TREM2 and Neurodevelopmental delay: The first NDD-associated TREM2 variants identified were W78X and W44X, which result in premature truncation of the protein, a variant at the consensus splice site which results in exclusion of exon 3, and the K186N mutation, which disrupts association of TREM2 with its obligate intracellular signaling adaptor, DAP12 [18].