PAK3 activation promotes the tangential to radial migration switch of cortical interneurons by increasing leading process dynamics and disrupting cell polarity.

Mutations of PAK3, a p21-activated kinase, are associated in humans with cognitive deficits suggestive of defective cortical circuits and with frequent brain structural abnormalities. Most human variants no longer exhibit kinase activity. Since GABAergic interneurons express PAK3 as they migrate within the cortex, we here examined the role of PAK3 kinase activity in the regulation of cortical interneuron migration. During the embryonic development, cortical interneurons migrate a long distance tangentially and then re-orient radially to settle in the cortical plate, where they contribute to cortical circuits. We showed that interneurons expressing a constitutively kinase active PAK3 variant (PAK3-ca) extended shorter leading processes and exhibited unstable polarity. In the upper cortical layers, they entered the cortical plate and extended radially oriented processes. In the deep cortical layers, they exhibited erratic non-processive migration movements and accumulated in the deep pathway. Pharmacological inhibition of PAK3 kinase inhibited the radial migration switch of interneurons to the cortical plate and reduced their accumulation in the deep cortical layers. Interneurons expressing a kinase dead PAK3 variant (PAK3-kd) developed branched leading processes, maintained the same polarity during migration and exhibited processive and tangentially oriented movements in the cortex. These results reveal that PAK3 kinase activity, by promoting leading process shortening and cell polarity changes, inhibits the tangential processive migration of interneurons and favors their radial re- orientation and targeting to the cortical plate. They suggest that patients expressing PAK3 variants with impaired kinase activity likely present alterations in the cortical targeting of their GABAergic interneurons.

Complications after Heller myotomy in children: a national multicenter study on the impact of prior endoscopic dilatation and identification of risk factors.

BACKGROUND: Although esophageal achalasia has been historically treated by Heller myotomy, endoscopic esophageal dilatations are nowadays often the first-line treatment in children. The aim was to assess whether performing an endoscopic dilatation before a Heller myotomy is associated with higher risks of esophageal perforation in children. METHODS: A retrospective multicentric study was performed, including children that underwent a Heller myotomy (2000-2022, 10 centers). Two groups were compared based on the history of previous dilatation before myotomy. Outcomes esophageal perforation (intra-operative or secondary) and post-operative complications requiring surgery (Clavien-Dindo III). Statistics Comparisons using contingency tables or Kruskal-Wallis when appropriate. Statistical significance: p-value < 0.05. RESULTS: A Heller myotomy was performed in 77 children (median age: 11.8 years), with prior endoscopic dilatation in 53% (n = 41). A laparoscopic approach was used in 90%, with associated fundoplication in 95%. Esophageal perforation occurred in 19% of children (n = 15), including 12 patients with intra-operative mucosal tear and 3 with post-operative complications related to an unnoticed esophageal perforation. Previous endoscopic dilatation did not increase the risk of esophageal perforation (22% vs 17%, OR: 1.4, 95%CI: 0.43-4.69). Post-operative complications occurred in 8% (n = 6), with similar rates regardless of prior endoscopic dilatation. Intra-operative mucosal tear was the only risk factor for post-operative complications, increasing the risk of complications from 5 to 25% (OR: 6.89, 95%CI: 1.38-31.87). CONCLUSIONS: Prior endoscopic dilatations did not increase the risk of esophageal perforation or postoperative complications of Heller myotomy in this cohort of children with achalasia. Mucosal tear was identified as a risk factor for post-operative complications.

CD44 loss of function sensitizes AML cells to the BCL-2 inhibitor venetoclax by decreasing CXCL12-driven survival cues.

Acute myeloid leukemia (AML) has a poor prognosis under the current standard of care. In recent years, venetoclax, a BCL-2 inhibitor, was approved to treat patients who are ineligible for intensive induction chemotherapy. However, complete remission rates with venetoclax-based therapies are hampered by minimal residual disease (MRD) in a proportion of patients, leading to relapse. MRD is a result of leukemic stem cells being retained in bone marrow protective environments; activation of the CXCL12-CXCR4 pathway was shown to be relevant to this process. An important role is also played by cell adhesion molecules such as CD44, which has been shown to be crucial for the development of AML. Here we show that CD44 is involved in CXCL12 promotion of resistance to venetoclax-induced apoptosis in human AML cell lines and AML patient samples, which could be abrogated by CD44 knock down, knockout, or blocking with an anti-CD44 antibody. Split-Venus bimolecular fluorescence complementation showed that CD44 and CXCR4 physically associate at the cell membrane upon CXCL12 induction. In the venetoclax-resistant OCI-AML3 cell line, CXCL12 promoted an increase in the proportion of cells expressing high levels of embryonic stem cell core transcription factors (ESC-TFs: Sox2, Oct4, Nanog) abrogated by CD44 knockdown. This ESC-TF-expressing subpopulation which could be selected by venetoclax treatment, exhibited a basally enhanced resistance to apoptosis and expressed higher levels of CD44. Finally, we developed a novel AML xenograft model in zebrafish, which showed that CD44 knockout sensitizes OCI-AML3 cells to venetoclax treatment in vivo. Our study shows that CD44 is a potential molecular target for sensitizing AML cells to venetoclax-based therapies.

Retrospective evaluation of clinical and molecular data of 148 cases of esophageal atresia.

Developmental abnormalities provide a unique opportunity to seek for the molecular mechanisms underlying human organogenesis. Esophageal development remains incompletely understood and elucidating causes for esophageal atresia (EA) in humans would contribute to achieve a better comprehension. Prenatal detection, syndromic classification, molecular diagnosis, and prognostic factors in EA are challenging. Some syndromes have been described to frequently include EA, such as CHARGE, EFTUD2-mandibulofacial dysostosis, Feingold syndrome, trisomy 18, and Fanconi anemia. However, no molecular diagnosis is made in most cases, including frequent associations, such as Vertebral-Anal-Cardiac-Tracheo-Esophageal-Renal-Limb defects (VACTERL). This study evaluates the clinical and genetic test results of 139 neonates and 9 fetuses followed-up at the Necker-Enfants Malades Hospital over a 10-years period. Overall, 52 cases were isolated EA (35%), and 96 were associated with other anomalies (65%). The latter group is divided into three subgroups: EA with a known genomic cause (9/148, 6%); EA with Vertebral-Anal-Cardiac-Tracheo-Esophageal-Renal-Limb defects (VACTERL) or VACTERL/Oculo-Auriculo-Vertebral Dysplasia (VACTERL/OAV) (22/148, 14%); EA with associated malformations including congenital heart defects, duodenal atresia, and diaphragmatic hernia without known associations or syndromes yet described (65/148, 44%). Altogether, the molecular diagnostic rate remains very low and may underlie frequent non-Mendelian genetic models.

Usefulness of routine early œsophagogram after primary repair of œsophageal atresia: a multicenter study.

BACKGROUND: Advances in surgical and neonatal care have led to improved survival of patients with œsophageal atresia (OA) over time. Morbidity remains significant, with one-third of patients being affected by a postoperative complication. Several aspects of management are not consensual, such as the use of œsophagogram before starting oral feeding. METHODS: We conducted a multicenter retrospective study, including all children with OA that underwent a primary anastomosis in the first days of life, between 2012 and 2018 in five French centers, to determine the usefulness of postoperative œsophagogram during the 10 days after early primary repair of OA to diagnose the anastomotic leak and congenital œsophageal stenosis. RESULTS: Among 225 included children, 90 (40%) had a routine œsophagogram and 25 (11%) had an anastomotic leak, clinically diagnosed before the scheduled œsophagogram in 24/25 (96%) children at median postoperative day 4. Ten patients had associated congenital œsophageal stenosis diagnosed on the œsophagogram in only 30% of cases. CONCLUSION: Early œsophagogram is rarely useful in the diagnosis of an anastomotic leak, which is clinically diagnosed before performing an œsophagogram in the majority of cases. The need for a postoperative œsophagogram should be evaluated on a case-by-case basis. IMPACT: Early œsophagogram is not helpful in the diagnosis of an anastomotic leak in the majority of cases. An anastomotic leak is most often diagnosed clinically before performing an œsophagogram. Early postoperative œsophagogram could be helpful for the diagnosis of congenital œsophageal stenosis. However, dysphagia occurs later and early diagnosis of congenital œsophageal stenosis has no impact on the management and outcome of asymptomatic children. Indication of postoperative œsophagogram has to be evaluated on a case-by-case basis.

Peri- and neonatal factors influencing mortality and morbidity 2 years after esophageal atresia primary repair: a single center retrospective study.

Long-term digestive, respiratory, and neurological morbidity is significant in children who have undergone surgery for esophageal atresia (EA), especially after staged repair for long-gap EA. Risk factors for morbidity after primary repair (non-long-gap populations) have been less documented. We investigated peri- and neonatal factors associated with unfavorable outcomes in children 2 years after primary esophageal anastomosis. This was a single-center retrospective study, based on neonatal, surgical, and pediatric records of children born between December 1, 2002, and December 31, 2018, and followed up to age 2 years. The primary endpoint was unfavorable outcome at 2 years of age, defined by death or survival with severe respiratory, digestive, or neurologic morbidity. Univariate analyses followed by logistic regression analyses were performed to identify the peri- and neonatal risk factors of unfavorable outcomes among survivors at discharge. A total of 150 neonates were included (mean birth weight 2520 ± 718 g, associated malformations 61%); at age 2, 45 (30%) had one or more severe morbidities and 11 had died during the neonatal stay and 2 after discharge (8.7% deaths). In multivariate analyses of the 139 survivors at discharge, duration of ventilatory support (invasive and non-invasive) for more than 8 days (OR 3.74; CI95% [1.68-8.60]; p = 0.001) and achievement of full oral feeding before hospital discharge (OR 0.20; CI95% [0.06-0.56]; p = 0.003) were independently associated with adverse outcome after adjustment for sex, preterm birth, associated heart defect, any surgical complication, and the occurrence of more than one nosocomial infections during the neonatal stay. CONCLUSIONS: Post-operative ventilation and feeding management strategies may represent an opportunity for quality-of-care improvement to positively impact long-term outcomes after primary esophageal atresia repair. WHAT IS KNOWN: • Children operated on for esophageal atresia experience long-term digestive, respiratory, and neurologic morbidity, especially after multiple-stage esophageal repair. • Exclusive oral feeding at discharge is associated with a decreased risk of medical complications in the first years of life, in studies including all types of esophageal atresia repair. Outcomes of children after primary repair (non-long gap populations) have been less documented. WHAT IS NEW: • In our retrospective cohort of children with one-stage esophageal atresia repair, ventilatory support for more than 8 days and inability to achieve full oral feeding before hospital discharge in the neonatal period were independently associated with adverse digestive, respiratory, and neurologic outcomes at 2 years in survivors. • Both these factors are potentially modifiable, representing an opportunity for quality-of-care improvement to positively impact long-term outcomes. These results might also help identify children at risk of unfavorable evolution, to customize a multi-disciplinary follow-up program.

Predicting Factors of Protracted Intestinal Failure in Children with Gastroschisis.

OBJECTIVE: To identify prenatal and neonatal predictors of short bowel syndrome-related intestinal failure (SBS-IF) in gastroschisis. STUDY DESIGN: This retrospective study included all patients with gastroschisis born between 2000 and 2017 who were enrolled in our home parenteral nutrition program, and all patients with gastroschisis born in our institution who survived 2 weeks, during the same time period. Prenatal ultrasound features, neonatal status, anatomic features, oral feeding, and parenteral nutrition dependency were analyzed. RESULTS: Among 180 patients, 35 required long-term parenteral nutrition (SBS-IF group) and 145 acquired full oral feeding within 6 months (oral feeding group). The mean follow-up was 7.9 years (IQR, 1.6-17.5 years) and 5.0 years (IQR, 0.1-18.2 years), respectively. Both bowel matting (OR, 14.23; 1.07-16.7; P = .039) and secondarily diagnosed atresia or stenosis (OR, 17.78; 3.13-100.98; P = .001) were independent postnatal predictors of SBS-IF. Eighteen children (51% of the SBS-IF group) were still dependent on artificial nutrition at the last follow-up. patients with SBS-IF who achieved full oral feeding had a median residual small-bowel length of 74 cm (IQR, 51-160 cm) vs 44 cm (IQR, 10-105 cm) for those still dependent on artificial nutrition (P = .02). An initial residual small bowel length of more than 50 cm was the best predictive cut-off for nutritional autonomy, with a sensitivity of 67% and a specificity of 100%. CONCLUSIONS: Bowel matting, complex gastroschisis, and secondary intestinal obstruction were associated with SBS-IF in gastroschisis. For patients with SBS-IF, a small bowel length of more than 50 cm was predictive of secondary nutritional autonomy.

Different Involvement of Vimentin during Invasion by Listeria monocytogenes at the Blood-Brain and the Blood-Cerebrospinal Fluid Barriers In Vitro.

The human central nervous system (CNS) is separated from the blood by distinct cellular barriers, including the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CFS) barrier (BCSFB). Whereas at the center of the BBB are the endothelial cells of the brain capillaries, the BCSFB is formed by the epithelium of the choroid plexus. Invasion of cells of either the BBB or the BCSFB is a potential first step during CNS entry by the Gram-positive bacterium Listeria monocytogenes (Lm). Lm possesses several virulence factors mediating host cell entry, such as the internalin protein family-including internalin (InlA), which binds E-cadherin (Ecad) on the surface of target cells, and internalin B (InlB)-interacting with the host cell receptor tyrosine kinase Met. A further family member is internalin (InlF), which targets the intermediate filament protein vimentin. Whereas InlF has been shown to play a role during brain invasion at the BBB, its function during infection at the BCSFB is not known. We use human brain microvascular endothelial cells (HBMEC) and human choroid plexus epithelial papilloma (HIBCPP) cells to investigate the roles of InlF and vimentin during CNS invasion by Lm. Whereas HBMEC present intracellular and surface vimentin (besides Met), HIBCPP cells do not express vimentin (except Met and Ecad). Treatment with the surface vimentin modulator withaferin A (WitA) inhibited invasion of Lm into HBMEC, but not HIBCPP cells. Invasion of Lm into HBMEC and HIBCPP cells is, however, independent of InlF, since a deletion mutant of Lm lacking InlF did not display reduced invasion rates.

BeadNet: deep learning-based bead detection and counting in low-resolution microscopy images.

MOTIVATION: An automated counting of beads is required for many high-throughput experiments such as studying mimicked bacterial invasion processes. However, state-of-the-art algorithms under- or overestimate the number of beads in low-resolution images. In addition, expert knowledge is needed to adjust parameters. RESULTS: In combination with our image labeling tool, BeadNet enables biologists to easily annotate and process their data reducing the expertise required in many existing image analysis pipelines. BeadNet outperforms state-of-the-art-algorithms in terms of missing, added and total amount of beads. AVAILABILITY AND IMPLEMENTATION: BeadNet (software, code and dataset) is available at https://bitbucket.org/t_scherr/beadnet. The image labeling tool is available at https://bitbucket.org/abartschat/imagelabelingtool. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Risk Factors of Early Mortality and Morbidity in Esophageal Atresia with Distal Tracheoesophageal Fistula: A Population-Based Cohort Study.

OBJECTIVE: To identify the risk factors for early mortality and morbidity in a population with distal esophageal atresia (EA)-tracheoesophageal fistula. STUDY DESIGN: Cohort study from a national register. Main outcomes and measures included early mortality, hospital length of stay (LoS), need for nutritional support at 1 year of age as a proxy measure of morbidity, and complications during the first year of life. RESULTS: In total, 1008 patients with a lower esophageal fistula were included from January 1, 2008, to December 31, 2014. The survival rate at 3 months was 94.9%. The cumulative hospital LoS was 31.0 (17.0-64.0) days. Multivariate analysis showed that intrahospital mortality at 3 months was associated with low birth weight (OR 0.52, 95% CI [0.38-0.72], P < .001), associated cardiac abnormalities (OR 6.09 [1.96-18.89], P = .002), and prenatal diagnosis (OR 2.96 [1.08-8.08], P = .034). LoS was associated with low birth weight (-0.225 ± 0.035, P < .001), associated malformations (0.082 ± 0.118, P < .001), surgical difficulties (0.270 ± 0.107, P < .001), and complications (0.535 ± 0.099, P < .001) during the first year of life. Predictive factors for dependency on nutrition support at 1 year of age were complications before 1 year (OR 3.28 [1.23-8.76], P < .02) and initial hospital LoS (OR 1.96 [1.15-3.33], P < .01). CONCLUSIONS: EA has a low rate of early mortality, but morbidity is high during the first year of life. Identifying factors associated with morbidity may help to improve neonatal care of this population.

CD44 engagement enhances acute myeloid leukemia cell adhesion to the bone marrow microenvironment by increasing VLA-4 avidity.

Adhesive properties of leukemia cells shape the degree of organ infiltration and the extent of leukocytosis. CD44 and the integrin VLA-4, a CD49d/CD29 heterodimer, are important factors of progenitor cell adhesion in bone marrow (BM). Here, we report their cooperation in acute myeloid leukemia (AML) by a novel non-classical CD44-mediated way of inside-out VLA-4 activation. In primary AML BM samples from patients and the OCI-AML3 cell line, CD44 engagement by hyaluronan induced inside-out activation of VLA-4 resulting in enhanced leukemia cell adhesion on VCAM-1. This was independent from VLA-4 affinity regulation but based on ligand-induced integrin clustering on the cell surface. CD44-induced VLA-4 activation could be inhibited by the Src family kinase inhibitor PP2 and the multikinase inhibitor midostaurin. In further consequence, the increased adhesion on VCAM-1 allowed AML cells to strongly bind stromal cells. Thereby VLA-4/VCAM-1 interaction promoted activation of Akt, MAPK, NF-kB and mTOR signaling and decreased AML cell apoptosis. Collectively, our investigations provide a mechanistic description of an unusual CD44 function in regulating VLA-4 avidity in AML, supporting AML cell retention in the supportive BM microenvironment.

Ultrasound and Fetal MRI Complementary Contributions to Appropriate Counseling in Small Bowel Obstruction.

OBJECTIVE: Bowel obstructions beyond the duodenum represent a heterogeneous group of congenital anomalies with a highly variable prognosis, the main issue being postnatal short bowel syndrome (SBS). The objective of our study was to evaluate the contributions of fetal MRI in cases of bowel obstruction. MATERIALS AND METHODS: A retrospective analysis of all newborns, for whom both ante-natal ultrasound and fetal MRI were available, referred to our center for suspected bowel obstruction was performed. Examinations were reviewed blinded to the postnatal outcome. Key outcome measures included exact diagnosis and the existence of postoperative SBS. We evaluated the contribution of MRI in determining precise location and etiology of the bowel obstruction, dilatation of the proximal bowel loops, and assessment of the quality of the remaining distal bowel loops. RESULTS: Twenty-five newborns were included. There were 19 single obstructions and 6 complex forms (4 apple peel syndromes and 2 multiple atresias). MRI correctly identified the affected segment of the small bowel in 59.1% of the cases. MRI identified the mechanism of obstruction in 72% of cases. MRI reliably predicted an abnormal appearance of the bowel distal to the obstruction in 100% of the severe cases (3/3) and in 66.7% of complex forms (4/6). CONCLUSION: Our study suggests that fetal MRI, when done in addition to prenatal ultrasound, is contributory in the management of fetuses with suspected bowel obstruction. MRI may be particularly useful in determining the location and origin of the bowel obstruction and in assessing the quality of the bowel distal to the obstruction, which might assist in the prediction of SBS and more detailed prenatal counseling.

PAK3 mutations responsible for severe intellectual disability and callosal agenesis inhibit cell migration.

Corpus callosum agenesis (CCA) is a brain malformation associated with a wide clinical spectrum including intellectual disability (ID) and an etiopathological complexity. We identified a novel missense G424R mutation in the X-linked p21-activated kinase 3 (PAK3) gene in a boy presenting with severe ID, microcephaly and CCA and his fetal sibling with CCA and severe hydrocephaly. PAK3 kinase is known to control synaptic plasticity and dendritic spine dynamics but its implication is less characterized in brain ontogenesis. In order to identify developmental functions of PAK3 impacted by mutations responsible for CCA, we compared the biochemical and biological effects of three PAK3 mutations localized in the catalytic domain. These mutations include two "severe" G424R and K389N variants (responsible for severe ID and CCA) and the "mild" A365E variant (responsible for nonsyndromic mild ID). Whereas they suppressed kinase activity, only the two severe variants displayed normal protein stability. Furthermore, they increased interactions between PAK3 and the guanine exchange factor αPIX/ARHGEF6, disturbed adhesion point dynamics and cell spreading, and severely impacted cell migration. Our findings highlight new molecular defects associated with mutations responsible for severe clinical phenotypes with developmental brain defects.

Combinatorial Synthesis of a Lipidoid Library by Thiolactone Chemistry: In Vitro Screening and In Vivo Validation for siRNA Delivery.

Transcriptional inhibition by small interfering RNA (siRNA) delivery using synthetic transfection agents eliminates the subsequent risk of introducing mutations in relevant genes, as opposed to viral vectors. However, synthetic vectors with comparable transfection efficiency to that of viral vectors are yet to be developed. Hence, synthesizing new transfection vehicles with low toxicity is important. In this study, a library of lipid-like molecules (lipidoids) was synthesized by thiolactone chemistry. This library facilitated nonviral delivery of siRNA to mammalian cells, inducing sequence-specific knockdown of a target gene. The liposomal nanoparticles complexed with anti-green fluorescent protein (GFP) siRNA were successfully screened for transfection efficiency using a HeLa-GFP cell line. The five best-performing lipidoids identified in the screening were found to exhibit superior GFP-knockdown efficiency compared with commercially available transfection reagents. The efficiency of siRNA delivery by one of these lipidoids with minimal toxicity was further successfully evaluated in vivo using Kdrl:EGFP zebrafish embryos as a model system. Our study would be important as a facile synthetic route of efficient nonviral nucleic acid delivery to live cells and organisms.

Microenvironment-induced CD44v6 promotes early disease progression in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) outgrowth depends on signals from the microenvironment. We have previously found that in vitro reconstitution of this microenvironment induces specific variant isoforms of the adhesion molecule CD44, which confer human CLL with high affinity to hyaluronan (HA). Here, we determined the in vivo contribution of standard CD44 and its variants to leukemic B-cell homing and proliferation in Tcl1 transgenic mice with a B-cell-specific CD44 deficiency. In these mice, leukemia onset was delayed and leukemic infiltration of spleen, liver, and lungs, but not of bone marrow, was decreased. Competitive transplantation revealed that CLL homing to spleen and bone marrow required functional CD44. Notably, enrichment of CD44v6 variants particularly in spleen enhanced CLL engraftment and proliferation, along with increased HA binding. We recapitulated CD44v6 induction in the human disease and revealed the involvement of MAPK and NF-κB signaling upon CD40 ligand and B-cell receptor stimulation by in vitro inhibition experiments and chromatin immunoprecipitation assays. The investigation of downstream signaling after CD44v6-HA engagement uncovered the activation of extracellular signal-regulated kinase and p65. Consequently, anti-CD44v6 treatment reduced leukemic cell proliferation in vitro in human and mouse, confirming the general nature of the findings. In summary, we propose a CD44-NF-κB-CD44v6 circuit in CLL, allowing tumor cells to gain HA binding capacity and supporting their proliferation.

Predictors of the Performance of Early Antireflux Surgery in Esophageal Atresia.

OBJECTIVE: To identify predictors of and factors associated with the performance of antireflux surgery during the first year of life in children born with esophageal atresia. STUDY DESIGN: All patients were included in a French registry for esophageal atresia. All 38 multidisciplinary French centers completed questionnaires about perinatal characteristics and one-year outcome for children born with esophageal atresia. RESULTS: Of 835 infants with esophageal atresia born in France from 2010 to 2014, 682 patients, excluding those with long-gap esophageal atresia, were included. Three patients had type I, 669 had type III, and 10 had type IV esophageal atresia. Fifty-three children (7.8%) received fundoplication during the first year of life. The median age at the time of the end-to-end esophageal anastomosis was 1.1 day (range 0-15). Multivariate analysis identified three perioperative factors that predicted the need for early antireflux surgery: anastomotic tension (P = .004), associated malformations (P = .019), and low birth weight (P = .018). Six other factors, measured during the first year of life, were associated with the need for antireflux surgery: gastroesophageal reflux (P < .001), anastomotic stricture (P < .001), gastrostomy (P < .001), acute life-threatening event (P = .002), respiratory complications (P = .045), and poor nutritional status (P < .001). CONCLUSIONS: Gastroesophageal reflux disease, low birth weight, poor nutrition, and surgical anastomosis difficulties predicted the performance of antireflux surgery in the first year of life in infants with esophageal atresia.

Live cell imaging shows hepatocyte growth factor-induced Met dimerization.

The canonical model of receptor tyrosine kinase (RTK) activation assumes that ligand-induced dimerization of inactive receptor monomers is a prerequisite for autophosphorylation. For several RTK families, recent results of fluorescence microscopy provided evidence for preformed receptor dimers that may or may not require ligand binding for kinase activity. Here we report, for the first time, the application of advanced quantitative fluorescence microscopy techniques to study changes in the oligomerization state of the RTK Met in response to stimulation by its endogenous ligand hepatocyte growth factor (HGF). We used inducible C-terminal fusions between Met and enhanced green fluorescent protein (EGFP) or red fluorescent protein (RFP) in combination with fluorescence resonance energy transfer (FRET)-based fluorescence-lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS). A small fraction of HGF-independent Met dimers appeared to be present in cells even at low receptor density. At high receptor density, both the fraction of Met dimers and the level of Met autophosphorylation increased in the absence of HGF. Stimulation with HGF at low receptor density significantly increased the fraction of Met dimers on live cells. We found no indications of Met oligomers larger than dimers. Our findings thus confirm a model of Met activation through HGF-induced dimerization and at the same time they support previous reports of Met dimers in unstimulated cells. The tools established in this work will be useful to further characterize the mechanism of Met activation and to define the contribution of co-receptors.

Inhibition of Tumor Growth and Metastasis in Pancreatic Cancer Models by Interference With CD44v6 Signaling.

BACKGROUND & AIMS: Cancer cells with high metastatic potential and stem cell-like characteristics express the cell surface marker CD44. CD44 isoforms that include the v6 exon are co-receptors for the receptor tyrosine kinases MET and Vascular Endothelial Growth factor Receptor-2 (VEGFR-2). We studied CD44v6 signaling in several pancreatic cancer cell lines, and its role in tumor growth and metastasis in several models of pancreatic cancer. METHODS: We analyzed the effects of v6 peptides that interfere with the co-receptor functions of CD44v6 for MET and VEGFR-2 in tumors and metastases grown from cells that express different CD44 isoforms, including CD44v6. The peptides were injected into rats with syngeneic tumors and mice with orthotopic or xenograft tumors. We also tested the effects of the peptides in mice with xenograft tumors grown from patient tumor samples and mice that express an oncogenic form of RAS and develop spontaneous pancreatic cancer (KPC mice). We measured levels of CD44v6 messenger RNA (mRNA) in pancreatic cancer tissues from 136 patients. RESULTS: Xenograft tumors grown from human cancer cells injected with v6 peptides were smaller and formed fewer metastases in mice. The v6 peptide was more efficient than the MET inhibitor crizotinib and/or the VEGFR-2 inhibitor pazopanib in reducing xenograft tumor growth and metastasis. Injection of KPC mice with the v6 peptide increased their survival time. Injection of mice and rats bearing metastases with the v6 peptide induced regression of metastases. Higher levels of CD44v6 mRNA in human pancreatic tumor tissues were associated with increased expression of MET, tumor metastasis, and shorter patient survival times. CONCLUSIONS: Peptide inhibitors of CD44v6 isoforms block tumor growth and metastasis in several independent models of pancreatic cancer. The v6 peptides induced regression of metastases. Levels of CD44v6 mRNA are increased, along with those of MET mRNA, in patients with metastatic pancreatic tumors, compared with nonmetastatic tumors; the increased levels correlated with shorter patient survival time.

CD44 plays a functional role in Helicobacter pylori-induced epithelial cell proliferation.

The cytotoxin-associated gene (Cag) pathogenicity island is a strain-specific constituent of Helicobacter pylori (H. pylori) that augments cancer risk. CagA translocates into the cytoplasm where it stimulates cell signaling through the interaction with tyrosine kinase c-Met receptor, leading cellular proliferation. Identified as a potential gastric stem cell marker, cluster-of-differentiation (CD) CD44 also acts as a co-receptor for c-Met, but whether it plays a functional role in H. pylori-induced epithelial proliferation is unknown. We tested the hypothesis that CD44 plays a functional role in H. pylori-induced epithelial cell proliferation. To assay changes in gastric epithelial cell proliferation in relation to the direct interaction with H. pylori, human- and mouse-derived gastric organoids were infected with the G27 H. pylori strain or a mutant G27 strain bearing cagA deletion (∆CagA::cat). Epithelial proliferation was quantified by EdU immunostaining. Phosphorylation of c-Met was analyzed by immunoprecipitation followed by Western blot analysis for expression of CD44 and CagA. H. pylori infection of both mouse- and human-derived gastric organoids induced epithelial proliferation that correlated with c-Met phosphorylation. CagA and CD44 co-immunoprecipitated with phosphorylated c-Met. The formation of this complex did not occur in organoids infected with ∆CagA::cat. Epithelial proliferation in response to H. pylori infection was lost in infected organoids derived from CD44-deficient mouse stomachs. Human-derived fundic gastric organoids exhibited an induction in proliferation when infected with H. pylori that was not seen in organoids pre-treated with a peptide inhibitor specific to CD44. In the well-established Mongolian gerbil model of gastric cancer, animals treated with CD44 peptide inhibitor Pep1, resulted in the inhibition of H. pylori-induced proliferation and associated atrophic gastritis. The current study reports a unique approach to study H. pylori interaction with the human gastric epithelium. Here, we show that CD44 plays a functional role in H. pylori-induced epithelial cell proliferation.

Fetal MRI compared with ultrasound for the diagnosis of obstructive genital malformations.

OBJECTIVE: To compare the accuracy of magnetic resonance imaging (MRI) and ultrasound (US) to diagnose and characterize congenital obstructive genital abnormalities. METHOD: Retrospective cohort of 20 fetuses who underwent a fetal MRI following a US diagnosis of obstructive urogenital malformation. We compared MRI and US findings and their correlation with the definitive diagnosis. RESULT: The correct diagnosis was obtained in 6/20 (30%) cases and 19/20 cases (95%) with US and MRI, respectively. MRI revealed additional information to US in 15/20 cases (75%) and modified the prenatal management in 14 fetuses (70%). The identification rates of the most important anatomical landmarks for the diagnosis, using US and MRI, were compared. Bladder: US 17/20 (85%) vs MRI 20/20 (100%) P = 0.23; vagina: US 6/19 (31.5%) vs MRI 19/19 (100%) P < 10-4 ; uterus: US 11/19 (57.8%) vs MRI 19/19 (100%) P = 0.003, kidneys: US: 40/40 (100%) MRI: 40/40 (100%) P = 1, ureters: US 14/40 (35%) vs MRI 30/40 (75%) P=0.001, rectum: US 6/20 (30%) MRI 20/20 (100%) P < 10-4 , and sacrum: US 20/20 (100%) vs MRI 17/20 (85%) P = 0.23. CONCLUSION: In fetuses with obstructive urogenital malformations, MRI facilitates assessment of major pelvic organs and provides significant information that may alter the prenatal management.