scholarly journals Dominant monoallelic variant in the PAK2 gene causes Knobloch syndrome type 2

2020 ◽  
Author(s):  
Stylianos E. Antonarakis ◽  
Ales Holoubek ◽  
Melivoia Rapti ◽  
Jesse Rademaker ◽  
Jenny Meylan ◽  
...  
Keyword(s):  
Cell Cycle Progression ◽  
Kinase Activity ◽  
De Novo ◽  
Synonymous Substitution ◽  
Kinase Domain ◽  
Germline Mosaicism ◽  
Knobloch Syndrome ◽  
Pathogenic Variants ◽  
Cytoskeletal Dynamics

AbstractKnobloch syndrome is an autosomal recessive phenotype mainly characterized by retinal detachment and encephalocele caused by biallelic pathogenic variants in the COL18A1 gene. However, there are patients clinically diagnosed as Knobloch syndrome with unknown molecular etiology not linked to COL18A1. We studied an historical pedigree (published in 1998) designated as KNO2 (Knobloch type 2 syndrome with intellectual disability, autistic behavior, retinal degeneration, encephalocele). Whole exome sequencing of the two affected siblings and the normal parents resulted in the identification of a PAK2 non-synonymous substitution p.(Glu435Lys) as a causative variant. The variant was monoallelic and apparently de novo in both siblings indicating a likely germline mosaicism in one of the parents; the mosaicism however could not be observed after deep sequencing of blood parental DNA. PAK2 encodes a member of a small group of serine/threonine kinases; these P21-activating kinases (PAKs) are essential in signal transduction and cellular regulation (cytoskeletal dynamics, cell motility, death and survival signaling, and cell cycle progression). Structural analysis of the PAK2 p.(Glu435Lys) variant which is located in the kinase domain of the protein predicts a possible compromise in the kinase activity. Functional analysis of the p.(Glu435Lys) PAK2 variant in transfected HEK293T cells results in a partial loss of the kinase activity. PAK2 has been previously suggested as an autism related gene. Our results show that PAK2 induced phenotypic spectrum is broad and not fully understood. We conclude that the KNO2 syndrome in the studied family is dominant and caused by a deleterious variant in the PAK2 gene.

scholarly journals CNNM2-Related Disorders: Phenotype and Its Severity Were Associated With the Mode of Inheritance

2021 ◽  
Vol 9 ◽  
Author(s):  
Han Zhang ◽  
Ye Wu ◽  
Yuwu Jiang
Keyword(s):  
De Novo ◽  
Serum Magnesium ◽  
Brain Magnetic Resonance Imaging ◽  
Functional Studies ◽  
Pathogenic Variants ◽  
Significant Difference ◽  
Domain Variations ◽  
Type 3

CNNM2 (Cystathionine-β-synthase-pair Domain Divalent Metal Cation Transport Mediator 2) pathogenic variants have been reported to cause hypomagnesemia, epilepsy, and intellectual disability/developmental delay (ID/DD). We identified two new cases with CNNM2 novel de novo pathogenic variants, c.814T>C and c.976G>C. They both presented with infantile-onset epilepsy with DD and hypomagnesemia refractory to magnesium supplementation. To date, 21 cases with CNNM2-related disorders have been reported. We combined all 23 cases to analyze the features of CNNM2-related disorders. The phenotypes can be classified into three types: type 1, autosomal dominant (AD) inherited simple hypomagnesemia; type 2, AD inherited hypomagnesemia with epilepsy and ID/DD; and type 3, autosomal recessive (AR) inherited hypomagnesemia with epilepsy and ID/DD. All five type 1 cases had no epilepsy or ID/DD; they all had hypomagnesemia, and three of them presented with symptoms secondary to hypomagnesemia. Fifteen type 2 patients could have ID/DD and seizures, which can be controlled with antiseizure medications (ASMs); their variations clustered in the DUF21 domain of CNNM2. All three type 3 patients had seizures from 1 to 6 days after birth; the seizures were refractory, and 1/3 had status epilepticus; ID/DD in these AR-inherited cases was more severe than that of AD-inherited cases; they all had abnormalities of brain magnetic resonance imaging (MRI). Except for one patient whose serum magnesium was the lower limit of normal, others had definite hypomagnesemia. Hypomagnesemia could be improved after magnesium supplement but could not return to the normal level. Variations in the CBS2 domain may be related to lower serum magnesium. However, there was no significant difference in the level of serum magnesium among the patients with three different types of CNNM2-related disorders. The severity of different phenotypes was therefore not explained by decreased serum magnesium. We expanded the spectrum of CNNM2 variants and classified the phenotypes of CNNM2-related disorders into three types. We found that DUF21 domain variations were most associated with CNNM2-related central nervous system phenotypes, whereas hypomagnesemia was more pronounced in patients with CBS2 domain variations, and AR-inherited CNNM2-related disorders had the most severe phenotype. These results provide important clues for further functional studies of CNNM2 and provide basic foundations for more accurate genetic counseling.

scholarly journals Tyr198 is the Essential Autophosphorylation Site for STK16 Localization and Kinase Activity

2019 ◽  
Vol 20 (19) ◽  
pp. 4852 ◽  
Author(s):  
Junjun Wang ◽  
Juanjuan Liu ◽  
Xinmiao Ji ◽  
Xin Zhang
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Kinase Domain ◽  
Serine Threonine Kinase ◽  
Cycle Progression ◽  
Threonine Kinase ◽  
Cellular Processes ◽  
Activation Segment ◽  
And Function

STK16, reported as a Golgi localized serine/threonine kinase, has been shown to participate in multiple cellular processes, including the TGF-β signaling pathway, TGN protein secretion and sorting, as well as cell cycle and Golgi assembly regulation. However, the mechanisms of the regulation of its kinase activity remain underexplored. It was known that STK16 is autophosphorylated at Thr185, Ser197, and Tyr198 of the activation segment in its kinase domain. We found that STK16 localizes to the cell membrane and the Golgi throughout the cell cycle, but mutations in the auto-phosphorylation sites not only alter its subcellular localization but also affect its kinase activity. In particular, the Tyr198 mutation alone significantly reduced the kinase activity of STK16, abolished its Golgi and membrane localization, and affected the cell cycle progression. This study demonstrates that a single site autophosphorylation of STK16 could affect its localization and function, which provides insights into the molecular regulatory mechanism of STK16’s kinase activity.

scholarly journals Functional Dynamics of Polo-Like Kinase 1 at the Centrosome

2009 ◽  
Vol 29 (11) ◽  
pp. 3134-3150 ◽  
Author(s):  
Kazuhiro Kishi ◽  
Marcel A. T. M. van Vugt ◽  
Ken-ichi Okamoto ◽  
Yasunori Hayashi ◽  
Michael B. Yaffe
Keyword(s):  
Dna Damage ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Kinase Domain ◽  
Cycle Progression ◽  
Functional Dynamics ◽  
Dynamic Exchange ◽  
And Control ◽  
Substrate Proteins ◽  
Kinetics Of

ABSTRACT Polo-like kinase 1 (Plk1) functions as a key regulator of mitotic events by phosphorylating substrate proteins on centrosomes, kinetochores, the mitotic spindle, and the midbody. Through mechanisms that are incompletely understood, Plk1 is released from and relocalizes to different mitotic structures as cells proceed through mitosis. We used fluorescence recovery after photobleaching to examine the kinetics of this process in more detail. We observed that Plk1 displayed a range of different recovery rates that differ at each mitotic substructure and depend on both the Polo-box domain and a functional kinase domain. Upon mitotic entry, centrosomal Plk1 becomes more dynamic, a process that is directly enhanced by Plk1 kinase activity. In contrast, Plk1 displays little dynamic exchange at the midbody, a process that again is modulated by the kinase activity of Plk1. Our findings suggest that the intrinsic kinase activity of Plk1 triggers its release from early mitotic structures and its relocalization to late mitotic structures. To assess the importance of Plk1 dynamic relocalization, Plk1 was persistently tethered to the centrosome. This resulted in a G2 delay, followed by a prominent prometaphase arrest, as a consequence of defective spindle formation and activation of the spindle checkpoint. The dynamic release of Plk1 from early mitotic structures is thus crucial for mid- to late-stage mitotic events and demonstrates the importance of a fully dynamic Plk1 at the centrosome for proper cell cycle progression. This dependence on dynamic Plk1 was further observed during the mitotic reentry of cells after a DNA damage G2 checkpoint, as this process was significantly delayed upon centrosomal tethering of Plk1. These results indicate that mitotic progression and control of mitotic reentry after DNA damage resides, at least in part, on the dynamic behavior of Plk1.

scholarly journals ‘Isolated’ germline mosaicism in the phenotypically normal father of a girl with X-linked hypophosphatemic rickets

2020 ◽  
Vol 182 (1) ◽  
pp. K1-K6 ◽  
Author(s):  
Yunting Lin ◽  
Yanna Cai ◽  
Jianan Xu ◽  
Chunhua Zeng ◽  
Huiying Sheng ◽  
...  
Keyword(s):  
Sanger Sequencing ◽  
De Novo ◽  
Hypophosphatemic Rickets ◽  
Dominant Inheritance ◽  
Germline Mosaicism ◽  
Pathogenic Variants ◽  
First Case ◽  
Heterozygous Variant ◽  
The Family ◽  
Normal Father

Objective X-linked hypophosphatemic rickets (XLHR) is the most common form of inherited rickets caused by pathogenic variants of PHEX gene with an X-linked dominant inheritance pattern. Precise molecular diagnosis of pathogenic variant will benefit the genetic counseling and prenatal diagnosis for the family with XLHR. Here, we presented an ‘isolated’ germline mosaicism in the phenotypically normal father of a girl with XLHR. Methods and results For the initial molecular screen of PHEX gene, DNA samples of the proband and her parents were extracted from their peripheral blood samples respectively. Sanger sequencing found a ‘de novo’ novel heterozygous variant, c.1666C>T(p.Q556X), at the PHEX gene in the proband, but not in her phenotypically healthy parents. Due to an occasional abnormality of his serum phosphate previously, further examinations for the father were taken to exclude the possibility of paternal mosaicism. Eight samples from different tissues were analyzed for PHEX gene by Sanger sequencing. Surprisingly, one ‘isolated’ germline mosaicism was detected only in his sperm with an estimated frequency of 26.67%. The mosaic allele was identical to the c.1666C>T(p.Q556X) variant in the proband. Conclusions This is the first case of ‘isolated’ germline mosaicism with pathogenic PHEX variant. Our study provides accurate diagnosis and valuable counseling for this family. This report also alerts clinicians and geneticists to exclude the possibility of the isolated germline mosaicism and prevent intrafamilial recurrences of inherited diseases.

scholarly journals Inherited and de novo biallelic pathogenic variants in COL11A1 result in type 2 Stickler syndrome with severe hearing loss

2020 ◽  
Vol 8 (9) ◽  
Author(s):  
Thomas Nixon ◽  
Allan J. Richards ◽  
Adrian Lomas ◽  
Stephen Abbs ◽  
Pradeep Vasudevan ◽  
...  
Keyword(s):  
Hearing Loss ◽  
De Novo ◽  
Stickler Syndrome ◽  
Severe Hearing Loss ◽  
Pathogenic Variants

scholarly journals A novel variant in the PDE4D gene is the cause of Acrodysostosis type 2 in a Lithuanian patient: a case report

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Gunda Petraitytė ◽  
Kamilė Šiaurytė ◽  
Violeta Mikštienė ◽  
Loreta Cimbalistienė ◽  
Dovilė Kriaučiūnienė ◽  
...  
Keyword(s):  
De Novo ◽  
Bone Dysplasia ◽  
Neurological Involvement ◽  
Mild Intellectual Disability ◽  
Pathogenic Variants ◽  
Novel Variant ◽  
Hormonal Resistance ◽  
Primary Bone ◽  
Conserved Region

Abstract Background Acrodysostosis is a rare hereditary disorder described as a primary bone dysplasia with or without hormonal resistance. Pathogenic variants in the PRKAR1A and PDE4D genes are known genetic causes of this condition. The latter gene variants are more frequently identified in patients with midfacial and nasal hypoplasia and neurological involvement. The aim of our study was to analyse and confirm a genetic cause of acrodysostosis in a male patient. Case presentation We report on a 29-year-old Lithuanian man diagnosed with acrodysostosis type 2. The characteristic phenotype includes specific skeletal abnormalities, facial dysostosis, mild intellectual disability and metabolic syndrome. Using patient’s DNA extracted from peripheral blood sample, the novel, likely pathogenic, heterozygous de novo variant NM_001104631.2:c.581G > C was identified in the gene PDE4D via Sanger sequencing. This variant causes amino acid change (NP_001098101.1:p.(Arg194Pro)) in the functionally relevant upstream conserved region 1 domain of PDE4D. Conclusions This report further expands the knowledge of the consequences of missense variants in PDE4D that affect the upstream conserved region 1 regulatory domain and indicates that pathogenic variants of the gene PDE4D play an important role in the pathogenesis mechanism of acrodysostosis type 2 without significant hormonal resistance.

scholarly journals Pathogenesis of CDK8-associated disorder: two patients with novel CDK8 variants and in vitro and in vivo functional analyses of the variants

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Tomoko Uehara ◽  
Kota Abe ◽  
Masayuki Oginuma ◽  
Shizuka Ishitani ◽  
Hiroshi Yoshihashi ◽  
...  
Keyword(s):  
Kinase Activity ◽  
De Novo ◽  
Kinase Domain ◽  
Kinase Assay ◽  
Zebrafish Model ◽  
Specific Chemical ◽  
Hypomorphic Alleles ◽  
Functional Analyses

Abstract Cyclin-dependent kinase 8 (CDK8) is a member of the CDK/Cyclin module of the mediator complex. A recent study reported that heterozygous missense CDK8 mutations cause a neurodevelopmental disorder in humans. The mechanistic basis of CDK8-related disorder has yet to be delineated. Here, we report 2 patients with de novo missense mutations within the kinase domain of CDK8 along with the results of in vitro and in vivo functional analyses using a zebrafish model. Patient 1 and Patient 2 had intellectual disabilities and congenital anomalies. Exome analyses showed that patient 1 had a heterozygous de novo missense p.G28A variant in the CDK8 (NM_001260.3) gene and patient 2 had a heterozygous de novo missense p.N156S variant in the CDK8 gene. We assessed the pathogenicity of these two variants using cultured-cells and zebrafish model. An in vitro kinase assay of human CDK8 showed that enzymes with a p.G28A or p.N156S substitution showed decreased kinase activity. An in vivo assays of zebrafish overexpression analyses also showed that the p.G28A and p.N156S alleles were hypomorphic alleles. Importantly, the inhibition of CDK8 kinase activity in zebrafish embryos using a specific chemical inhibitor induced craniofacial and heart defects similar to the patients’ phenotype. Taken together, zebrafish studies showed that non-synonymous variants in the kinase domain of CDK8 act as hypomorphic alleles causing human congenital disorder.

SCN8A and Its Related Epileptic Phenotypes

2021 ◽  
Author(s):  
Andrea Praticò ◽  
Carmela Gulizia ◽  
Gloria Gangi ◽  
Claudia Oliva ◽  
Catia Romano ◽  
...  
Keyword(s):  
De Novo ◽  
Wide Spectrum ◽  
Single Gene ◽  
Great Majority ◽  
Epileptic Encephalopathy ◽  
Specific Gene ◽  
Channel Blockers ◽  
Germline Mosaicism ◽  
Pathogenic Variants ◽  
Genetic Epilepsies

AbstractSodium channelopathies are among the most common single-gene causes of epilepsy and have been considered model disorders for the study of genetic epilepsies. Epilepsies due to SCN8A pathogenic variants can present with a broad range of phenotypes varying from a severe epileptic encephalopathy with multiple types of drug-resistant seizure to neurodevelopmental delay, mental retardation, and electroencephalogram (EEG) findings of multifocal spike and waves (mostly in the temporal/parietal/occipital areas). In rare cases, benign familial infantile seizures and developmental delay with/without ataxia have been reported. A first-level, specific SCN8A Sanger's sequencing, although available, is rarely performed because the clinical phenotype is not strictly characteristic and several overlaps with other genetic epilepsies may occur. Given its indistinctive phenotype, diagnosis is usually performed through a specific gene panel for epileptic encephalopathies, early epilepsies, or genetic epilepsy in general, or through whole exome sequencing (WES) and more rarely through whole genome sequencing (WGS). Mutations in SCN8A occur as an autosomal dominant trait. The great majority of individuals diagnosed with SCN8A epilepsy do not have an affected parent, because usually SCN8A patients do not reproduce, and mutations are inherited as a “de novo” trait. In rare cases, SCN8A mutations may be inherited in the setting of parental germline mosaicism. SCN8A-related epilepsies have not shown a clear genotype–phenotype correlation, the same variants have been described with different clinical expressivity and this could be due to other genetic factors or to interacting environmental factors. There is no standardized treatment for SCN8A-related epilepsy because of the rarity of the disease and the unavailability of specific, targeted drugs. Treatment is based mainly on antiepileptic drugs which include classic wide-spectrum drugs such as valproic acid, levetiracetam, and lamotrigine. Sodium-channel blockers (phenytoin, carbamazepine, oxcarbazepine, and lamotrigine) have shown appreciable results in terms of seizure reduction, in particular, in patients presenting gain-of-function mutations. Nowadays, new potentially transformative gene therapy treatment approaches are currently being explored, allowing in the next future, a precision-based treatment directed against the gene defect and protein alterations.

scholarly journals Protein Kinase Activity and Identification of a Toxic Effector Domain of the Target of Rapamycin TOR Proteins in Yeast

1999 ◽  
Vol 10 (8) ◽  
pp. 2531-2546 ◽  
Author(s):  
Clara M. Alarcon ◽  
Joseph Heitman ◽  
Maria E. Cardenas
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Kinase Domain ◽  
Protein Kinase Activity ◽  
Tor Signaling ◽  
Site Mutation ◽  
Effector Domain ◽  
Kinase Cascade

In complex with FKBP12, the immunosuppressant rapamycin binds to and inhibits the yeast TOR1 and TOR2 proteins and the mammalian homologue mTOR/FRAP/RAFT1. The TOR proteins promote cell cycle progression in yeast and human cells by regulating translation and polarization of the actin cytoskeleton. A C-terminal domain of the TOR proteins shares identity with protein and lipid kinases, but only one substrate (PHAS-I), and no regulators of the TOR-signaling cascade have been identified. We report here that yeast TOR1 has an intrinsic protein kinase activity capable of phosphorylating PHAS-1, and this activity is abolished by an active site mutation and inhibited by FKBP12-rapamycin or wortmannin. We find that an intact TOR1 kinase domain is essential for TOR1 functions in yeast. Overexpression of a TOR1 kinase-inactive mutant, or of a central region of the TOR proteins distinct from the FRB and kinase domains, was toxic in yeast, and overexpression of wild-type TOR1 suppressed this toxic effect. Expression of the TOR-toxic domain leads to a G1 cell cycle arrest, consistent with an inhibition of TOR function in translation. Overexpression of the PLC1gene, which encodes the yeast phospholipase C homologue, suppressed growth inhibition by the TOR-toxic domains. In conclusion, our findings identify a toxic effector domain of the TOR proteins that may interact with substrates or regulators of the TOR kinase cascade and that shares sequence identity with other PIK family members, including ATR, Rad3, Mei-41, and ATM.

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