Citations

Targeting three defects with one strategy The neurodegenerative diseases amyotrophic lateral sclerosis and frontotemporal dementia are most commonly caused by a mutation in the C9orf72 gene. The mutation is an expanded hexanucleotide repeat in a noncoding region. The expanded repeat produces sense and antisense RNA transcripts, which accumulate in patient cells and appear to sequester RNA-binding proteins. The sense and antisense transcripts are also translated into dipeptide repeat proteins, which are aggregation-prone and accumulate in the brain and spinal cord. Last, loss of function from reduced expression of C9orf72 in neurons and glia could contribute to the disease. Kramer et al. targeted both sense and antisense repeats by blocking a single gene called SPT4 , which mitigated degeneration in human cells by reducing all three types of pathologies. Science , this issue p. 708

A mouse model for ALS A G4C2 repeat expansion in C9ORF72 is known to be the major genetic cause of frontotemporal dementia and amyotrophic lateral sclerosis (c9FTD/ALS). However, a lack of animal models recapitulating key disease features has hindered efforts to understand and prevent c9FTD/ALS-related neurodegeneration. Until now. Chew et al. describe a mouse model that mimics both neuropathological and clinical phenotypes of c9FTD/ALS. Science , this issue p. 1151

AbstractMutations in superoxide dismutase 1 (SOD1) associated with familial amyotrophic lateral sclerosis induce misfolding and aggregation of the protein with the inherent propensity of mutant SOD1 to aggregate generally correlating, with a few exceptions, to the duration of illness in patients with the same mutation. One notable exception was the D101N variant, which has been described as wild‐type‐like. The D101N mutation is associated with rapidly progressing motor neuron degeneration but shows a low propensity to aggregate. By assaying the kinetics of aggregation in a well‐characterized cultured cell model, we show that the D101N mutant is slower to initiate aggregation than the D101G mutant. In this cell system of protein over‐expression, both mutants were equally less able to acquire Zn than WT SOD1. In addition, both of these mutants were equivalently less able to fold into the trypsin‐resistant conformation that characterizes WT SOD1. A second major difference between the two mutants was that the D101N variant more efficiently formed a normal intramolecular disulfide bond. Overall, our findings demonstrate that the D101N and D101G variants exhibit clearly distinctive features, including a different rate of aggregation, and yet both are associated with rapidly progressing disease. image We sought to better characterize the biochemical features of two SOD1 mutants associated with rapidly progressing disease, the D101G and wild‐type like D101N mutants. We observed using our cell model that that although similarities were observed when comparing the ability to bind metals and resist trypsin digestion, these mutants differed in their ability to initiate aggregation and to form the normal intramolecular disulfide bond. We conclude that these mutants exhibit distinct properties despite producing similar disease phenotypes in patients.

Pulmonary fibrosis in surgical lung biopsies is said to have a ‘usual interstitial pneumonia- pattern ’ (UIP- pattern ) of disease when scarring of the parenchyma is present in a patchy, ‘temporally heterogeneous’ distribution. These biopsies are one of the more common non-neoplastic specimens surgical pathologists encounter and often pose a number of challenges. UIP is the expected histopathological pattern in patients with clinical idiopathic pulmonary fibrosis (IPF), but the UIP- pattern can be seen in other conditions on occasion. Most important among these are the rheumatic interstitial lung diseases (RILD) and chronic hypersensitivity pneumonitis (CHrHP). Because theses entities have different mechanisms of injury, approach to therapy, and expected clinical progression, it is imperative for the surgical pathologist to correctly classify them. Taken in isolation, the UIP- pattern seen in patients with IPF may appear to overlap with that of RILD and CHrHP, at least when using the broadest definition of this term (patchy fibrosis). However, important distinguishing features are nearly always present in our experience, and the addition of a multidisciplinary approach will often resolve the critical differences between these diseases. In this manuscript, we review the distinguishing clinical, radiologic and histopathological features of UIP of IPF, RILD and CHrHP, based, in part, on the existing literature, but also lessons learned from a busy lung biopsy consultation practice.

Sortilin 1 regulates the levels of brain progranulin (PGRN), a neurotrophic growth factor that, when deficient, is linked to cases of frontotemporal lobar degeneration with TAR DNA-binding protein-43 (TDP-43)–positive inclusions (FTLD-TDP). We identified a specific splicing enhancer element that regulates the inclusion of a sortilin exon cassette (termed Ex17b) not normally present in the mature sortilin mRNA. This enhancer element is consistently present in sortilin RNA of mice and other species but absent in primates, which carry a premature stop codon within the Ex17b sequence. In the absence of TDP-43, which acts as a regulatory inhibitor, Ex17b is included in the sortilin mRNA. In humans, in contrast to mice, the inclusion of Ex17b in sortilin mRNA generates a truncated, nonfunctional, extracellularly released protein that binds to but does not internalize PGRN, essentially acting as a decoy receptor. Based on these results, we propose a potential mechanism linking misregulation of sortilin splicing with altered PGRN metabolism.

Paraneoplastic neurologic disorders are extremely rare in cancer patients and are most commonly associated with certain tumors, such as ovarian cancer, small cell lung cancer, and breast cancer. We report here a paraneoplastic neurological syndrome in a 53-year-old man with colonic adenocarcinoma with a solitary liver metastasis. His paraneoplastic syndrome was successfully treated by methylprednisolone and primary oncologic therapies including neoadjuvant chemotherapy and definitive surgery. This is also the first documented case of simultaneous manifestation of a sensory neuropathy and limbic encephalitis with colon cancer.

OBJECTIVE To examine elevated depressive symptoms and antidepressant use in relation to diabetes incidence in the Women’s Health Initiative. RESEARCH DESIGN AND METHODS A total of 161,808 postmenopausal women were followed for over an average of 7.6 years. Hazard ratios (HRs) estimating the effects of elevated depressive symptoms and antidepressant use on newly diagnosed incident diabetes were obtained using Cox proportional hazards models adjusted for known diabetes risk factors. RESULTS Multivariable-adjusted HRs indicated an increased risk of incident diabetes with elevated baseline depressive symptoms (HR 1.13 [95% CI 1.07–1.20]) and antidepressant use (1.18 [1.10–1.28]). These associations persisted through year 3 data, in which respective adjusted HRs were 1.23 (1.09–1.39) and 1.31 (1.14–1.50). CONCLUSIONS Postmenopausal women with elevated depressive symptoms who also use antidepressants have a greater risk of developing incident diabetes. In addition, longstanding elevated depressive symptoms and recent antidepressant medication use increase the risk of incident diabetes.