Generation of human induced pluripotent stem cell lines derived from four Rett syndrome patients with MECP2 mutations.

Rett syndrome is characterized by severe global developmental impairments with autistic features and loss of purposeful hand skills. Here we show that human induced pluripotent stem cell (hiPSC) lines derived from four Japanese female patients with Rett syndrome are generated from peripheral blood mononuclear cells using Sendai virus vectors. The generated hiPSC lines showed self-renewal and pluripotency and carried heterozygous frameshift, missense, or nonsense mutations in the MECP2 gene. Since the molecular pathogenesis caused by MECP2 dysfunction remains unclear, these cell resources are useful tools to establish disease models and develop new therapies for Rett syndrome.

Simple Method for the Preparation of Postsynaptic Density Fraction from Mouse Brain.

Postsynaptic density (PSD) is a morphologically and functionally specialized postsynaptic membrane structure of excitatory synapses. It contains hundreds of proteins such as neurotransmitter receptors, adhesion molecules, cytoskeletal proteins, and signaling enzymes. The study of the molecular architecture of the PSD is one of the most intriguing issues in neuroscience research. The isolation of the PSD from the brain of an animal is necessary for subsequent biochemical and morphological analyses. Many laboratories have developed methods to isolate PSD from the animal brain. In this chapter, we present a simple method to isolate PSD from the mouse brain using sucrose density gradient-based purification of synaptosomes followed by detergent extraction.

Expression analysis of type I ARF small GTPases ARF1-3 during mouse brain development.

BACKGROUND: ARF (ADP-ribosylation factor) GTPases are major regulators of intracellular trafficking, and classified into 3 groups (Type I - III), among which the type I group members, ARF1 and 3, are responsible genes for neurodevelopmental disorders. METHODS: In this study, we analysed the expression of Type I ARFs ARF1-3 during mouse brain development using biochemical and morphological methods. RESULTS: Western blotting analyses revealed that ARF1-3 are weakly expressed in the mouse brain at embryonic day 13 and gradually increase until postnatal day 30. ARF1-3 appear to be abundantly expressed in various telencephalon regions. Biochemical fractionation studies detected ARF1-3 in the synaptosome fraction of cortical neurons containing both pre- and post-synapses, however ARF1-3 were not observed in post-synaptic compartments. In immunohistochemical analyses, ARF1-3 appeared to be distributed in the cytoplasm and dendrites of cortical and hippocampal neurons as well as in the cerebellar molecular layer including dendrites of Purkinje cells and granule cell axons. Immunofluorescence in primary cultured hippocampal neurons revealed that ARF1-3 are diffusely distributed in the cytoplasm and dendrites with partial colocalization with a pre-synaptic marker, synaptophysin. CONCLUSIONS: Overall, our results support the notion that ARF1-3 could participate in vesicle trafficking both in the dendritic shaft (excluding spines) and axon terminals (pre-synaptic compartments).

Partial penectomy for severe penile ulceration caused by cholesterol crystal embolization.

Introduction: Cholesterol crystal embolism is a rare microembolic disease caused by cholesterol crystals that can present with various symptoms after vascular surgery, catheterization, or anticoagulation therapy. We report a case of penile ulceration caused by cholesterol crystal embolism. Case presentation: A 72-year-old man undergoing maintenance dialysis for end-stage renal failure presented with penile pain and a black glans ulcer. Despite low-density lipoprotein apheresis, he was referred to our hospital because of lack of improvement. Based on his medical history and clinical presentation, including artificial vascular replacement and right toe amputation, cholesterol crystal embolism was suspected and partial penectomy was performed, thus confirming the diagnosis. Penile pain resolved after surgery, and he was discharged on Day 10. Unfortunately, he died after small bowel perforation developed 2 months after surgery. Conclusion: Penile ulcers caused by cholesterol crystal embolism may indicate the severity and progression of disease and typically require surgical intervention.

Expression analyses of WAC, a responsible gene for neurodevelopmental disorders, during mouse brain development.

WAC is an adaptor protein involved in gene transcription, protein ubiquitination, and autophagy. Accumulating evidence indicates that WAC gene abnormalities are responsible for neurodevelopmental disorders. In this study, we prepared anti-WAC antibody, and performed biochemical and morphological characterization focusing on mouse brain development. Western blotting analyses revealed that WAC is expressed in a developmental stage-dependent manner. In immunohistochemical analyses, while WAC was visualized mainly in the perinuclear region of cortical neurons at embryonic day 14, nuclear expression was detected in some cells. WAC then came to be enriched in the nucleus of cortical neurons after birth. When hippocampal sections were stained, nuclear localization of WAC was observed in Cornu ammonis 1 - 3 and dentate gyrus. In cerebellum, WAC was detected in the nucleus of Purkinje cells and granule cells, and possibly interneurons in the molecular layer. In primary cultured hippocampal neurons, WAC was distributed mainly in the nucleus throughout the developing process while it was also localized at perinuclear region at 3 and 7 days in vitro. Notably, WAC was visualized in Tau-1-positive axons and MAP2-positive dendrites in a time-dependent manner. Taken together, results obtained here suggest that WAC plays a crucial role during brain development.

A missense variant at the RAC1-PAK1 binding site of RAC1 inactivates downstream signaling in VACTERL association.

RAC1 at 7p22.1 encodes a RAC family small GTPase that regulates actin cytoskeleton organization and intracellular signaling pathways. Pathogenic RAC1 variants result in developmental delay and multiple anomalies. Here, exome sequencing identified a rare de novo RAC1 variant [NM_018890.4:c.118T > C p.(Tyr40His)] in a male patient. Fetal ultrasonography indicated the patient to have multiple anomalies, including persistent left superior vena cava, total anomalous pulmonary venous return, esophageal atresia, scoliosis, and right-hand polydactyly. After birth, craniofacial dysmorphism and esophagobronchial fistula were confirmed and VACTERL association was suspected. One day after birth, the patient died of respiratory failure caused by tracheal aplasia type III. The molecular mechanisms of pathogenic RAC1 variants remain largely unclear; therefore, we biochemically examined the pathophysiological significance of RAC1-p.Tyr40His by focusing on the best characterized downstream effector of RAC1, PAK1, which activates Hedgehog signaling. RAC1-p.Tyr40His interacted minimally with PAK1, and did not enable PAK1 activation. Variants in the RAC1 Switch II region consistently activate downstream signals, whereas the p.Tyr40His variant at the RAC1-PAK1 binding site and adjacent to the Switch I region may deactivate the signals. It is important to accumulate data from individuals with different RAC1 variants to gain a full understanding of their varied clinical presentations.

5-Aminolevulinic acid hydrochloride enhances bupivacaine-induced hypotension in spontaneously hypertensive rats.

PURPOSE: Oral administration of 5-aminolevulinic acid hydrochloride (5-ALA-HCl) has been reported to enhance the hypotensive effects associated with anesthetics, especially in elderly hypertensive patients treated with antihypertensive agents. The present study aimed to clarify the effects of antihypertensive-agent- and anesthesia-induced hypotension by 5-ALA-HCl in spontaneously hypertensive rats (SHRs). METHODS: We measured blood pressure (BP) of SHRs and normotensive Wistar Kyoto (WKY) rats treated with amlodipine or candesartan before and after administration of 5-ALA-HCl. We also investigated the change in BP following intravenous infusion of propofol and intrathecal injection of bupivacaine in relation to 5-ALA-HCl administration. FINDINGS: Oral administration of 5-ALA-HCl significantly reduced BP in SHRs and WKY rats with amlodipine and candesartan. Infusion of propofol significantly reduced BP in SHRs treated with 5-ALA-HCl. Intrathecal injection of bupivacaine significantly declined SBP and DBP in both SHRs and WKY rats treated with 5-ALA-HCl. The bupivacaine-induced decline in SBP was significantly larger in SHRs compared with WKY rats. CONCLUSION: These findings suggest that 5-ALA-HCl does not affect the antihypertensive agents-induced hypotensive effect, but enhances the bupivacaine-induced hypotensive effect, especially in SHRs, indicating that 5-ALA may contribute to anesthesia-induced hypotension via suppression of sympathetic nerve activity in patients with hypertension.

The Relationship between the Presence of an Earlobe Crease and Overactive Bladder: A Cross-Sectional Case-Controlled Study.

Background and Objectives: To examine the relationship between the presence of earlobe crease (EC) and overactive bladder (OAB). Materials and Methods: The earlobes of the participants were examined macroscopically. ECs were further divided into four groups (grades 0-3) according to severity. Subjective symptoms were assessed using the OAB symptom score (OABSS), and objective findings were assessed using uroflowmetry. The relationship between these findings and the presence or absence and severity of EC was also examined. A score of ≥2 points on OABSS question 3 (urinary urgency), with a total score of ≥3 points, indicated OAB. Results: We analyzed 246 participants, including 120 (48.8%) in the EC group and 126 (51.2%) in the non-EC (N-EC) group. On the OABSS, the EC group scored higher than the N-EC group for all questions and for the total score. The total OABSS of EC grade 3 was the highest of all groups. A total of 115 (95.8%) patients in the EC group (100% in grade 3) and 69 (54.8%) in the N-EC group met the OAB criteria (p < 0.001). The voided volume and maximum flow rate of the EC group were significantly lower than those of the N-EC group (both p < 0.001). The post-void residual urine volume in the EC group was significantly higher than that in the N-EC group (p = 0.029). Multivariate analysis revealed that EC was an independent risk factor for OAB (odds ratio, 8.15; 95% confidence interval, 2.84-24.75; p < 0.001). Conclusions: The presence of an earlobe crease may be a predictive marker for OAB.

Expression Analyses of Rich2/Arhgap44, a Rho Family GTPase-Activating Protein, during Mouse Brain Development.

Rho family small GTPases, such as Rho, Rac, and Cdc42, play essential roles during brain development, by regulating cellular signaling and actin cytoskeletal reorganization. Rich2/Arhgap44, a Rac- and Cdc42-specific GTPase-activating protein, has been reported to be a key regulator for dendritic spine morphology and synaptic function. Given the essential roles of Rac and Cdc42 in brain development, Rich2 is supposed to take part in brain development. However, not only the molecular mechanism involved but also the expression profile of Rich2 during neurodevelopment has not yet been elucidated. In this study, we carried out expression analyses of Rich2 by focusing on mouse brain development. In immunoblotting, Rich2 exhibited a tissue-dependent expression profile in the young adult mouse, and the expression was increased during brain development. In immunohistochemical analyses, Rich2 was observed in the cytoplasm of cortical neurons at postnatal day (P) 0 and then came to be enriched in the nucleus with moderate distribution in neuropils at P7. Later at P30, a complex immunostaining pattern of Rich2 was observed; Rich2 was distributed in the nucleus, cytoplasm, and neuropils in many cortical neurons, whereas other neurons frequently displayed little expression. In the hippocampus at P7, Rich2 was distributed mainly in the cytoplasm of excitatory neurons in the cornu ammonis regions, while it was moderately detected in the nucleus in the dentate granule cells. Notably, Rich2 was distributed in excitatory synapses of the cornu ammonis 1 region at P30. Biochemical fractionation analyses also detected Rich2 in the postsynaptic density. Taken together, Rich2 is found to be expressed in the central nervous system in a developmental stage-dependent manner and may be involved in synapse formation/maintenance in cortical neurons.

Gain-of-function p.F28S variant in RAC3 disrupts neuronal differentiation, migration and axonogenesis during cortical development, leading to neurodevelopmental disorder.

BACKGROUND: RAC3 encodes a Rho family small GTPase that regulates the behaviour and organisation of actin cytoskeleton and intracellular signal transduction. Variants in RAC3 can cause a phenotypically heterogeneous neurodevelopmental disorder with structural brain anomalies and dysmorphic facies. The pathomechanism of this recently discovered genetic disorder remains unclear. METHODS: We investigated an early adolescent female with intellectual disability, drug-responsive epilepsy and white matter abnormalities. Through exome sequencing, we identified the novel de novo variant (NM_005052.3): c.83T>C (p.Phe28Ser) in RAC3. We then examined the pathophysiological significance of the p.F28S variant in comparison with the recently reported disease-causing p.Q61L variant, which results in a constitutively activated version of RAC3. RESULTS: In vitro analyses revealed that the p.F28S variant was spontaneously activated by substantially increased intrinsic GTP/GDP-exchange activity and bound to downstream effectors tested, such as PAK1 and MLK2. The variant suppressed the differentiation of primary cultured hippocampal neurons and caused cell rounding with lamellipodia. In vivo analyses using in utero electroporation showed that acute expression of the p.F28S variant caused migration defects of excitatory neurons and axon growth delay during corticogenesis. Notably, defective migration was rescued by a dominant negative version of PAK1 but not MLK2. CONCLUSION: Our results indicate that RAC3 is critical for brain development and the p.F28S variant causes morphological and functional defects in cortical neurons, likely due to the hyperactivation of PAK1.

Erratic and blood vessel-guided migration of astrocyte progenitors in the cerebral cortex.

Astrocytes are one of the most abundant cell types in the mammalian brain. They play essential roles in synapse formation, maturation, and elimination. However, how astrocytes migrate into the gray matter to accomplish these processes is poorly understood. Here, we show that, by combinational analyses of in vitro and in vivo time-lapse observations and lineage traces, astrocyte progenitors move rapidly and irregularly within the developing cortex, which we call erratic migration. Astrocyte progenitors also adopt blood vessel-guided migration. These highly motile progenitors are generated in the restricted prenatal stages and differentiate into protoplasmic astrocytes in the gray matter, whereas postnatally generated progenitors do not move extensively and differentiate into fibrous astrocytes in the white matter. We found Cxcr4/7, and integrin ß1 regulate the blood vessel-guided migration, and their functional blocking disrupts their positioning. This study provides insight into astrocyte development and may contribute to understanding the pathogenesis caused by their defects.

Variant-specific changes in RAC3 function disrupt corticogenesis in neurodevelopmental phenotypes.

Variants in RAC3, encoding a small GTPase RAC3 which is critical for the regulation of actin cytoskeleton and intracellular signal transduction, are associated with a rare neurodevelopmental disorder with structural brain anomalies and facial dysmorphism. We investigated a cohort of 10 unrelated participants presenting with global psychomotor delay, hypotonia, behavioural disturbances, stereotyped movements, dysmorphic features, seizures and musculoskeletal abnormalities. MRI of brain revealed a complex pattern of variable brain malformations, including callosal abnormalities, white matter thinning, grey matter heterotopia, polymicrogyria/dysgyria, brainstem anomalies and cerebellar dysplasia. These patients harboured eight distinct de novo RAC3 variants, including six novel variants (NM_005052.3): c.34G > C p.G12R, c.179G > A p.G60D, c.186_188delGGA p.E62del, c.187G > A p.D63N, c.191A > G p.Y64C and c.348G > C p.K116N. We then examined the pathophysiological significance of these novel and previously reported pathogenic variants p.P29L, p.P34R, p.A59G, p.Q61L and p.E62K. In vitro analyses revealed that all tested RAC3 variants were biochemically and biologically active to variable extent, and exhibited a spectrum of different affinities to downstream effectors including p21-activated kinase 1. We then focused on the four variants p.Q61L, p.E62del, p.D63N and p.Y64C in the Switch II region, which is essential for the biochemical activity of small GTPases and also a variation hot spot common to other Rho family genes, RAC1 and CDC42. Acute expression of the four variants in embryonic mouse brain using in utero electroporation caused defects in cortical neuron morphology and migration ending up with cluster formation during corticogenesis. Notably, defective migration by p.E62del, p.D63N and p.Y64C were rescued by a dominant negative version of p21-activated kinase 1. Our results indicate that RAC3 variants result in morphological and functional defects in cortical neurons during brain development through variant-specific mechanisms, eventually leading to heterogeneous neurodevelopmental phenotypes.

Impact of Mirabegron Administration on the Blood Pressure and Pulse Rate in Patients with Overactive Bladder.

Background and Objectives: To determine changes in the blood pressure (BP) and pulse rate (PR) before and after the administration of mirabegron in real-world clinical practice for patients with overactive bladder (OAB). Materials and Methods: This study was conducted in patients newly diagnosed with OAB. Before and 12 weeks after mirabegron treatment, we evaluated the effects on BP and PR. An overall examination was conducted, and the patients were divided into two groups according to their age: a young group (<65 years old) and an old group (≥65 years old). Results: A total of 263 patients were enrolled in this study. In the overall and intragroup comparisons, the systolic BP (SBP) did not change significantly after mirabegron administration. However, an increase in SBP of ≥10 mmHg was observed in 53 (20.2%), 4 (7.4%), and 49 (23.4%) in the entire group, young group, and old group, respectively (p = 0.009). Regarding diastolic BP, a significant decrease after the treatment was detected in entire (71.2 ± 11.4 versus 69.8 ± 10.7 mmHg; p = 0.041) and old patients (71.5 ± 10.6 versus 69.5 ± 10.2 mmHg; p = 0.012). There was no significant change in PR in our study population. Further examination using a propensity match score revealed that age was the risk factor for the increase in SBP after mirabegron administration. Conclusions: Mirabegron does not have any adverse effects on BP and PR. However, since some patients in this study had elevated SBP after administration, we suggest regular BP monitoring during mirabegron treatment.

Effects of ß3 Agonists and Anticholinergic Drugs on Defecation in Patients With Overactive Bladder.

BACKGROUND/AIM: In clinical practice, constipation is one of the most frequent adverse events caused by drugs for overactive bladder (OAB). The occurrence of constipation greatly deteriorates the patient's quality of life. The aim of the study was to evaluate and compare the effects of three commonly used ß3 agonists and anticholinergic drugs on the defecation status in patients with OAB. PATIENTS AND METHODS: We retrospectively reviewed the defecation status in patients who received mirabegron, solifenacin, or fesoterodine for OAB. We evaluated changes in the (a) urological parameters using the OAB symptom score (OABSS) and (b) defecation status using the Bristol Stool Form Scale (BSFS) and constipation scoring system (CSS) following 12 weeks of drug administration. RESULTS: We analyzed data from 165 patients (mirabegron=56, fesoterodine=52, and solifenacin=57). The solifenacin group showed a significant decrease in BSFS (from 3.2±1.0 at baseline to 2.3±12 post-treatment) and an increase in hardened stools (p<0.001). Elimination worsened as assessed by almost all items, and the total modified CSS scores worsened significantly from 4.8±2.6 points at baseline to 8.O±4.8 points after 12 weeks of solifenacin treatment (p<0.001). The mirabegron group showed no changes in any of the CSS items. In the fesoterodine group, the CSS scores for "completeness" and "assistance" increased significantly after treatment (p<0.001 and p=0.013, respectively). CONCLUSION: All three drugs were effective for OAB. Mirabegron had almost no effect on constipation; fesoterodine, an anticholinergic drug, also had hardly any effect on defecation.

Pathological Significance and Prognostic Role of WWC1 in Upper Urinary Tract Urothelial Cancer.

BACKGROUND/AIM: WW and C2 domain-containing 1 (WWC1) protein is a suppressor of malignancies. However, there is no information on the pathological significance of WWC1 in upper urinary tract cancer (UTUC). PATIENTS AND METHODS: In this study, WWC1 immunoreactivity was investigated in 152 non-metastatic UTUC samples. The relationships between WWC1 expression and grade, pT stage, proliferative index (using an antibody to Ki-67), and the immunohistochemical expression of matrix metalloproteinase (MMP)-2 and -9 were evaluated. RESULTS: WWC1 expression was negatively associated with tumor grade and pT stage (p<0.001). Positive expression of WWC1 was a better predictor of the UTUC recurrence and subsequent metastasis, and the multivariate analysis showed that WWC1 expression was a significant predictor of subsequent metastasis (hazard ratio=0.29, p=0.020). WWC1 expression inversely correlated with the proliferative index (odds ratio=2.59, p=0.023) and expression of MMP9 (odds ratio=2.19, p=0.040) but not with MMP2 expression, by multivariate analyses. CONCLUSION: WWC1 expression was negatively associated with malignant aggressiveness via the suppression of cancer cell proliferation and MMP9 expression in patients with UTUC. This suggests WWC1 to be a useful predictor and novel therapeutic target in patients with UTUC.

Expression Analyses of Cep152, a Responsible Gene Product for Autosomal Recessive Primary Microcephaly, during Mouse Brain Development.

Centrosomal protein 152 (Cep152) regulates centriole duplication as a molecular scaffold during the cell cycle. Its gene abnormalities are responsible for autosomal recessive primary microcephaly 9 and Seckel syndrome. In this study, we prepared an antibody against mouse Cep152, anti-Cep152, and performed expression analyses focusing on mouse brain development. Western blotting analyses revealed that Cep152 with a molecular mass of ∼150 kDa was expressed strongly at embryonic day (E)13 and then gradually decreased during the brain development process. Instead, protein bands of ∼80 kDa and ∼60 kDa came to be recognized after postnatal day (P)15 and P30, respectively. In immunohistochemical analyses, Cep152 was enriched in the centrosome of neuronal progenitors in the ventricular zone at E14, whereas it was diffusely distributed mainly in the cytoplasm of cortical neurons at P18. In developing cerebellum at P7, Cep152 was localized at the centrosome in the external granular layer, where neurogenesis takes place. Notably, biochemical analysis revealed that Cep152 was also present in the postsynaptic density fraction. Subsequent immunofluorescent analyses showed co-localization of Cep152 with excitatory synaptic markers, PSD95 and synaptophysin, but not with an inhibitory synaptic marker gephyrin in differentiated primary cultured hippocampal neurons. The obtained results suggest that Cep152 takes part not only in neurogenesis during corticogenesis but also in the regulation of synaptic function in differentiated neurons.

Relationship between Urinary Calcium Excretion and Lower Urinary Tract Symptoms.

To date, few detailed studies have been conducted on the convenient and useful markers for the prevalence of lower urinary tract symptoms (LUTS), including overactive bladder (OAB) and nocturia. A high level of calcium (Ca) excretion (hypercalciuria) is indicative of lifestyle-related diseases such as hypertension, which are associated with the onset of LUTS. Hence, in this study we attempted to clarify the relationship between urinary Ca excretion and OAB, nocturia, and nocturnal polyuria in adults. The present study showed that patients with hypercalciuria frequently experienced OAB, nocturia, and nocturnal polyuria. In addition, this study revealed that the severity of LUTS is significantly associated with urinary Ca excretion and that hypercalciuria is an important risk factor for OAB, nocturia, and nocturnal polyuria.

Impaired Function of PLEKHG2, a Rho-Guanine Nucleotide-Exchange Factor, Disrupts Corticogenesis in Neurodevelopmental Phenotypes.

Homozygosity of the p.Arg204Trp variation in the Pleckstrin homology and RhoGEF domain containing G2 (PLEKHG2) gene, which encodes a Rho family-specific guanine nucleotide-exchange factor, is responsible for microcephaly with intellectual disability. However, the role of PLEKHG2 during neurodevelopment remains unknown. In this study, we analyzed mouse Plekhg2 function during cortical development, both in vitro and in vivo. The p.Arg200Trp variant in mouse (Plekhg2-RW), which corresponds to the p.Arg204Trp variant in humans, showed decreased guanine nucleotide-exchange activity for Rac1, Rac3, and Cdc42. Acute knockdown of Plekhg2 using in utero electroporation-mediated gene transfer did not affect the migration of excitatory neurons during corticogenesis. On the other hand, silencing Plekhg2 expression delayed dendritic arbor formation at postnatal day 7 (P7), perhaps because of impaired Rac/Cdc42 and p21-activated kinase 1 signaling pathways. This phenotype was rescued by expressing an RNAi-resistant version of wildtype Plekhg2, but not of Plekhg2-RW. Axon pathfinding was also impaired in vitro and in vivo in Plekhg2-deficient cortical neurons. At P14, knockdown of Plekhg2 was observed to cause defects in dendritic spine morphology formation. Collectively, these results strongly suggest that PLEKHG2 has essential roles in the maturation of axon, dendrites, and spines. Moreover, impairment of PLEKHG2 function is most likely to cause defects in neuronal functions that lead to neurodevelopmental disorders.

Functions of CNKSR2 and Its Association with Neurodevelopmental Disorders.

The Connector Enhancer of Kinase Suppressor of Ras-2 (CNKSR2), also known as CNK2 or MAGUIN, is a scaffolding molecule that contains functional protein binding domains: Sterile Alpha Motif (SAM) domain, Conserved Region in CNK (CRIC) domain, PSD-95/Dlg-A/ZO-1 (PDZ) domain, Pleckstrin Homology (PH) domain, and C-terminal PDZ binding motif. CNKSR2 interacts with different molecules, including RAF1, ARHGAP39, and CYTH2, and regulates the Mitogen-Activated Protein Kinase (MAPK) cascade and small GTPase signaling. CNKSR2 has been reported to control the development of dendrite and dendritic spines in primary neurons. CNKSR2 is encoded by the CNKSR2 gene located in the X chromosome. CNKSR2 is now considered as a causative gene of the Houge type of X-linked syndromic mental retardation (MRXHG), an X-linked Intellectual Disability (XLID) that exhibits delayed development, intellectual disability, early-onset seizures, language delay, attention deficit, and hyperactivity. In this review, we summarized molecular features, neuronal function, and neurodevelopmental disorder-related variations of CNKSR2.