Biology subjects

Pratt, K. J. B.

Publications and source records attributed to Pratt, K. J. B..

3 recordsLinked to original sources

bioRxiv2024

Spatial Coding Dysfunction and Network Instability in the Aging Medial Entorhinal Cortex

Across species, spatial memory declines with age, possibly reflecting altered hippocampal and medial entorhinal cortex (MEC) function. However, the integrity of cellular and network-level spatial coding in aged MEC is unknown. Here, we leveraged in vivo electrophysiology to assess MEC function in young, middle-aged, and aged mice navigating virtual environments. In aged grid cells, we observed impaired stabilization of context-specific spatial firing, correlated with spatial memory deficits. Additionally, aged grid networks shifted firing patterns often but with poor alignment to context changes. Aged spatial firing was also unstable in an unchanging environment. In these same mice, we identified 458 genes differentially expressed with age in MEC, 61 of which had expression correlated with spatial firing stability. These genes were enriched among interneurons and related to synaptic transmission. Together, these findings identify coordinated transcriptomic, cellular, and network changes in MEC implicated in impaired spatial memory in aging.

neuroscience↗

bioRxiv2023

Neuronal Activation of the Gαq Protein EGL-30/GNAQ Late in Life Rejuvenates Cognition Across Species

Cognitive decline is perhaps the most devastating aging loss. EGL-30/GNAQ and Gq signaling pathways are highly conserved between C. elegans and mammals. We find that activation of EGL-30 in aged worms at least triples memory span, and we wondered if this highly conserved pathway could also improve memory in very old mice. Murine Gnaq is enriched in hippocampal excitatory neurons and declines with age. Furthermore, GNAQ gain-of-function significantly improved memory in aged mice: GNAQ(gf) in hippocampal neurons of 24-month-old mice rescued age-related impairments in health metrics and long-term memory. Single-nucleus RNAseq revealed gene expression changes related to synaptic function, axon guidance, and learning and memory pathways. Several worm orthologs of mouse genes upregulated by GNAQ(gf) overexpression are required for EGL-30(gf)-dependent memory improvement. These results demonstrate that the molecular and genetic pathways between C. elegans and mammals are highly conserved, as activation of EGL-30/GNAQ, a pathway first identified in worms, rejuvenates cognitive function in two-year old mice (the equivalent of 70-80 yo humans). To our knowledge, this is the oldest age an intervention has successfully improved age-related cognitive decline. One-Sentence SummaryNeuronal activation of the Gq protein EGL-30/GNAQ restores long-term memory at old age in worms and mice.

neuroscience↗

bioRxiv2019

Unique Transcription Factor Functions Regulate Epigenetic and Transcriptional Dynamics During Cardiac Reprogramming

Direct lineage conversion, whereby a somatic cell assumes a new cellular identity, can be driven by ectopic expression of combinations of lineage-enriched transcription factors. To determine the molecular mechanisms by which expression of Gata4, Mef2c, and Tbx5 (GMT) induces direct reprogramming from a cardiac fibroblast toward an induced cardiomyocyte, we performed a comprehensive transcriptomic and epigenomic interrogation of the reprogramming process. Single cell RNA sequencing indicated that a reprogramming trajectory was acquired within 48 hours of GMT introduction, did not require cell division, and was limited mainly by successful expression of GMT. Evaluation of chromatin accessibility by ATAC-seq supported the expression dynamics and revealed widespread chromatin remodeling at early stages of the reprogramming process. Chromatin immunoprecipitation followed by sequencing of each factor alone or in combinations revealed that GMT bind DNA individually and in combination, and that ectopic expression of either Mef2c or Tbx5 is sufficient in some contexts to increase accessibility. We also find evidence for cooperative facilitation and refinement of each factors binding in a combinatorial setting. A random-forest classifier that integrated the observed gene expression dynamics with regions of dynamic chromatin accessibility suggested Tbx5 binding is a primary driver of gene expression changes and revealed additional transcription factor motifs co-segregating with reprogramming factor motifs, suggesting new factors that may be involved in the reprogramming process. These results begin to explain the mechanisms by which transcription factors normally expressed in multiple germ layers can function combinatorially to direct lineage conversion.

molecular biology↗