MAP1B and Cognitive impairment: We have shown that LoF mutations produce stable truncated MAP1B and that LoF carriers develop both a neurological deficit and a cognitive impairment phenotype providing a comprehensive description of a syndrome involving MAP1B. LoF variants in MAP1B are found at a frequency of ~1 in 10,000, in publicly available databases, which places it within the range of the more common, single gene causes of syndromic ID.