An unstable variant of GAP43 leads to neurodevelopmental deficiency

Multiple signaling pathways are thought to control the selective expression of genes over the course of neuronal differentiation. One approach to elucidating these pathways is to identify specific cis-acting elements that serve as the final targets for these signaling pathways in neural-specific genes. We now identify a novel repressive element from the growth-associated protein 43 (GAP-43) gene that can contribute to neuron-specific gene expression by inhibiting transcription in a wide range of non-neuronal cell types. This repressive element is located downstream of the GAP-43 TATA box and is highly position-dependent. When transferred to viral promoters this element preferentially inhibits transcription in non-neuronal cells. Electrophoretic mobility shift assays show that the repressive element comprises at least two protein recognition sites. One of these is a novel sequence motif that we designate the SNOG element, because it occurs downstream of the TATA boxes of the synaptosomal-associated protein of 25 kDa and neuronal nitric oxide synthase genes, as well as the GAP-43 gene. The GAP-43 repressive element is distinct in sequence and position dependence from the repressor element 1/neuron-restrictive silencer element previously described in other neural genes and therefore is a likely target for a distinct set of signaling pathways involved in the control of neuronal differentiation.

Focused Revision: ACMG practice resource: Genetic evaluation of short stature

To observe the effect of acupuncture serum on the expression of microtubule associated protein-2 (MAP-2) and nerve growth associated protein-43 (GAP-43) in cultured hippocampal neurons of convulsive rats. The acute convulsion model was induced by intraperitoneal injection of pentylenetetrazol in SD rats who were then randomized into model group and acupuncture group. Rats of the acupuncture group received manual acupuncture stimulation of "Baihui" (GV20) and "Dazhui" (GV14) for 30 min, once daily for 7 days. Then, the blood samples taken from the abdominal aorta of rats in the convulsion model and acupuncture groups were processed into serum samples, i.e. non-acupuncture serum and acupuncture se-rum. The primary-cultured hippocampal neurons of fetal rats were cultured for 10 days and then divided into normal extracellular fluid (normal) group, magnesium (Mg2+) free extracellular fluid group, acupuncture serum group and non-acupuncture serum group. At the 10th day, the neurons in the normal group were cultured continuously in extracellular fluid for 3 h, and then cultured in DMEM/F12(1∶1) medium (planting fluid); neurons in the Mg2+ free group were cultured in magnesium-free fluid medium to induce epileptic-like discharge; neurons in the acupuncture serum group were cultured in the mixed medium of planting fluid and 10% acupuncture serum; and neurons in the non-acupuncture serum were cultured in the mixed culture medium of planting fluid and non-acupuncture serum (10%). At last, these neurons in the above-mentioned groups were cultured in the magnesium-free extracellular fluid continuously for 2, 12 and 48 h, respectively, followed by detecting the expression levels of MAP-2 and GAP-43 proteins at the 3 time points by using immunofluorescence and Western blot, separately. The rate of MAP-2 positive cells and protein expression at 2, 12 and 48 h, and the rate of GAP-43 positive cells and protein expression at 12 and 48 h in the hippocampal neurons were significantly down-regulated in the Mg2+ free group in contrast to the normal group (P<0.05，P<0.01). Compared to the Mg2+ free group, the rates of MAP-2 and GAP-43 positive cells and protein expression at 2, 12 and 48 h were considerably up-regulated in the acupuncture serum group (P<0.05，P<0.01), but not in the non-acupuncture serum group (P>0.05). Acupuncture serum can significantly up-regulate the expression of MAP-2 and GAP-43 proteins in hip-pocampal neurons, which may play a positive role in improving synaptic plasticity and neuronal damage in convulsion rats.

Tissue-specific gene transcription can be determined by the use of either positive-acting or negative-acting DNA regulatory elements. We have analyzed a promoter from the growth-associated protein 43 (GAP-43) gene and found that it uses both of these mechanisms to achieve its high degree of neuron-specific activity. Two novel transcription factor binding sites, designated Cx1 and Cx2, drive promoter activity in neurons from developing cerebral cortex but not in several other cell types. The promoter also contains an activator protein 1 (AP-1) site that contributes to activity in neurons. The AP-1 site can drive promoter activity in a wide range of non-neuronal cells that express little or no endogenous GAP-43, but only in the absence of a tissue-specific repressive element located downstream of the GAP-43 TATA box. These findings suggest that the GAP-43 repressive element plays an important role in allowing AP-1 signaling pathways to modulate activity of the GAP-43 gene in neurons, without also causing inappropriate activation by AP-1 transcription factors in other cell types.

Colocalization of CB 1 receptors with L1 and GAP-43 in forebrain white matter regions during fetal rat brain development: Evidence for a role of these receptors in axonal growth and guidance

Objective To evaluate the influence of sevoflurane anesthesia on the expression of growth-associated protein 43(GAP-43)and neural cell adhesion molecule(NCAM)in hippocampal neurons of neonatal rats. Methods Thirty-six pathogen-free Sprague-Dawley rats, aged 7 weeks, weighing 15-20 g, were randomly divided into 4 groups(n=9 each)using a random number table: control group(C group), 1.5% sevoflurane 6 h group(L group), 3% sevoflurane 2 h group(H1 group)and 3% sevoflurane 6 h group(H2 group). Group L inhaled 1.5% sevoflurane in oxygen for 6 h. H1 and H2 groups inhaled 3% sevoflurane in oxygen for 2 and 6 h, respectively.Group C inhaled 30% oxygen only.When the neonatal rats were 14 days old, the rats underwent Morris water maze test for 7 consecutive days.Place navigation and spatial probe tests were carried out.After the end of Morris water maze test, the rats were sacrificed, and the hippocampus was obtained for determination of the expression of GAP-43 and NCAM in hippocampal neurons. Results Compared with group C, the escape latency was significantly prolonged, the time of staying at the original platform quadrant was shortened, and the expression of GAP-43 was down-regulated in L, H1 and H2 groups, and the frequency of crossing the original platform was decreased in L and H2 groups.There was no significant difference in NCAM expression among the four groups. Conclusion The mechanism by which sevoflurane anesthesia decreases the cognitive function may be related to down-regulated expression of GAP-43, but not related to NCAM expression in hippocampal neurons of neonatal rats. Key words: Anesthetics, inhalation; Anesthesia; Infant; Cognition disorders; GAP-43 protein; Neural cell adhesion molecules; Hippocampus; Neurons

Objective To analyze the clinical and biochemical, as well as genetic characteristics of a patient with Wiedemann-Steiner syndrome (WDSTS). Methods The clinical data of a patient with WDSTS were collected. The patient was treated with recombinant human growth hormone (rhGH) combined with gonadotrophine-releasing hormone agonist (GnRHa). Blood samples of the patient and her parents were taken for whole-Exome Sequencing (WES). Relevant literatures about KMT2A mutations were reviewed. Results The 5-year old girl presented with growth retardation, with height 100 cm (-2.4 SD), torpid reaction, and facial anomalies including low hairline, thick eyebrow and hair, hypertelorism, a wide nasal bridge. She had small and puffy hands and feet, excessive hair around back of neck, bilateral forearm and lower limbs. Her GH peak level was 26.6 ng/ml during GH stimulation test. She was re-examined at the age of 10.4 years, with severe short stature (120 cm/-3.58 SD) and a Tanner stage 2 of breast development. Her bone age was found to be approximately 11.4 years. Height increased from 120 cm at the age of 10.4 years to 147.3 cm after rhGH treatment combined with GnRHa for 2.5 years. rhGH therapy alone continued for 1.1 years and a height of 150 cm was reached at the age of 14.9 years, with bone age 14 years. Gene sequencing revealed a de novo frameshift mutation (c.10051delA, p. Thr3351Leufs*17) of exon 27 in KMT2A gene of the patient, but without any mutation in her parents. Through a literature review, seventy-one patients with WDSTS (including present case) presented with intellectual disability(70/71), facial anomalies (70/71), short stature (50/71), and hypertrichosis(39/71). Conclusion Patients presented with short stature, typical facial dysmorphism, intellectual disability, and hypertrichosis should be considered for WDSTS. The mutation p. Thr3351Leufs*17 in the KMT2A gene detected in our patient is a novel mutation. This is so far the first report of WDSTS patient who was successfully treated with a combination of GH and GnRHa at the onset of puberty to improve her adult height. Key words: Wiedemann-Steiner syndrome; KMT2A gene; Short stature; Hypertrichosis; Therapy

KLHL13 functional defects cause neurodevelopmental disorder in humans that can be rescued via inhibition of AURKB in cellular and animal models.

Intellectual disability (ID) is a group of neurodevelopmental disorders with high heterogeneous in both genotypes and phenotypes and its definitive diagnosis is increasingly dependent ongenome-wide molecular diagnostics.Based on next generation sequencing(NGS), panel sequencing, whole exome sequencing (WES) and even whole genome sequencing are well applied to the molecular diagnosis of ID. Based on these, we recommend WES, especially trio-WES as the preferred detection method. NGS data analysis and reanalysis for ID have clinical significance for diagnosis, and can detect small scale variation and copy number variation in the genome reliably. Therefore, it has the potential to become the next recommended molecular diagnostic toolfor ID. Key words: Intellectual disability; Next generation sequencing; Whole exome sequencing; Mutation

KBG syndrome is a rare autosomal dominant disorder caused by ANKRD11 variants, characterized by distinctive craniofacial features, short stature, skeletal anomalies, and neurodevelopmental impairment. Regional studies, particularly from underrepresented populations, are essential to broaden the clinical and molecular spectrum of the syndrome. We retrospectively analyzed the clinical, molecular, and anthropometric data of 23 Turkish individuals with molecularly confirmed KBG syndrome. Molecular analyses included whole exome sequencing, clinical exome sequencing, and targeted gene panels. Variants were classified according to ACMG guidelines, and phenotypic features were systematically assessed using standardized criteria. Eighteen distinct ANKRD11 pathogenic or likely pathogenic variants were identified, including eight novel variants, predominantly located in exon 9. Short stature (height SDS < -2) was documented in 30.4% of patients. Intellectual disability was observed in 82.6%, and behavioral anomalies in 52.2% of the cohort. Craniofacial dysmorphism, including long philtrum, triangular facial shape, and macrodontia, was prominent. No genotype-phenotype correlation could be established. This study expands the mutational landscape of ANKRD11 and underscores the clinical variability of KBG syndrome in a Turkish cohort. Our findings emphasize the importance of integrating molecular and detailed clinical evaluations for early diagnosis, especially in diverse populations with limited prior representation.

The telomerase reverse transcriptase protein, TERT, is expressed in the adult brain and its exogenic expression protects neurons from oxidative stress and from the cytotoxicity of amyloid beta (Aβ). We previously showed that telomerase increasing compounds (AGS) protected neurons from oxidative stress. Therefore, we suggest that increasing TERT by AGS may protect neurons from the Aβ-induced neurotoxicity by influencing genes and factors that participate in neuronal survival and plasticity. Here we used a primary hippocampal cell culture exposed to aggregated Aβ and hippocampi from adult mice. AGS treatment transiently increased TERT gene expression in hippocampal primary cell cultures in the presence or absence of Aβ and protected neurons from Aβ induced neuronal degradation. An increase in the expression of Growth associated protein 43 (GAP43), and Feminizing locus on X-3 genes (NeuN), in the presence or absence of Aβ, and Synaptophysin (SYP) in the presence of Aβ was observed. GAP43, NeuN, SYP, Neurotrophic factors (NGF, BDNF), beta-catenin and cyclin-D1 expression were increased in the hippocampus of AGS treated mice. This data suggests that increasing TERT by pharmaceutical compounds partially exerts its neuroprotective effect by enhancing the expression of neurotrophic factors and neuronal plasticity genes in a mechanism that involved Wnt/beta-catenin pathway.

Neonatal ketamine exposure results in changes in biochemical substrates of neuronal growth and synaptogenesis, and alters adult behavior irreversibly

Medications acting as mood stabilizers work by enhancing and maintaining the concentration of circulating synaptic neurotransmitters, which then activate a plethora of various intracellular signal transduction and second messenger cascades. Previously, we showed that two of these cascades, the PI-3K and MAPK pathways, are activated by cross-talk with the protein kinase A cAMP cascade and by brain-derived neurotrophic factor (BDNF), an immediate-early gene whose expression is the result of phosphorylation of the transcription factor, cAMP response element binding protein (CREB). In the current study, we extend these findings to include the protein kinase C (PKC) pathway. Western blotting studies show that application of norepinephrine to cultured hippocampal neurons leads to increased expression of BDNF, phosphorylation of CREB, activation of growth-associated protein-43 (GAP-43) and activation of PKCμ and PKCt538. Because GAP-43 is a putative substrate for PKC, the results of this study lend further support of a G-protein coupled receptor cross-talking to an entirely distinct intracellular pathway that is known to be involved in neuritogenesis.

BackgroundNeuroanatomical defects are often present in children with severe developmental delay and intellectual disabilities. Few genetic loci have been associated with disorders of neurodevelopment. Our objective of the present study...

The etiology of intellectual disabilities (ID) remains unknown for the majority of patients. Due to reduced reproductive fitness in many individuals with ID, de novo mutations account for a significant portion of severe ID. The ATP-dependent SWI/SNF chromatin modifier has been linked with neurodevelopmental disorders including ID and autism. ARID2 is an intrinsic component of polybromo-associated BAF (PBAF), the SWI/SNF subcomplex. In this study, we used clinical whole exome sequencing (WES) in proband-parent-trios to identify the etiology of ID. We identified four independent, novel, loss of function variants in ARID2 gene in four patients, three of which were confirmed to be de novo. The patients all have ID and share other clinical characteristics including attention deficit hyperactivity disorder, short stature, dysmorphic facial features, and Wormian bones. All four novel variants are predicted to lead to a premature termination with the loss of the two conservative zinc finger motifs. This is the first report of mutations in ARID2 associated with developmental delay and ID.