Unique among ciliopathies: primary ciliary dyskinesia, a motile cilia disorder

ABSTRACTPrimary ciliary dyskinesia (PCD) is a human condition of dysfunctional motile cilia characterized by recurrent lung infection, infertility, organ laterality defects and partially penetrant hydrocephalus. We recovered a mouse mutant from a forward genetic screen that developed many of the hallmark phenotypes of PCD. Whole-exome sequencing identified this primary ciliary dyskinesia only (Pcdo) allele to be a nonsense mutation (c.5236A>T) in the Spag17 coding sequence creating a premature stop codon (K1746*). The Pcdo variant abolished several isoforms of SPAG17 in the Pcdo mutant testis but not in the brain. Our data indicate differential requirements for SPAG17 in different types of motile cilia. SPAG17 is essential for proper development of the sperm flagellum and is required for either development or stability of the C1 microtubule structure within the central pair apparatus of the respiratory motile cilia, but not the brain ependymal cilia. We identified changes in ependymal ciliary beating frequency, but these did not appear to alter lateral ventricle cerebrospinal fluid flow. Aqueductal stenosis resulted in significantly slower and abnormally directed cerebrospinal fluid flow, and we suggest that this is the root cause of the hydrocephalus. The Spag17Pcdo homozygous mutant mice are generally viable to adulthood but have a significantly shortened lifespan, with chronic morbidity. Our data indicate that the c.5236A>T Pcdo variant is a hypomorphic allele of Spag17 that causes phenotypes related to motile, but not primary, cilia. Spag17Pcdo is a useful new model for elucidating the molecular mechanisms underlying central pair PCD pathogenesis in the mouse.This article has an associated First Person interview with the first author of the paper.

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TTC12 Loss-of-Function Mutations Cause Primary Ciliary Dyskinesia and Unveil Distinct Dynein Assembly Mechanisms in Motile Cilia Versus Flagella

The American Journal of Human Genetics ◽

10.1016/j.ajhg.2019.12.010 ◽

2020 ◽

Vol 106 (2) ◽

pp. 153-169 ◽

Cited By ~ 9

Author(s):

Lucie Thomas ◽

Khaled Bouhouche ◽

Marjorie Whitfield ◽

Guillaume Thouvenin ◽

Andre Coste ◽

...

Keyword(s):

Primary Ciliary Dyskinesia ◽

Loss Of Function ◽

Motile Cilia ◽

Ciliary Dyskinesia

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Mutation of CFAP57 causes primary ciliary dyskinesia by disrupting the asymmetric targeting of a subset of ciliary inner dynein arms

10.1101/773028 ◽

2019 ◽

Author(s):

Ximena M. Bustamante-Marin ◽

Amjad Horani ◽

Mihaela Stoyanova ◽

Wu-Lin Charng ◽

Mathieu Bottier ◽

...

Keyword(s):

Epithelial Cells ◽

Primary Ciliary Dyskinesia ◽

Large Population ◽

Exome Capture ◽

Swimming Velocity ◽

Population Sampling ◽

Dynein Arms ◽

Motile Cilia ◽

Ciliary Dyskinesia ◽

Sampling Probability

AbstractPrimary ciliary dyskinesia (PCD) is characterized by chronic airway disease, male infertility, and randomization of the left/right body axis, and is caused by defects of motile cilia and sperm flagella. We screened a cohort of affected individuals that lack an obvious TEM structural phenotype for pathogenic variants using whole exome capture and next generation sequencing. The population sampling probability (PSAP) algorithm identified one subject with a homozygous nonsense variant [(c.1762C>T) p.(Arg588*) exon 11] in the uncharacterized CFAP57 gene. In normal human nasal epithelial cells, CFAP57 localizes throughout the ciliary axoneme. Analysis of cells from the PCD patient shows a loss of CFAP57, reduced beat frequency, and an alteration in the ciliary waveform. Knockdown of CFAP57 in human tracheobronchial epithelial cells (hTECs) recapitulates these findings. Phylogenetic analysis showed that CFAP57 is conserved in organisms that assemble motile cilia, and CFAP57 is allelic with the BOP2 gene identified previously in Chlamydomonas. Two independent, insertional fap57 Chlamydomonas mutant strains show reduced swimming velocity and altered waveforms. Tandem mass spectroscopy showed that CFAP57 is missing, and the “g” inner dyneins (DHC7 and DHC3) and the “d” inner dynein (DHC2) are reduced. Our data demonstrate that the FAP57 protein is required for the asymmetric assembly of inner dyneins on only a subset of the microtubule doublets, and this asymmetry is essential for the generation of an effective axonemal waveform. Together, our data identifies mutations in CFAP57 as a cause of PCD with a specific defect in the inner dynein arm assembly process.SignificanceMotile cilia are found throughout eukaryotic organisms and performs essential functions. Primary ciliary dyskinesia (PCD) is a rare disease that affects the function of motile cilia. By applying a novel population sampling probability algorithm (PSAP) that uses large population sequencing databases and pathogenicity prediction algorithms, we identified a variant in an uncharacterized gene, CFAP57. This is the first reported example of PCD caused by a mutation that affects only a subset of the inner dynein arms, which are needed to generate the waveform. CFAP57 identifies an address for specific dynein arms. These findings demonstrate the effectiveness of the PSAP algorithm, expand our understanding of the positioning of dynein arms, and identify mutations in CFAP57 as a cause of PCD.

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Faculty Opinions recommendation of Primary Ciliary Dyskinesia (PCD): A genetic disorder of motile cilia.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.736702497.793576547 ◽

2020 ◽

Author(s):

Miles Weinberger

Keyword(s):

Primary Ciliary Dyskinesia ◽

Genetic Disorder ◽

Motile Cilia ◽

Ciliary Dyskinesia

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Primary ciliary dyskinesia: a major player in a bigger game

Breathe ◽

10.1183/20734735.0047-2020 ◽

2020 ◽

Vol 16 (2) ◽

pp. 200047

Author(s):

Reena Bhatt ◽

Claire Hogg

Keyword(s):

Primary Ciliary Dyskinesia ◽

Heart Defects ◽

List Type ◽

Loss Of Function ◽

Brush Biopsy ◽

Disease Mechanisms ◽

Major Player ◽

Motile Cilia ◽

Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is an inherited disorder of clinical and genetic heterogeneity resulting from mutations in genes involved in the transport, assembly and function of motile cilia. The resulting impairment in mucociliary clearance means patients suffer from chronic progressive lung disease, bronchiectasis, rhinosinusitis and middle ear disease. Subfertility is common to both male and female patients. Situs abnormalities occur in around half of patients, with a subgroup suffering more complex situs arrangements where congenital heart defects or other organ abnormalities frequently coexist. Variations from the classical PCD phenotype are increasingly recognised where overlapping features across a range of motile and nonmotile ciliopathies are redefining our approach to both diagnosis and management of these complex conditions. PCD offers an ideal opportunity for direct visualisation of ciliary function and structure, following nasal brush biopsy, allowing opportunities for researchers to directly interrogate the downstream impact of loss of function mutations. In turn, this has led to rapid advances in the development of new diagnostic tests. These advances mean that PCD is an excellent disease model for understanding the genetic and mechanistic causes of the clinical phenotype for all respiratory ciliopathies. Furthermore, the overlapping role of motile ciliary defects in a wider set of complex and syndromic disorders related to loss of function mutations in primary, nonmotile cilia has been recognised. As we better understand the role of ciliary defects in a broad spectrum of diseases, we should aim to map out a framework through which we can identify, diagnose and treat all respiratory ciliopathies.Key pointsPrimary ciliary dyskinesia is just one of a group of conditions where a heterogeneous array of genetic mutations affect the assembly or structure of motile cilia.Overlapping phenotypes between motile and nonmotile ciliopathies are redefining the diagnostic and therapeutic approach to encompass all ciliopathy patients with a respiratory phenotype.An extended diagnostic algorithm may be required to capture the majority of cases with a respiratory ciliopathy, including patients with syndromic ciliopathies.The terminology around disorders of motile cilia is becoming more descriptive to better reflect the heterogeneity and underlying disease mechanisms across the spectrum of respiratory ciliopathies.Educational aimsTo summarise the existing knowledge base around the disease mechanisms for respiratory ciliopathies, including primary ciliary dyskinesia (PCD).To explore and understand the reasons for changing terminology around respiratory ciliopathies.To emphasise key messages around the diagnosis and treatment of all ciliopathies.Diagnosing PCD is complex and time consuming, and there is no single stand-alone test that can confirm or exclude a diagnosis in all cases.

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Rare Human Diseases: Model Organisms in Deciphering the Molecular Basis of Primary Ciliary Dyskinesia

Cells ◽

10.3390/cells8121614 ◽

2019 ◽

Vol 8 (12) ◽

pp. 1614 ◽

Cited By ~ 1

Author(s):

Martyna Poprzeczko ◽

Marta Bicka ◽

Hanan Farahat ◽

Rafal Bazan ◽

Anna Osinka ◽

...

Keyword(s):

Molecular Basis ◽

Primary Ciliary Dyskinesia ◽

State Of The Art ◽

Model Organisms ◽

Phenotypic Changes ◽

Current State ◽

Evolutionarily Conserved ◽

Motile Cilia ◽

The Impact ◽

Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is a recessive heterogeneous disorder of motile cilia, affecting one per 15,000–30,000 individuals; however, the frequency of this disorder is likely underestimated. Even though more than 40 genes are currently associated with PCD, in the case of approximately 30% of patients, the genetic cause of the manifested PCD symptoms remains unknown. Because motile cilia are highly evolutionarily conserved organelles at both the proteomic and ultrastructural levels, analyses in the unicellular and multicellular model organisms can help not only to identify new proteins essential for cilia motility (and thus identify new putative PCD-causative genes), but also to elucidate the function of the proteins encoded by known PCD-causative genes. Consequently, studies involving model organisms can help us to understand the molecular mechanism(s) behind the phenotypic changes observed in the motile cilia of PCD affected patients. Here, we summarize the current state of the art in the genetics and biology of PCD and emphasize the impact of the studies conducted using model organisms on existing knowledge.

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CAMSAP3 facilitates basal body polarity and the formation of the central pair of microtubules in motile cilia

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1907335117 ◽

2020 ◽

Vol 117 (24) ◽

pp. 13571-13579 ◽

Cited By ~ 2

Author(s):

Alan M. Robinson ◽

Satoe Takahashi ◽

Eva J. Brotslaw ◽

Aisha Ahmad ◽

Emma Ferrer ◽

...

Keyword(s):

Primary Ciliary Dyskinesia ◽

Basal Bodies ◽

Nasal Airway ◽

Directional Flow ◽

Multiple Phenotypes ◽

Multiciliated Cells ◽

Motile Cilia ◽

Ciliary Dyskinesia ◽

Different Tissues ◽

Proper Orientation

Synchronized beating of cilia on multiciliated cells (MCCs) generates a directional flow of mucus across epithelia. This motility requires a “9 + 2” microtubule (MT) configuration in axonemes and the unidirectional array of basal bodies of cilia on the MCCs. However, it is not fully understood what components are needed for central MT-pair assembly as they are not continuous with basal bodies in contrast to the nine outer MT doublets. In this study, we discovered that a homozygous knockdown mouse model for MT minus-end regulator calmodulin-regulated spectrin-associated protein 3 (CAMSAP3),Camsap3tm1a/tm1a, exhibited multiple phenotypes, some of which are typical of primary ciliary dyskinesia (PCD), a condition caused by motile cilia defects. Anatomical examination ofCamsap3tm1a/tm1amice revealed severe nasal airway blockage and abnormal ciliary morphologies in nasal MCCs. MCCs from different tissues exhibited defective synchronized beating and ineffective generation of directional flow likely underlying the PCD-like phenotypes. In normal mice, CAMSAP3 localized to the base of axonemes and at the basal bodies in MCCs. However, inCamsap3tm1a/tm1a, MCCs lacked CAMSAP3 at the ciliary base. Importantly, the central MT pairs were missing in the majority of cilia, and the polarity of the basal bodies was disorganized. These phenotypes were further confirmed in MCCs ofXenopusembryos when CAMSAP3 expression was knocked down by morpholino injection. Taken together, we identified CAMSAP3 as being important for the formation of central MT pairs, proper orientation of basal bodies, and synchronized beating of motile cilia.

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Proteome of the central apparatus of a ciliary axoneme

The Journal of Cell Biology ◽

10.1083/jcb.201902017 ◽

2019 ◽

Vol 218 (6) ◽

pp. 2051-2070 ◽

Cited By ~ 21

Author(s):

Lei Zhao ◽

Yuqing Hou ◽

Tyler Picariello ◽

Branch Craige ◽

George B. Witman

Keyword(s):

Mass Spectrometry ◽

Knowledge Base ◽

Genetic Screening ◽

Primary Ciliary Dyskinesia ◽

The Other ◽

Wild Type ◽

Central Apparatus ◽

Motile Cilia ◽

Ciliary Dyskinesia

Nearly all motile cilia have a “9+2” axoneme containing a central apparatus (CA), consisting of two central microtubules with projections, that is essential for motility. To date, only 22 proteins are known to be CA components. To identify new candidate CA proteins, we used mass spectrometry to compare axonemes of wild-type Chlamydomonas and a CA-less mutant. We identified 44 novel candidate CA proteins, of which 13 are conserved in humans. Five of the latter were studied more closely, and all five localized to the CA; therefore, most of the other candidates are likely to also be CA components. Our results reveal that the CA is far more compositionally complex than previously recognized and provide a greatly expanded knowledge base for studies to understand the architecture of the CA and how it functions. The discovery of the new conserved CA proteins will facilitate genetic screening to identify patients with a form of primary ciliary dyskinesia that has been difficult to diagnose.

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