SHH and holoprosencephaly: (mice) knockout of SIL is embryonic lethal at E10.5. Between E7.5 and E8.5. the knockout embryos are smaller, display pericardial swelling, midline neural tube defects, failure of neural tube closure and holoprosencephaly. Failure in left-right specification. Due to block in Sonic Hedgehog (Shh) signalling, and increased apoptosis