Developmental plasticity shapes synaptic phenotypes of autism-associated neuroligin-3 mutations in the calyx of Held.

Neuroligins are postsynaptic cell-adhesion molecules that bind to presynaptic neurexins. Mutations in neuroligin-3 predispose to autism, but how such mutations affect synaptic function remains incompletely understood. Here we systematically examined the effect of three autism-associated mutations, the neuroligin-3 knockout, the R451C knockin, and the R704C knockin, on synaptic transmission in the calyx of Held, a central synapse ideally suited for high-resolution analyses of synaptic transmission. Surprisingly, germline knockout of neuroligin-3 did not alter synaptic transmission, whereas the neuroligin-3 R451C and R704C knockins decreased and increased, respectively, synaptic transmission. These puzzling results prompted us to ask whether neuroligin-3 mutant phenotypes may be reshaped by developmental plasticity. Indeed, conditional knockout of neuroligin-3 during late development produced a marked synaptic phenotype, whereas conditional knockout of neuroligin-3 during early development caused no detectable effect, mimicking the germline knockout. In canvassing potentially redundant candidate genes, we identified developmentally early expression of another synaptic neurexin ligand, cerebellin-1. Strikingly, developmentally early conditional knockout of cerebellin-1 only modestly impaired synaptic transmission, whereas in contrast to the individual single knockouts, developmentally early conditional double knockout of both cerebellin-1 and neuroligin-3 severely decreased synaptic transmission. Our data suggest an unanticipated mechanism of developmental compensation whereby cerebellin-1 and neuroligin-3 functionally occlude each other during development of calyx synapses. Thus, although acute manipulations more likely reveal basic gene functions, developmental plasticity can be a major factor in shaping the overall phenotypes of genetic neuropsychiatric disorders.

The EIF4EBP3 translational repressor is a marker of CDC73 tumor suppressor haploinsufficiency in a parathyroid cancer syndrome.

Germline mutation of the tumor suppressor gene CDC73 confers susceptibility to the hyperparathyroidism-jaw tumor syndrome associated with a high risk of parathyroid malignancy. Inactivating CDC73 mutations have also been implicated in sporadic parathyroid cancer, but are rare in sporadic benign parathyroid tumors. The molecular pathways that distinguish malignant from benign parathyroid transformation remain elusive. We previously showed that a hypomorphic allele of hyrax (hyx), the Drosophila homolog of CDC73, rescues the loss-of-ventral-eye phenotype of lobe, encoding the fly homolog of Akt1s1/ PRAS40. We report now an interaction between hyx and Tor, a central regulator of cell growth and autophagy, and show that eukaryotic translation initiation factor 4E-binding protein (EIF4EBP), a translational repressor and effector of mammalian target of rapamycin (mTOR), is a conserved target of hyx/CDC73. Flies heterozygous for Tor and hyx, but not Mnn1, the homolog of the multiple endocrine neoplasia type 1 (MEN1) tumor suppressor associated with benign parathyroid tumors, are starvation resistant with reduced basal levels of Thor/4E-BP. Human peripheral blood cell levels of EIF4EBP3 were reduced in patients with CDC73, but not MEN1, heterozygosity. Chromatin immunoprecipitation demonstrated occupancy of EIF4EBP3 by endogenous parafibromin. These results show that EIF4EBP3 is a peripheral marker of CDC73 function distinct from MEN1-regulated pathways, and suggest a model whereby starvation resistance and/or translational de-repression contributes to parathyroid malignant transformation.

[The alliance of the parent, child and the nurse to challenge medical error]. / L'alliance parents-enfant-soignants à l'épreuve de l'erreur médicale.

A group composed of parents, nurses, and physicians involved in pediatric cancerology has reflected on medical errors within the Espace Éthique de l'Assistance publique-Hôpitaux de Paris. Based on narratives and qualitative analysis of histories and testimonies, this discussion aimed at exploring the causes, circumstances, and impacts of medical errors on the relations between these individuals. The study demonstrated that some circumstances actually promote medical errors, such as hard working conditions, mistrust, unreliable control procedures, not listening to parents, and caring for children in extreme situations of pain and suffering. Errors almost always result from the accumulation of several shortcomings. The tensions raised by a medical error can be overcome, provided that parents and caregivers trust each other from the onset of disease and that the medical errors are disclosed in a sincere way, whatever the medical consequences. The feelings raised by the painful experience of a medical error do not solely depend on the severity of the consequences, since seemingly benign errors may lead to long-term trauma, whereas severe errors, even those leading to death, do not necessarily breach trust. The keyword here is permanent vigilance. The capacity of caregivers to question their practice, from both a technical and ethical point of view, will determine their ability to learn from an error for the future. The depth and quality of this questioning, in the best of times encouraged by the institution, may also help children affected by a medical error and their family to move forward in their personal history, beyond such painful experiences.

Cytoplasmic polyadenylation element binding protein is a conserved target of tumor suppressor HRPT2/CDC73.

Parafibromin, a tumor suppressor protein encoded by HRPT2/CDC73 and implicated in parathyroid cancer and the hyperparathyroidism-jaw tumor (HPT-JT) familial cancer syndrome, is part of the PAF1 transcriptional regulatory complex. Parafibromin has been implicated in apoptosis and growth arrest, but the mechanism by which its loss of function promotes neoplasia is poorly understood. In this study we report that a hypomorphic allele of hyrax (hyx), the Drosophila homolog of HRPT2/CDC73, rescues the loss-of-ventral-eye phenotype of lobe (Akt1s1). Such rescue is consistent with previous reports that hyx/parafibromin is required for the nuclear transduction of Wingless (Wg)/Wnt signals and that Wg signaling antagonizes lobe function. A screen using double hyx/lobe heterozygotes identified an additional interaction with orb and orb2, the homologs of mammalian cytoplasmic polyadenylation element binding protein (CPEB), a translational regulatory protein. Hyx and orb2 heterozygotes lived longer and were more resistant to starvation than controls. In mammalian cells, knockdown of parafibromin expression reduced levels of CPEB1. Chromatin immunoprecipitation (ChIP) showed occupancy of CPEB1 by endogenous parafibromin. Bioinformatic analysis revealed a significant overlap between human transcripts potentially regulated by parafibromin and CPEB. These results show that parafibromin may exert both transcriptional and, through CPEB, translational control over a subset of target genes and that loss of parafibromin (and CPEB) function may promote tumorigenesis in part by conferring resistance to nutritional stress.

[Risk announcement in paediatric cancerology: strengthen the therapeutic alliance]. / L'annonce des risques en cancérologie pédiatrique: consolider l'alliance thérapeutique.

Although announcement of the risks related to treatment has become a general rule in the healthcare relationship, doctors, nurses and parents of severely ill children tend to feel uncomfortable in relation to this mandatory information. The work conducted by the AP-HP Espace éthique working party in collaboration with parents, healthcare personnel and a philosopher demonstrates the need to announce these risks, even beyond the legal framework, while bearing in mind the difficulties and hazards inherent to changes in legislation and by observing the philosophical values that subtend this legislation. Faced with the broad range of diverse and complex risks, the working party proposes a classification of risks and hierarchisation of the difficulties encountered by the doctor during this announcement, which is difficult to make, and difficult to hear, as intimately related to the child's quality of life. The very concept of the probability of a risk raises concepts that are difficult to accept: chance, randomness, and uncertainty. Informing the patient involves hearing as much as talking, listening as much as explaining and requires availability, time, space and an ability to listen to the patient. This article proposes several good practice guidelines designed to consolidate the therapeutic alliance by sharing the uncertainty of the risk and allowing the various partners to remain actors. Nonconfiscation of knowledge by doctors does not lead to a loss or transfer of their responsibility, but allows decisions to be taken in the context of the alliance, while taking the risks into account.