Mutations in CKAP2L, the human homolog of the mouse Radmis gene, cause Filippi syndrome

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Item Type:	Article
Title:	Mutations in CKAP2L, the human homolog of the mouse Radmis gene, cause Filippi syndrome
Creators Name:	Hussain, M.S., Battaglia, A., Szczepanski, S., Kaygusuz, E., Toliat, M.R., Sakakibara, S., Altmüller, J., Thiele, H., Nürnberg, G., Moosa, S., Yigit, G., Beleggia, F., Tinschert, S., Clayton-Smith, J., Vasudevan, P., Urquhart, J.E., Donnai, D., Fryer, A., Percin, F., Brancati, F., Dobbie, A., Smigiel, R., Gillessen-Kaesbach, G., Wollnik, B., Noegel, A.A., Newman, W.G. and Nürnberg, P.
Abstract:	Filippi syndrome is a rare, presumably autosomal-recessive disorder characterized by microcephaly, pre- and postnatal growth failure, syndactyly, and distinctive facial features, including a broad nasal bridge and underdeveloped alae nasi. Some affected individuals have intellectual disability, seizures, undescended testicles in males, and teeth and hair abnormalities. We performed homozygosity mapping and whole-exome sequencing in a Sardinian family with two affected children and identified a homozygous frameshift mutation, c.571dupA (p.Ile191Asnfs*6), in CKAP2L, encoding the protein cytoskeleton-associated protein 2-like (CKAP2L). The function of this protein was unknown until it was rediscovered in mice as Radmis (radial fiber and mitotic spindle) and shown to play a pivotal role in cell division of neural progenitors. Sanger sequencing of CKAP2L in a further eight unrelated individuals with clinical features consistent with Filippi syndrome revealed biallelic mutations in four subjects. In contrast to wild-type lymphoblastoid cell lines (LCLs), dividing LCLs established from the individuals homozygous for the c.571dupA mutation did not show CKAP2L at the spindle poles. Furthermore, in cells from the affected individuals, we observed an increase in the number of disorganized spindle microtubules owing to multipolar configurations and defects in chromosome segregation. The observed cellular phenotypes are in keeping with data from in vitro and in vivo knockdown studies performed in human cells and mice, respectively. Our findings show that loss-of-function mutations in CKAP2L are a major cause of Filippi syndrome.
Keywords:	Base Sequence, Confocal Microscopy, Cytogenetic Analysis, Cytoskeletal Proteins, DNA Sequence Analysis, Facies, Frameshift Mutation, Gene Components, Growth Disorders, Intellectual Disability, Italy, Microcephaly, Molecular Sequence Data, Recessive Genes, Syndactyly, Animals, Mice
Source:	American Journal of Human Genetics
ISSN:	0002-9297
Publisher:	Cell Press
Volume:	95
Number:	5
Page Range:	622-632
Date:	6 November 2014
Official Publication:	https://doi.org/10.1016/j.ajhg.2014.10.008
PubMed:	View item in PubMed

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