POC1A truncation mutation causes a ciliopathy in humans characterized by primordial dwarfism - PubMed (original) (raw)

Case Reports

. 2012 Aug 10;91(2):330-6.

doi: 10.1016/j.ajhg.2012.05.025. Epub 2012 Jul 26.

Eissa Faqeih, Hanan E Shamseldin, Ramil R Noche, Asma Sunker, Muneera J Alshammari, Tarfa Al-Sheddi, Nouran Adly, Mohammed S Al-Dosari, Sean G Megason, Muneera Al-Husain, Futwan Al-Mohanna, Fowzan S Alkuraya

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Case Reports

POC1A truncation mutation causes a ciliopathy in humans characterized by primordial dwarfism

Ranad Shaheen et al. Am J Hum Genet. 2012.

Abstract

Primordial dwarfism (PD) is a phenotype characterized by profound growth retardation that is prenatal in onset. Significant strides have been made in the last few years toward improved understanding of the molecular underpinning of the limited growth that characterizes the embryonic and postnatal development of PD individuals. These include impaired mitotic mechanics, abnormal IGF2 expression, perturbed DNA-damage response, defective spliceosomal machinery, and abnormal replication licensing. In three families affected by a distinct form of PD, we identified a founder truncating mutation in POC1A. This gene is one of two vertebrate paralogs of POC1, which encodes one of the most abundant proteins in the Chlamydomonas centriole proteome. Cells derived from the index individual have abnormal mitotic mechanics with multipolar spindles, in addition to clearly impaired ciliogenesis. siRNA knockdown of POC1A in fibroblast cells recapitulates this ciliogenesis defect. Our findings highlight a human ciliopathy syndrome caused by deficiency of a major centriolar protein.

Copyright © 2012 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

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Figures

Figure 1

Figure 1

Identification of a POC1A-Related PD Phenotype (A) Pedigrees of the three PD-affected families included in the study and the haplotype shared between the affected individuals in the three families. (B) Clinical photographs of the affected individuals (a, b, and c are of VI1 from family 1, d is of VI2 from family 1, e and f are of VI3 from family 1, g and h are of IV1 from family 2, and i and j are of IV1 from family 3). (C) The upper panel shows a diagram of POC1A (the triangle indicates the site of the mutation). The middle panel shows a sequence chromatogram of the nonsense mutation and the parent tracing shown for comparison (the location of the mutation is indicated by a triangle). The bottom panel shows a diagram of POC1A (note that the truncated alteration is upstream of the five WD40 domains).

Figure 2

Figure 2

Mutation in POC1A Leads to Abnormal Mitotic Spindles and Centrioles Fibroblast cells stained with anti-PCNT (red), anti-α-tubulin (green), and DAPI. (A) The control fibroblast cell in the metaphase stage shows the normal number of centrioles and mitotic spindles. (B–D) Fibroblasts derived from the index individual show an abnormal number of centrioles and the tri- and quadri-polar spindle phenotype (arrowheads). The scale bars represent 5 μm.

Figure 3

Figure 3

_POC1A_-Related PD Is a Ciliopathy (A–B') Control fibroblasts and fibroblasts derived from the index individual were visualized by fluorescent microscopy for acetylated-α-tubulin staining of cilia (green) and DAPI-stained nuclei (blue). Control fibroblasts are uniformly capable of forming normal cilia after serum starvation (A), whereas fibroblasts derived from the index individual show severely deficient cilia formation (B) (the same numbers of cells were seeded on the coverslip for each cell line). Higher magnifications (A' and B') show that the axonemal lengths of the cilia from control fibroblasts (A') and fibroblasts derived from the index individual (B') are significantly different. The scale bars represent 10 μm. (C) The cilia frequencies of gelatin-plated control fibroblasts and fibroblasts derived from the index individual are significantly different (p = 5.4 × 10−7). Error bars represent the standard error of the mean (SEM). (D) The average cilia lengths from control cells and cells derived from the index individual are significantly different (p = 1.28 × 10−11). Error bars represent the SEM. (E–H) Control fibroblasts and fibroblasts derived from the index individual were visualized by confocal fluorescent microscopy for acetylated-α-tubulin staining of cilia (green) and IFT88 (1:1000; a generous gift from Dr. Bradley K. Yoder) or THM1 (1:500; a generous gift from Dr. Pamela V. Tran) (red). Control fibroblasts show the colocalization of IFT88 (E) and THM1 (G) with acetylated-α-tubulin staining of cilia. Normal IFT88 (F) and THM1 (H) staining patterns are shown in the few short cilia observed in the fibroblasts derived from the index individual.

Figure 4

Figure 4

siRNA Knockdown of POC1A in Fibroblast Cells Recapitulates the Ciliogenesis Defect (A and B) siRNA knockdown of POC1A in control fibroblasts cells and fibroblasts treated with scrambled siRNA (Ambion Silencer Select 4390846) were visualized by fluorescent microscopy for acetylated-α-tubulin staining of cilia (green) and DAPI-stained nuclei (blue). (One hundred picomoles of RNAi was diluted in 500 μl Opti-MEM I medium without serum in the 6-well tissue culture with the use of Ambion Silencer Select s24676). Fibroblast cells treated with scrambled siRNA are uniformly capable of forming normal cilia after serum starvation (A), whereas siRNA POC1A fibroblasts show severely deficient cilia formation (B). The scale bars represent 10 μm. (C) The average cilia frequency of siRNA-knockdown POC1A and the negative control are significantly different (p = 1.5 × 10−9). Error bars represent the SEM. (D–G) siRNA knockdown of POC1A in control fibroblasts and fibroblasts treated with scrambled siRNA were stained with anti-PCNT (red), anti-α-tubulin (green), and DAPI (blue). (D and F) Scrambled siRNA-treated cells show the normal number of centrioles and mitotic spindles. (E and F) Cells treated with siRNA-knockdown POC1A show abnormal numbers of centrioles and the multipolar spindle phenotype. (H) A gel image shows the siRNA depletion of POC1A and the normal expression of POC1B.

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References

    1. Klingseisen A., Jackson A.P. Mechanisms and pathways of growth failure in primordial dwarfism. Genes Dev. 2011;25:2011–2024. - PMC - PubMed
    1. Karlberg N., Jalanko H., Lipsanen-Nyman M. Growth and growth hormone therapy in subjects with mulibrey nanism. Pediatrics. 2007;120:e102–e111. - PubMed
    1. Eggermann T., Begemann M., Binder G., Spengler S. Silver-Russell syndrome: Genetic basis and molecular genetic testing. Orphanet J. Rare Dis. 2010;5:19. - PMC - PubMed
    1. Al-Dosari M.S., Al-Shammari M., Shaheen R., Faqeih E., Alghofely M.A., Boukai A., Alkuraya F.S. 3M Syndrome: An Easily Recognizable yet Underdiagnosed Cause of Proportionate Short Stature. J. Pediatr. 2012;161:139–145. e1. - PubMed
    1. Bongers E.M., Opitz J.M., Fryer A., Sarda P., Hennekam R.C., Hall B.D., Superneau D.W., Harbison M., Poss A., van Bokhoven H. Meier-Gorlin syndrome: Report of eight additional cases and review. Am. J. Med. Genet. 2001;102:115–124. - PubMed

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