👤 Arie Horowitz

Medial temporal lobe amnestic syndrome (MTLA) is classically considered a hallmark of Alzheimer's disease (AD). However, emerging evidence suggests etiological heterogeneity, challenging the assumption that MTLA universally reflects AD pathology. To determine the prevalence of amyloid pathology in isolated MTLA, identify phenotypic and genetic risk factors, and characterize associated network vulnerabilities in amnestic mild cognitive impairment (aMCI). This retrospective observational study analyzed 55 patients with isolated MTLA at the aMCI stage. Participants underwent neuropsychological testing, cerebrospinal fluid (CSF) biomarker analysis, amyloid PET, and 18FDG-PET. Patients were stratified by amyloid status (positive/negative) and compared for APOE genotype, clinical features, and metabolic patterns. Statistical analyses included the Kruskal-Wallis test for non-parametric group comparisons and chi-square tests for categorical genetic associations. Amyloid pathology was observed in only 67% (37/55) of MTLA patients, dissociating the syndrome from AD in one-third of cases. Amyloid-positive patients demonstrated a significantly higher APOE ɛ4 carrier rate compared to amyloid-negative peers (χ MTLA syndrome is not homogeneous on the biological level and amyloid pathology and APOE ɛ4 genotype stratify patients into distinct subgroups. Amyloid-positive cases demonstrate inferotemporal hypometabolism, suggesting AD-related network vulnerability. By contrast, amyloid-negative MTLA group shows no systemic brain network vulnerabilities, likely due to its heterogeneous etiological origins. These findings advocate for a precision medicine framework integrating biomarkers to guide therapeutic strategies, moving beyond syndromic diagnoses to target underlying mechanisms. Show less

In a phase II study, letrozole/abemaciclib demonstrated an objective response rate of 30% and a median progression-free survival (PFS) of 9.1 months in recurrent estrogen receptor-positive endometrial cancer (EC). While tissue-based tumor profiling revealed several mechanistically relevant candidate baseline genomic predictors of response, circulating tumor DNA (ctDNA) is a less invasive alternative to monitor therapeutic efficacy and define acquired resistance. Serial plasma specimens were obtained at baseline, C2D1, C3D1, C8D1, the time of objective response, and the time of progression. Samples were analyzed using the Guardant Reveal assay to assess methylation-based tumor fraction (TF), with the Guardant360 assay providing genotyping of >700 genes in samples with detectable ctDNA. Treatment response was assessed using a measure of the relative change in TF pre- versus on-treatment. A total of 99 of 102 (97%) samples from 28 patients were successfully analyzed. Patients with above median baseline TF exhibited worse median PFS (2.0 months Baseline and on-treatment ctDNA dynamics may provide an early indication of benefit from letrozole/abemaciclib in EC. ctDNA at the time of progression may identify resistance alterations that may inform subsequent therapy. Show less

Fat mass may be modulated by the number of brown-like adipocytes in white adipose tissue (WAT) in humans and rodents. Bone remodeling is dependent on systemic energy metabolism and, with age, bone remodeling becomes uncoupled and brown adipose tissue (BAT) function declines. To test the interaction between BAT and bone, we employed Misty (m/m) mice, which were reported be deficient in BAT. We found that Misty mice have accelerated age-related trabecular bone loss and impaired brown fat function (including reduced temperature, lower expression of Pgc1a, and less sympathetic innervation compared to wild-type (+/ +)). Despite reduced BAT function, Misty mice had normal core body temperature, suggesting heat is produced from other sources. Indeed, upon acute cold exposure (4°C for 6 hours), inguinal WAT from Misty mice compensated for BAT dysfunction by increasing expression of Acadl, Pgc1a, Dio2, and other thermogenic genes. Interestingly, acute cold exposure also decreased Runx2 and increased Rankl expression in Misty bone, but only Runx2 was decreased in wild-type. Browning of WAT is under the control of the sympathetic nervous system (SNS) and, if present at room temperature, could impact bone metabolism. To test whether SNS activity could be responsible for accelerated trabecular bone loss, we treated wild-type and Misty mice with the β-blocker, propranolol. As predicted, propranolol slowed trabecular bone volume/total volume (BV/TV) loss in the distal femur of Misty mice without affecting wild-type. Finally, the Misty mutation (a truncation of DOCK7) also has a significant cell-autonomous role. We found DOCK7 expression in whole bone and osteoblasts. Primary osteoblast differentiation from Misty calvaria was impaired, demonstrating a novel role for DOCK7 in bone remodeling. Despite the multifaceted effects of the Misty mutation, we have shown that impaired brown fat function leads to altered SNS activity and bone loss, and for the first time that cold exposure negatively affects bone remodeling. Show less

Controlled regulation of Rho GTPase activity is an essential component mediating growth factor-stimulated migration. We have previously shown that angiomotin (Amot), a membrane-associated scaffold protein, plays a critical role during vascular patterning and endothelial migration during embryogenesis. However, the signaling pathways by which Amot controls directional migration are not known. Here we have used peptide pull-down and yeast 2-hybrid (Y2H) screening to identify proteins that interact with the C-terminal PDZ-binding motifs of Amot and its related proteins AmotL1 and 2. We report that Amot and its related proteins bind to the RhoA GTPase exchange factor (RhoGEF) protein Syx. We show that Amot forms a ternary complex together with Patj (or its paralogue Mupp1) and Syx. Using FRET analysis, we provide evidence that Amot controls targeting of RhoA activity to lamellipodia in vitro. We also report that, similar to Amot, morpholino knockdown of Syx in zebrafish results in inhibition of migration of intersegmental arteries. Taken together, our results indicate that the directional migration of capillaries in the embryo is governed by the Amot:Patj/Mupp1:Syx signaling that controls local GTPase activity. Show less