(A) E12.5 transverse section through r1 showing transcription factor and GABA patterning in relation to PITX2. (B) E18.5 transverse section through r1 showing nuclei patterning based on “Atlas of the Prenatal Mouse Brain” (Schambra et al., 1992) in relation to PITX2 (red circles). Abbreviations: DR, dorsal raphe nucleus; DTN, dorsal tegmental nucleus; LC, locus coeruleus; LDTN, laterodorsal tegmental nucleus; ML, medial lemniscus; PbN, parabrachial nucleus; PPTn, pedunculopontine nucleus; TN, trochlear nucleus; TGN, trigeminal motor nucleus.