Identification of two novel critical mutations in PCNT gene resulting in microcephalic osteodysplastic primordial dwarfism type II associated with multiple intracranial aneurysms

Intracranial Aneurysms and Genetics: An Extensive Overview of Genomic Variations, Underlying Molecular Dynamics, Inflammatory Indicators, and Forward-Looking Insights

This review initiates by outlining the clinical relevance of IA, underlining the pressing need to comprehend its foundational elements. We delve into the assorted risk factors tied to IA, spotlighting both environmental and genetic influences. Additionally, we illuminate distinct genetic syndromes linked to a pronounced prevalence of intracranial aneurysms, underscoring the pivotal nature of genetics in this ailment's susceptibility. A detailed scrutiny of genome-wide association studies allows us to identify key genomic changes and locations associated with IA risk. We further detail the molecular and physiopathological dynamics instrumental in IA's evolution and escalation, with a focus on inflammation's role in affecting the vascular landscape. Wrapping up, we offer a glimpse into upcoming research directions and the promising horizons of personalized therapeutic strategies in IA intervention, emphasizing the central role of genetic insights. This thorough review solidifies genetics' cardinal role in IA, positioning it as a cornerstone resource for professionals in the realms of neurology and genomics.

Genetic Primary Microcephalies: When Centrosome Dysfunction Dictates Brain and Body Size

Primary microcephalies (PMs) are defects in brain growth that are detectable at or before birth and are responsible for neurodevelopmental disorders. Most are caused by biallelic or, more rarely, dominant mutations in one of the likely hundreds of genes encoding PM proteins, i.e., ubiquitous centrosome or microtubule-associated proteins required for the division of neural progenitor cells in the embryonic brain. Here, we provide an overview of the different types of PMs, i.e., isolated PMs with or without malformations of cortical development and PMs associated with short stature (microcephalic dwarfism) or sensorineural disorders. We present an overview of the genetic, developmental, neurological, and cognitive aspects characterizing the most representative PMs. The analysis of phenotypic similarities and differences among patients has led scientists to elucidate the roles of these PM proteins in humans. Phenotypic similarities indicate possible redundant functions of a few of these proteins, such as ASPM and WDR62, which play roles only in determining brain size and structure. However, the protein pericentrin (PCNT) is equally required for determining brain and body size. Other PM proteins perform both functions, albeit to different degrees. Finally, by comparing phenotypes, we considered the interrelationships among these proteins.

Time is of the essence: the molecular mechanisms of primary microcephaly

In this review, Phan et al. discuss the different models that have been proposed to explain how centrosome dysfunction impairs cortical development, and review the evidence supporting a unified model in which centrosome defects reduce cell proliferation in the developing cortex by prolonging mitosis and activating a mitotic surveillance pathway. Last, they also extend their discussion to centrosome-independent microcephaly mutations, such as those involved in DNA replication and repair

Primary microcephaly is a brain growth disorder characterized by a severe reduction of brain size and thinning of the cerebral cortex. Many primary microcephaly mutations occur in genes that encode centrosome proteins, highlighting an important role for centrosomes in cortical development. Centrosomes are microtubule organizing centers that participate in several processes, including controlling polarity, catalyzing spindle assembly in mitosis, and building primary cilia. Understanding which of these processes are altered and how these disruptions contribute to microcephaly pathogenesis is a central unresolved question. In this review, we revisit the different models that have been proposed to explain how centrosome dysfunction impairs cortical development. We review the evidence supporting a unified model in which centrosome defects reduce cell proliferation in the developing cortex by prolonging mitosis and activating a mitotic surveillance pathway. Finally, we also extend our discussion to centrosome-independent microcephaly mutations, such as those involved in DNA replication and repair.

A novel homozygous mutation of the PCNT gene in a Chinese patient with microcephalic osteodysplastic primordial dwarfism type II

Background

Microcephalic osteodysplastic primordial dwarfism type II (MOPD II) is a rare autosomal recessive disorder characterized by severe pre‐ and postnatal growth restrictions, microcephaly, skeletal dysplasia, severe teeth deformities, and typical facial features. Previous studies have shown that MOPD II is associated with mutations in the pericentrin (PCNT) gene.

Methods

We evaluated the clinical features of a 10‐year and 7‐month‐old Chinese girl with MOPD II. Subsequently, next‐generation sequencing and flow cytometry were performed to investigate genetic characteristics and the expression of PCNT protein respectively.

Results

The patient presented with short stature, microcephaly, typical craniofacial features, teeth deformity, thrombocytosis, and a delayed bone age (approximately 7 years). No abnormality in growth hormone or insulin‐like growth factor 1 was detected. Notably, the patient was found to carry a novel homozygous PCNT mutation (c.6157G>T, p.Glu2053Ter), which was inherited from her healthy heterozygous parents. Meanwhile, significant deficiency of PCNT expression was identified in the patient.

Conclusion

Our study identified a novel PCNT mutation associated with MOPD II, expanded the mutation spectrum of the PCNT gene and improved our understanding of the molecular basis of MOPD II.

RAB33B and PCNT variants in two Pakistani families with skeletal dysplasia and short stature

Background

Skeletal dysplasia is a heterogeneous group of disorders resulting from different genetic variants in humans. The current study was designed to identify the genetic causes of skeletal dysplasia and short stature in two consanguineous families from Pakistan, both comprised of multiple affected individuals. Patients in one family had proportionate short stature with reduced head circumference while affected individuals in the other family had disproportionate short stature.

Methods

Clinical data were obtained and radiological examinations of the index patients were completed. Whole genome sequencing for probands from both families were performed followed by Sanger sequencing to confirm segregation of identified variants in the respective families. In-silico pathogenicity score prediction for identified variant and amino acid conservation analysis was completed.

Results

Whole Genome Sequencing identified a known biallelic variant c.6176_6189delGTCAGCTGCCGAAG; p.(Gln2060ArgfsTer48) in PCNT gene and a novel biallelic variant c.174delC; p.(Asp60ThrfsTer7) in RAB33B gene respectively in affected members of the two families. Clinical imaging revealed platyspondyly and varus deformity in the legs of the affected members in the first family. Radiographs indicated severe platyspondyly, genu valgus deformity of legs and pectus carinatum for the patients in the second family.

Conclusion

In this study we report the phenotypes and genetic variants in two unrelated families with two distinct forms of skeletal dysplasia. This study strengthens the previous findings that patients harboring PCNT variants are phenotypically homogeneous and also extends the genotypic spectrum of RAB33B variants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04503-2.

A non-canonical function for Centromere-associated protein-E controls centrosome integrity and orientation of cell division

Centromere-associated protein-E (CENP-E) is a kinesin motor localizing at kinetochores. Although its mitotic functions have been well studied, it has been challenging to investigate direct consequences of CENP-E removal using conventional methods because CENP-E depletion resulted in mitotic arrest. In this study, we harnessed an auxin-inducible degron system to achieve acute degradation of CENP-E. We revealed a kinetochore-independent role for CENP-E that removes pericentriolar material 1 (PCM1) from centrosomes in late S/early G2 phase. After acute loss of CENP-E, centrosomal Polo-like kinase 1 (Plk1) localization is abrogated through accumulation of PCM1, resulting in aberrant phosphorylation and destabilization of centrosomes, which triggers shortened astral microtubules and oblique cell divisions. Furthermore, we also observed centrosome and cell division defects in cells from a microcephaly patient with mutations in CENPE. Orientation of cell division is deregulated in some microcephalic patients, and our unanticipated findings provide additional insights into how microcephaly can result from centrosomal defects.

Novel compound heterozygous mutations of PCNT gene in MOPD type II with central precocious puberty

We report on a 6-year and 11-month old girl with short stature, microcephaly, proboscis nose, small teeth, left breast Tanner stage II, and nasopharynx adenoid hypertrophy. Her gestational age was 37 weeks and birth weight was 800 g. Her growth hormone peak was higher than 35.2 ng/ml, luteinizing hormone peak 8.97 IU/l, and blood glucose of 120 min 7.82 mmol/l in oral glucose tolerance test. Genetic testing revealed two novel heterozygous mutations in the PCNT gene, an insertion mutation at c.1828dupT (p.S610Ffs*32), and a splice site mutation at c.1207 + 1G>A, which were inherited from healthy carrier patients. This case shows that MOPDII can be associated with central precocious puberty and impaired glucose tolerance in addition to intrauterine growth restriction, postpartum growth defect, and microcephaly.

Identification of three novel mutations in PCNT in vietnamese patients with microcephalic osteodysplastic primordial dwarfism type II

BACKGROUND

Primordial dwarfism (PD) is a group of genetically heterogeneous disorders related to developmental disabilities occurring in the uterus and prolongs during all stages of life, resulting in short stature, facial deformities and abnormal brain.

OBJECTIVE

To determine the exact cause of the disease in two Vietnamese patients priory diagnosed with PD by severe pre-and postnatal growth retardation with marked microcephaly and some bone abnormalities.

METHODS

Whole-exome sequencing was performed for the two patients and mutations in genes related to PD were screened. Sanger sequencing was applied to examine the mutations in the patients of their families.

RESULTS

Three novel mutations in the PCNT gene which have not been reported previously were identified in the two patients. Of which, two frameshift mutations (p.Thr479Profs*6 and p.Glu2742Alafs*8) were detected in patient I and one stop-gained mutation (p.Gln1907*) was detected in the patient II. These mutations may result in a truncated PCNT protein, leading to an inactivated PACT domain corresponding to residue His3138-Trp3216 of PCNT protein. Therefore, the three mutations may cause a deficiency of protein functional activity and result in the phenotypes of primordial dwarfism in the two patients.

CONCLUSIONS

Clinical presentations in combination with genetic analyses supported an accurate diagnosis of the two patients with microcephalic osteodysplastic primordial dwarfism type II (MOPD II). In addition, these results have important implications for prenatal genetic screening and genetic counseling for the families.

Intracranial aneurysms in microcephalic primordial dwarfism: a systematic review

BACKGROUND

Microcephalic primordial dwarfism (MPD) is a heterogeneous group of rare disorders. Recent studies have reported a significant percentage of patients with MPD suffering from a spectrum of cerebrovascular abnormalities, including intracranial aneurysms (IAs) and moyamoya syndrome. The neurological literature has not as yet specifically assessed IAs in this population. This systematic review aimed to assess the clinical behavior, characteristics, treatment modalities and outcomes of IAs in patients with MPD.

METHODS

We performed a systematic search in PubMed, Ovid MEDLINE and Ovid EMBASE for cases of MPD with IAs. We included three illustrative cases from our institution.

RESULTS

Twenty-four patients with 71 aneurysms were included in this study. Twelve patients (50%) presented with subarachnoid hemorrhage. The majority of patients were aged ≤18 years (70.8%), with a mean age of 16.2 years at presentation. Median aneurysm size was 3 (IQR 1.8-6) mm, and the most frequent locations were the internal carotid (37.3%) and middle cerebral arteries (23.8%). Concomitant moyamoya disease was reported in nine (37.5%) patients. Median age of aneurysm detection in screened patients was significantly lower than in non-screened patients (P=0.02). Microsurgical clipping (55.3%) and endovascular coiling (26.3%) were the most used modalities. Twenty-two cases were managed conservatively. Overall, mortality occurred in 45.8% of cases.

CONCLUSIONS

Screening for cerebrovascular disease seems reasonable and effective to detect aneurysms at an earlier age in this population. Efforts in the literature to emphasize early and regular screening for these patients can positively impact outcomes in this population, however more evidence is needed.

Microcephalic osteodysplastic primordial dwarfism type II: Additional nine patients with implications on phenotype and genotype correlation

PCNT encodes a large coiled- protein localizing to pericentriolar material and is associated with microcephalic osteodysplastic primordial dwarfism type II syndrome (MOPD II). We report our experience of nine new patients from seven unrelated consanguineous Egyptian families with the distinctive clinical features of MOPD II in whom a customized NGS panel showed homozygous truncating variants of PCNT. The NGS panel results were validated thereafter using Sanger sequencing revealing three previously reported and three novel PCNT pathogenic variants. The core phenotype appeared homogeneous to what had been reported before although patients differed in the severity showing inter and intra familial variability. The orodental pattern showed atrophic alveolar ridge (five patients), rootless tooth (four patients), tooth agenesis (three patients), and malformed tooth (three patients). In addition, mesiodens was a novel finding found in one patient. The novel c.9394-1G>T variant was found in two sibs who had tooth agenesis. CNS anomalies with possible vascular sequelae were documented in two male patients (22.2%). Simplified gyral pattern with poor development of the frontal horns of lateral ventricles was seen in four patients and mild thinning of the corpus callosum in two patients. Unilateral coronal craniosynstosis was noted in one patient and thick but short corpus callosum was an unusual finding noted in another. The later has not been reported before. Our results refine the clinical, neuroradiological, and orodental features and expand the molecular spectrum of MOPD II.

Ocular characteristics in a variant microcephalic primordial dwarfism type II

BACKGROUND

Microcephalic osteodysplastic primordial dwarfism, type II (MOPD II) is a rare disease that is assumed to be caused by a pericentrin (PCNT) gene mutation. Clinical manifestations have been reported in pediatrics and neurology; however, only a few ocular findings have been documented.

CASE PRESENTATION

We present three unrelated cases of MOPD II with similar facial features and short stature. Unlike the cases described in the literature, all subjects had normal birth weight and height but their growth was retarded thereafter. In addition to delayed milestones, they have a broad forehead, maxillary protrusion, long peaked nose, high nasal bridge, low-set large ears, extreme reromicrogenia, and normal-sized teeth. These three patients had similar ocular manifestations with the short axial length associated with high hyperopia more than + 9 diopters (D) and macular scarring. The oldest subject was a 20 year-old male without neurological symptoms. One female subject had developed alopecia during the previous 2 years. The other female subject had moyamoya disease, but a genetic study revealed a normal PCNT gene.

CONCLUSION

This is the first report of MOPD II focusing on ocular findings, suggesting that macular dystrophy and high hyperopia are the common ocular characteristics of MOPD II. Prompt referral to an ophthalmologist is essential. Although refractive amblyopia can be treated with optical correction, visual prognosis may be poor due to maculopathy.

New PCNT candidate missense variant in a patient with oral and maxillofacial osteodysplasia: a case report

Background

Osteodysplasia of the oral and maxillofacial bone is generally accompanied by systemic bone abnormalities (such as short stature, joint contracture) or other systemic abnormalities (such as renal, dermatological, cardiovascular, optic, or hearing disorders). However, it does not always present this way. Recent reports have suggested that genome-wide sequencing is an effective method for identifying rare or new disorders. Here, we performed whole-exome sequencing (WES) in a patient with a unique form of acquired, local osteodysplasia of the oral and maxillofacial region.

Case presentation

A 46-year-old woman presented to our hospital with the complaint of gradually moving mandibular teeth (for 6 months), changing facial appearance, and acquired osteolysis of the oral and maxillofacial bones, showing mandibular hypoplasia without family history. Upon skeletal examination, there were no abnormal findings outside of the oral and maxillofacial area; the patient had a height of 157 cm and bone mineral density (according to dual energy x-ray absorptiometry) of 90%. Results of blood and urine tests, including evaluation of bone metabolism markers and neurological and cardiovascular examinations, were normal. We performed WES of genomic DNA extracted from the blood of this patient and her mother, who did not have the disease, as a negative control. We identified 83 new missense variants in the patient, not detected in her mother, including a candidate single nucleotide variant in exon 14 of PCNT (pericentrin). Critical homozygous or compound heterozygous variants in PCNT are a known cause of microcephalic osteodysplastic primordial dwarfism type II accompanied by mandibular hypoplasia, which is similar to the maxillofacial phenotype in this patient.

Conclusions

Protein simulations performed using Polymorphism Phenotyping v2 and Combined Annotation Dependent Depletion software indicated that this missense variant is likely to disrupt the PCNT protein structure. These results suggest that this is a new form of osteolysis related to this PCNT variant.

Genetic basis of intracranial aneurysm formation and rupture: clinical implications in the postgenomic era

OBJECTIVE

Despite the prevalence and impact of intracranial aneurysms (IAs), the molecular basis of their pathogenesis remains largely unknown. Moreover, there is a dearth of clinically validated biomarkers to efficiently screen patients with IAs and prognosticate risk for rupture. The aim of this study was to survey the literature to systematically identify the spectrum of genetic aberrations that have been identified in IA formation and risk of rupture.

METHODS

A literature search was performed using the Medical Subject Headings (MeSH) system of databases including PubMed, EMBASE, and Google Scholar. Relevant studies that reported on genetic analyses of IAs, rupture risk, and long-term outcomes were included in the qualitative analysis.

RESULTS

A total of 114 studies were reviewed and 65 were included in the qualitative synthesis. There are several well-established mendelian syndromes that confer risk to IAs, with variable frequency. Linkage analyses, genome-wide association studies, candidate gene studies, and exome sequencing identify several recurrent polymorphic variants at candidate loci, and genes associated with the risk of aneurysm formation and rupture, including ANRIL (CDKN2B-AS1, 9p21), ARGHEF17 (11q13), ELN (7q11), SERPINA3 (14q32), and SOX17 (8q11). In addition, polymorphisms in eNOS/NOS3 (7q36) may serve as predictive markers for outcomes following intracranial aneurysm rupture. Genetic aberrations identified to date converge on posited molecular mechanisms involved in vascular remodeling, with strong implications for an associated immune-mediated inflammatory response.

CONCLUSIONS

Comprehensive studies of IA formation and rupture have identified candidate risk variants and loci; however, further genome-wide analyses are needed to identify high-confidence genetic aberrations. The literature supports a role for several risk loci in aneurysm formation and rupture with putative candidate genes. A thorough understanding of the genetic basis governing risk of IA development and the resultant aneurysmal subarachnoid hemorrhage may aid in screening, clinical management, and risk stratification of these patients, and it may also enable identification of putative mechanisms for future drug development.

A catalog of single nucleotide changes distinguishing modern humans from archaic hominins

Throughout the past decade, studying ancient genomes has provided unique insights into human prehistory, and differences between modern humans and other branches like Neanderthals can enrich our understanding of the molecular basis of unique modern human traits. Modern human variation and the interactions between different hominin lineages are now well studied, making it reasonable to go beyond fixed genetic changes and explore changes that are observed at high frequency in present-day humans. Here, we identify 571 genes with non-synonymous changes at high frequency. We suggest that molecular mechanisms in cell division and networks affecting cellular features of neurons were prominently modified by these changes. Complex phenotypes in brain growth trajectory and cognitive traits are likely influenced by these networks and other non-coding changes presented here. We propose that at least some of these changes contributed to uniquely human traits, and should be prioritized for experimental validation.

Intracranial Aneurysms: Pathology, Genetics, and Molecular Mechanisms

Intracranial aneurysms (IA) are local dilatations in cerebral arteries that predominantly affect the circle of Willis. Occurring in approximately 2-5% of adults, these weakened areas are susceptible to rupture, leading to subarachnoid hemorrhage (SAH), a type of hemorrhagic stroke. Due to its early age of onset and poor prognosis, SAH accounts for > 25% of years lost for all stroke victims under the age of 65. In this review, we describe the cerebrovascular pathology associated with intracranial aneurysms. To understand IA genetics, we summarize syndromes with elevated incidence, genome-wide association studies (GWAS), whole exome studies on IA-affected families, and recent research that established definitive roles for Thsd1 (Thrombospondin Type 1 Domain Containing Protein 1) and Sox17 (SRY-box 17) in IA using genetically engineered mouse models. Lastly, we discuss the underlying molecular mechanisms of IA, including defects in vascular endothelial and smooth muscle cells caused by dysfunction in mechanotransduction, Thsd1/FAK (Focal Adhesion Kinase) signaling, and the Transforming Growth Factor β (TGF-β) pathway. As illustrated by THSD1 research, cell adhesion may play a significant role in IA.

Characterization of variations in IL23A and IL23R genes: possible roles in multiple sclerosis and other neuroinflammatory demyelinating diseases

Multiple sclerosis is among the most serious inflammatory demyelinating diseases (IDD). Interleukin-23A (IL23A) regulates and coordinates the activities of immune cells by interacting with its receptor IL23R and plays key roles in the pathogenesis of immune inflammatory diseases. IDD, deemed to be a kind of autoimmune diseases, may involve IL23A in the pathogenesis. The aim of this work was to validate the hypothesized involvement of IL-23A and its receptor in IDD. We sequenced the IL-23A and IL-23R genes for 206 Chinese Han IDD patients and evaluated SNPs within or near those genes. The serum levels of IL23A in IDD participants were analyzed using ELISA. The statistical analyses were conducted using Chi-Square Tests as implemented in SPSS (version 19.0). The Hardy-Weinberg equilibrium test of the population was carried out using online software OEGE. Three variants rs2066808, rs2371494, rs11575248 in IL-23A gene and one variant rs1884444 in IL-23R gene were demonstrated to be associated with the risk of MS or other IDD diseases, and the expression level of serum IL-23A in the MS patients was also altered. We conclude that variants in IL-23A and IL-23R genes were associated with the risk of MS or other IDD diseases.