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Mutations in CSPP1, Encoding a Core Centrosomal Protein, Cause a Range of Ciliopathy Phenotypes in Humans

2013; Elsevier BV; Volume: 94; Issue: 1 Linguagem: Inglês

10.1016/j.ajhg.2013.11.010

1537-6605

Ranad Shaheen, Hanan E. Shamseldin, Catrina M. Loucks, Mohammed Zain Seidahmed, Shinu Ansari, M. I. Khalil, Nadya Al‐Yacoub, Erica E. Davis, Natalie Mola, Katarzyna Szymańska, Warren Herridge, Albert E. Chudley, Bernard N. Chodirker, Jeremy Schwartzentruber, Jacek Majewski, Nicholas Katsanis, Coralie Poizat, Colin A. Johnson, Jillian S. Parboosingh, Kym M. Boycott, A. Micheil Innes, Fowzan S. Alkuraya,

Hedgehog Signaling Pathway Studies

Ciliopathies are characterized by a pattern of multisystem involvement that is consistent with the developmental role of the primary cilium. Within this biological module, mutations in genes that encode components of the cilium and its anchoring structure, the basal body, are the major contributors to both disease causality and modification. However, despite rapid advances in this field, the majority of the genes that drive ciliopathies and the mechanisms that govern the pronounced phenotypic variability of this group of disorders remain poorly understood. Here, we show that mutations in CSPP1, which encodes a core centrosomal protein, are disease causing on the basis of the independent identification of two homozygous truncating mutations in three consanguineous families (one Arab and two Hutterite) affected by variable ciliopathy phenotypes ranging from Joubert syndrome to the more severe Meckel-Gruber syndrome with perinatal lethality and occipital encephalocele. Consistent with the recently described role of CSPP1 in ciliogenesis, we show that mutant fibroblasts from one affected individual have severely impaired ciliogenesis with concomitant defects in sonic hedgehog (SHH) signaling. Our results expand the list of centrosomal proteins implicated in human ciliopathies. Ciliopathies are characterized by a pattern of multisystem involvement that is consistent with the developmental role of the primary cilium. Within this biological module, mutations in genes that encode components of the cilium and its anchoring structure, the basal body, are the major contributors to both disease causality and modification. However, despite rapid advances in this field, the majority of the genes that drive ciliopathies and the mechanisms that govern the pronounced phenotypic variability of this group of disorders remain poorly understood. Here, we show that mutations in CSPP1, which encodes a core centrosomal protein, are disease causing on the basis of the independent identification of two homozygous truncating mutations in three consanguineous families (one Arab and two Hutterite) affected by variable ciliopathy phenotypes ranging from Joubert syndrome to the more severe Meckel-Gruber syndrome with perinatal lethality and occipital encephalocele. Consistent with the recently described role of CSPP1 in ciliogenesis, we show that mutant fibroblasts from one affected individual have severely impaired ciliogenesis with concomitant defects in sonic hedgehog (SHH) signaling. Our results expand the list of centrosomal proteins implicated in human ciliopathies. The centrosome is a nonmembranous cellular organelle composed of a pair of unequal centrioles embedded in an electron-dense matrix known as the pericentriolar matrix.1Bettencourt-Dias M. Glover D.M. Centrosome biogenesis and function: centrosomics brings new understanding.Nat. Rev. Mol. Cell Biol. 2007; 8: 451-463Crossref PubMed Scopus (411) Google Scholar Centrosomes are best known for their role during mitosis, when they undergo duplication and migrate from their perinuclear location to opposite poles in the cell, where they organize the microtubules that are bundled as spindles. These spindles emanate from each centrosome and tether the chromosomes by their kinetochores, an essential requirement for normal alignment during metaphase and proper segregation during anaphase.2Nigg E.A. Stearns T. The centrosome cycle: Centriole biogenesis, duplication and inherent asymmetries.Nat. Cell Biol. 2011; 13: 1154-1160Crossref PubMed Scopus (420) Google Scholar However, centrosomes also play important regulatory roles for microtubules in nonmitotic cells; these include regulation of intracellular transport3Rusan N.M. Rogers G.C. Centrosome function: sometimes less is more.Traffic. 2009; 10: 472-481Crossref PubMed Scopus (35) Google Scholar and formation of the primary cilium through a series of highly orchestrated steps involving the relocation of the centrosome to the cell surface and subsequent recruitment of key structural and functional proteins.4Kobayashi T. Dynlacht B.D. Regulating the transition from centriole to basal body.J. Cell Biol. 2011; 193: 435-444Crossref PubMed Scopus (219) Google Scholar The primary cilium can function as a mechanosensor, but its role in signal transduction during development is increasingly recognized in view of the widespread developmental anomalies that accompany primary-cilium defects, collectively known as ciliopathies.5Gerdes J.M. Davis E.E. Katsanis N. The vertebrate primary cilium in development, homeostasis, and disease.Cell. 2009; 137: 32-45Abstract Full Text Full Text PDF PubMed Scopus (560) Google Scholar, 6Goetz S.C. Anderson K.V. The primary cilium: a signalling centre during vertebrate development.Nat. Rev. Genet. 2010; 11: 331-344Crossref PubMed Scopus (1344) Google Scholar Ciliopathies comprise a wide-range of phenotypes, consistent with the near ubiquitous presence of primary cilia in mammalian tissues. Over 60 genes have been associated with various ciliopathy phenotypes, and it has become increasingly clear with the plethora of reports that link apparently distinct clinical phenotypes to mutations in the same individual genes that these phenotypes represent a spectrum in which isolated retinal dystrophy or nephronophthisis (MIM 256100) represent the mild end and perinatal lethal Meckel-Gruber syndrome (MKS [MIM 249000]) with severe brain malformation, polydactyly, and multicystic and/or dysplastic kidneys represents the extreme end.7Lee J.E. Gleeson J.G. A systems-biology approach to understanding the ciliopathy disorders.Genome Med. 2011; 3: 59Crossref PubMed Scopus (72) Google Scholar, 8Ware S.M. Aygun M.G. Hildebrandt F. Spectrum of clinical diseases caused by disorders of primary cilia.Proc. Am. Thorac. Soc. 2011; 8: 444-450Crossref PubMed Scopus (82) Google Scholar, 9Davis E.E. Katsanis N. The ciliopathies: a transitional model into systems biology of human genetic disease.Curr. Opin. Genet. Dev. 2012; 22: 290-303Crossref PubMed Scopus (118) Google Scholar The subset of affected individuals who can be explained by mutations in recognized genes varies greatly. For example, primary driver mutations have been identified in the majority of individuals with the intermediate Bardet-Biedl ciliopathy (MIM 209900),10Abu-Safieh L. Al-Anazi S. Al-Abdi L. Hashem M. Alkuraya H. Alamr M. Sirelkhatim M.O. Al-Hassnan Z. Alkuraya B. Mohamed J.Y. et al.In search of triallelism in Bardet-Biedl syndrome.Eur. J. Hum. Genet. 2012; 20: 420-427Crossref PubMed Scopus (91) Google Scholar whereas for other ciliopathies, such as Joubert syndrome (JBTS [MIM 213300]) and MKS, additional genes remain to be identified.11Alazami A.M. Alshammari M.J. Salih M.A. Alzahrani F. Hijazi H. Seidahmed M.Z. Abu Safieh L. Aldosary M. Khan A.O. Alkuraya F.S. Molecular characterization of Joubert syndrome in Saudi Arabia.Hum. Mutat. 2012; 33: 1423-1428Crossref PubMed Scopus (48) Google Scholar, 12Shaheen R. Faqeih E. Alshammari M.J. Swaid A. Al-Gazali L. Mardawi E. Ansari S. Sogaty S. Seidahmed M.Z. AlMotairi M.I. et al.Genomic analysis of Meckel-Gruber syndrome in Arabs reveals marked genetic heterogeneity and novel candidate genes.Eur. J. Hum. Genet. 2013; 21: 762-768Crossref PubMed Scopus (45) Google Scholar In this report, we describe three families affected by JBTS or a syndrome similar to MKS (Table 1) but not linked to any of the established genes and identify CSPP1 (MIM 611654) as another member of the genes associated with ciliopathy phenotypes in humans.Table 1Clinical Features of Each of the Affected Individuals in This StudyCharacteristicsFamily 1Family 2Family 3V:1V:3II:1II:1II:2Agestillbirth (26 weeks)stillbirth (18 weeks)7 years28 days (died of unknown cause)24 days (died of unknown cause)GendermalefemalefemalefemalefemaleEthnicitySaudiSaudiHutteriteHutteriteHutteriteConsanguinityyesyesyesyesyesCNShydranencephaly, occipital encephaloceleoccipital encephalocelemolar tooth sign, heterotopiamolar tooth sign, posterior fossa cystmolar tooth sign, posterior fossa cystKidneyshyperechogenichyperechogenicnormalnormal imagingnormal imagingCraniofacial featuressingle nostrilsingle nostrilnormalnormalnormalEyesanophthalmiapartially fused eyesstrabismusnot availablenot availableOthers--tracheesophageal fistula (also in sister unaffected with CNS malformations and not homozygous for CSPP1)-- Open table in a new tab The first family (family 1) is from Saudi Arabia and consists of healthy parents who are first cousins once removed (Table 1 and Figure 1A). Their first pregnancy was induced at 26 weeks when prenatal sonography showed hydranencephaly, a single nostril, and bilateral hyperechogenic kidneys. The baby was a stillborn male, delivered vaginally after cephalocentesis, with a weight of 1,990 g and occipitofrontal circumference (OFC) of 39 cm. He had large fontanels and wide cranial sutures, occipital encephalocele, anophthalmia, and a single nostril (Figures 1B and 1C). The second pregnancy ended in a spontaneous first-trimester abortion. The third pregnancy was similar to the first in that it showed sonographic findings of occipital encephalocele and bilateral hyperechogenic kidneys (Figures 1D–1F). She was stillborn at 18 weeks and was found to have, in addition to encephalocele, partially fused eyes. The second family (family 2) is a Schmiedeleut Hutterite Canadian family with one child affected by typical clinical and radiological features of JBTS (Table 1 and Figures 1A, 1G, and 1H). The proband is now 7 years old and has a history of global developmental delay, hypotonia, ataxia, and strabismus. Neuroimaging confirmed the presence of a molar tooth sign. She is otherwise healthy, with the exception of a history of tracheoesophageal fistula, also seen in her otherwise healthy sister, who has age-appropriate development and normal neuroimaging. The third family (family 3) is also a Schmiedeleut Hutterite Canadian family with two children affected by classic JBTS (Table 1 and Figure 1A). The first child was born at 42 weeks and received care in the neonatal intensive care unit for respiratory distress. At birth, her weight was 3,979 g and her OFC was 37.5 cm. Brain MRI showed absent inferior cerebellar vermis, dysplastic superior cerebellar vermis, posterior fossa cyst communicating with the fourth ventricle, and a molar tooth sign secondary to thickened horizontal superior cerebellar peduncles and a reduced anteroposterior (AP) dimension of the mesencephalon. She died at 28 days. In the second child, a Dandy-Walker variant was noted antenatally at the age of 19 weeks, suggesting a recurrence. Brain MRI showed that the AP dimension of the mesencephalon was smaller than expected. The superior cerebellar peduncles were thick and had a more parallel configuration, giving rise to the molar tooth sign. The cerebellar vermis appeared hypoplastic, the medulla was mildly narrowed, and a mega cisterna magna was also seen. This child died at 3 weeks of age. Autopsy was not performed on either child, but neither had clinical evidence of renal malformations or other congenital anomalies. The Hutterite founder mutation in TMEM237 (MIM 614423)14Huang L. Szymanska K. Jensen V.L. Janecke A.R. Innes A.M. Davis E.E. Frosk P. Li C. Willer J.R. Chodirker B.N. et al.TMEM237 is mutated in individuals with a Joubert syndrome related disorder and expands the role of the TMEM family at the ciliary transition zone.Am. J. Hum. Genet. 2011; 89: 713-730Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar and the recurrent NPHP1 (MIM 607100) deletion, which is common in the Hutterites13Boycott K.M. Parboosingh J.S. Chodirker B.N. Lowry R.B. McLeod D.R. Morris J. Greenberg C.R. Chudley A.E. Bernier F.P. Midgley J. et al.Clinical genetics and the Hutterite population: a review of Mendelian disorders.Am. J. Med. Genet. A. 2008; 146A: 1088-1098Crossref PubMed Scopus (39) Google Scholar and shown rarely to cause JBTS,15Parisi M.A. Bennett C.L. Eckert M.L. Dobyns W.B. Gleeson J.G. Shaw D.W. McDonald R. Eddy A. Chance P.F. Glass I.A. The NPHP1 gene deletion associated with juvenile nephronophthisis is present in a subset of individuals with Joubert syndrome.Am. J. Hum. Genet. 2004; 75: 82-91Abstract Full Text Full Text PDF PubMed Scopus (196) Google Scholar were excluded in the proband from each Hutterite family prior to further investigations. Family 1 was recruited according to a protocol approved by the institutional review board (IRB) at King Faisal Specialist Hospital and Research Center, whereas families 2 and 3 were recruited according to a protocol approved by the University of Calgary IRB; written informed consent was obtained from all research participants. This was followed by DNA extraction from whole blood and autozygome determination as previously described.16Alkuraya F.S. Homozygosity mapping: one more tool in the clinical geneticist’s toolbox.Genet. Med. 2010; 12: 236-239Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 17Alkuraya F.S. Discovery of rare homozygous mutations from studies of consanguineous pedigrees.Curr. Protoc. Hum. Genet. 2012; Chapter 6: 12PubMed Google Scholar, 18Innes A.M. Boycott K.M. Puffenberger E.G. Redl D. MacDonald I.M. Chudley A.E. Beaulieu C. Perrier R. Gillan T. Wade A. Parboosingh J.S. A founder mutation in BBS2 is responsible for Bardet-Biedl syndrome in the Hutterite population: utility of SNP arrays in genetically heterogeneous disorders.Clin. Genet. 2010; 78: 424-431Crossref PubMed Scopus (17) Google Scholar None of these families mapped to any of the genes associated with JBTS or MKS. Therefore, the probands from families 1 and 2 were exome sequenced, and the resulting variants were filtered by consideration of only homozygous coding and/or splicing variants that were absent from publically available databases and that occurred within the autozygome of each proband (Table S1, available online).17Alkuraya F.S. Discovery of rare homozygous mutations from studies of consanguineous pedigrees.Curr. Protoc. Hum. Genet. 2012; Chapter 6: 12PubMed Google Scholar, 19Alkuraya F.S. The application of next-generation sequencing in the autozygosity mapping of human recessive diseases.Hum. Genet. 2013; 132: 1197-1211Crossref PubMed Scopus (92) Google Scholar Consistent with the nature of their founder population, exome analysis of Hutterite family 2 highlighted only a single variant in CSPP1, c.363_364delTA (RefSeq accession number NM_024790.6), which is predicted to cause premature truncation of the protein (p.His121Glnfs∗22). This mutation was subsequently identified by Sanger sequencing in Hutterite family 3 (Figure 2). In family 1, analysis of the homozygous exome variants restricted to the autozygome revealed one missense variant in TTC7A (MIM 609332) and one CSPP1 frameshift deletion (c.2244_2247del [RefSeq NM_024790.6]) that is also predicted to cause premature truncation (p.Glu750Lysfs∗7; Figure 2). TTC7A is unlikely to play a causal role in family 1 given its recent link to a Mendelian form of immunodeficiency and intestinal atresia, a phenotype that does not overlap with MKS or JBTS.20Chen R. Giliani S. Lanzi G. Mias G.I. Lonardi S. Dobbs K. Manis J. Im H. Gallagher J.E. Phanstiel D.H. et al.Whole-exome sequencing identifies tetratricopeptide repeat domain 7A (TTC7A) mutations for combined immunodeficiency with intestinal atresias.J. Allergy Clin. Immunol. 2013; 132 (656–664.e17)Google Scholar, 21Samuels M.E. Majewski J. Alirezaie N. Fernandez I. Casals F. Patey N. Decaluwe H. Gosselin I. Haddad E. Hodgkinson A. et al.Exome sequencing identifies mutations in the gene TTC7A in French-Canadian cases with hereditary multiple intestinal atresia.J. Med. Genet. 2013; 50: 324-329Crossref PubMed Scopus (93) Google Scholar Homozygosity for the CSPP1 mutation segregated with the affected status of the children in each of the three families. Given the established overlap in the genetic etiology of JBTS and MKS, it is likely that the convergence of exome variant filtration in these families on homozygous truncating variants in CSPP1 is explained by the causal nature of these variants. In addition, CSPP1 has previously been proposed as a candidate ciliopathy gene given its role in ciliary biology.22Patzke S. Redick S. Warsame A. Murga-Zamalloa C.A. Khanna H. Doxsey S. Stokke T. CSPP is a ciliary protein interacting with Nephrocystin 8 and required for cilia formation.Mol. Biol. Cell. 2010; 21: 2555-2567Crossref PubMed Scopus (40) Google Scholar CSPP1 encodes two protein isoforms: CSPP1 and CSPP-L, in which the “L” denotes the longer sequence that is derived by an extended N terminus (an additional 294 amino acids) and an interstitial insertion of 51 amino acids between the glutamine-rich coiled-coiled domains (Figure 2). It was first identified in a screen for genes that are overexpressed in B cell lymphoma and was found later to encode a core centrosomal protein whose deficiency leads to delayed cell-cycle progression.23Patzke S. Hauge H. Sioud M. Finne E.F. Sivertsen E.A. Delabie J. Stokke T. Aasheim H.C. Identification of a novel centrosome/microtubule-associated coiled-coil protein involved in cell-cycle progression and spindle organization.Oncogene. 2005; 24: 1159-1173Crossref PubMed Scopus (41) Google Scholar Although the exact mechanism remains unclear, CSPP1 was found to localize in the central spindles during metaphase and the central furrow during anaphase and cytokinesis.24Asiedu M. Wu D. Matsumura F. Wei Q. Centrosome/spindle pole-associated protein regulates cytokinesis via promoting the recruitment of MyoGEF to the central spindle.Mol. Biol. Cell. 2009; 20: 1428-1440Crossref PubMed Scopus (33) Google Scholar The nonmitotic function of CSPP1 was demonstrated recently when it was shown that CSPP1 localizes to the transition zone, as well as to the axoneme of the primary cilium, in a pattern identical to that of the products of other genes associated with ciliopathy phenotypes; such genes include NPHP1, NPHP4 (MIM 607215), and RPGRIP1L (NPHP8 [MIM 610937]).22Patzke S. Redick S. Warsame A. Murga-Zamalloa C.A. Khanna H. Doxsey S. Stokke T. CSPP is a ciliary protein interacting with Nephrocystin 8 and required for cilia formation.Mol. Biol. Cell. 2010; 21: 2555-2567Crossref PubMed Scopus (40) Google Scholar Furthermore, RPGRIP1L (NPHP8) can interact directly with CSPP1, and loss of this interaction leads to mislocalization of RPGRIP1L.22Patzke S. Redick S. Warsame A. Murga-Zamalloa C.A. Khanna H. Doxsey S. Stokke T. CSPP is a ciliary protein interacting with Nephrocystin 8 and required for cilia formation.Mol. Biol. Cell. 2010; 21: 2555-2567Crossref PubMed Scopus (40) Google Scholar Moreover, knockdown of CSPP1 results in a severe ciliogenesis defect.22Patzke S. Redick S. Warsame A. Murga-Zamalloa C.A. Khanna H. Doxsey S. Stokke T. CSPP is a ciliary protein interacting with Nephrocystin 8 and required for cilia formation.Mol. Biol. Cell. 2010; 21: 2555-2567Crossref PubMed Scopus (40) Google Scholar In view of the above, and given that all genes associated with JBTS and MKS have been found to play a role in ciliary biology,9Davis E.E. Katsanis N. The ciliopathies: a transitional model into systems biology of human genetic disease.Curr. Opin. Genet. Dev. 2012; 22: 290-303Crossref PubMed Scopus (118) Google Scholar we asked whether the truncating variants we identified in CSPP1 similarly impair ciliogenesis and/or ciliary function. With informed consent, a skin biopsy was obtained from the proband in family 1. Using a standard serum-starvation-induced ciliogenesis assay,25Walczak-Sztulpa J. Eggenschwiler J. Osborn D. Brown D.A. Emma F. Klingenberg C. Hennekam R.C. Torre G. Garshasbi M. Tzschach A. et al.Cranioectodermal Dysplasia, Sensenbrenner syndrome, is a ciliopathy caused by mutations in the IFT122 gene.Am. J. Hum. Genet. 2010; 86: 949-956Abstract Full Text Full Text PDF PubMed Scopus (149) Google Scholar we observed that the frequency of ciliated fibroblasts from the proband was markedly lower than that of control fibroblasts. Furthermore, by assessing the mRNA expression of GLI1 (MIM 165220) in the affected individual’s fibroblasts after SAG stimulation and serum starvation, we found that sonic hedgehog (SHH) signaling was markedly impaired, indicating that the ciliogenesis defect we observed has downstream consequences (Figure 3). No fibroblasts were available for testing the effect of the Hutterite mutation on ciliogenesis, but we suspect that it would result in a similar defect because it has been shown that knockdown of the transcript that encodes CSPP-L, despite sparing CSPP1, is sufficient to cause a ciliogenesis defect.22Patzke S. Redick S. Warsame A. Murga-Zamalloa C.A. Khanna H. Doxsey S. Stokke T. CSPP is a ciliary protein interacting with Nephrocystin 8 and required for cilia formation.Mol. Biol. Cell. 2010; 21: 2555-2567Crossref PubMed Scopus (40) Google Scholar To assess the effect of the CSPP1 mutation on the cell cycle, we used flow cytometry to perform cell-cycle analysis in the fibroblasts from the proband in family 1. We observed no significant difference in the G0/G1 and G2/M cell-cycle phases between this affected individual’s cells and control cells (Figure S1). Our findings are consistent with what is known about the two isoforms of CSPP1 and allow us to speculate on a potential genotype-phenotype correlation. We posit that the redundancy between the two isoforms in certain ciliary functions might contribute, at least in part, to the differences between the clinical presentations of the Hutterite and Saudi mutations. The JBTS phenotype observed with the Hutterite mutation (families 2 and 3) presumably spares the short isoform, whereas the MKS phenotype caused by the Saudi mutation (family 1) truncates both isoforms. Both isoforms share similar expression profiles (expression in the brain, eyes, and kidneys) in the developing mouse embryo and both colocalize, interact, and stabilize RPGRIP1L in the transition zone.22Patzke S. Redick S. Warsame A. Murga-Zamalloa C.A. Khanna H. Doxsey S. Stokke T. CSPP is a ciliary protein interacting with Nephrocystin 8 and required for cilia formation.Mol. Biol. Cell. 2010; 21: 2555-2567Crossref PubMed Scopus (40) Google Scholar Indeed, we show that the ciliary localization of RPGRIP1L was completely lost in the fibroblasts from the proband in family 1 (Figure 4). We note, however, that the clinical variability even within the Hutterite families ranged from neonatal death to relatively milder involvement in an older child. Therefore, any potential role for the two CSPP1 isoforms in affecting clinical severity would be unlikely to occur in isolation, and additional factors are predicted to be involved. To investigate the contribution of CSPP1 to MKS cases, we sequenced this gene in 89 affected individuals by using a PCR amplicon high-throughput sequencing strategy on an Ion Torrent platform according to the manufacturer’s (Life Technologies) instructions and by using subsequent Sanger-based confirmatory sequencing of all alleles found at A [p.Arg740His], c.2966G>A [p.Arg989Gln], and c.1376 C>G [p.Ser459Cys]), the first two of which were carried by individuals in a heterozygous state and the third of which was carried in a homozygous state. These variants are absent in variant databases (1000 Genomes and the NHLBI EVS) and are predicted to be pathogenic by PolyPhen-2, SIFT, and MutationTaster. The homozygous variant was carried by an individual identified previously to also harbor two variants (one truncating and one missense) in RPGRIP1L, mutations in which are known to cause JBTS and MKS. Although we are unable to resolve the significance of these alleles, it is possible that CSPP1 is the primary driver instead of RPGRIP1L. Thus, it appears that CSPP1 mutations account for only a small percentage of MKS alleles. Germline mutations in genes that encode various centrosomal proteins appear to fall broadly under two categories: (1) microcephaly and/or primordial dwarfism and (2) classical ciliopathy. It appears that the former is the outcome of more severe mitotic dysfunction of the centrosome, whereas the latter is the result of dominating postmitotic ciliary dysfunction. This model incorporates accumulating evidence that the genes associated with either class of disorders encode proteins that are essential for both mitotic and ciliary functions of the centrosome. For example, deficiency of POC1A (MIM 614783) and CENPJ (MIM 609279) has been shown to impair both mitosis and ciliogenesis, yet mutations in these genes cause primordial dwarfism lacking all of the phenotypic features of a classic ciliopathy.26Shaheen R. Faqeih E. Shamseldin H.E. Noche R.R. Sunker A. Alshammari M.J. Al-Sheddi T. Adly N. Al-Dosari M.S. Megason S.G. et al.POC1A truncation mutation causes a ciliopathy in humans characterized by primordial dwarfism.Am. J. Hum. Genet. 2012; 91: 330-336Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar, 27Al-Dosari M.S. Shaheen R. Colak D. Alkuraya F.S. Novel CENPJ mutation causes Seckel syndrome.J. Med. Genet. 2010; 47: 411-414Crossref PubMed Scopus (121) Google Scholar, 28Wu K.-S. Tang T.K. CPAP is required for cilia formation in neuronal cells.Biol. Open. 2012; 1: 559-565Crossref PubMed Scopus (16) Google Scholar Similarly, CEP290 (MIM 610142), mutations in which result in a wide-array of ciliopathy phenotypes, is known to be essential for mitosis.29Kim J. Krishnaswami S.R. Gleeson J.G. CEP290 interacts with the centriolar satellite component PCM-1 and is required for Rab8 localization to the primary cilium.Hum. Mol. Genet. 2008; 17: 3796-3805Crossref PubMed Scopus (225) Google Scholar, 30Kim K. Rhee K. The pericentriolar satellite protein CEP90 is crucial for integrity of the mitotic spindle pole.J. Cell Sci. 2011; 124: 338-347Crossref PubMed Scopus (66) Google Scholar We demonstrate here that mutations in CSPP1, another gene with an established function in both mitosis and ciliogenesis, result in a restricted cilia-related phenotype, consistent with our findings of a severe ciliogenesis defect but lack of a significant observable effect on mitosis. In summary, we identified CSPP1 truncating mutations in several individuals with ciliopathy phenotypes ranging from JBTS to MKS-like syndromes and observed a ciliogenesis defect in cells from an affected individual. Our findings further delineate the genetic heterogeneity of these two disorders in the Saudi and Hutterite (and potentially other) populations. It remains to be seen whether additional mutations in this gene can result in other ciliopathy phenotypes and whether differential involvement of the two isoforms can indeed provide insight into potential genotype-phenotype correlations. We thank the families for their enthusiastic participation. We also thank the genotyping and sequencing core facilities at King Faisal Specialist Hospital and Research Center for their technical help. This work was supported by a Dubai Harvard Foundation for Medical Research Collaborative Research Grant (F.S.A.), a grant from King Abdulaziz City for Science and Technology (10-BIO 1350-20 to C.P.), funding from the SickKids Foundation and Canadian Institutes of Health Research (CIHR) Institute of Human Development, Child, and Youth Health (NI10-008 to K.M.B.), grants from the National Institutes of Health (DK072301, HD042601, and DK075972 to N.K. and EY021872 to E.E.D.), and funding from the European Union Seventh Framework Programme (FP7/2009) under grant agreement 241955 (project SYSCILIA) to C.A.J., N.K., and E.E.D. K.M.B. was supported by a Clinical Investigatorship Award from the CIHR Institute of Genetics. C.M.L. was supported by a CIHR Training Program in Genetics, Child Development, and Health. C.A.J. received a Sir Jules Thorn Award for Biomedical Research (JTA/09). N.K. is an Endowed Brumley Professor. W.H. receives funding from the Rosetrees Trust (grant M333). Download .pdf (.12 MB) Help with pdf files Document S1. Figure S1 and Table S1 The URLs for data presented herein are as follows:Burrows-Wheeler Aligner, http://bio-bwa.sourceforge.net/Ensembl Genome Browser, http://www.ensembl.org/index.htmlMutationTaster, www.mutationtaster.org/Online Mendelian Inheritance in Man (OMIM), http://www.omim.orgPolyPhen-2, www.genetics.bwh.harvard.edu/pph2/SIFT, http://sift.bii.a-star.edu.sg/UCSC Genome Browser, http://genome.ucsc.edu/