NLGN4X and autism spectrum disorder: Beyond the peculiarities of neuroligin-4 gene evolution (Maxeiner et al., 2020), mutations in human neuroligin genes, particularly in NLGN3 and NLGN4, have been linked to monogenic autism spectrum disorders (ASD) and other neurodevelopmental conditions (Jamain et al., 2003; Avdjieva-Tzavella et al., 2012; Steinberg et al., 2012; Xu et al., 2014; Bourgeron, 2015; Kilaru et al., 2016; Nakanishi et al., 2017; Parente et al., 2017).