L1 Cell Adhesion Molecule Gene Research Articles

Functional study of a rare L1CAM gene c.1759G>C variant prove its pathogenicity.

L1 syndrome, a neurological disorder with an X-linked inheritance pattern, mainly results from mutations occurring in the L1 cell adhesion molecule (L1CAM) gene. The L1CAM molecule, belonging to the immunoglobulin (Ig) superfamily of neurocyte adhesion molecules, plays a pivotal role in facilitating intercellular signal transmission across membranes and is indispensable for proper neuronal development and function. This study identified a rare missense variant (c.1759G>C; p.G587R) in the L1CAM gene within a male fetus presenting with hydrocephalus. Due to a lack of functional analysis, the significance of the L1CAM mutation c.1759G>C (p.G587R) remains unknown. We aimed to perform further verification for its pathogenicity. Blood samples were obtained from the proband and his parents for trio clinical exome sequencing and mutation analysis. Expression level analysis was conducted using western blot techniques. Immunofluorescence was employed to investigate L1CAM subcellular localization, while cell aggregation and cell scratch assays were utilized to assess protein function. The study showed that the mutation (c.1759G>C; p.G587R) affected posttranslational glycosylation modification and induced alterations in the subcellular localization of L1-G587R in the cells. It resulted in the diminished expression of L1CAM on the cell surface and accumulation in the endoplasmic reticulum. The p.G587R altered the function of L1CAM protein and reduced homophilic adhesion capacity of proteins, leading to impaired adhesion and migration of proteins between cells. Our findings provide first biological evidence for the association between the missense mutation (c.1759G>c; p.G587R) in the L1CAM gene and L1 syndrome, confirming the pathogenicity of this missense mutation.

L1 Syndrome-Associated Phenotypes and a Novel L1CAM Variant: A Clinical Report

AbstractL1 syndrome is a group of X-linked diseases caused by pathogenic variants in the human L1 cell adhesion molecule gene (L1CAM; OMIM 308840). The L1CAM gene is expressed primarily in the nervous system, where it plays important roles in neuronal development, including the guidance of neurite outgrowth, neuronal cell migration, axon bundling, synaptogenesis, myelination, neuronal cell survival, and long-term potentiation. L1 syndrome comprises a group of overlapping phenotypes including partial agenesis of corpus callosum, congenital X-linked hydrocephalus, and mental retardation, aphasia, shuffling gait, and adducted thumbs syndrome. Molecular analysis was performed in four patients with congenital hydrocephalus (CH) and adducted thumbs. Three pathogenic variants were identified in the L1CAM gene, novel c.539dupA (p.Gln181Alafs*46) common to the two siblings, c.791G > A (p.Cys264Tyr) and c.1453C > T (p.Arg485*) variants. A correlation between genotype and phenotype has been reported in L1-related disorders. Two families with intrafamilial variability are presented and a novel pathogenic variant in the L1CAM gene has been reported. L1 syndrome should be considered primarily in patients with CH and adducted thumbs.

L1CAM expression as a predictor of platinum response in high-risk endometrial carcinoma.

For high‐risk endometrial cancer (EC) patients, adjuvant chemotherapy is recommended to improve outcome. Yet, predictive biomarkers for response to platinum‐based chemotherapy (Pt‐aCT) are currently lacking. We tested expression of L1 cell‐adhesion molecule (L1CAM), a well‐recognised marker of poor prognosis in EC, in tumour samples from high‐risk EC patients, to explore its role as a predictive marker of Pt‐aCT response. L1CAM expression was determined using RT‐qPCR and immunohistochemistry in a cohort of high‐risk EC patients treated with Pt‐aCT and validated in a multicentric independent cohort. The association between L1CAM and clinicopathologic features and L1CAM additive value in predicting platinum response were determined. The effect of L1CAM gene silencing on response to carboplatin was functionally tested on primary L1CAM‐expressing cells. Increased L1CAM expression at both genetic and protein level correlated with high‐grade, non‐endometrioid histology and poor response to platinum treatment. A predictive model adding L1CAM to prognostic clinical variables significantly improved platinum response prediction (C‐index 78.1%, P = .012). In multivariate survival analysis, L1CAM expression was significantly associated with poor outcome (HR: 2.03, P = .019), potentially through an indirect effect, mediated by its influence on response to chemotherapy. In vitro, inhibition of L1CAM significantly increased cell sensitivity to carboplatin, supporting a mechanistic link between L1CAM expression and response to platinum in EC cells. In conclusion, we have demonstrated the role of L1CAM in the prediction of response to Pt‐aCT in two independent cohorts of high‐risk EC patients. L1CAM is a promising candidate biomarker to optimise decision making in high‐risk patients who are eligible for Pt‐aCT.

L1 Syndrome Prenatal Diagnosis Supplemented by Functional Analysis of One L1CAM Gene Missense Variant

L1 syndrome, a complex X-linked neurological disorder, is caused by mutations in the L1 cell adhesion molecule (L1CAM) gene. L1CAM molecule is a member of immunoglobulin (Ig) superfamily of neural cell adhesion molecules (CAMs), which plays a pivotal role in the developing nervous system. In this study, a L1CAM gene exonic missense variant (c.1108G > A, p.G370R) was identified in two induced fetuses (abnormal fetuses), who presented corpus callosum agenesis accompanied with hydrocephalus. Clinical data, published literature, online database, and bioinformatic analysis suggest that the single-nucleotide variant of L1CAM gene is a likely pathogenic mutation. In vitro assays were performed to evaluate the effects of this variant. Based on NSC-34/COS-7 cells transfected with wild-type (L1-WT) and mutated (L1-G370R) plasmids, the L1CAM gene exonic missense variant (c.1108G > A, p.G370R) reduced cell surface expression, induced partial endoplasmic reticulum retention, affected posttranslational modification, and reduced protein’s homophilic adhesive ability, but did not induce endoplasmic reticulum stress, which might probably associate with L1 syndrome. Finally, 35 isolated fetuses were screened for L1CAM gene variants by Sanger sequencing. These cases all prenatally suspected of corpus callosum agenesis accompanied with hydrocephalus, which may relate to L1 syndrome. Consequently, one L1CAM gene single missense variant (c.550C > T, p.R184W) was detected in one fetus. Our results provided evidence that the L1CAM gene missense variant (c.1108G > A, p.G370R) may relate to L1 syndrome. The findings of this study suggest a potential possibility of L1CAM gene screening for prenatal diagnoses for fetuses presented corpus callosum agenesis accompanied with hydrocephalus.

Prenatal diagnosis of a nonsense mutation in the L1CAM gene resulting in congenital hydrocephalus: A case report and literature review

Congenital hydrocephalus is frequently caused by mutations in the L1 cell adhesion molecule (L1CAM) gene. The purpose of the present study was to identify possible causes of fetal hydrocephalus in a Chinese family. The samples from the parents and the hydrocephalic fetus were collected. Whole-exome sequencing and in-depth mutation analysis were performed. The identified variant, c.1267C>T.(p.Q423X), is situated on exon 11 of L1CAM gene (chromosome X:153134975). The fetus was confirmed to be hemizygous for the nonsense mutation and the mother was a heterozygous carrier. The mutation turns a glutamine into a premature stop codon at amino acid position 423. In conclusion, in the present study, a nonsense mutation in the L1CAM gene was identified during the prenatal diagnosis of a congenital hydrocephalic fetus from a Chinese family. The diagnosis highlighted the necessity of genetic screening for prenatal diagnosis.

Familly with two different cases of post- and pre-natal l1 syndrome: When hydrocephaly become “multidisciplinary headache”

In middle 90?s the scientific community classified as CRASH syndrome a clinical situation characterized by Corpus callosum hypoplasia, Retardation, Adducted thumbs, Spastic paraplegia, and Hydrocephalus. This pathology is also known as L1 syndrome and includes a spectrum of related neurological disorders with an X-linked recessive mode of inheritance associated to mutations in the human L1 Cell Adhesion Molecule gene (L1CAM;OMIM 308840). Here we report regarding a couple pass through our Genetic Counseling, during clinical diagnostic procedure in ~3 years old son, due to presence of multiple malformations such as hydrocephalus, agenesis of corpus callosum, tetraparesys, axial hypotony, cognitive and motor incompetency. The proband was the first male child of a healthy, non-consanguineous Italian couple with no family history of brain abnormalities, recurrent miscarriages, other birth defects and/or genetic illnesses. During Genetic Counseling, a diagnostic hypothesis of L1 syndrome was made, with in deep explanation of genetic testing possibilities. On the basis of our protocol, we fixed another appointment 2 weeks later, but unfortunately the family never showed up. Approximately one year later, the Department of Gynecology and Obstetrics requested Genetic Counseling for a 33 years old woman, secondigravida (22? gestation week), with abnormal ultrasound findings showing severe fetal ventriculomegaly. The family history was unremarkable with no consanguinity; she was one of two sisters and had a healthy brother. Surprisingly the woman was the mother of our proband. On the basis of a diagnostic hypothesis of L1 syndrome (includes a spectrum of related neurological disorders with an X-linked recessive mode of inheritance), we performed molecular analysis on the proband?s DNA, mother?s DNA and fetal DNA. The mutational screening revealed the presence of a non sense c.2701C>T (p.Arg901

Paraplejía espástica hereditaria ligada al cromosoma X por mutación en el gen L1CAM: presentación de tres casos del síndrome CRASH

Hereditary spastic paraplegia (HSP) is a set of neurodegenerative clinical features characterised by a progressive loss of strength in the lower limbs together with spasticity. It is the result of an axonal lesion in the corticospinal tracts. Type 1, known as SPG1, is the most common form of X-linked HSP. This is produced by a mutation in the gene for the L1 cell adhesion molecule (L1CAM). SPG1 presents with CRASH syndrome (corpus callosum hypoplasia, retardation, adducted thumbs, spasticity and hydrocephalus). We report the cases of three males, two brothers and a cousin (on the mother's side), with clinical features including intellectual disability, spastic paraparesis, long tract signs, facial dysmorphism and adducted thumbs. Neuroimaging revealed agenesis of the corpus callosum and ventriculomegaly in all three of them. Neurophysiological and metabolic studies were normal. The genetic study evidenced a specific mutation of the L1CAM gene (Xq28) in all three cases. We describe the clinical-radiological findings in three males with CRASH syndrome due to mutation c.516G>A in exon 5 of the L1CAM gene. These seem to be the first cases reported in Spain, according to the current literature. We recommend suspecting this syndrome when spastic paraparesis, intellectual disability and adducted thumbs are associated.

Identical by descent L1CAM mutation in two apparently unrelated families with intellectual disability without L1 syndrome

Mutations in the L1 Cell Adhesion Molecule (L1CAM) gene (MIM#308840) cause a variety of X-linked recessive neurological disorders collectively called L1 syndrome. Using massively parallel sequencing (MPS) of the X-chromosome exome, we identified a novel missense variant in L1CAM in two Caucasian families with mild-moderate intellectual disability without obvious L1 syndrome features. These families were not known to be related. SNP data extracted from MPS identified a 5.6 cM tract of identity by descent (IBD), encompassing the L1CAM gene, between the DNA of the two probands. This cannot be explained by chance alone and strongly implies that the two families are related. It also suggests that the L1CAM (NM_000425.3, c.604G > A, p.D202N) variant is pathogenic. This report also demonstrates the usefulness of additional information, which can be extracted from exome sequencing data.

MiR-21-3p is a positive regulator of L1CAM in several human carcinomas

Expression of L1 cell adhesion molecule (L1CAM) occurs frequently in human cancers and is associated with poor prognosis in cancers such as ovarian, endometrial, breast, renal cell carcinoma and pancreatic ductal adenocarcinoma. L1CAM promotes cell motility, invasion, chemoresistance and metastasis formation. Elucidating genetic processes involved in the expression of L1CAM in cancers is of considerable importance. Transcription factors such as SLUG, β-catenin/TCF-LEF, PAX8 and VHL have been implicated in the re-activation of L1CAM in various types of cancers. There is increasing evidence that micro-RNAs can also have strong effects on gene expression. Here we have identified miR-21-3p as a positive regulator of L1CAM expression. Over-expression of miR-21-3p (miR-21*) but not the complementary sequence miR-21-5p (miR-21) could strongly augment L1CAM expression in renal, endometrial and ovarian carcinoma derived cell lines by an unknown mechanism involving transcriptional activation of the L1CAM gene. In patient cohorts from renal, endometrial and ovarian cancers we observed a strong positive correlation of L1CAM and miR-21-3p expressions. Although L1CAM alone was a reliable marker for overall and disease free survival, the combination of L1CAM and miR-21-3p expressions strongly enhanced the predictive power. Our findings shed new light on the complex regulation of L1CAM in cancers and advocate the use of L1CAM/miR-21-3p for diagnostic application.

Effect of L1 cell adhesion molecule gene silencing on perineural invasion ability of pancreatic cancer Capan-2 cells

Effect of L1 cell adhesion molecule gene silencing on perineural invasion ability of pancreatic cancer Capan-2 cells

Heterozygosity for the mutated X-chromosome-linked L1 cell adhesion molecule gene leads to increased numbers of neurons and enhanced metabolism in the forebrain of female carrier mice

Mutations in the X-chromosomal L1CAM gene lead to severe neurological deficits. In this study, we analyzed brains of female mice heterozygous for L1 (L1+/-) to gain insights into the brain structure of human females carrying one mutated L1 allele. From postnatal day 7 onward into adulthood, L1+/- female mice show an increased density of neurons in the neocortex and basal ganglia in comparison to wild-type (L1+/+) mice, correlating with enhanced metabolic parameters as measured in vivo. The densities of astrocytes and parvalbumin immunoreactive interneurons were not altered. No significant differences between L1+/- and L1+/+ mice were seen for cell proliferation in the cortex during embryonic days 11.5-15.5. Neuronal differentiation as estimated by analysis of doublecortin-immunoreactive cortical cells of embryonic brains was similar in L1+/- and L1+/+ mice. Interestingly, at postnatal days 3 and 5, apoptosis was reduced in L1+/- compared to L1+/+ mice. We suggest that reduced apoptosis leads to increased neuronal density in adult L1+/- mice. In conclusion, L1+/- mice display an unexpected phenotype that is not an intermediate between L1+/+ mice and mice deficient in L1 (L1-/y), but a novel phenotype which is challenging to understand regarding its underlying molecular and cellular mechanisms.

Abstract 1634: Targeting L1 cell adhesion molecule using lentivirus-mediated short hairpin RNA interference reverses aggressiveness of oral squamous cell carcinoma

Abstract Oral cancer consistently ranks as one of the ten most frequently diagnosed cancers in the world. Despite multidisciplinary treatment with surgery, chemotherapy, and radiation, more than 50% of patients with oral squamous cell carcinoma (OSCC) receiving therapy will eventually develop recurrent and metastatic disease, which carries a particularly poor prognosis. Characterization of the specific molecular alternations associated with OSCC cell growth, invasion, and metastasis can advance our understanding of the molecular mechanisms underlying cancer induction and progression as well provide a basis for the development of new and effective therapeutic treatments for cancer patients. The L1 cell adhesion molecule (L1CAM) has been implicated in tumor progression of many types of cancers, but its role in OSCC has not been investigated. In the present study, we demonstrated overexpression of L1CAM in OSCC cells, but not in normal keratinocytes, using both clinical specimens and cell lines. This overexpression demonstrated a strong correlation with less differentiation and a higher invasion potential of cancer cells, supporting the significance of L1CAM in human OSCC tumor progression. Targeting L1CAM gene expression in SCC4 cells overexpressing L1CAM using a lentivirusmediated small hairpin RNA (shRNA) led to a significant reduction in cell proliferation in vitro via retardation of cell cycle at the G1 phase. In addition, shRNA knockdown of L1CAM strongly attenuated the migration and invasion of SCC4 cells, and this was also observed to parallel increased E-cadherin levels and decreased levels vimentin, fibronectin, and Snail-family transcription factors, indicating that L1CAM expression was related to the epithelial-mesenchymal transition. Furthermore, while mice receiving orthotopically placed control SCC4 cells died within 40 days due to invasive tumor growth and regional lymph node metastasis, prolonged animal survival and complete suppression of tumor progression was observed in mice implanted with L1CAM-deficent SCC4 cells, further substantiating the fundamental importance of L1CAM in OSCC pathophysiology. Our findings suggested that L1CAM is a critical mediator of tumor progression in OSCC, and targeting L1CAM using lentivirus-mediated shRNA may be a useful molecular pharmaceutical approach for the treatment of advanced OSCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1634. doi:10.1158/1538-7445.AM2011-1634

Targeting L1 Cell Adhesion Molecule Using Lentivirus-Mediated Short Hairpin RNA Interference Reverses Aggressiveness of Oral Squamous Cell Carcinoma

The L1 cell adhesion molecule (L1CAM) has been implicated in tumor progression of many types of cancers, but its role in oral squamous cell carcinoma (OSCC) has not been investigated. In the present study, we demonstrated overexpression of L1CAM in OSCC cells, but not in normal keratinocytes, using both clinical specimens and cell lines. This overexpression demonstrated a strong correlation with less differentiation and a higher invasion potential of cancer cells, supporting the significance of L1CAM in human OSCC tumor progression. Targeting L1CAM gene expression in SCC4 cells overexpressing L1CAM using a lentivirus-mediated small hairpin RNA (shRNA) led to a significant reduction in cell proliferation in vitro via retardation of cell cycle at the G1 phase. In addition, shRNA knockdown of L1CAM strongly attenuated the migration and invasion of SCC4 cells, and this was also observed to parallel increased E-cadherin levels and decreased levels of vimentin, fibronectin, and Snail-family transcription factors, indicating that L1CAM expression was related to the epithelial-mesenchymal transition. Furthermore, while mice receiving orthotopically placed control SCC4 cells died within 40 days due to invasive tumor growth and regional lymph node metastasis, prolonged animal survival and complete suppression of tumor progression was observed in mice implanted with L1CAM-deficent SCC4 cells, further substantiating the fundamental importance of L1CAM in OSCC pathophysiology. Our findings suggested that L1CAM is a critical mediator of tumor progression in OSCC, and targeting L1CAM using lentivirus-mediated shRNA may be a useful molecular pharmaceutical approach for the treatment of advanced OSCC.

L1CAM expression in endometrial carcinomas is regulated by usage of two different promoter regions

BackgroundThe L1 cell adhesion molecule (L1CAM) was originally identified as a neural adhesion molecule involved in axon guidance. In many human epithelial carcinomas L1CAM is overexpressed and thereby augments cell motility, invasion and metastasis formation. L1CAM positive carcinomas are associated with bad prognosis. Recent data point out that L1CAM is regulated in a fashion similar to epithelial-mesenchymal transition (EMT). Previous studies have implied the transcription factors Slug and/or β-catenin in L1CAM transcriptional regulation. However, the regulation of human L1CAM expression at the transcriptional level is not well understood.ResultsTo better understand the molecular basis of L1CAM transcriptional regulation, we carried out a detailed characterization of the human L1CAM promoter. We identified two transcription start sites, the first in front of a non-translated exon 0 (promoter 1) and the other next to the first protein-coding exon 1 (promoter 2). Both sites could be verified in endometrial carcinoma (EC) cell lines and appear to be used in a cell-type specific manner. The two identified promoter regions showed activity in luciferase reporter assays. Chromatin-IP analyses confirmed the in silico predicted E-boxes, binding sites for transcription factors Snail and Slug, as well as Lef-1 sites, which are related to β-catenin-mediated transcriptional regulation, in both promoters. Overexpression of β-catenin exclusively augmented activity of promoter 1 whereas Slug enhanced promoter 1 and 2 activity suggesting that both promoters can be active. Overexpression of β-catenin or Slug could upregulate L1CAM expression in a cell-type specific manner.ConclusionsOur results, for the first time, provide evidence that the L1CAM gene has two functionally active promoter sites that are used in a cell-type specific manner. Slug and β-catenin are involved L1CAM transcriptional regulation. Nevertheless, Slug rather than β-catenin levels are correlated with L1CAM expression in EC cell lines. Our findings suggest that the L1CAM transcriptional regulation is more complex than anticipated and this study provides the basis for a better understanding of L1CAM regulation in non-neuronal/tumor cells.

Prenatal Identification of a Novel R937P L1CAM Missense Mutation

The L1 cell adhesion molecule (L1CAM) is a protein encoded by a gene that has been localized to Xq28, is a member of the immunoglobulin superfamily of neuronal cell adhesion molecules, and plays a role in CNS development and maturation. L1CAM is expressed in neurons and Schwann cells, where it is active in neurite overgrowth, adhesion fasciculation, migration, myelination, and axon guidance. Mutations within the gene have been associated with phenotypic changes that include hydrocephalus due to aqueductal stenosis, agenesis or hypoplasia of the corpus callosum and corticospinal tracts, mental retardation, spastic paraplegia, and adducted thumbs. Here, we present a 19-year-old primigravida Caucasian woman who was referred to us in the 27th week of the pregnancy because of fetal polyhydramnios and ventriculomegaly. Our evaluation identified a male fetus with hydrocephalus, ventriculomegaly, aqueductal stenosis, and polyhydramnios. An amniocentesis was performed, and isolated fetal DNA revealed a hemizygous G > C mutation in codon 2809 of exon 21 of the L1CAM gene. The patient was later tested and identified to be a carrier of the same mutation. The fetus was delivered during the 38th week. Neonatal physical examination revealed marked frontal bossing, contractures of the feet with rocker bottom appearance, and hyperactive reflexes with ankle and knee clonus. He died at 4 months of life.

DNA hypomethylation at the CpG island is involved in aberrant expression of the L1 cell adhesion molecule gene in colorectal cancer

The L1 cell adhesion molecule (L1CAM) has been identified as a target gene of beta-catenin-TCF signaling in colorectal cancer (CRC) and associated with aggressive tumor behavior such as invasion and metastasis. We investigated the methylation status at the L1CAM gene promoter and/or L1CAM mRNA/protein expression in 4 CRC cell lines and 71 primary CRCs. Aberrant L1CAM expression was immuno histochemically observed in 31 (43.7%) of 71 cases, and correlated with advanced stage and presence of lymph node and distant metastases (P<0.05). Treatment with a demethylating agent induced L1CAM mRNA/protein expression in two cell lines lacking L1CAM expression. Bisulfite-modified genome sequencing suggested that DNA methylation status at core promoter and putative TCF-binding sites within the L1CAM promoter was correlated with L1CAM mRNA/protein expression in 4 CRC cell lines. Using the crypt isolation followed by bisulfite-modified genome sequencing and methylation-specific PCR methods, we confirmed that the DNA hypomethylation at core promoter and putative TCF-binding sites was well correlated with the aberrant L1CAM protein expression in primary CRC samples. These results suggest that DNA hypomethylation at the L1CAM CpG islands might induce L1CAM aberrant expression and contribute to the acquisition of aggressive tumor behavior in CRC.

Pathogenic human L1-CAM mutations reduce the adhesion-dependent activation of EGFR.

L1-cell adhesion molecule (L1-CAM) belongs to a functionally conserved group of neural cell adhesion molecules that are implicated in many aspects of nervous system development. In many neuronal cells the adhesive function of L1-type CAMs induces cellular signaling processes that involves the activation of neuronal tyrosine protein kinases and among other functions regulates axonal growth and guidance. Mutations in the human L1-CAM gene are responsible for a complex neurodevelopmental condition, generally referred to as L1 syndrome. Several pathogenic L1-CAM mutations have been identified in humans that cause L1 syndrome in affected individuals without affecting the level of L1-CAM-mediated homophilic cell adhesion when tested in vitro. In this study, an analysis of two different pathogenic human L1-CAM molecules indicates that although both induce normal L1-CAM-mediated cell aggregation, they are defective in stimulating human epidermal growth factor receptor tyrosine kinase activity in vitro and are unable to rescue L1 loss-of-function conditions in a Drosophila transgenic model in vivo. These results indicate that the L1 syndrome-associated phenotype might involve the disruption of L1-CAM's functions at different levels. Either by reducing or abolishing L1-CAM protein expression, by interfering with L1-CAM's cell surface expression, by reducing L1-CAM's adhesive ability or by impeding further downstream adhesion-dependent signaling processes.

L1-CAM in cancerous tissues

Background: L1-cell adhesion molecule (L1-CAM) is a cell adhesion receptor of the immunoglobulin superfamily, known for its roles in nerve cell function. While originally believed to be present only in brain cells, in recent years L1-CAM has been detected in other tissues, and in a variety of cancer cells, including some common types of human cancer. Objective/methods: We review the prevalence of L1-CAM in human cancer, the possible mechanisms involved in L1-CAM-mediated tumorigenesis, and cancer therapies based upon L1-CAM antibody treatment. Results/conclusions: In colon cancer cells, the L1-CAM gene was identified as a target of the Wnt/β-catenin-TCF signaling pathway, and L1-CAM was exclusively detected at the invasive front of colon and ovarian cancer tissue. The expression of L1-CAM in normal and cancer cells enhanced tumorigenesis and conferred metastasis in colon cancer cells. Antibodies against the L1-CAM ectodomain severely inhibited the proliferation of a variety of cancer cells in culture and reduced tumor burden when injected into mice harboring cancer cells expressing L1-CAM. These results, in addition to the presence of L1-CAM on the cell surface and its restricted distribution in normal tissues, make it an ideal target for tumor therapy.

Contiguous gene deletion involving L1CAM and AVPR2 causes X‐linked hydrocephalus with nephrogenic diabetes insipidus

X-linked hydrocephalus with aqueductal stenosis (HSAS) is caused by mutation or deletion of the L1 cell adhesion molecule gene (L1CAM) at Xq28. Central diabetes insipidus (CDI) can arise as a consequence of resultant hypothalamic dysfunction from hydrocephalus and must be distinguished from nephrogenic diabetes insipidus (NDI) by exogenous vasopressin response. Causes of NDI are heterogeneous and include mutation or deletion of the arginine vasopressin receptor 2 gene (AVPR2), which is located approximately 29 kb telomeric to L1CAM. We identified a patient with both HSAS and NDI where DNA sequencing failure suggested the possibility of a contiguous gene deletion. A 32.7 kb deletion mapping from L1CAM intron1 to AVPR2 exon2 was confirmed. A 90 bp junctional insertion fragment sharing short direct repeat homology with flanking sequences was identified. To our knowledge this is the first reported case of an Xq28 microdeletion involving both L1CAM and AVPR2, defining a new contiguous gene syndrome comprised of HSAS and NDI. Contiguous gene deletion should be considered as a mechanism for all patients presenting with hydrocephalus and NDI.

Recurrent Infections, Hypotonia, and Mental Retardation Caused by Duplication of MECP2 and Adjacent Region in Xq28

Our goal was to describe the neurologic and clinical features of affected males from families with X-linked patterns of severe mental retardation, hypotonia, recurrent respiratory infection, and microduplication of Xq28 that consistently includes the MECP2 (methyl-CpG binding protein 2) gene. To identify duplications, multiplex ligation-dependent probe amplification of the MECP2 gene was performed on male probands from families with X-linked mental retardation. The males either had linkage to Xq28 or had a phenotype consistent with previous reports involving Xq28 functional disomy. After detection of a duplication of MECP2, additional family members were tested to confirm the MECP2 duplication segregated with the affected phenotype, and X-inactivation studies were performed on carrier females. Six families with multiple affected males having MECP2 duplications were identified by multiplex ligation-dependent probe amplification, and the carrier mothers were subsequently shown to have highly skewed X inactivation. In 5 of 6 families, the microduplication extended proximally to include the L1 cell adhesion molecule gene. The primary clinical features associated with this microduplication are infantile hypotonia, recurrent respiratory infection, severe mental retardation, absence of speech development, seizures, and spasticity. Although many of the phenotypic features of our patients are rather nonspecific in cohorts of individuals with syndromic and nonsyndromic mental retardation, the proneness to infection is quite striking because the patients had normal growth and were not physically debilitated. Although the etiology of the infections is not understood, we recommend considering MECP2 dosage studies and a genetics referral in individuals with severe developmental delay and neurologic findings, especially when a history of recurrent respiratory ailments has been documented.