Fabian Fernandez

Fabian Fernandez

Assistant Professor, BIO5 Institute
Assistant Professor, Evelyn F Mcknight Brain Institute
Assistant Professor, Neurology
Assistant Professor, Neuroscience - GIDP
Assistant Professor, Psychology
Primary Department
Department Affiliations
Contact
(520) 621-7447

Work Summary

Work Summary
Fabian-Xosé Fernandez's work includes a focus on parsing the logic used by the circadian pacemaker to interpret multidimensional light patterns, developing light-emitting diode (LED) photo-stimulation protocols to improve mental and physical health across the lifespan, and understanding the role that nocturnal wakefulness plays in suicide risk and developing countermeasures centered around light exposure.

Research Interest

Research Interest
Fabian-Xosé Fernandez, PhD, Departments of Psychology and Neurology, McKnight Brain InstituteCircadian timekeeping is fundamental to human health. Unfortunately, under many clinical circumstances, the temporal organization of our minds and bodies can stray slowly from the Universal Time (UT) that is set with the Earth’s rotation. This disorganization has been linked to progression of several age-related and psychiatric diseases. Non-invasive phototherapy has the potential to improve disease outcomes, but the information that the brain’s clock tracks in twilight (or any electric light signal) to assure that a person entrains their sleep-wake cycles to the outside world is not understood. The central theme of my research program is to fill in this blank and to usher in an era where therapeutically relevant “high-precision” light administration protocols are institutionalized at the level of the American Medical and Psychiatric Associations to change the standard of care for a wide variety of conditions that impair quality of life. Of the conditions my lab is currently studying, we are particularly interested in how chronic and quick, sequenced light exposure can be designed to: 1. promote normal healthy aging and 2. strengthen adaptive cognitive/emotional responses to being awake in the middle of the night (12-6AM), a key interval of the 24-h cycle that we have associated with increased suicidal ideation and mortality. Our circadian work on suicide is done in very close partnership with the University of Arizona Sleep Health and Research Program directed by Dr. Michael A. Grandner.

Publications

Fernandez, F. (2018). Precision Light for the Treatment of Psychiatric Disorders. Neural Plasticity.
Fernandez, F., & Garner, C. C. (2008). Episodic-like memory in Ts65Dn, a mouse model of Down syndrome. Behavioural brain research, 188(1), 233-7.

Ts65Dn mice, like individuals with Down syndrome (DS), demonstrate a functional dissociation between explicit and implicit forms of memory, showing selective impairment in explicit or declarative learning tasks. Here, we explored Ts65Dn explicit memory deficits further by evaluating the ability of these mice to assimilate the temporal and spatial contexts under which previously novel objects had been encountered. We found that Ts65Dn mice could in fact form contextual representations of objects over the course of a few hours, contrary to their inability to discriminate object novelty over a more prolonged period of 24h. These results suggest that Ts65Dn mice might have particular difficulties in declarative tasks requiring long-term memory, presenting an especially important putative therapeutic target for pre-clinical and clinical DS research.

Torres, V., Barra, L., Garcés, F., Ordenes, K., Leal-Ortiz, S., Garner, C. C., Fernandez, F., & Zamorano, P. (2010). A bicistronic lentiviral vector based on the 1D/2A sequence of foot-and-mouth disease virus expresses proteins stoichiometrically. Journal of biotechnology, 146(3), 138-42.

Classic IRES sequences are notorious for exerting biased expression in favor of upstream coding regions when placed into polycistronic vectors. Here, we report the development of a bicistronic lentiviral system based on the 1D/2A sequence from the foot-and-mouth disease virus that is able to maintain tightly balanced control of upstream and downstream protein expression for several days at a stoichiometry very closely approaching 1.0. Our results suggest that the 1D/2A sequence can be optimized in an FUGW lentiviral setting to coordinate expression of multiple polypeptides, presenting a potentially valuable tool to signaling network researchers and to the gene therapy community.

Clark, C. A., Fernandez, F., Sakhon, S., Spanò, G., & Edgin, J. O. (2017). The medial temporal memory system in Down syndrome: Translating animal models of hippocampal compromise. Hippocampus, 27(6), 683-691.

Recent studies have highlighted the dentate gyrus as a region of increased vulnerability in mouse models of Down syndrome (DS). It is unclear to what extent these findings are reflected in the memory profile of people with the condition. We developed a series of novel tasks to probe distinct medial temporal functions in children and young adults with DS, including object, spatial, and temporal order memory. Relative to mental age-matched controls (n = 45), individuals with DS (n = 28) were unimpaired on subtests involving short-term object or configural recall that was divorced from spatial or temporal contexts. By contrast, the DS group had difficulty recalling spatial locations when contextual information was salient and recalling the order in which objects were serially presented. Results are consistent with dysfunction of spatial and temporal contextual pattern separation abilities in individuals with DS, mediated by the hippocampus, including the dentate gyrus. Amidst increasing calls to bridge human and animal work, the memory profile demonstrated here in humans with DS is strikingly similar to that of the Ts65Dn mouse model of DS. The study highlights the trisynaptic circuit as a potentially fruitful intervention target to mitigate cognitive impairments associated with DS.

Ruby, N. F., Hwang, C. E., Wessells, C., Fernandez, F., Zhang, P., Sapolsky, R., & Heller, H. C. (2008). Hippocampal-dependent learning requires a functional circadian system. Proceedings of the National Academy of Sciences of the United States of America, 105(40), 15593-8.

Decades of studies have shown that eliminating circadian rhythms of mammals does not compromise their health or longevity in the laboratory in any obvious way. These observations have raised questions about the functional significance of the mammalian circadian system, but have been difficult to address for lack of an appropriate animal model. Surgical ablation of the suprachiasmatic nucleus (SCN) and clock gene knockouts eliminate rhythms, but also damage adjacent brain regions or cause developmental effects that may impair cognitive or other physiological functions. We developed a method that avoids these problems and eliminates rhythms by noninvasive means in Siberian hamsters (Phodopus sungorus). The present study evaluated cognitive function in arrhythmic animals by using a hippocampal-dependent learning task. Control hamsters exhibited normal circadian modulation of performance in a delayed novel-object recognition task. By contrast, arrhythmic animals could not discriminate a novel object from a familiar one only 20 or 60 min after training. Memory performance was not related to prior sleep history as sleep manipulations had no effect on performance. The GABA antagonist pentylenetetrazol restored learning without restoring circadian rhythms. We conclude that the circadian system is involved in memory function in a manner that is independent of sleep. Circadian influence on learning may be exerted via cyclic GABA output from the SCN to target sites involved in learning. Arrhythmic hamsters may have failed to perform this task because of chronic inhibitory signaling from the SCN that interfered with the plastic mechanisms that encode learning in the hippocampus.