The Habituation/Cross-Habituation Test Revisited: Guidance from Sniffing and Video Tracking

The habituation/cross-habituation test (HaXha) is a spontaneous odor discrimination task that has been used for many decades to evaluate olfactory function in animals. Animals are presented repeatedly with the same odorant after which a new odorant is introduced. The time the animal explores the odor object is measured. An animal is considered to cross-habituate during the novel stimulus trial when the exploration time is higher than the prior trial and indicates the degree of olfactory patency. On the other hand, habituation across the repeated trials involves decreased exploration time and is related to memory patency, especially at long intervals. Classically exploration is timed using a stopwatch when the animal is within 2 cm of the object and aimed toward it. These criteria are intuitive, but it is unclear how they relate to olfactory exploration, that is, sniffing. We used video tracking combined with plethysmography to improve accuracy, avoid observer bias, and propose more robust criteria for exploratory scoring when sniff measures are not available. We also demonstrate that sniff rate combined with proximity is the most direct measure of odorant exploration and provide a robust and sensitive criterion

Fus1 KO mouse as a model of oxidative stress-mediated sporadic Alzheimer’s disease: circadian disruption and long-term spatial and olfactory memory impairments.

Insufficient advances in the development of effective therapeutic treatments of sporadic Alzheimer's Disease (sAD) to date are largely due to the lack of sAD-relevant animal models. While the vast majority of models do recapitulate AD's hallmarks of plaques and tangles by virtue of tau and/or beta amyloid overexpression, these models do not reflect the fact that in sAD (unlike familial AD) these genes are not risk factors per se and that other mechanisms like oxidative stress, metabolic dysregulation and inflammation play key roles in AD etiology. Here we characterize and propose the Fus1 KO mice that lack a mitochondrial protein Fus1/Tusc2 as a new sAD model. To establish sAD relevance, we assessed sAD related deficits in Fus1 KO and WT adult mice of 4-5 months old, the equivalent human age when the earliest cognitive and olfactory sAD symptoms arise. Fus1 KO mice showed oxidative stress (increased levels of ROS, decreased levels of PRDX1), disruption of metabolic homeostasis (decreased levels of ACC2, increased phosphorylation of AMPK), autophagy (decreased levels of LC3-II), PKC (decreased levels of RACK1) and calcium signaling (decreased levels of Calb2) in the olfactory bulb and/or hippocampus. Mice were behaviorally tested using objective and accurate video tracking (Noldus), in which Fus1 KO mice showed clear deficits in olfactory memory (decreased habituation/cross-habituation in the short and long term), olfactory guided navigation memory (inability to reduce their latency to find the hidden cookie), spatial memory (learning impairments on finding the platform in the Morris water maze) and showed more sleep time during the diurnal cycle. Fus1 KO mice did not show clear deficits in olfactory perception (cross-habituation), association memory (passive avoidance) or in species-typical behavior (nest building) and no increased anxiety (open field, light-dark box) or depression/anhedonia (sucrose preference) at this relatively young age. These neurobehavioral deficits of the Fus1 KO mice at this relatively young age are highly relevant to sAD, making them suitable for effective research on pharmacological targets in the context of early intervention of sAD

Olfatory behaviour in a murine alzheimer model

Tema del mesEn el Instituto de Neurobiología campus UNAM-Juriquilla se estudian los aspectos conductuales, neuronales y moleculares, relacionados con la enfermedad de Alzheimer (EA) en un modelo de ratón transgénico (3XTg-AD, donado por el Dr. F. LaFerla, de la Universidad de California) y que es homocigótico para las tres proteínas humanas asociadas a la enfermedad. La ventaja de trabajar con este modelo es que además de su viabilidad, permite estudiar los cambios progresivos de las alteraciones neuronales, principalmente en las áreas más susceptibles como son la corteza cerebral y el hipocampo. En el humano, un aspecto del diagnóstico temprano de la enfermedad se relaciona con la disminución en la calidad de la olfacción que culmina con la incapacidad para discriminar diferentes olores volátiles, un aspecto relacionado con la presencia de agregados de beta amiloide en el bulbo olfatorio principal (BOP). Nuestro interés se centra en caracterizar la discriminación olfativa en el ratón transgénico (3xTg-AD) que es un homocigoto para la ED, con la finalidad de comprobar si también se presenta una alteración temprana asociada a la patología. Hasta ahora los datos obtenidos, a través de las pruebas conductuales de preferencia y motivación olfatoria, demuestran un deterioro en la olfacción del 3xTg-AD a los 10 meses de edad, principalmente asociada al BOPAt the Institute of Neurobiology UNAM campus-Juriquilla explores behavioral, neural and molecular aspects, associated with Alzheimer’s Disease (EA) in a model of transgenic mouse (3XTg-AD), donated by Dr. F. LaFerla, at the University of California, and that is homozygous for the three human proteins associated with the disease. The advantage of working with this model is that in addition to its viability, allows us to study the progressive changes of the neuronal alterations mainly in the areas more susceptible as are the cerebral cortex and the hippocampus. In the human, an aspect of early diagnosis of the disease is related to the decline in the quality of the olfaction that culminates with the inability to discriminate different smells volatile an issue relating to the presence of aggregates of beta amyloid in the olfactory bulb main (BOP). Our interest focuses on characterize the olfactory discrimination in the transgenic mouse (3xTg-AD) that is a homozygous for ED, with the aim of check if also an alteration early associated with the pathology. Until now the data obtained through the evidence behavioral preference and the olfactory motivation showed deterioration in the smelling of 3xTg-AD for the 10 months of age, mainly associated with the BO

Single cell RNA sequencing of human microglia uncovers a subset associated with Alzheimer's disease

The extent of microglial heterogeneity in humans remains a central yet poorly explored question in light of the development of therapies targeting this cell type. Here, we investigate the population structure of live microglia purified from human cerebral cortex samples obtained at autopsy and during neurosurgical procedures. Using single cell RNA sequencing, we find that some subsets are enriched for disease-related genes and RNA signatures. We confirm the presence of four of these microglial subpopulations histologically and illustrate the utility of our data by characterizing further microglial cluster 7, enriched for genes depleted in the cortex of individuals with Alzheimer’s disease (AD). Histologically, these cluster 7 microglia are reduced in frequency in AD tissue, and we validate this observation in an independent set of single nucleus data. Thus, our live human microglia identify a range of subtypes, and we prioritize one of these as being altered in AD

Single cell RNA sequencing of human microglia uncovers a subset associated with Alzheimer’s disease

© 2020, The Author(s). The extent of microglial heterogeneity in humans remains a central yet poorly explored question in light of the development of therapies targeting this cell type. Here, we investigate the population structure of live microglia purified from human cerebral cortex samples obtained at autopsy and during neurosurgical procedures. Using single cell RNA sequencing, we find that some subsets are enriched for disease-related genes and RNA signatures. We confirm the presence of four of these microglial subpopulations histologically and illustrate the utility of our data by characterizing further microglial cluster 7, enriched for genes depleted in the cortex of individuals with Alzheimer’s disease (AD). Histologically, these cluster 7 microglia are reduced in frequency in AD tissue, and we validate this observation in an independent set of single nucleus data. Thus, our live human microglia identify a range of subtypes, and we prioritize one of these as being altered in AD