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GluN2B-mediated regulation of silent synapses for receptor specification and addiction memory
Psychostimulants, including cocaine, elicit stereotyped, addictive behaviors. The reemergence of silent synapses containing only NMDA-type glutamate receptors is a critical mediator of addiction memory and seeking behaviors. Despite the predominant abundance of GluN2B-containing NMDA-type glutamate receptors in silent synapses, their operational mechanisms are not fully understood. Here, using conditional depletion/deletion of GluN2B in D1-expressing accumbal medium spiny neurons, we examined the synaptic and behavioral actions that silent synapses incur after repeated exposure to cocaine. GluN2B ablation reduces the proportion of silent synapses, but some of them can persist by substitution with GluN2C, which drives the aberrantly facilitated synaptic incorporation of calcium-impermeable AMPA-type glutamate receptors (AMPARs). The resulting precocious maturation of silent synapses impairs addiction memory but increases locomotor activity, both of which can be normalized by the blockade of calcium-impermeable AMPAR trafficking. Collectively, GluN2B supports the competence of cocaine-induced silent synapses to specify the subunit composition of AMPARs and thereby the expression of addiction memory and related behaviors.
Myosteatosis is associated with adiposity, metabolic derangements and mortality in patients with chronic kidney disease
Myosteatosis has been associated with sarcopenia, and increased mortality risk in patients on hemodialysis. We aimed to explore the associations between myosteatosis, as assessed by computed tomography (CT), with demographic parameters, body composition metrics, muscle strength, metabolic parameters and mortality in patients with chronic kidney disease (CKD).
Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia
X-linked hypophosphataemia (XLH) is a rare metabolic bone disorder caused by pathogenic variants in the PHEX gene, which is predominantly expressed in osteoblasts, osteocytes and odontoblasts. XLH is characterized by increased synthesis of the bone-derived phosphaturic hormone fibroblast growth factor 23 (FGF23), which results in renal phosphate wasting with consecutive hypophosphataemia, rickets, osteomalacia, disproportionate short stature, oral manifestations, pseudofractures, craniosynostosis, enthesopathies and osteoarthritis. Patients with XLH should be provided with multidisciplinary care organized by a metabolic bone expert. Historically, these patients were treated with frequent doses of oral phosphate supplements and active vitamin D, which was of limited efficiency and associated with adverse effects. However, the management of XLH has evolved in the past few years owing to the availability of burosumab, a fully humanized monoclonal antibody that neutralizes circulating FGF23. Here, we provide updated clinical practice recommendations for the diagnosis and management of XLH to improve outcomes and quality of life in these patients.
Genotype of PAX2-related disorders correlates with kidney and ocular manifestations
PAX2-related disorders encompass renal coloboma syndrome (RCS) and hereditary focal segmental glomerulosclerosis (FSGS) type 7. We retrospectively analyzed 27 Korean patients with PAX2 pathogenic variants detected between 2004 and 2022 and conducted a literature review of 328 cases, including 301 previously reported. In our cohort, 19 had RCS, 4 had FSGS, and 4 had isolated congenital anomalies of the kidneys and urinary tract. Patients were classified by variant type into predicted loss of function (pLoF) and non-pLoF variant groups, and by variant location into paired domain and other sites group. pLoF variants were predominantly associated with RCS, observed in 82% of patients in both our data (18 of 22, P = 0.017) and the literature (140 of 171, P < 0.001). Kidney failure developed in 52% of Korean patients at a median age of 14.5 years, with no difference in kidney survival between variant types. However, the literature review indicated faster progression to kidney failure in patients with pLoF variants (11.0 vs. 24.0 years; pLoF, n = 138 vs. non-pLoF, n = 71; P = 0.002), with no significant difference by variant location. Ocular manifestations were more common, had earlier onset, and were more severe in the pLoF variants group in our cohort (P = 0.038). The literature confirmed a higher prevalence of ocular involvement in patients with pLoF variants (pLoF, n = 175 vs. non-pLoF, n = 88; P < 0.001) and in those with paired domain variants (P = 0.01). pLoF variants in PAX2 were associated with worse kidney and ocular outcomes. These findings support genotype-phenotype correlations, contributing to tailored management in patients with PAX2-related disorders.
Prognostic impact of expression of CD2, CD25, and/or CD30 in/on mast cells in systemic mastocytosis: a registry study of the European Competence Network on Mastocytosis
Expression of CD2, CD25 and/or CD30 in extracutaneous mast cells (MC) is a minor diagnostic criterion for systemic mastocytosis (SM) in the classification of the World Health Organization and International Consensus Classification. So far, it remains unknown whether expression of these antigens on MC is of prognostic significance in SM. We performed a retrospective multi-center study of patients with SM using the data set of the registry of the European Competence Network on Mastocytosis, including 5034 patients with various MC disorders. The percentage of CD2–, CD25+ and/or CD30+ MC was considerably lower in patients with indolent SM compared to patients with advanced SM, including aggressive SM and MC leukemia. Whereas CD25 and CD30 expression in MC could not be associated with prognosis, we found that lack of CD2 expression in MC is associated with a significantly reduced overall survival (OS) in patients with SM (p < 0.0001). Lack of CD2 was also associated with the presence of extramedullary involvement affecting the spleen, liver, and/or lymph nodes (odds ratio 2.63 compared to SM with CD2+ MC). Together, lack of CD2 expression in MC is a prognostic marker and indicator of reduced OS and extramedullary disease expansion in patients with SM.
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