The SP is a largely transient zone beneath the CP that plays an important role in establishment of thalamocortical connectivity (see35 for review). SP generation is protracted in primates8, and its thickness particularly expanded in human8. In mouse and other species18 this layer is molecularly distinct, and our laminar profiling also identified many SP-enriched genes in human (Fig. 2). For example, NPY is enriched in SP at 21pcw (but not 15–16pcw) as shown both by microarray and ISH (Fig. 4a). To facilitate a comparative analysis, we identified a high confidence set of 150 SP-enriched genes in human and mouse (Suppl. Table 8). Many genes showed similar enrichment in the developing mouse and human SP, including the known SP markers KCNAB1 and NR4A217,18,44 (Fig. 4b). Several genes showed enrichment in developing human but not mouse SP, including the hypocretin (orexin) receptor HCRTR2 (Fig. 4c; Extended Data Fig. 8a), which is thought to regulate sleep-wakefulness and is highly expressed in mouse hypothalamus45. Conversely, Trh and Nxph4 show enriched expression in mouse but not human SP (Fig. 4d; Extended Data Fig. 8b). Interestingly,
