Correlation of early neurodevelopmental features of children with SYNGAP1 variants and their genotypes / 中华医学遗传学杂志

OBJECTIVE@#To explore the early neurodevelopmental features of young children with SYNGAP1 variants and their genotype-phenotype correlation.@*METHODS@#Young children with neurodevelopmental disorders (NDDs) (< 5 years old) who were referred to the Children's Hospital Affiliated to the Capital Institute of Pediatrics between January 2019 and July 2022 were selected as the study subjects. All children had undergone whole-exome sequencing, comprehensive pediatric neuropsychological assessment, familial segregation analysis, and pathogenicity classification. Meanwhile, young Chinese NDD children (< 5 years old) with pathogenic/likely pathogenic SYNGAP1 variants were retrieved from the literature, with information including detailed clinical and genetic testing, neurodevelopmental quotient (DQ) of the Children Neuropsychological and Behavior Scale-Revision 2016 (CNBS-R2016). Children who did not have a detailed DQ but had their developmental status assessed by a medical professional were also included. The correlation between neurodevelopmental severity, comorbidity and SYNGAP1 variants were summarized.@*RESULTS@#Four young NDD children carrying SYNGAP1 variants were recruited (1 male and 3 females, with a mean age of 34.0 ± 18.2 months), among whom one harboring a novel variant (c.437C>G, p.S146*). Combined with 19 similar cases retrieved from the literature, 23 Chinese NDD young children were included in our study (8 males and 10 females, 5 with unknown sex, with a mean age of 37.1 ± 14.2 months). A loss of function (LOF) variant was found in 19 (82.6%) children. All of the children had presented global developmental delay (GDD) before the age of two. In addition, 16 (69.6%) had seizure/epilepsy at the age of 27.0 ± 12.1 months, among whom 15 had occurred independent of the global developmental delay. Myoclonic and absence were common types of seizures. Compared with those with variants of exons 8 to 15, the severity of developmental delay was milder among children with variants in exons 1 to 5.@*CONCLUSION@#The early neurodevelopment features of the SYNGAP1 variants for young children (< 5 years old) have included global developmental delay and seizure/epilepsy. All of the children may present GDD before the age of two. The severity of developmental delay may be related to the type and location of the SYNGAP1 variants.

A case of mental retardation caused by a frameshift variant of SYNGAP1 gene / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for a child with mental retardation.@*METHODS@#Whole exome sequencing was carried out for the child. Candidate variant was screened based on his clinical features and verified by Sanger sequencing.@*RESULTS@#The child was found to harbor a c.995_1002delAGACAAAA(p.Asp332AlafsTer84) frameshift variant in the SYNGAP1 gene. Bioinformatic analysis suggested it to be pathogenic. The same variant was not detected in either parent.@*CONCLUSION@#The c.995_1002delAGACAAAA(p.Asp332AlafsTer84) frameshift variant of the SYNGAP1 gene probably underlay the mental retardation in this child. Above finding has expanded the spectrum of SYNGAP1 gene variants and provided a basis for the diagnosis and treatment for this child.

Autosomal dominant mental retardation type 5 caused by SYNGAP1 gene mutations: a report of 8 cases and literature review / 中国当代儿科杂志

OBJECTIVES@#To summarize the clinical phenotype and genetic characteristics of children with autosomal dominant mental retardation type 5 caused by SYNGAP1 gene mutations.@*METHODS@#A retrospective analysis was performed on the medical data of 8 children with autosomal dominant mental retardation type 5 caused by SYNGAP1 gene mutations who were diagnosed and treated in the Department of Pediatrics, Xiangya Hospital of Central South University.@*RESULTS@#The mean age of onset was 9 months for the 8 children. All children had moderate-to-severe developmental delay (especially delayed language development), among whom 7 children also had seizures. Among these 8 children, 7 had novel heterozygous mutations (3 with frameshift mutations, 2 with nonsense mutations, and 2 with missense mutations) and 1 had 6p21.3 microdeletion. According to the literature review, there were 48 Chinese children with mental retardation caused by SYNGAP1 gene mutations (including the children in this study), among whom 40 had seizures, and the mean age of onset of seizures was 31.4 months. Frameshift mutations (15/48, 31%) and nonsense mutations (19/48, 40%) were relatively common in these children. In terms of treatment, among the 33 children with a history of epileptic medication, 28 (28/33, 85%) showed response to valproic acid antiepileptic treatment and 16 (16/33, 48%) achieved complete seizure control after valproic acid monotherapy or combined therapy.@*CONCLUSIONS@#Children with autosomal dominant mental retardation type 5 caused by SYNGAP1 gene mutations tend to have an early age of onset, and most of them are accompanied by seizures. These children mainly have frameshift and nonsense mutations. Valproic acid is effective for the treatment of seizures in most children.

Toxoplasma gondii infection induces cell apoptosis via multiple pathways revealed by transcriptome analysis / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Toxoplasma gondii is a worldwide parasite that can infect almost all kinds of mammals and cause fatal toxoplasmosis in immunocompromised patients. Apoptosis is one of the principal strategies of host cells to clear pathogens and maintain organismal homeostasis, but the mechanism of cell apoptosis induced by T. gondii remains obscure. To explore the apoptosis influenced by T. gondii, Vero cells infected or uninfected with the parasite were subjected to apoptosis detection and subsequent dual RNA sequencing (RNA-seq). Using high-throughput Illumina sequencing and bioinformatics analysis, we found that pro-apoptosis genes such as DNA damage-inducible transcript 3 (DDIT3), growth arrest and DNA damage-inducible α (GADD45A), caspase-3 (CASP3), and high-temperature requirement protease A2 (HtrA2) were upregulated, and anti-apoptosis genes such as poly(adenosine diphosphate (ADP)-ribose) polymerase family member 3 (PARP3), B-cell lymphoma 2 (Bcl-2), and baculoviral inhibitor of apoptosis protein (IAP) repeat containing 5 (BIRC5) were downregulated. Besides, tumor necrosis factor (TNF) receptor-associated factor 1 (TRAF1), TRAF2, TNF receptor superfamily member 10b (TNFRSF10b), disabled homolog 2 (DAB2)‍-interacting protein (DAB2IP), and inositol 1,4,5-trisphosphate receptor type 3 (ITPR3) were enriched in the upstream of TNF, TNF-related apoptosis-inducing ligand (TRAIL), and endoplasmic reticulum (ER) stress pathways, and TRAIL-receptor 2 (TRAIL-R2) was regarded as an important membrane receptor influenced by T. gondii that had not been previously considered. In conclusion, the T. gondii RH strain could promote and mediate apoptosis through multiple pathways mentioned above in Vero cells. Our findings improve the understanding of the T. gondii infection process through providing new insights into the related cellular apoptosis mechanisms.

Identification of a novel SYNGAP1 mutation in a child with intellectual disability / 中华医学遗传学杂志

OBJECTIVE@#To report on a child with mental retardation caused by SYNGAP1 gene mutation.@*METHODS@#Peripheral blood samples were collected from the proband and her parents. High throughput sequencing (HTS) was employed for screening for potential mutation in the patient. Suspected mutation was validated by Sanger sequencing of the child and her parents.@*RESULTS@#By HTS, a previously unknown mutation [c.1656C>A (p.C552*)] was found in exon 10 of the SYNGAP1 gene in the proband. Sanger sequencing confirmed the heterozygous nature of the mutation and that neither of her parents carried the same mutation.@*CONCLUSION@#The dysmorphism and developmental delay of the child were probably due to the pathogenic mutation of the SYNGAP1 gene. HTS can facilitate elucidation of the genetic etiology with efficiency, which has great significance in the diagnosis, treatment and prognosis of the child.

Research Advances in the Role of RAS-GTPase-activating Proteins in Tumors / 中国医学科学院学报

A variety of molecules are involved in tumorigenesis,during which the RAS pathway-related molecules play key roles. RAS gene mutations exist in about 30% of human tumors;in some tumors(e.g. pancreatic adenocarcinomas),the mutation rates may rise to 75%-95%. Even in tumors without RAS mutations,the RAS pathway-related molecules can also be highly activated. RAS-GTPase-activating proteins(RASGAPs)are a group of tumor suppressors. They normally turn off RAS pathway by catalyzing the hydrolysis of RAS-GTP. However,the mutation or hypermethylation of their promoters will inactivate their roles and thus provide an alternative mechanism of activating Ras. This article reviews the research advances in the role of RASGAPs in the development of tumors.

IQGAP1 is overexpressed in hepatocellular carcinoma and promotes cell proliferation by Akt activation

The scaffold protein IQGAP1 shows elevated levels in several cancer types, but its expression in hepatocellular carcinoma is unknown. We found that 58% of human hepatocellular carcinoma tissue samples had increased IQGAP1 expression compared to adjacent normal tissue. Overexpressing IQGAP1 raised the in vivo tumorigenicity of hepatocellular carcinoma cells, and forced overexpression of IQGAP1 in vitro stimulated cell proliferation. Cell growth was reduced by knockdown or mutation of IQGAP1, or by treatment of cells with a phosphotidylinositol 3-kinase inhibitor. To determine the mechanism by which IQGAP1 overexpression affected hepatocellular carcinoma cells, we confirmed its interaction in these cells with mammalian target of rapamycin (mTOR), a serine/threonine kinase that integrates signals about nutrient and energy status with downstream effectors that influence cell division. In addition, we discovered a new interaction involving IQGAP1, mTOR and Akt, which is a downstream target of mTOR. Akt phosphorylation on Ser-473, which is catalyzed by mTOR and required for Akt activation, increased with increasing amounts of IQGAP1, and decreased with IQGAP1 mutation. We hypothesize that IQGAP1 is a scaffold that facilitates mTOR and Akt interaction.

G3BP: a promising target for cancer therapy / 药学学报

G3BP (Ras-GTPase-activating protein SH3 domain binding protein), a protein which binds to RasGAP SH3 domain, belongs to RNA-binding protein family, implicating in the downstream of Ras signaling. G3BP harbors the activities of endoribonuclease and DNA helicase, and can induce stress granules formation. G3BP plays a general role in the signal pathways of cell proliferation, differentiation, apoptosis and RNA metabolism. It has been shown to be over-expressed in a number of human malignancies and has a close relationship with tumor invasion and metastasis. Given that it has been implicated in several pathways that are known to be involved in cancer biology, G3BP may provide a new target for cancer therapy.

IQ domain GTPase-activating protein 1 mediates the process of injury and repair in bronchial epithelial cells / 生理学报

The process of injury and repair in airway epithelium involves cell spreading and migration followed by cell proliferation. IQ domain GTPase-activating protein 1 (IQGAP1) acts in a series of cell processes, but has not been clarified in lung epithelial cells. In this study, a widely used model of injury and repair in vitro by scratching bronchial epithelial cells (BECs) was utilized to investigate the function of IQGAP1. The results showed that IQGAP1 was abundant in BECs of mouse, rat, pig and human. IQGAP1 was colocalized with tubulin cytoskeleton, but was destroyed by nocodazole, a microtubule disassembly reagent. IQGAP1 mRNA and protein expressions increased at 6-9 h after scratching. In addition, overexpression of IQGAP1 translocated β-catenin from the cytoplasm into the nucleus and activated the Tcf/Lef signal. Scratching altered the associations of IQGAP1 with β-catenin, adenomatous polyposis coli (APC) and cytoplasmic linker protein-170 (CLIP-170). Silencing IQGAP1 expression by small interference RNA (siRNA) blocked the wound closure. It is concluded that IQGAP1 signal is involved in the wound closure of BECs induced by scratching.

Inhibition of Ras-GTpase Improves diabetes-induced abnormal vascular reactivity in the rat perfused mesenteric vascular bed

The signalling mechanisms involved in regulating altered vascular reactivity in diabetes are not fully understood. The aim of this study was to investigate the role of Ras-GTPase in the development of abnormal vascular reactivity in diabetes. Materials and We investigated the ability of chronic administration of FPTIII [1.5 mg/kg], an inhibitor of Ras-GTPase, to modulate the altered vasoreactivity of the rat perfused mesenteric bed to common vasoconstrictors and vasodilators in streptozotocin [STZ]-induced diabetes. The vasoconstrictor responses induced by norepinephrine [NE] and endothelin-1 [ET-1] were significantly increased whereas vasodilator responses to carbachol, histamine and isoprenaline were significantly reduced in the perfused mesenteric bed of the STZ-diabetic rats. Inhibition of Ras-GTPase by chronic administration of FPTIII produced a significant normalization of the altered agonist-induced vasoconstrictor and vasodilator responses without affecting blood glucose levels. Inhibition of Ras-GTPase did not affect the agonist-induced vasoconstrictor and vasodilator responses in the control animals. These data suggest that signal transduction pathways activated by Ras-GTPase are involved in the development of diabetic vascular dysfunction. Potential strategies aimed at modifying actions of signal transduction pathways involving Ras-GTPase may therefore prove to be beneficial in treatment of vascular complications in diabetes