gcm transcripts are expressed in glial precursors and immature glial cells during a short period of gliogenesis. Expression is first detected in early stage 11 in the longitudinal glioblast. By mid stage 11, 2-3 other cells per hemisegment express gcm. Two of these have been identified as NB6-4 and the medial-most cell body glial cell (VUM support cell). By early stage 12, expression is detected in several other cells which are also developing glial cells. Expression fades during stage 12 and is hardly detectable in stage 13. Enhancer trap expression was used to trace the gcm-expressing cells to later developmental stages. It was found that gcm is expressed in all glial precursors and immature glial cells except those derived from the mesectoderm. Outside of the CNS, gcm is expressed in the most anterior region of the presumptive mesoderm beginning at the cellular blastoderm stage, in the brain neurogenic region, and in the PNS neurogenic region.

lacZ expression visible in whole cell body. No expression observed in midline glia.