Infection with a lentiviral vector expressing short hairpin ribonucleic acids (shRNAs) against all Nrxns (Nrxn triple knock down [TKD]) [46] mimicked the defect in Sorcs1 KO neurons (Fig 4G and 4H), suggesting that Nlgn1-induced presynaptic differentiation is impaired in Sorcs1 KO neurons because of decreased axonal surface levels of Nrxn. This evidence concerns the gene NLGN1 and infection.