To date, most studies have focused on generating brain organoids resembling cortex development (Kadoshima et al., 2013; Lancaster et al., 2013; Mariani et al., 2012; Pasca et al., 2015; Qian et al., 2016). Methods to generate organoids resembling MGE development have been recently described (Bagley et al., 2017; Birey et al., 2017), however further study is warranted given the paucity of protocols for generating ventrally-specified orgnoids. Moreover, cell transplantation or explant cultures have been used to model interneuron migration in vivo or in vitro (Bellion et al., 2005; Maroof et al., 2013; Nicholas et al., 2013), but these studies have largely relied upon xenografts of human cells into immunodeficient mice. To recapitulate 3-D neuronal migration in vitro, biomaterial-based methods were recently established (Zhang et al., 2016). However, such systems still lack a physiological cellular environment, necessitating 3-D culture systems to model interneuron migration in the context of human developing cortex, which have been recently reported (Bagley et al., 2017; Birey et al., 2017).
