Novel STIL Compound Heterozygous Mutations Cause Severe Fetal Microcephaly and Centriolar Lengthening

STIL (SCL/TAL1 interrupting locus) is a core component of the centriole duplication process. STIL mutations have been associated with both autosomal recessive primary microcephaly (MCPH) and holoprosencephaly. In this report, we describe a family with multiple miscarriages and 2 terminations of pregnancy due to marked fetal microcephaly, delayed cortical gyrification, and dysgenesis of the corpus callosum. Whole exome sequencing allowed us to identify novel compound heterozygous mutations in STIL. The mutations lie, respectively, in the CPAP/CENPJ and the hsSAS6 interacting domains of STIL. M-phase synchronized amniocytes from both affected fetuses did not display an aberrant number of centrioles, as shown previously for either STIL-depleted or overexpressing cells. However, we observed an elongation of at least 1 centriole for each duplicated centrosome. These preliminary results may point to a novel mechanism causing MCPH and embryonic lethality in humans.