HGTX transcripts are first detected at embryonic stage six in the procephalic region. By the end of stage 7 they are strongly expressed in the developing brain and are detected in the midline as gastrulation is completed. They continue to be expressed in the developing brain and the ventral midline.

Expression assayed at stages 9, 11, 13, and 17. Expression may be continuous between assayed stages in some tissues.

HGTX transcript expression initiates at embryonic stage 6 as two bilateral clusters in the procephalic neurogenic region. By embryonic stage 8, expression is seen in the hindgut primordium and ventral midline precursors. Expression in the nerve cord neuroectoderm, which is limited to anterior segments, begins at embryonic stage 9. Ventral nerve cord neuroblasts begin expressing transcripts at embryonic stage 10 . During early embryonic stage 10, transient weak expression occurs in most neuroblasts immediately flanking the midline (ventral neuroblasts) and some intermediate neuroblasts. Expression then becomes restricted to two bilateral clusters of 3–5 neuroblasts per neuromere by the end of embryonic stage 10, concomitant with declining midline expression. Transcripts are detected in ganglion mother cells from late embryonic stage 10 onwards. By late embryonic stage 11, only one to two neuroblasts per hemineuromere express HGTX transcript. Strong expression in the ventral maxillary epidermis can be distinguished from anterior neuroectodermal expression at this embryonic stage. Expression in the nerve cord shifts from a tightly clustered distribution to a disperse pattern during early embryonic stage 12. By embryonic stage 13 there are approximately 15–20 HGTX-positive cells per hemineuromere. Expression in the CNS, head structures, and hindgut persists at least until late embryonic stage 16.