Alzheimer’s disease (AD) is characterized by the selective vulnerability of specific neuronal populations, the molecular signatures of which are largely unknown. To identify and characterize selectively vulnerable neuronal populations, we used single-nucleus RNA sequencing to profile the caudal entorhinal cortex and the superior frontal gyrus – brain regions where neurofibrillary inclusions and neuronal loss occur early and late in AD, respectively – from postmortem brains spanning the progression of AD-type tau neurofibrillary pathology. We identified RORB as a marker of selectively vulnerable excitatory neurons in the entorhinal cortex, and subsequently validated their depletion and selective susceptibility to neurofibrillary inclusions during disease progression using quantitative neuropathological methods. We also discovered an astrocyte subpopulation, likely representing reactive astrocytes, characterized by decreased expression of genes involved in homeostatic functions. Our characterization of selectively vulnerable neurons in AD paves the way for future mechanistic studies of selective vulnerability and potential therapeutic strategies for enhancing neuronal resilience.

A radiolabeled murine monoclonal antibody (T101) was used for imaging and therapy of six patients with cutaneous T cell lymphoma (CTCL). Radioimmunodetection was performed with a 5.6 to 13.1 mCi 131I-T101 preparation (9.6 to 10.5 mg). A therapeutic dose of 100.5 to 150.1 mCi 131I on 9.9 to 16.9 mg of antibody was administered to five patients, with subsequent retreatment following plasmapheresis in three patients at the time of disease progression. All patients responded to their initial therapy and two patients responded to retreatment. Regression of skin lesions and peripheral adenopathy was witnessed. All patients reported resolution of their chronic pruritus. The duration of response ranged from 3 weeks to 3 months. Acute toxicity included fevers, pruritus, and mild dyspnea in two instances. Myelosuppression was seen in patients receiving the 144.7 mCi, 145.0 mCi, and 150.1 mCi 131I-T101 doses. Radioimmunodiagnostic and therapy studies included gamma scintigraphy, plasma, urinary, and wholebody antibody clearances, and biodistribution determined from skin, bone marrow, and liver biopsies. Immunologic studies included immunoperoxidase staining of target tissues, immunofluorescent flow cytometric analysis on peripheral blood and bone marrow, assays for serum blocking factors, determination of a human antimouse antibody (HAMA) response, and quantitation of circulating T101 levels. These preliminary data suggest that 131I-T101 has therapeutic potential in CTCL and that myelosuppression will be the limiting toxicity.

Alzheimer's disease (AD) is characterized by the selective vulnerability of specific neuronal populations, the molecular signatures of which are largely unknown. To identify and characterize selectively vulnerable neuronal populations, we used single-nucleus RNA sequencing to profile the caudal entorhinal cortex and the superior frontal gyrus -brain regions where neurofibrillary inclusions and neuronal loss occur early and late in AD, respectively -from individuals spanning the neuropathological progression of AD. We identified RORB as a marker of selectively vulnerable excitatory neurons in the entorhinal cortex, and subsequently validated their depletion and selective susceptibility to neurofibrillary inclusions during disease progression using quantitative neuropathological methods. We also discovered an astrocyte subpopulation, likely representing reactive astrocytes, characterized by decreased expression of genes involved in homeostatic functions. Our characterization of selectively vulnerable neurons in AD paves the way for future mechanistic studies of selective vulnerability and potential therapeutic strategies for enhancing neuronal resilience. MAIN TEXTSelective vulnerability is a fundamental feature of neurodegenerative diseases, in which different neuronal populations show a gradient of susceptibility to degeneration 1, 2 . Selective vulnerability at the network level has been extensively explored in Alzheimer's disease (AD) 3-5 , currently the leading cause of dementia and lacking in effective therapies. However, little is known about the mechanisms underlying selective vulnerability at the cellular level in AD, which could provide insight into disease mechanisms and lead to therapeutic strategies.The entorhinal cortex (EC), an allocortex, is one of the first cortical brain regions to exhibit neuronal loss in AD 6 . Neurons in the external EC layers, especially in layer II (also known as alpha clusters of the lamina principalis externa, abbreviated "Pre-alpha") 7 , accumulate taupositive neurofibrillary changes and die early on in the course of AD 8-13 . However, these selectively vulnerable neurons have yet to be characterized extensively at the molecular level. Furthermore, it is unknown whether there are differences in vulnerability among subpopulations of these neurons. Although rodent models of AD have offered some insights [14][15][16] , the human brain has unique features with regard to cellular physiology, composition and aging [17][18][19] , limiting the extrapoloation of findings from animal models to address selective vulnerability.Previous studies have combined laser capture microdissection with microarray analysis of gene expression 20, 21 to characterize EC neurons in AD, but focused on disease-related changes in gene expression, rather than selective vulnerability. More recently, single-nucleus RNA-sequencing (snRNA-seq) has enabled large-scale characterization of transcriptomic profiles of individual cells from post-mortem human brain tissue 22, 23 . However, snRNA-seq studies of AD p...

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