed to understand and characterize brain cell differences between FVB.129P2-Pde6b+Tyrc-ch/AntJ (wild-type) mice and FVB.129P2-Pde6b+Tyrc-chFmr1tm1Cgr/J (Fmr1 KO) mice, a murine model to study fragile X syndrome (FXS).