BMPR1B and holoprosencephaly: However, recent reports clearly documented the loss of DI1 and DI2 interneurons in the spinal cord [25] and of cerebellar granule neurons in the cerebellum [26] of mice lacking both Bmpr1a and Bmpr1b. Ablation of Bmpr1a and Bmpr1b in the telencephalon resulted in holoprosencephaly and embryonic death by 11.5 d.p.c. [27], thereby precluding analysis of the importance of BMP2 and 4 for the major periods of neurogenesis and astrogliogenesis.