Cilia, hair-like projections involved in cell motility and cell signaling, are generated through a process called ciliogenesis. Defects in ciliogenesis have been linked to the incidence of a neurodevelopmental disorder called primary microcephaly (MCPH). MCPH is a debilitating disease that causes babies to be born with a reduced brain size that results in a global developmental delay, intellectual disability, and a large number of other issues. Unfortunately, this disease is currently incurable, and the diagnostic and treatment options are very limited.

One mutation that has been linked by a previous study with MCPH is the sas-6(L69T) mutation, which is a mutation in the sas-6 gene. The sas-6 gene plays an important role in regulating the process of ciliogenesis, but the effect of the sas-6(L69T) MCPH-associated mutation on ciliogenesis is currently unknown. Furthermore, the sas-6 gene was first discovered in C. elegans and is highly conserved between humans and the microscopic nematode, C. elegans. Importantly, the amino acid in SAS-6 whose mutation causes MCPH in humans is also conserved in humans and C. elegans. Therefore, in order to investigate if the sas-6(L69T) mutation has any effect on ciliogenesis, we modeled this mutation in C. elegans.

To generate the sas-6(L69T) mutation, CRISPR/Cas9 was utilized to edit the C. elegans genome. To determine the effect of the sas-6(L69T) mutation on ciliogenesis, a genetic crossing was performed to introduce a pan-ciliary marker to visualize C. elegans cilia. A variety of ciliary defects were observed in C. elegans carrying the sas-6(L69T) mutation including short phasmid cilia, defective cilia morphology, and neurodegeneration. Thus, our data have identified a novel role for the sas-6(L69T) MCPH-associated mutation in regulating ciliogenesis.

Ramon Duran

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