Autosomal Recessive Microcephaly Research Articles

Second report of TEDC1-related microcephaly caused by a novel biallelic mutation in an Iranian consanguineous family.

Primary autosomal recessive microcephaly (MCPH) is a rare developmental disorder characterized by cognitive impairment, delayed neurodevelopment, and reduced brain size. It is a genetically heterogeneous condition, and several genes have been identified as associated with MCPH. In this study, we utilized whole-exome sequencing (WES) to identify disease-causing variations in two brothers from an Iranian family affected by MCPH, who had consanguineous parents. In the patients, we detected a novel homozygous missense mutation (c.806A > G, p.Gln269Arg) in the TEDC1 gene in one of the patients. Co-segregation analysis using Sanger sequencing confirmed that this variant was inherited from parents. The identified variant was evaluated for its pathogenicity and novelty using various databases. Additionally, bioinformatics tools were employed to predict the three-dimensional structure of the mutant TEDC1 protein. This study presents the second documented report of a mutation in the TEDC1 gene associated with MCPH. The identification of this novel biallelic mutation as a causative factor for MCPH in the proband further underscores the utility of genetic testing techniques, such as WES, as reliable diagnostic tools for individuals with this condition.

Loss of Aspm causes increased apoptosis of developing neural cells during mouse cerebral corticogenesis.

Abnormal spindle-like microcephaly associated (ASPM) is a causative gene of primary autosomal recessive microcephaly. Microcephaly is considered to be a consequence of a small brain, but the associated molecular mechanisms are not fully understood. In this study, we generated brain-specific Aspm knockout mice to evaluate the fetal brain phenotype and observed cortical reduction in the late stage of murine cortical development. It has been reported that the total number of neurons is regulated by the number of neural stem and progenitor cells. In the Aspm knockout mice, no apparent change was shown in the neural progenitor cell proliferation and there was no obvious effect on the number of newly generated neurons in the developing cortex. On the other hand, the knockout mice showed a constant increase in apoptosis in the cerebral cortex from the early through the late stages of cortical development. Furthermore, apoptosis occurred in the neural progenitor cells associated with DNA damage. Overall, these results suggest that apoptosis of the neural progenitor cells is involved in the thinning of the mouse cerebral cortex, due to the loss of the Aspm gene in neocortical development.

Deficiency in the omega-3 lysolipid transporter Mfsd2a leads to aberrant oligodendrocyte lineage development and hypomyelination

Patients with Autosomal Recessive Microcephaly 15 caused by deficiency in the sodium-dependent lysophosphatidylcholine (LPC) transporter Major Facilitator Superfamily Domain containing 2a (Mfsd2a) present with both microcephaly and hypomyelination, suggesting an important role of LPC uptake by oligodendrocytes in the process of myelination. Here, we demonstrate that Mfsd2a is specifically expressed in oligodendrocyte precursor cells (OPC) and is critical for oligodendrocyte development. Single cell sequencing of the oligodendrocyte lineage revealed that OPCs from OPC-specific Mfsd2a KO mice (2aOKO) underwent precocious differentiation into immature oligodendrocytes (iOLs) and impaired maturation into myelinating oligodendrocytes, correlating with postnatal brain hypomyelination. 2aOKO mice did not exhibit microcephaly, consistent with microcephaly being consequential to absence of LPC uptake at the blood-brain barrier and not from deficiency in OPCs. Lipidomic analysis showed that OPCs and iOLs from 2aOKO mice had significantly decreased phospholipids containing omega-3 fatty acids with an opposite increase in unsaturated fatty acids, that latter being products of de novo synthesis governed by Srebp-1. RNA sequencing indicated activation of the Srebp-1 pathway and defective expression of regulators of oligodendrocyte development. Taken together, these findings indicate that the transport of LPCs by Mfsd2a in OPCs is important for maintaining OPC cell state to regulate postnatal brain myelination.

Expression Analyses of Polo-Like Kinase 4, a Gene Product Responsible for Autosomal Recessive Microcephaly and Seckel Syndrome, during Mouse Brain Development

Polo-like kinase 4 (Plk4) is a ser/thr kinase, which plays a central role in centriole duplication during the cell cycle. PLK4 gene abnormalities are responsible for autosomal recessive chorioretinopathy-microcephaly syndrome and Seckel syndrome. In this study, we performed expression analyses of Plk4 by focusing on mouse brain development. Western blotting analyses revealed that Plk4 with a molecular mass of ∼100 kDa was broadly expressed in adult mouse tissues with specific subcellular distribution. As to the central nervous system, Plk4 was expressed throughout the developmental process with drastic increase after P15, suggesting an essential role of Plk4 in differentiated neurons. In immunohistochemical analyses with mouse brain at embryonic day 14, Plk4 was detected dominantly at the cell-cell contact sites of neuronal progenitors in the ventricular zone. Plk4 was then diffusely distributed in the cell body of cortical neurons at P7, while it was enriched in the neuropil as well as soma of excitatory neurons in the cerebral cortex and hippocampus and Purkinje cells in the cerebellum at P30. Notably, biochemical fractionation analysis found an enrichment of Plk4 in the postsynaptic density fraction. Then, immunofluorescent analyses showed partial co-localization of Plk4 with excitatory synaptic markers, PSD95 and synaptophysin, in differentiated primary cultured hippocampal neurons. These results suggest that Plk4 takes part in the regulation of synaptic function in differentiated neurons.

WARS1 and SARS1: Two tRNA synthetases implicated in autosomal recessive microcephaly.

Aminoacylation of transfer RNA(tRNA) is a key step in protein biosynthesis, carried out by highly specific aminoacyl-tRNA synthetases (ARSs). ARSs have been implicated in autosomal dominant and autosomal recessive human disorders. Autosomal dominant variants in tryptophanyl-tRNA synthetase 1 (WARS1) are known to cause distal hereditary motor neuropathy and Charcot-Marie-Tooth disease, but a recessively inherited phenotype is yet to be clearly defined. Seryl-tRNA synthetase 1 (SARS1) has rarely been implicated in an autosomal recessive developmental disorder. Here, we report five individuals with biallelic missense variants in WARS1 or SARS1, who presented with an overlapping phenotype of microcephaly, developmental delay, intellectual disability, and brain anomalies. Structural mapping showed that the SARS1 variant is located directly within the enzyme's active site, most likely diminishing activity, while the WARS1 variant is located in the N-terminal domain. We further characterize the identified WARS1 variant by showing that it negatively impacts protein abundance and is unable to rescue the phenotype of a CRISPR/Cas9 wars1 knockout zebrafish model. In summary, we describe two overlapping autosomal recessive syndromes caused by variants in WARS1 and SARS1, present functional insights into the pathogenesis of the WARS1-related syndrome and define an emerging disease spectrum: ARS-related developmental disorders with or without microcephaly.

Overexpression of the PLK4 Gene as a Novel Strategy for the Treatment of Autosomal Recessive Microcephaly by Improving Centrosomal Dysfunction.

Autosomal recessive microcephaly and chorioretinopathy (MCCRP) is a neurodevelopmental disorder characterized by delayed psychomotor development, growth retardation with dwarfism, and ocular abnormalities, and its occurrence has been found to be closely related to variants of the gene encoding centrosomes. However, the association between centrosomal duplication defects and the etiology of microcephaly syndromes is poorly understood. It is well known that polo-like kinase 4 (PLK4) is a key regulator of centriole duplication, and the abnormalities of centrosomal function caused by its protein variation need to be further explored in the pathogenesis of microcephaly. In our study, we found that a patient with microcephaly and chorioretinopathy harbored compound heterozygous missense variants NM_014264.4: c.2221C > T (p.Gln741*) and NM_014264.4: c.2062T > C (p.Tyr688His) in the PLK4 gene. Overexpression experiments of the variant PLK4 proteins then showed that the G741 variant rather than the T688H variant had lost centrosomal amplification ability, and the G741 variant but not the T688H variant induced centrosomal replication disorder, which further inhibited cell proliferation, cycle division and cytoskeleton morphology in HeLa cells. Moreover, the overexpression of the two variant proteins had inconsistent effects on the target protein PLK4 by western blot analysis, also indicating that T688H variant overexpression is not functionally equivalent to WT-PLK4 overexpression. Therefore, all data support the idea that the PLK4 mutation induces centriolar duplication disorder and reduces the efficiency of mitosis inducing cell death or cell proliferation in the etiology of microcephaly disorder.

Expanding the phenotype of NUP85 mutations beyond nephrotic syndrome to primary autosomal recessive microcephaly and Seckel syndrome spectrum disorders.

Primary autosomal recessive microcephaly and Seckel syndrome spectrum disorders (MCPH-SCKS) include a heterogeneous group of autosomal recessive inherited diseases characterized by primary (congenital) microcephaly, the absence of visceral abnormalities, and a variable degree of cognitive impairment, short stature and facial dysmorphism. Recently, biallelic variants in the nuclear pore complex (NPC) component nucleoporin 85 gene (NUP85) were reported to cause steroid-resistant nephrotic syndrome (SRNS). Here, we report biallelic variants in NUP85 in two pedigrees with an MCPH-SCKS phenotype spectrum without SRNS, thereby expanding the phenotypic spectrum of NUP85-linked diseases. Structural analysis predicts the identified NUP85 variants cause conformational changes that could have an effect on NPC architecture or on its interaction with other NUPs. We show that mutant NUP85 is, however, associated with a reduced number of NPCs but unaltered nucleocytoplasmic compartmentalization, abnormal mitotic spindle morphology, and decreased cell viability and proliferation in one patient's cells. Our results also indicate the link of common cellular mechanisms involved in MCPH-SCKS spectrum disorders and NUP85-associated diseases. In addition to the previous studies, our results broaden the phenotypic spectrum of NUP85-linked human disease and propose a role for NUP85 in nervous system development.

Clinical and genetic characteristics of 2 patients from Russia with autosomal-recessive microcephaly type 2, due to mutations of the WDR62 gene (OMIM: 604317)

The article describes the clinical and genetic characteristics of 2 patients from Russia with autosomal recessive primary microcephaly type 2, caused by previously described and newly identified mutations in the WDR62 gene. The data obtained the support the hypothesis that there are no clear correlations between the type and location of the mutation and the severity of clinical manifestations of the disease. There is discussed the possible influence of a mutation in the WDR62 gene on the occurrence of a fibrillar astrocytoma.

The Load and Diversity of Monogenic Hereditary Pathology among the Child Population of Kirov Region

The results of the study of genetic load and diversity of monogenic forms of hereditary pathology (MHP) among the child population from 11 districts of Kirov region (KR) obtained during genetic and epidemiological study of the region are presented. The total size of surveyed population is 286 616 individuals (including 37 348 children—13.03%), mainly Russians (88.1%). MHP included 91 diseases (287 patients from 255 families): 50 with autosomal dominant (AD) inheritance (153 patients from 129 families), 33 with autosomal recessive (AR) (107 patients from 104 families), and 8 nosologies with X-linked inheritance (27 patients from 22 families). All diseases were found in previously surveyed populations of the Russian Federation. Nine forms of MHP were detected with a prevalence higher than 1 : 5000: hereditary motor-sensory neuropathy (21.42/100 000), AD ichthyosis vulgaris (83.00/100 000), AD congenital ptosis (24.10/100 000), AD congenital cataract (29.45/100 000), AD syndactyly, type 1 (24.10/100 000), AR undifferentiated mental retardation (26.76/100 000), AR microcephaly with mental retardation (50.87/100 000), AR congenital cataract (26.78/100 000), and AR nonsyndromic sensorineural hearing loss (58.91/100 000). The average prevalence of MHP among the child population of KR was 1 : 130 children, with variation from 1 : 236 children in Vyatskopolyansky district to 1 : 51 children in Sunsky district. On the basis of the correlation analysis between load estimations and Fst values carried out, the reasons for revealed differentiation between districts are assumed.

Generation of a MCPH1 knockout human embryonic stem cell line by CRISPR/Cas9 technology.

Human MCPH1 (Microcephalin 1) encodes a DNA damage response protein. Mutations in this gene have been associated with Primary Autosomal Recessive Microcephaly and premature chromosome condensation syndrome. To further understand the roles of MCPH1 in neural differentiation and brain development, here we generated a MCPH1 knockout human embryonic stem cell line by CRISPR/Cas9 genome editing technology. This cell line maintained a normal karyotype and typical undifferentiated state in terms of morphology, pluripotent gene expression, and had differentiation potential in vitro. This cell line provides a good resource to study the role of MCPH1 gene in neurogenesis and regulation of the size of the cerebral cortex in vitro.

Microcephaly family protein MCPH1 stabilizes RAD51 filaments.

Microcephalin 1 (MCPH1) was identified from genetic mutations in patients with primary autosomal recessive microcephaly. In response to DNA double-strand breaks (DSBs), MCPH1 forms damage-induced foci and recruits BRCA2–RAD51 complex, a key component of the DSB repair machinery for homologous recombination (HR), to damage sites. Accordingly, the efficiency of HR is significantly attenuated upon depletion of MCPH1. The biochemical characteristics of MCPH1 and its functional interaction with the HR machinery had remained unclear due to lack of highly purified MCPH1 recombinant protein for functional study. Here, we established a mammalian expression system to express and purify MCPH1 protein. We show that MCPH1 is a bona fide DNA-binding protein and provide direct biochemical analysis of this MCPH family protein. Furthermore, we reveal that MCPH1 directly interacts with RAD51 at multiple contact points, providing evidence for how MCPH1 physically engages with the HR machinery. Importantly, we demonstrate that MCPH1 enhances the stability of RAD51 on single-strand DNA, a prerequisite step for RAD51-mediated recombination. Single-molecule tethered particle motion analysis showed a ∼2-fold increase in the lifetime of RAD51–ssDNA filaments in the presence of MCPH1. Thus, our study demonstrates direct crosstalk between microcephaly protein MCPH1 and the recombination component RAD51 for DSB repair.

Loss of function of SVBP leads to autosomal recessive intellectual disability, microcephaly, ataxia, and hypotonia

PurposeIdentifying and characterizing novel causes of autosomal recessive intellectual disability based on systematic clinical and genetic evaluation, followed by functional experiments. MethodsClinical examinations, genome-wide positional mapping, and sequencing were followed by quantitative polymerase chain reaction and western blot of the protein SVBP and its interaction partners. We then knocked down the gene in rat primary hippocampal neurons and evaluated the consequences on synapses. ResultsWe identified a founder, homozygous stop-gain variant in SVBP (c.82C>T; p.[Gln28*]) in four affected individuals from two independent families with intellectual disability, microcephaly, ataxia, and muscular hypotonia. SVBP encodes a small chaperone protein that transports and stabilizes two angiogenesis regulators, VASH1 and VASH2. The altered protein is unstable and nonfunctional since transfected HeLa cells with mutant SVBP did not reveal evidence for immunoreactive SVBP protein fragments and cotransfection with VASH1 showed a severe reduction of VASH1 in medium and cell lysate. Knocking down Svbp in rat primary hippocampal neurons led to a significant decrease in the number of excitatory synapses. ConclusionSVBP is not only involved in angiogenesis, but also has vital functions in the central nervous system. Biallelic loss-of-function variants in SVBP lead to intellectual disability.

Genetic association and functional characterization of MCPH1 gene variation in bipolar disorder and schizophrenia.

A rare microcephalin 1 gene (MCPH1) variant rs61749465A>G (p.Asp61Gly) with prior evidence for association with schizophrenia (p = 3.78 × 10-7 ) was tested for association in 2,300 bipolar disorder (BPD) participants, 1,930 SCZ participants and 1,820 normal comparison subjects. We report evidence for association of rs61749465A>G with BPD (p = 0.0009). rs61749465 is located in the N-terminal of the BRCT1 domain of MCPH1. Bioinformatic analysis predicted the Asp61Gly substitution to be damaging to MCPH1 function. A second MCPH1 BRCT1 domain variant (rs199422124C>G; p.Thr27Arg), reported to cause autosomal recessive microcephaly, was not detected in the participants tested here. We sought to characterize the functional effects of these variants on MCPH1 function. Cell count assays indicated that rs199422124 allele G had a greater impact on cell survival compared to the G allele of rs61749465. Gene expression analysis combined with gene network and pathway analysis indicated that rs61749465 allele G may impact protein translation and cell cycle control. The evidence for association between rs61749465A>G and psychosis in both BPD and SCZ warrants further replication. Likewise, the data from the functional analyses point to molecular mechanisms that may underlie the proposed MCPH1 mediated risk of psychosis and pathogenesis in autosomal recessive microcephaly require additional experimental validation.

The ESCRT-III Protein CHMP1A Mediates Secretion of Sonic Hedgehog on a Distinctive Subtype of Extracellular Vesicles

SUMMARYEndosomal sorting complex required for transport (ESCRT) complex proteins regulate biogenesis and release of extracellular vesicles (EVs), which enable cell-to-cell communication in the nervous system essential for development and adult function. We recently showed human loss-of-function (LOF) mutations in ESCRT-III member CHMP1A cause autosomal recessive microcephaly with pontocerebellar hypoplasia, but its mechanism was unclear. Here, we show Chmp1a is required for progenitor proliferation in mouse cortex and cerebellum and progenitor maintenance in human cerebral organoids. In Chmp1a null mice, this defect is associated with impaired sonic hedgehog (Shh) secretion and intraluminal vesicle (ILV) formation in multivesicular bodies (MVBs). Furthermore, we show CHMP1A is important for release of an EV subtype that contains AXL, RAB18, and TMED10 (ART) and SHH. Our findings show CHMP1A loss impairs secretion of SHH on ART-EVs, providing molecular mechanistic insights into the role of ESCRT proteins and EVs in the brain.

TLE1, a key player in neurogenesis, a new candidate gene for autosomal recessive postnatal microcephaly

Postnatal microcephaly comprises a heterogeneous group of neurodevelopmental disorders of varying severity, characterized by normal head size at birth, followed by a postnatal deceleration in head circumference of greater than 3 standard deviations (SD) below the mean. Many postnatal microcephaly syndromes are caused by mutations in genes known to be important for the regulation of gene expression in the developing forebrain.We studied a consanguineous Pakistani family with postnatal microcephaly, orofacial dyskinesia, spastic quadriplegia and, on MRI, cortical atrophy with myelination delay, suggestive of a FOXG1-like presentation. Using trio-based exome sequencing, we identified a homozygous missense mutation in the Transducin-like enhancer of split-1 (TLE1) gene, encoding for a non DNA-binding transcriptional corepressor, highly expressed in the postnatal brain. The regulation of the post-mitotic neural survival activity of TLE1 depends critically on an interaction with FOXG1, a gene shown to be involved in a postnatal microcephaly syndrome. Functional analysis on affected dermal fibroblasts showed a significant decrease in mitotic and proliferative index, indicating a lengthening of the cell cycle and a delay in mitosis, supporting that this gene could be a new candidate for postnatal microcephaly.

Expanding the clinical spectrum of biallelic ZNF335 variants.

ZNF335 plays an essential role in neurogenesis and biallelic variants in ZNF335 have been identified as the cause of severe primary autosomal recessive microcephaly in 2 unrelated families. We describe, herein, 2 additional affected individuals with biallelic ZNF335 variants, 1 individual with a homozygous c.1399 T > C, p.(Cys467Arg) variant, and a second individual with compound heterozygous c.2171_2173delTCT, p.(Phe724del) and c.3998A > G, p.(Glu1333Gly) variants with the latter variant predicted to affect splicing. Whereas the first case presented with early death and a severe phenotype characterized by anterior agyria with prominent extra-axial spaces, absent basal ganglia, and hypoplasia of the brainstem and cerebellum, the second case had a milder clinical presentation with hypomyelination and otherwise preserved brain structures on MRI. Our findings expand the clinical spectrum of ZNF335-associated microcephaly.

Autosomal recessive primary microcephaly due to ASPM mutations: An update.

Autosomal recessive microcephaly or microcephaly primary hereditary (MCPH) is a genetically heterogeneous neurodevelopmental disorder characterized by a reduction in brain volume, indirectly measured by an occipitofrontal circumference (OFC) 2 standard deviations or more below the age- and sex-matched mean (-2SD) at birth and -3SD after 6 months, and leading to intellectual disability of variable severity. The abnormal spindle-like microcephaly gene (ASPM), the human ortholog of the Drosophila melanogaster "abnormal spindle" gene (asp), encodes ASPM, a protein localized at the centrosome of apical neuroprogenitor cells and involved in spindle pole positioning during neurogenesis. Loss-of-function mutations in ASPM cause MCPH5, which affects the majority of all MCPH patients worldwide. Here, we report 47 unpublished patients from 39 families carrying 28 new ASPM mutations, and conduct an exhaustive review of the molecular, clinical, neuroradiological, and neuropsychological features of the 282 families previously reported (with 161 distinct ASPM mutations). Furthermore, we show that ASPM-related microcephaly is not systematically associated with intellectual deficiency and discuss the association between the structural brain defects (strong reduction in cortical volume and surface area) that modify the cortical map of these patients and their cognitive abilities.

Comprehensive review on the molecular genetics of autosomal recessive primary microcephaly (MCPH).

Primary microcephaly (MCPH) is an autosomal recessive sporadic neurodevelopmental ailment with a trivial head size characteristic that is below 3-4 standard deviations. MCPH is the smaller upshot of an architecturally normal brain; a significant decrease in size is seen in the cerebral cortex. At birth MCPH presents with non-progressive mental retardation, while secondary microcephaly (onset after birth) presents with and without other syndromic features. MCPH is a neurogenic mitotic syndrome nevertheless pretentious patients demonstrate normal neuronal migration, neuronal apoptosis and neural function. Eighteen MCPH loci (MCPH1-MCPH18) have been mapped to date from various populations around the world and contain the following genes: Microcephalin, WDR62, CDK5RAP2, CASC5, ASPM, CENPJ, STIL, CEP135, CEP152, ZNF335, PHC1, CDK6, CENPE, SASS6, MFSD2A, ANKLE2, CIT and WDFY3, clarifying our understanding about the molecular basis of microcephaly genetic disorder. It has previously been reported that phenotype disease is caused by MCB gene mutations and the causes of this phenotype are disarrangement of positions and organization of chromosomes during the cell cycle as a result of mutated DNA, centriole duplication, neurogenesis, neuronal migration, microtubule dynamics, transcriptional control and the cell cycle checkpoint having some invisible centrosomal process that can manage the number of neurons that are produced by neuronal precursor cells. Furthermore, researchers inform us about the clinical management of families that are suffering from MCPH. Establishment of both molecular understanding and genetic advocating may help to decrease the rate of this ailment. This current review study examines newly identified genes along with previously identified genes involved in autosomal recessive MCPH.

Biallelic variants in LINGO1 are associated with autosomal recessive intellectual disability, microcephaly, speech and motor delay

PurposeTo elucidate the novel molecular cause in two unrelated consanguineous families with autosomal recessive intellectual disability.MethodsA combination of homozygosity mapping and exome sequencing was used to locate the plausible genetic defect in family F162, while only exome sequencing was followed in the family PKMR65. The protein 3D structure was visualized with the University of California–San Francisco Chimera software.ResultsAll five patients from both families presented with severe intellectual disability, aggressive behavior, and speech and motor delay. Four of the five patients had microcephaly. We identified homozygous missense variants in LINGO1, p.(Arg290His) in family F162 and p.(Tyr288Cys) in family PKMR65. Both variants were predicted to be pathogenic, and segregated with the phenotype in the respective families. Molecular modeling of LINGO1 suggests that both variants interfere with the glycosylation of the protein.ConclusionLINGO1 is a transmembrane receptor, predominantly found in the central nervous system. Published loss-of-function studies in mouse and zebrafish have established a crucial role of LINGO1 in normal neuronal development and central nervous system myelination by negatively regulating oligodendrocyte differentiation and neuronal survival. Taken together, our results indicate that biallelic LINGO1 missense variants cause autosomal recessive intellectual disability in humans.

Electron Microscopy Structural Insights into CPAP Oligomeric Behavior: A Plausible Assembly Process of a Supramolecular Scaffold of the Centrosome.

Centrosomal P4.1-associated protein (CPAP) is a cell cycle regulated protein fundamental for centrosome assembly and centriole elongation. In humans, the region between residues 897–1338 of CPAP mediates interactions with other proteins and includes a homodimerization domain. CPAP mutations cause primary autosomal recessive microcephaly and Seckel syndrome. Despite of the biological/clinical relevance of CPAP, its mechanistic behavior remains unclear and its C-terminus (the G-box/TCP domain) is the only part whose structure has been solved. This situation is perhaps due in part to the challenges that represent obtaining the protein in a soluble, homogeneous state for structural studies. Our work constitutes a systematic structural analysis on multiple oligomers of HsCPAP897−1338, using single-particle electron microscopy (EM) of negatively stained (NS) samples. Based on image classification into clearly different regular 3D maps (putatively corresponding to dimers and tetramers) and direct observation of individual images representing other complexes of HsCPAP897−1338 (i.e., putative flexible monomers and higher-order multimers), we report a dynamic oligomeric behavior of this protein, where different homo-oligomers coexist in variable proportions. We propose that dimerization of the putative homodimer forms a putative tetramer which could be the structural unit for the scaffold that either tethers the pericentriolar material to centrioles or promotes procentriole elongation. A coarse fitting of atomic models into the NS 3D maps at resolutions around 20 Å is performed only to complement our experimental data, allowing us to hypothesize on the oligomeric composition of the different complexes. In this way, the current EM work represents an initial step toward the structural characterization of different oligomers of CPAP, suggesting further insights to understand how this protein works, contributing to the elucidation of control mechanisms for centriole biogenesis.