Moreover, specific mutations are associated with schizophrenia, including alterations in the 22q11.2 deletion syndrome (22qDS) -strongest monogenic risk allele for this disorder, and polymorphisms in claudin-5, a densely expressed tight junction molecule (Gur et al., 2017; Greene et al., 2018; Carrier et al., 2020) altogether revealing barrier dysfunction in schizophrenia patients (Greene et al., 2018; Crockett et al., 2021). The gene discussed is CLDN5; the disease is schizophrenia.