The early ubiquitous expression suggest that the mRNA is maternally supplied .
Expression is absent from the amnioserosa during germ band extension.
After stage 10, smid expression becomes restricted to two specific tissues. Most obvious is the neurogenic ectoderm , where by stage 12 expression of smid is localized to the NBs that have enlarged and are actively dividing. All NBs express smid at this stage. Expression can be detected in NBs up to stage 15, but throughout this period there is a gradual decline in the number of NBs expressing smid . At stage 13 high expression can be seen in NBs of the thoracic and abdominal NBs.