Synaptic architecture of a memory engram in the mouse hippocampus.

Memory engrams are formed through experience-dependent remodeling of neural circuits, but their detailed architectures have remained unresolved. Using 3D electron microscopy, we performed nanoscale reconstructions of the hippocampal CA3-CA1 pathway following chemogenetic labeling of cellular ensembles with a remote history of correlated excitation during associative learning. Projection neurons involved in memory acquisition expanded their connectomes via multi-synaptic boutons without altering the numbers and spatial arrangements of individual axonal terminals and dendritic spines. This expansion was driven by presynaptic activity elicited by specific negative valence stimuli, regardless of the co-activation state of postsynaptic partners. The rewiring of initial ensembles representing an engram coincided with local, input-specific changes in the shapes and organelle composition of glutamatergic synapses, reflecting their weights and potential for further modifications. Our findings challenge the view that the connectivity among neuronal substrates of memory traces is governed by Hebbian mechanisms, and offer a structural basis for representational drifts.

Shared Decision-Making on Using a CDK4/6 Inhibitor plus an Aromatase Inhibitor for HR+/HER2- Metastatic Breast Cancer: A Podcast.

Shared decision-making involves patients engaging with their physicians to make informed decisions regarding treatment selection, a process that empowers patients and ensures that treatment decisions reflect their individual values and preferences. However, shared decision-making can be challenging to implement for various reasons, including time, staffing, or resource limitations at community practices and differences in patients' cultural backgrounds or health literacy. In this podcast, we discuss how to ensure that individual patients' needs and concerns are addressed, including an overview of different approaches for initial consultations, strategies for tailoring conversations based on a patient's background or health literacy, and trustworthy resources that can help improve patients' understanding. As an illustrative example, we focus on how to implement shared decision-making to address the needs of a patient with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer who is eligible for combination therapy with a cyclin-dependent kinase 4/6 inhibitor plus an aromatase inhibitor. Overall, this podcast illustrates how shared decision-making is an achievable goal, even in small or underresourced practices, and provides an instructive guide on how to facilitate shared decision-making for patients with HR+/HER2- metastatic breast cancer. Podcast Discussion (MP4 29880 KB) INFOGRAPHIC.

Delayed hemorrhagic gastritis caused by immunotherapy in a patient With metastatic melanoma.

Pembrolizumab is a monoclonal antibody which targets the programmed cell death protein 1 (PD-1) receptor of lymphocytes. It is commonly used to treat many types of malignancies. Immunotherapy-related adverse events are relatively common and include pneumonitis, colitis and hepatitis. A rare side effect of immunotherapy is gastrointestinal (GI) bleeding secondary to hemorrhagic gastritis. Side effects from immunotherapy most commonly occur eight to twelve weeks after initiation of therapy but can vary from days after the first dose to even months later. We present a rare case of a patient with metastatic melanoma who had confirmed immune-mediated hemorrhagic gastritis which occurred after 23 cycles of Pembrolizumab. Biopsies for Heliobacter Pylori (H. pylori) and cytomegalovirus (CMV) were negative. The patient's immunotherapy was discontinued, and he was started on high dose steroids. The symptoms (nausea, vomiting, and abdominal pain) improved dramatically with a long steroid taper. An esophagogastroduodenoscopy (EGD) performed three months after hospital discharge showed improvement in gastric mucosa, but biopsies continued to show evidence of acute and chronic gastritis. As cancer patients continue to live longer with immunotherapy, it is important for all providers to be aware of the less common side effects of newer agents such as pembrolizumab.

Cardiomyopathy is associated with ribosomal protein gene haplo-insufficiency in Drosophila melanogaster.

The Minute syndrome in Drosophila melanogaster is characterized by delayed development, poor fertility, and short slender bristles. Many Minute loci correspond to disruptions of genes for cytoplasmic ribosomal proteins, and therefore the phenotype has been attributed to alterations in translational processes. Although protein translation is crucial for all cells in an organism, it is unclear why Minute mutations cause effects in specific tissues. To determine whether the heart is sensitive to haplo-insufficiency of genes encoding ribosomal proteins, we measured heart function of Minute mutants using optical coherence tomography. We found that cardiomyopathy is associated with the Minute syndrome caused by haplo-insufficiency of genes encoding cytoplasmic ribosomal proteins. While mutations of genes encoding non-Minute cytoplasmic ribosomal proteins are homozygous lethal, heterozygous deficiencies spanning these non-Minute genes did not cause a change in cardiac function. Deficiencies of genes for non-Minute mitochondrial ribosomal proteins also did not show abnormal cardiac function, with the exception of a heterozygous disruption of mRpS33. We demonstrate that cardiomyopathy is a common trait of the Minute syndrome caused by haplo-insufficiency of genes encoding cytoplasmic ribosomal proteins. In contrast, most cases of heterozygous deficiencies of genes encoding non-Minute ribosomal proteins have normal heart function in adult Drosophila.

The diversity of O-linked glycans expressed during Drosophila melanogaster development reflects stage- and tissue-specific requirements for cell signaling.

Appropriate glycoprotein O-glycosylation is essential for normal development and tissue function in multicellular organisms. To comprehensively assess the developmental and functional impact of altered O-glycosylation, we have extensively analyzed the non-glycosaminoglycan, O-linked glycans expressed in Drosophila embryos. Through multidimensional mass spectrometric analysis of glycans released from glycoproteins by beta-elimination, we detected novel as well as previously reported O-glycans that exhibit developmentally modulated expression. The core 1 mucin-type disaccharide (Galbeta1-3GalNAc) is the predominant glycan in the total profile. HexNAcitol, hexitol, xylosylated hexitol, and branching extension of core 1 with HexNAc (to generate core 2 glycans) were also evident following release and reduction. After Galbeta1-3GalNAc, the next most prevalent glycans were a mixture of novel, isobaric, linear, and branched forms of a glucuronyl core 1 disaccharide. Other less prevalent structures were also extended with HexA, including an O-fucose glycan. Although the expected disaccharide product of the Fringe glycosyltransferase, (GlcNAcbeta1-3)fucitol, was not detectable in whole embryos, mass spectrometry fragmentation and exoglycosidase sensitivity defined a novel glucuronyl trisaccharide as GlcNAcbeta1-3(GlcAbeta1-4)fucitol. Consistent with the spatial distribution of the Fringe function, the GlcA-extended form of the Fringe product was enriched in the dorsal portion of the wing imaginal disc. Furthermore, loss of Fringe activity reduced the prevalence of the O-Fuc trisaccharide. Therefore, O-Fuc glycans necessary for the modulation of important signaling events in Drosophila are, as in vertebrates, substrates for extension beyond the addition of a single HexNAc.