Severine Leclerc

Genetic interaction between members of the Vangl family causes neural tube defects in mice

Neural tube defects (NTDs) are very frequent congenital abnormalities in humans. Recently, we have documented independent association of Vangl1 and Vangl2 gene mutations with NTDs. In the Looptail mouse, homozygosity (but not heterozygosity) for loss-of-function alleles at Vangl2 causes the severe NTD craniorachischisis, whereas heterozygosity for mutant variants of VANGL1 is associated with NTDs in a human cohort of sporadic and familial cases. To understand the role of Vangl1 in normal development, we created a mouse mutant with an inactivating mutation at Vangl1 (Vangl1gt). Vangl1 shows a dynamic pattern of expression in the developing neural tube and notochord at the time of neural tube closure. Vangl1gt/+ heterozygotes and Vangl1gt/gt homozygotes are viable and fertile, although Vangl1gt/gt display subtle alterations in polarity of inner hair cells of the cochlea. Remarkably, and as opposed to healthy Vangl1gt/+ and Vangl2lp/+ heterozygotes, Vangl1gt/+;Vangl2lp/+ double heterozygotes show profound developmental defects that include severe craniorachischisis, inner ear defects (disorganization of the stereociliary bundles of hair cells of the organ of Corti), and cardiac abnormality (aberrant right subclavian artery). These results show that genetic interaction between Vangl1 and Vangl2 genes causes neural tube defects and raise the possibility that interaction between individual Vangl genes and other genetic loci and/or environmental factors may additionally contribute to the etiology of NTDs.

Endothelin-1 (ET-1) promotes MMP-2 and MMP-9 induction involving the transcription factor NF-κB in human osteosarcoma

In the present study, we have investigated the effect of (i) ET-1 (endothelin-1) and its precursor, big ET-1, on MMP (matrix metalloproteinase)-2 and MMP-9 synthesis and activity in osteosarcoma tissue, and (ii) ET-1 receptor antagonists on cell invasion. Using Western blotting, zymography, RT-PCR (reverse transcription-PCR), immunohistochemistry, immunofluorescence and Northern blotting, we have shown that ET-1 and ET-1 receptors (ET(A) and ET(B)) were expressed in these cells. Additionally, we have demonstrated that ET-1 markedly induced the synthesis and activity of MMP-2, which was significantly increased when compared with MMP-9. Furthermore, inhibition of NF-kappaB (nuclear factor kappaB) activation blocked MMP-2 production and activity, indicating the involvement of NF-kappaB, a ubiquitous transcription factor playing a central role in the differentiation, proliferation and malignant transformation. Since ET-1 acts as an autocrine mediator through gelatinase induction and because inhibition of ET(A) receptor is beneficial for reducing both basal and ET-1-induced osteosarcoma cell invasion, targeting this receptor could be an attractive therapeutic alternative for the successful treatment of osteosarcoma.

Mutations in SGOL1 cause a novel cohesinopathy affecting heart and gut rhythm

The pacemaking activity of specialized tissues in the heart and gut results in lifelong rhythmic contractions. Here we describe a new syndrome characterized by Chronic Atrial and Intestinal Dysrhythmia, termed CAID syndrome, in 16 French Canadians and 1 Swede. We show that a single shared homozygous founder mutation in SGOL1, a component of the cohesin complex, causes CAID syndrome. Cultured dermal fibroblasts from affected individuals showed accelerated cell cycle progression, a higher rate of senescence and enhanced activation of TGF-β signaling. Karyotypes showed the typical railroad appearance of a centromeric cohesion defect. Tissues derived from affected individuals displayed pathological changes in both the enteric nervous system and smooth muscle. Morpholino-induced knockdown of sgol1 in zebrafish recapitulated the abnormalities seen in humans with CAID syndrome. Our findings identify CAID syndrome as a novel generalized dysrhythmia, suggesting a new role for SGOL1 and the cohesin complex in mediating the integrity of human cardiac and gut rhythm.

Expression of heat-shock protein 70 during limb development and regeneration in the axolotl.

Urodele amphibians (e.g., axolotls) have the unique ability, among vertebrates, to regenerate perfectly many parts of their body after amputation. The limb has been the most widely studied regenerating structure in these organisms and provides an ideal model in which to understand how vertebrates can regenerate complex tissues. The present study focuses on Hsp‐70, a member of the stress‐related heat‐shock protein family. This protein is normally induced after a stress or trauma such as heat‐shock, ultraviolet irradiation, or wounding. Thus, studying its expression during axolotl limb regeneration, a response to an important traumatic event (amputation), is of great interest to further understand how the regenerative process is mediated. Using molecular biology and biochemical techniques, we have characterized both the spatiotemporal and quantitative expression patterns of Hsp‐70 in axolotl development and regeneration. Our results show that Hsp‐70 is expressed and regulated during axolotl development as in other vertebrates. Our data also demonstrate an up‐regulation of the RNA transcript for Hsp‐70 during limb regeneration as early as 24 hr after amputation that is maintained up to early differentiation. We also demonstrate a similar pattern of expression for the protein during regeneration. Finally, we show that axolotl Hsp‐70 is induced threefold after heat‐shock as observed in other vertebrates. Developmental Dynamics 233:1525–1534, 2005.

Family Based Whole Exome Sequencing Reveals the Multifaceted Role of Notch Signaling in Congenital Heart Disease

Left-ventricular outflow tract obstructions (LVOTO) encompass a wide spectrum of phenotypically heterogeneous heart malformations which frequently cluster in families. We performed family based whole-exome and targeted re-sequencing on 182 individuals from 51 families with multiple affected members. Central to our approach is the family unit which serves as a reference to identify causal genotype-phenotype correlations. Screening a multitude of 10 overlapping phenotypes revealed disease associated and co-segregating variants in 12 families. These rare or novel protein altering mutations cluster predominantly in genes (NOTCH1, ARHGAP31, MAML1, SMARCA4, JARID2, JAG1) along the Notch signaling cascade. This is in line with a significant enrichment (Wilcoxon, p< 0.05) of variants with a higher pathogenicity in the Notch signaling pathway in patients compared to controls. The significant enrichment of novel protein truncating and missense mutations in NOTCH1 highlights the allelic and phenotypic heterogeneity in our pediatric cohort. We identified novel co-segregating pathogenic mutations in NOTCH1 associated with left and right-sided cardiac malformations in three independent families with a total of 15 affected individuals. In summary, our results suggest that a small but highly pathogenic fraction of family specific mutations along the Notch cascade are a common cause of LVOTO.

Aortic Dilatation Associated With a De Novo Mutation in the SOX18 Gene: Expanding the Clinical Spectrum of Hypotrichosis-Lymphedema-Telangiectasia Syndrome

BACKGROUND We report a 13-year-old female patient followed since birth for multiple rare congenital defects, including hypotrichosis, telangiectasia, and severe dilatation of the ascending aorta. METHODS Comprehensive phenotype assessment throughout childhood included repeated echocardiographic measurements, evaluation of renal function, and immunohistochemical analysis of skin biopsy samples. Whole-exome sequencing was performed for the patient and both unaffected parents. RESULTS We identified a novel de novo mutation in the transcription factor SOX18 (c.481C>T:p.Gln161*) in the patient, which was absent in all unaffected family members. Echocardiography revealed early onset and progressive dilatation of the ascending aorta. Skin biopsy results confirmed the defects of the blood vasculature in the presence of intact lymphatic vessels. Assessment of renal function did not show any signs of renal problems or renal failure in the patient. CONCLUSIONS The genetic finding of a pathogenic SOX18 mutation enabled the diagnosis of the rare hypotrichosis-lymphedema-telangiectasia syndrome in our patient. The identification of a novel stop gain mutation in the SOX18 gene in association with dilatation of the aorta highlights the importance of this gene during the development of the circulatory system. Our study highlights the importance of whole-exome sequencing in the rapid identification of genes and gene mutations involved in rare conditions and thus expanding the knowledge and spectrum of clinical manifestations associated with them.

Dataset of Sgo1 expression in cardiac, gastrointestinal, hepatic and neuronal tissue in mouse

The data shown in this article are related to the research article entitled “Characterization of Sgo1 expression pattern in developing and adult mouse” (Song et al., 2017) [3]. The article provides novel data on Sgo1 gene expression pattern utilizing Sgo1_LacZ_Knock in mouse line and immunohistochemistry in wild type mice. The data presents Sgo1 expression pattern during development, and in post-developmental proliferative and quiescent tissue. The article describes following tissues: developing heart, neural tube, adult colon, cerebellum, cerebral cortex, liver, and testis.

Molecular signature of CAID syndrome: non-canonical roles of SGO1 in regulation of TGF-β signalling and epigenomics

Background & Aims A generalized human pacemaking syndrome, chronic atrial and intestinal dysrhythmia (CAID) (OMIM 616201), is caused by a homozygous SGO1 mutation (K23E), leading to chronic intestinal pseudo-obstruction and arrhythmias. Because CAID patients do not show phenotypes consistent with perturbation of known roles of SGO1, we hypothesized that noncanonical roles of SGO1 drive the clinical manifestations observed. Methods To identify a molecular signature for CAID syndrome, we achieved unbiased screens in cell lines and gut tissues from CAID patients vs wild-type controls. We performed RNA sequencing along with stable isotope labeling with amino acids in cell culture. In addition, we determined the genome-wide DNA methylation and chromatin accessibility signatures using reduced representative bisulfite sequencing and assay for transposase-accessible chromatin with high-throughput sequencing. Functional studies included patch-clamp, quantitation of transforming growth factor-β (TGF-β) signaling, and immunohistochemistry in CAID patient gut biopsy specimens. Results Proteome and transcriptome studies converge on cell-cycle regulation, cardiac conduction, and smooth muscle regulation as drivers of CAID syndrome. Specifically, the inward rectifier current, an important regulator of cellular function, was disrupted. Immunohistochemistry confirmed overexpression of Budding Uninhibited By Benzimidazoles 1 (BUB1) in patients, implicating the TGF-β pathway in CAID pathogenesis. Canonical TGF-β signaling was up-regulated and uncoupled from noncanonical signaling in CAID patients. Reduced representative bisulfite sequencing and assay for transposase-accessible chromatin with high-throughput sequencing experiments showed significant changes of chromatin states in CAID, pointing to epigenetic regulation as a possible pathologic mechanism. Conclusions Our findings point to impaired inward rectifier potassium current, dysregulation of canonical TGF-β signaling, and epigenetic regulation as potential drivers of intestinal and cardiac manifestations of CAID syndrome. Transcript profiling and genomics data are as follows: repository URL: https://www.ncbi.nlm.nih.gov/geo; SuperSeries GSE110612 was composed of the following subseries: GSE110309, GSE110576, and GSE110601.