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Mejia, E.

Publications and source records attributed to Mejia, E..

2 recordsLinked to original sources
bioRxiv2024

Brain-wide projections of mouse dopaminergic zona incerta neurons

The zona incerta (ZI) supports diverse behaviors including binge feeding, sleep/wake cycles, nociception, and hunting. This diversity of functions can be attributed to the heterogenous neurochemicals, cytoarchitecture, and efferent connections that characterize the ZI. The ZI is predominantly GABAergic, but we recently identified a subset of medial ZI GABA cells that co-express dopamine (DA), as marked by the enzyme tyrosine hydroxylase (TH). While the role of GABA within the ZI is well studied, little is understood about the function of ZI DA cells. To identify potential roles of ZI DA cells we mapped the efferent fiber projections from Th-cre ZI cells. We first validated a Th-cre;L10-Egfp mouse line and found that medial Egfp ZI cells were more likely to co-express TH-immunoreactivity (TH-ir). We thus delivered a cre-dependent virus into the medial ZI of Th-cre or Th-cre;L10-Egfp mice and selected two injection cases for full brain mapping. We selected the cases with the lowest (17%) and highest (53%) percentage of colocalization between TH-ir and virus transfected cells labelled with DsRed. Overall, DsRed-labelled fibers were observed throughout the brain and were most prominent within motor-related regions of the midbrain (MBmot), notably the periaqueductal grey area and superior colliculus. We also observed considerable DsRed-labelled fibers within the polymodal cortex associated regions of the thalamus (DORpm), including the paraventricular thalamic nucleus and nucleus of reunions. Overall, ZI DA cells displayed a similar connectivity profile to ZI GABA cells, suggesting that ZI DA cells may perform synergistic or opposing functions at the same target sites. List of RRIDsAB_2201528, AB_10013483, AB_11177031, AB_2340593, AB_2315778, SCR_016477 Three key points- Tyrosine hydroxylase immunoreactivity was more prominent in the medial zona incerta - Intersection points from two Th-cre injection cases revealed common target regions - Dopaminergic zona incerta cells project predominantly to motor-related brain regions

neuroscience↗
bioRxiv2024

PI3K-dependant reprogramming of hexokinase isoforms controls glucose metabolism and functional responses of B lymphocytes

B lymphocyte metabolic reprogramming is essential for B cell differentiation and mounting a healthy immune response. The PI3K signaling pathway regulates B cell metabolism, but the mechanisms involved are not well understood. Here we report that signaling via PI3K8 can impact B cell glucose metabolism and immune functions via selective upregulation of hexokinase 2 (HK2). Three HK enzymes can catalyze the critical first step for glucose utilization and may selectively direct glucose into specific catabolic and anabolic pathways. While HK1 is constitutively expressed in B cells, HK2 is strikingly upregulated during B cell activation in a PI3K8-dependent manner. HK2 shows a unique distribution between mitochondrial and cytoplasmic pools that is also regulated by PI3K. Genetic deletion of HK2 significantly impairs extracellular acidification rate and glycolytic ATP production despite strong expression of HK1. B cell-specific deletion of HK2 in mice caused mild perturbations in B cell development but did not prevent generation of mature B cell subsets. HK2-deficient B cells show altered functional responses in vitro and evidence of metabolic adaptation to become less dependent on glucose and more dependent on glutamine. HK2-deficient B cells exhibit impaired glycolysis, altered metabolite profiles and altered flux of labeled glucose carbons into the pentose phosphate pathway. Upon immunization, HK2-deficient mice exhibit impaired generation of germinal centre B cells, plasmablasts and antibody responses. We further found that HK2 expression in primary human chronic lymphocytic leukemia (CLL) cells was associated with recent proliferation and could be reduced by PI3K inhibition. Our study identifies hexokinase 2 upregulation as a functionally important component of B cell metabolic reprogramming dependent on the PI3K pathway.

immunology↗