SIL (also called STIL/TAL1 interrupting locus) is an immediate-early gene that is essential for embryonic development and is implicated in T-cell leukemia-associated translocations [, ]. Sil protein is necessary for proper mitotic spindle organisation in zebrafish and human cells and localizes to the mitotic spindle poles only during metaphase []. Mouse Sil was suggested to play a role as a positive regulator of the sonic hedgehog pathway, acting downstream of PTCH1 []. In human, cell cycle-dependent phosphorylation of Sil is required for its interaction with Pin1, a regulator of mitosis [].Primary microcephaly (MCPH) is an autosomal-recessive congenital disorder characterised by smaller-than-normal brain size and mental retardation. Three different homozygous mutations in SIL were identified in patients from three of the five families linked to the MCPH7 locus; all are predicted to truncate the Sil protein [].
