To determine if the expression of mutant htt and the development of HD specific cellular pathology are related to the course of neural development, the expression patterns of mutant htt, the accumulation of mutant htt aggregate, the presence of oligomeric mutant htt and the formation of NIs were examined by quantitative real time PCR (Q-PCR), Western blot, immunostaining and cell count at various stages during in vitro development. The gene discussed is HTT; the disease is Huntington disease.