Neural Tube Closure Defects Research Articles

ADNP Differential Nucleus/Cytoplasm Localization in Neurons Suggests Multiple Roles in Neuronal Differentiation and Maintenance

Complete deficiency in activity-dependent neuroprotective protein (ADNP) results in neural tube closure defects and death at gestation day 9 in mice. ADNP-deficient embryos exhibit dramatic increases in gene transcripts associated with lipid metabolism coupled to reduction in organogenesis/neurogenesis-related transcripts. In the pluripotent teratocarcinoma cell line P19, ADNP was shown to interact with specific chromatin regions in the neurodifferentiated state, which was associated with binding to the heterochromatin protein 1 alpha. In this study, using P19 cells as a differentiation model, we showed that ADNP expression and cytoplasm/nucleus distribution is unique in neuronal-differentiated cells compared to cardiovascular and nondifferentiated pluripotent cells. ADNP-like immunohistochemical localization to the neuronal cytoplasm and neurites was shown in this study not only in the cellular model but also in the brain cerebral cortex and olfactory bulb. Small hairpin RNA ADNP downregulation was used to further investigate ADNP involvement in p19 neurodifferentiation. An approximately 80% robust reduction in ADNP led to a substantial reduction in embryoid body formation and a significant reduction (approximately 50%) in neurite numbers. These results position ADNP in direct association with neuronal cell differentiation and maturation.

Activity-dependent Neuroprotective Protein Constitutes a Novel Element in the SWI/SNF Chromatin Remodeling Complex

Complete deficiency in activity-dependent neuroprotective protein (ADNP), a heterochromatin 1-binding protein, results in dramatic changes in gene expression, neural tube closure defects, and death at gestation day 9 in mice. To further understand the cellular roles played by ADNP, the HEK293 human embryonic kidney cell line that allows efficient transfection with recombinant DNA was used as a model for the identification of ADNP-interacting proteins. Recombinant green fluorescent protein (GFP)-ADNP was localized to cell nuclei. When nuclear extracts were subjected to immunoprecipitation with specific GFP antibodies followed by polyacrylamide gel electrophoresis, several minor protein bands were observed in addition to GFP-ADNP. In-gel protein digests followed by mass spectrometry identified BRG1, BAF250a, and BAF170, all components of the SWI/SNF (mating type switching/sucrose nonfermenting) chromatin remodeling complex, as proteins that co-immunoprecipitate with ADNP. These results were verified utilizing BRG1 antibodies. ADNP short hairpin RNA down-regulation resulted in microtubule reorganization and changes in cell morphology including reduction in cell process formation and cell number. These morphological changes are closely associated with the SWI/SNF complex multifunctionality. Taken together, the current study uncovers a molecular basis for the essential function of the ADNP gene and protein.

Transcription factor TEAD2 is involved in neural tube closure.

TEAD2, one of the first transcription factors expressed at the beginning of mammalian development, appears to be required during neural development. For example, Tead2 expression is greatest in the dorsal neural crest where it appears to regulate expression of Pax3, a gene essential for brain development. Consistent with this hypothesis, we found that inactivation of the Tead2 gene in mice significantly increased the risk of exencephaly (a defect in neural tube closure). However, none of the embryos exhibited spina bifida, the major phenotype of Pax3 nullizygous embryos, and expression of Pax3 in E11.5 Tead2 nullizygous embryos was normal. Thus, Tead2 plays a role in neural tube closure that is independent of its putative role in Pax3 regulation. In addition, the risk of exencephaly was greatest with Tead2 nullizygous females, and could be suppressed either by folic acid or pifithrin-alpha. These results reveal a maternal genetic contribution to neural tube closure, and suggest that Tead2-deficient mice provide a model for anencephaly, a common human birth defect that can be prevented by folic acid.

Generation of a Twist1 conditional null allele in the mouse

Twist1 is the mouse ortholog of TWIST1, the human gene mutated in Saethre-Chotzen syndrome. Previously, a Twist1 null allele was generated by gene targeting in mouse embryonic stem cells. Twist1 heterozygous mice develop polydactyly and a craniofacial phenotype similar to Saethre-Chotzen patients. Mice homozygous for the Twist1 null allele die around embryonic day 11.5 (E11.5) with cranial neural tube closure and vascular defects, hindering in vivo studies of Twist1 function at later stages of development. Here, we report the generation of a Twist1 conditional null allele in mice that functions like a wild-type allele but can be converted to a null allele upon Cre-mediated recombination.

Disruption of palladin leads to defects in definitive erythropoiesis by interfering with erythroblastic island formation in mouse fetal liver

AbstractPalladin was originally found up-regulated with NB4 cell differentiation induced by all-trans retinoic acid. Disruption of palladin results in neural tube closure defects, liver herniation, and embryonic lethality. Here we further report that Palld−/− embryos exhibit a significant defect in erythropoiesis characterized by a dramatic reduction in definitive erythrocytes derived from fetal liver but not primitive erythrocytes from yolk sac. The reduction of erythrocytes is accompanied by increased apoptosis of erythroblasts and partial blockage of erythroid differentiation. However, colony-forming assay shows no differences between wild-type (wt) and mutant fetal liver or yolk sac in the number and size of colonies tested. In addition, Palld−/− fetal liver cells can reconstitute hematopoiesis in lethally irradiated mice. These data strongly suggest that deficient erythropoiesis in Palld−/− fetal liver is mainly due to a compromised erythropoietic microenvironment. As expected, erythroblastic island in Palld−/− fetal liver was found disorganized. Palld−/− fetal liver cells fail to form erythroblastic island in vitro. Interestingly, wt macrophages can form such units with either wt or mutant erythroblasts, while mutant macrophages lose their ability to bind wt or mutant erythroblasts. These data demonstrate that palladin is crucial for definitive erythropoiesis and erythroblastic island formation and, especially, required for normal function of macrophages in fetal liver.

PIP5KIγ is required for cardiovascular and neuronal development

All eukaryotic cells contain the phospholipid phosphatidylinositol 4, 5-bisphosphate (PIP2) that serves multiple roles in signal transduction cascades. Type I phosphatidylinositol-4-phosphate 5-kinase (PIP5KI) catalyzes the synthesis of PIP2 by phosphorylating phosphatidylinositol 4 phosphate. Although the classical isoforms of PIP5KI (designated as alpha, beta, and gamma) all generate the same phospholipid product, they have significantly dissimilar primary structures and expression levels in different tissues, and they appear to localize within different compartments within the cell. Therefore, it appears likely that PIP5KI isoforms have overlapping, but not identical, functions. Here we show that targeted disruption of PIP5KIgamma causes widespread developmental and cellular defects. PIP5KIgamma-null embryos have myocardial developmental defects associated with impaired intracellular junctions that lead to heart failure and extensive prenatal lethality at embryonic day 11.5 of development. Loss of PIP5KIgamma also results in neural tube closure defects that were associated with impaired PIP2 production, adhesion junction formation, and neuronal cell migration. These data, along with those of other PIP5KI isoforms, indicate that individual PIP5KI isoenzymes fulfill specific roles in embryonic development.

Lack of endothelial cell survivin causes embryonic defects in angiogenesis, cardiogenesis, and neural tube closure

AbstractWe explored the physiologic role of endothelial cell apoptosis during development by generating mouse embryos lacking the inhibitor of apoptosis protein (IAP) survivin in endothelium. This was accomplished by intercrossing survivinlox/lox mice with mice expressing cre recombinase under the control of the endothelial cell specific tie1 promoter (tie1-cre mice). Lack of endothelial cell survivin resulted in embryonic lethality. Mutant embryos had prominent and diffuse hemorrhages from embryonic day 9.5 (E9.5) and died before E13.5. Heart development was strikingly abnormal. Survivin-null endocardial lineage cells could not support normal epithelial-mesenchymal transformation (EMT), resulting in hypoplastic endocardial cushions and in utero heart failure. In addition, 30% of mutant embryos had neural tube closure defects (NTDs) that were not caused by bleeding or growth retardation, but were likely due to alterations in the release of soluble factors from endothelial cells that otherwise support neural stem cell proliferation and neurulation. Thus, regulation of endothelial cell survival, and maintenance of vascular integrity by survivin are crucial for normal embryonic angiogenesis, cardiogenesis, and neurogenesis.

Evidence for Small Ubiquitin-like Modifier-dependent Nuclear Import of the Thymidylate Biosynthesis Pathway

Perturbations in folate-mediated one-carbon metabolism increase rates of uracil misincorporation into DNA during replication, impair cellular methylation reactions, and increase risk for neural tube defects and cancer. One-carbon metabolism is compromised by folate deficiency and common genetic polymorphisms. In this study, the mechanism for the preferential partitioning of cytoplasmic serine hydroxymethyltransferase (cSHMT)-derived methylenetetrahydrofolate to de novo thymidylate biosynthesis was investigated. The cSHMT enzyme was shown to interact with UBC9 and was a substrate for UBC9-catalyzed small ubiquitin-like modifier (SUMO) modification in vitro. SUMOylated cSHMT was detected in extracts from S phase MCF-7 cells, and cSHMT was shown to localize to the nucleus and nuclear periphery during the S and G(2)/M phases of the cell cycle. A common single nucleotide polymorphism (L474F-cSHMT) impaired the UBC9-cSHMT interaction and inhibited cSHMT SUMOylation in vitro. The three folate-dependent enzymes that constitute the de novo thymidylate biosynthesis pathway, cSHMT, thymidylate synthase, and dihydrofolate reductase, all contain SUMO modification consensus sequences. Compartmentation of the folate-dependent de novo thymidylate biosynthesis pathway in the nucleus accounts for the preferential partitioning of cSHMT-derived folate-activated one-carbon units into thymidylate biosynthesis; the efficiency of nuclear folate metabolism is likely to be modified by the cSHMT L474F polymorphism.

Loss of Gcn5 Acetyltransferase Activity Leads to Neural Tube Closure Defects and Exencephaly in Mouse Embryos

Gcn5 was the first transcription-related histone acetyltransferase (HAT) to be identified. However, the functions of this enzyme in mammalian cells remain poorly defined. Deletion of Gcn5 in mice leads to early embryonic lethality with increased apoptosis in mesodermal lineages. Here we show that deletion of p53 allows Gcn5(-/-) embryos to survive longer, but Gcn5(-/-) p53(-/-) embryos still die in midgestation. Interestingly, embryos homozygous for point mutations in the Gcn5 catalytic domain survive significantly longer than Gcn5(-/-) or Gcn5(-/-) p53(-/-) mice. In contrast to Gcn5(-/-) embryos, Gcn5(hat/hat) embryos do not exhibit increased apoptosis but do exhibit severe cranial neural tube closure defects and exencephaly. Together, our results indicate that Gcn5 has important, HAT-independent functions in early development and that Gcn5 acetyltransferase activity is required for cranial neural tube closure in the mouse.

Plexin-B2 Controls the Development of Cerebellar Granule Cells

Cerebellar granule cell progenitors proliferate postnatally in the upper part of the external granule cell layer (EGL) of the cerebellum. Postmitotic granule cells differentiate and migrate, tangentially in the EGL and then radially through the molecular and Purkinje cell layers. The molecular control of the transition between proliferation and differentiation in cerebellar granule cells is poorly understood. We show here that the transmembrane receptor Plexin-B2 is expressed by proliferating granule cell progenitors. To study Plexin-B2 function, we generated a targeted mutation of mouse Plexin-B2. Most Plexin-B2(-/-) mutants die at birth as a result of neural tube closure defects. Some mutants survive but their cerebellum cytoarchitecture is profoundly altered. This is correlated with a disorganization of the timing of granule cell proliferation and differentiation in the EGL. Many differentiated granule cells migrate inside the cerebellum and keep proliferating. These results reveal that Plexin-B2 controls the balance between proliferation and differentiation in granule cells.

Sphingosine Kinase Type 2 Activation by ERK-mediated Phosphorylation

Sphingosine 1-phosphate (S1P), a potent lipid mediator, is a ligand for a family of five G protein-coupled receptors (S1P(1-5)) that have been shown to regulate a variety of biological responses important for cancer progression. The cellular level of S1P is low and tightly regulated in a spatio-temporal manner through its synthesis catalyzed by two sphingosine kinases, denoted SphK1 and SphK2. Many stimuli activate and translocate SphK1 to the plasma membrane by mechanisms that are dependent on its phosphorylation. Much less is known about activation of SphK2. Here we demonstrate that epidermal growth factor (EGF) as well as the protein kinase C activator, phorbol ester, induce rapid phosphorylation of hSphK2 which was markedly reduced by inhibition of MEK1/ERK pathway. Down-regulation of ERK1 blocked EGF-induced phosphorylation of SphK2. Recombinant ERK1 phosphorylated hSphK2 in vitro and increased its enzymatic activity. ERK1 also was found to be in a complex with hSphK2 in vivo. Site-directed mutagenesis indicated that hSphK2 is phosphorylated on Ser-351 and Thr-578 by ERK1 and that phosphorylation of these residues is important for EGF-stimulated migration of MDA-MB-453 cells. These studies provide the first clues to the mechanism of agonist-mediated SphK2 activation and enhance understanding of the regulation of SphK2 activity by phosphorylation and its role in movement of human breast cancer cells toward EGF.

Expression of p53/hgf/c-met/STAT3 signal in fetuses with neural tube defects

Neural tube defects (NTD) are morphogenetic alterations due to a defective closure of neural tube. Hepatocyte growth factor (HGF)/c-met system plays a role in morphogenesis of nervous system, lung, and kidney. HGF/c-met morphogenetic effects are mediated by signal transducers and activators of transcription (STAT)3 and both HGF and c-met genes are regulated from p53. The aim of our study was to analyze mRNA and protein expressions of p53, HGF, c-met, and STAT3 in fetuses with NTD. By reverse transcriptase-polymerase chain reaction and immunohistochemistry, we analyzed neural tissues from four NTD fetuses and the corresponding non-malformed lungs, kidneys and placentas. We found a reduced mRNA expression of HGF/c-met/STAT3 pathway, in the malformed nervous systems and placentas. The reduced expression of this pathway correlated with the absence of p53 in all these samples. On the contrary, detectable expression levels of p53, HGF, c-met, and STAT3 were observed in non-malformed lungs and kidneys obtained from the same fetuses. Comparable results were obtained by immunohistochemistry, with the exception of p53, which was undetected in all fetal tissues. In conclusion, in NTD fetuses, both the defective neural tube tissue and the placenta have a reduction in all components of the p53/HGF/c-met/STAT3 cascade. This raises the possibility of using the suppression of these genes for early diagnosis of NTD especially on chorionic villus sampling.

Mouse mutants with neural tube closure defects and their role in understanding human neural tube defects

The number of mouse mutants and strains with neural tube closure defects (NTDs) now exceeds 190, including 155 involving known genes, 33 with unidentified genes, and eight "multifactorial" strains. The emerging patterns of mouse NTDs are considered in relation to the unknown genetics of the common human NTDs, anencephaly, and spina bifida aperta. Of the 150 mouse mutants that survive past midgestation, 20% have risk of either exencephaly and spina bifida aperta or both, parallel to the majority of human NTDs, whereas 70% have only exencephaly, 5% have only spina bifida, and 5% have craniorachischisis. The primary defect in most mouse NTDs is failure of neural fold elevation. Most null mutations (>90%) produce syndromes of multiple affected structures with high penetrance in homozygotes, whereas the "multifactorial" strains and several null-mutant heterozygotes and mutants with partial gene function (hypomorphs) have low-penetrance nonsyndromic NTDs, like the majority of human NTDs. The normal functions of the mutated genes are diverse, with clusters in pathways of actin function, apoptosis, and chromatin methylation and structure. The female excess observed in human anencephaly is found in all mouse exencephaly mutants for which gender has been studied. Maternal agents, including folate, methionine, inositol, or alternative commercial diets, have specific preventative effects in eight mutants and strains. If the human homologs of the mouse NTD mutants contribute to risk of common human NTDs, it seems likely to be in multifactorial combinations of hypomorphs and low-penetrance heterozygotes, as exemplified by mouse digenic mutants and the oligogenic SELH/Bc strain.

Activity-dependent neuroprotective protein (ADNP) differentially interacts with chromatin to regulate genes essential for embryogenesis

Complete deficiency in activity-dependent neuroprotective protein (ADNP) results in neural tube closure defects and death at days 8.5–9.5 of gestation in the mouse (E8.5–9.5). To elucidate ADNP associated pathways, Affymetrix 22,690-oligonucleotide-based microarrays were used on ADNP knockout and control mouse embryos (E9) separated completely from extra embryonic tissue. Marked differences in expression profiles between ADNP-deficient embryos and ADNP-expressing embryos were discovered. Specifically, a group of dramatically up-regulated gene transcripts in the ADNP-deficient embryos were clustered into a family encoding for proteins enriched in the visceral endoderm such as apolipoproteins, cathepsins and methallotionins. In contrast, a down regulated gene cluster associated with ADNP-deficiency in the developing embryo consisted of organogenesis markers including neurogenesis ( Ngfr, neurogenin1, neurod1) and heart development ( Myl2). The pluripotent P19 cells were used for ADNP-chromatin-immunoprecipitation, showing direct interactions with multiple relevant gene promoters including members of the up-regulated as well as the down-regulated gene clusters. A comparison between non-differentiated and neuro-differentiated P19 cells revealed increased chromatin interaction of ADNP with chromatin from differentiated cells. These results place ADNP at a crucial point of gene regulation, repressing potential endoderm genes and enhancing genes associated with organogenesis/neurogenesis.

The folate metabolic enzyme ALDH1L1 is restricted to the midline of the early CNS, suggesting a role in human neural tube defects

Folate supplementation prevents up to 70% of human neural tube defects (NTDs), although the precise cellular and metabolic sites of action remain undefined. One possibility is that folate modulates the function of metabolic enzymes expressed in cellular populations involved in neural tube closure. Here we show that the folate metabolic enzyme ALDH1L1 is cell-specifically expressed in PAX3-negative radial glia at the midline of the neural tube during early murine embryogenesis. Midline restriction is not a general property of this branch of folate metabolism, as MTHFD1 displays broad and apparently ubiquitous expression throughout the neural tube. Consistent with previous work showing antiproliferative effects in vitro, ALDH1L1 upregulation during central nervous system (CNS) development correlates with reduced proliferation and most midline ALDH1L1(+) cells are quiescent. These data provide the first evidence for localized differences in folate metabolism within the early neural tube and suggest that folate might modulate proliferation via effects on midline Aldh1l1(+) cells. To begin addressing its role in neurulation, we analyzed a microdeletion mouse strain lacking Aldh1l1 and observed neither increased failure of neural tube closure nor detectable proliferation defects. Although these results indicate that loss-of-function Aldh1l1 mutations do not impair these processes in mice, the specific midline expression of ALDH1L1 and its ability to dominantly suppress proliferation in a folate responsive manner may suggest that mutations contributing to disease are gain-of-function, rather than loss-of-function. Moreover, a role for loss-of-function mutations in human NTDs remains possible, as Mthfr null mice do not develop NTDs even though MTHFR mutations increase human NTD risk.

Essential role of RGS-PX1/sorting nexin 13 in mouse development and regulation of endocytosis dynamics.

RGS-PX1 (also known as sorting nexin 13) is a member of both the regulator of G protein signaling (RGS) and sorting nexin (SNX) protein families. Biochemical and cell culture studies have shown that RGS-PX1/SNX13 attenuates Galphas-mediated signaling through its RGS domain and regulates endocytic trafficking and degradation of the epidermal growth factor receptor. To understand the functions of RGS-PX1/SNX13 in vivo, we generated mice carrying targeted mutations of Snx13 and found that systemic Snx13-null mice were embryonic lethal around midgestation. Snx13-null embryos had significant overall growth retardation and defects in neural tube closure, blood vessel formation, and the formation of the placental labyrinthine layer. Moreover, the Snx13-null visceral yolk sac endoderm cells showed dramatic changes in the organization of endocytic compartments, abundant autophagic vacuoles, and abnormal localization of several endocytic markers, including megalin, a receptor for nutrients and proteins; ARH, a coat protein that binds megalin; LAMP2; and LC3. These changes suggest that Snx13-null embryos are defective in nutrient uptake and transport, which may contribute to the other developmental abnormalities observed. Taken together, our findings demonstrate an essential role for RGS-PX1/SNX13 in mouse development and provide previously undescribed insights into its cellular function in the regulation of endocytosis dynamics.

Isoform-Specific Regulation of the Actin-Organizing Protein Palladin during TGF-β1-Induced Myofibroblast Differentiation

Contractile myofibroblasts are responsible for remodeling of extracellular matrix during wound healing; however, their continued activity results in various fibrocontractive diseases. Conversion of fibroblasts into myofibroblasts is induced by transforming growth factor-beta1 (TGF-beta1) and is hallmarked by the neo-expression of alpha-smooth muscle actin (alpha-SMA), a commonly used myofibroblast marker. Moreover, myofibroblast differentiation and acquisition of the contractile phenotype involves functionally important alterations in the expression of actin-organizing proteins. We investigated whether myofibroblast differentiation is accompanied by changes in the expression of palladin, a cytoskeletal protein that controls stress fiber integrity. Palladin is expressed as several isoforms, including major 3Ig (90 kDa) and 4Ig (140 kDa) forms that differ in their N-terminal sequence. Expression of the 4Ig isoform is strongly induced in fibroblast stress fibers upon TGF-beta1 treatment preceding alpha-SMA upregulation. TGF-beta1 induced upregulation of palladin is mediated both by Smad and mitogen-activated protein kinase pathways. Furthermore, palladin 4Ig-isoform is co-expressed with alpha-SMA in vivo in experimental rat wounds and in human myofibroblast-containing lesions. Taken together these results identify palladin 4Ig as a novel marker of myofibroblast conversion in vitro and in vivo. They also provide for the first time information about the signaling cascades involved in the regulation of palladin expression.

Knockout of Slc25a19 causes mitochondrial thiamine pyrophosphate depletion, embryonic lethality, CNS malformations, and anemia

SLC25A19 mutations cause Amish lethal microcephaly (MCPHA), which markedly retards brain development and leads to alpha-ketoglutaric aciduria. Previous data suggested that SLC25A19, also called DNC, is a mitochondrial deoxyribonucleotide transporter. We generated a knockout mouse model of Slc25a19. These animals had 100% prenatal lethality by embryonic day 12. Affected embryos at embryonic day 10.5 have a neural-tube closure defect with ruffling of the neural fold ridges, a yolk sac erythropoietic failure, and elevated alpha-ketoglutarate in the amniotic fluid. We found that these animals have normal mitochondrial ribo- and deoxyribonucleoside triphosphate levels, suggesting that transport of these molecules is not the primary role of SLC25A19. We identified thiamine pyrophosphate (ThPP) transport as a candidate function of SLC25A19 through homology searching and confirmed it by using transport assays of the recombinant reconstituted protein. The mitochondria of Slc25a19(-/-) and MCPHA cells have undetectable and markedly reduced ThPP content, respectively. The reduction of ThPP levels causes dysfunction of the alpha-ketoglutarate dehydrogenase complex, which explains the high levels of this organic acid in MCPHA and suggests that mitochondrial ThPP transport is important for CNS development.

Evaluation of the cranial base in amnion rupture sequence involving the anterior neural tube: Implications regarding recurrence risk

Amniotic bands can cause disruption of the cranial end of the developing fetus, leading in some cases to a neural tube closure defect. Although recurrence for unaffected parents of an affected child with a defect in which the neural tube closed normally but was subsequently disrupted by amniotic bands is negligible; for a primary defect in closure of the neural tube to which amnion has subsequently adhered, recurrence risk is 1.7%. In that primary defects of neural tube closure are characterized by typical abnormalities of the base of the skull, evaluation of the cranial base in such fetuses provides an approach for making a distinction between these 2 mechanisms. This distinction has implications regarding recurrence risk. The skull base of 2 fetuses with amnion rupture sequence involving the cranial end of the neural tube were compared to that of 1 fetus with anencephaly as well as that of a structurally normal fetus. The skulls were cleaned, fixed in 10% formalin, recleaned, and then exposed to 10% KOH solution. After washing and recleaning, the skulls were exposed to hydrogen peroxide for bleaching and photography. Despite involvement of the anterior neural tube in both fetuses with amnion rupture sequence, in Case 3 the cranial base was normal while in Case 4 the cranial base was similar to that seen in anencephaly. This technique provides a method for determining the developmental pathogenesis of anterior neural tube defects in cases of amnion rupture sequence. As such, it provides information that can be used to counsel parents of affected children with respect to recurrence risk.

The tumor suppressor protein p53 is required for neurite outgrowth and axon regeneration

Axon regeneration is substantially regulated by gene expression and cytoskeleton remodeling. Here we show that the tumor suppressor protein p53 is required for neurite outgrowth in cultured cells including primary neurons as well as for axonal regeneration in mice. These effects are mediated by two newly identified p53 transcriptional targets, the actin-binding protein Coronin 1b and the GTPase Rab13, both of which associate with the cytoskeleton and regulate neurite outgrowth. We also demonstrate that acetylation of lysine 320 (K320) of p53 is specifically involved in the promotion of neurite outgrowth and in the regulation of the expression of Coronin 1b and Rab13. Thus, in addition to its recognized role in neuronal apoptosis, surprisingly, p53 is required for neurite outgrowth and axonal regeneration, likely through a different post-translational pathway. These observations may suggest a novel therapeutic target for promoting regenerative responses following peripheral or central nervous system injuries.