Lack of centrioles and primary cilia inSTIL^−/−mouse embryos

Abstract

Although most animal cells contain centrosomes, consisting of a pair of centrioles, their precise contribution to cell division and embryonic development is unclear. Genetic ablation of STIL, an essential component of the centriole replication machinery in mammalian cells, causes embryonic lethality in mice around mid gestation associated with defective Hedgehog signaling. Here, we describe, by focused ion beam scanning electron microscopy, that STIL(-/-) mouse embryos do not contain centrioles or primary cilia, suggesting that these organelles are not essential for mammalian development until mid gestation. We further show that the lack of primary cilia explains the absence of Hedgehog signaling in STIL(-/-) cells. Exogenous re-expression of STIL or STIL microcephaly mutants compatible with human survival, induced non-templated, de novo generation of centrioles in STIL(-/-) cells. Thus, while the abscence of centrioles is compatible with mammalian gastrulation, lack of centrioles and primary cilia impairs Hedgehog signaling and further embryonic development.

The daughter centriole controls ciliogenesis by regulating Neurl-4 localization at the centrosome

“…The finding that monocentriolar cells with only a mother centriole were unable to form primary cilia suggests a possible role of the daughter centriole in cilia formation. These results are consistent with the reported absence of primary cilia from cells depleted of STIL or CPAP, two other regulators of centrosome duplication (Wu and Tang, 2012;David et al, 2014).…”

Recent advances in understanding inheritance of holoprosencephaly

“…A homozygous nonsense variant of STIL was independently reported by others (Kakar et al, 2015). STIL is localized to centrioles where it participates in SHH signaling through its function in primary cilia biology and is known to be involved in microcephaly (David et al, 2014). Notably, in these two families, HPE is transmitted as a recessive trait associated with severe microcephaly.…”

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

“…Most importantly, it represents a key factor required for proper centriole duplication [Stevens et al, 2010;Arquint et al, 2012]. Mutations in STIL are associated with MCPH7 in humans (OMIM 612703) [Kumar et al, 2009], while ablation of Stil (formerly Sil ) -the mouse orthologue of STIL -causes mid-gestation lethality with marked growth retardation, prominent midline neural tube defects, and randomized axial asymmetry due to an impaired response to Shh signaling [Izraeli et al, 1999[Izraeli et al, , 2001David et al, 2014]. The zebrafish stil (formerly sil ) loss-of-function homozygous mutant cassiopeia ( csp ) also displays embryonic lethal defects, with an increased number of mitotic cells displaying disorganized mitotic spindles often lacking one or both centrosomes [Pfaff et al, 2007].…”