Type 1 Dentinogenesis imperfecta is caused by mutation in:

Type 1 Dentinogenesis imperfecta is caused by a mutation in the DSPP gene (gene map locus 4q21.3), encoding dentin phosphoprotein and dentin sialoprotein. While Type 2 is caused by DMP-1, BSP-1, SPP1 gene. Ref: Shafer's textbook of oral pathology 7th edition page55