Biology subjects

Cleghorn, W. M.

Publications and source records attributed to Cleghorn, W. M..

3 recordsLinked to original sources

bioRxiv2021

Metabolic function in aging retina and retinal pigment epithelium remains robust despite vision loss

PurposeCharacterize how metabolic function in the murine retina and retinal pigment epithelium-choroid-sclera (eyecup) complex is impacted by natural aging. MethodsWe examined scotopic and photopic visual function of young (3-6 months) and aged (23-26 months) C57Bl/6J mice using electroretinograms (ERGs). Metabolic changes in retina and eyecup explants were characterized by measuring uptake and usage of U-13C-glucose or U-13C-glutamine at different timepoints by gas chromatography-mass spectrometry (GC-MS), measuring oxygen consumption rate (OCR) using a perifusion apparatus, and determining ATP levels with a bioluminescence assay. ResultsScotopic and photopic ERG responses declined in aged mice. Glucose metabolism, glutamine metabolism, OCR, and ATP pools in retinal explants were mostly unaffected by the age of the mouse. In eyecups, glutamine usage in the Krebs Cycle decreased while glucose metabolism, OCR, and ATP pools remained stable. ConclusionsThe ex vivo approach in our study to examine aging glucose and glutamine metabolism in retina and RPE showed negligible impact of age on retina and an impairment of glutamine anaplerosis in eyecups. The surprising metabolic stability of these tissues ex vivo suggests age-related metabolic alterations in these tissues may not be intrinsic. Future experiments should focus on determining whether external factors including nutrient supply, oxygen availability, or other structural changes influence ocular metabolism in vivo.

biochemistry↗

bioRxiv2020

Daily mitochondrial dynamics in cone photoreceptors

Cone photoreceptors in the retina are exposed to intense daylight, and have higher energy demands in darkness. Cones produce energy using a large cluster of mitochondria. Mitochondria are susceptible to oxidative damage, and healthy mitochondrial populations are maintained by regular turnover. Daily cycles of light exposure and energy consumption suggest that mitochondrial turnover is important for cone health. We investigated the 3-D ultrastructure and metabolic function of zebrafish cone mitochondria throughout the day. At night cones undergo a mitochondrial biogenesis event, corresponding to an increase in the number of smaller, simpler mitochondria and increased metabolic activity. In the daytime, ER and autophagosomes associate more with mitochondria, and mitochondrial size distribution across the cluster changes. We also report dense material shared between cone mitochondria that is extruded from the cell in darkness, sometimes forming extracellular structures. Our findings reveal an elaborate set of daily changes to cone mitochondrial structure and function. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/030262v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@101b1f9org.highwire.dtl.DTLVardef@4b79eeorg.highwire.dtl.DTLVardef@1320df3org.highwire.dtl.DTLVardef@131edf5_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2019

Mitochondrial Ca2+ influences photoresponse recovery, metabolism, and mitochondrial localization in cone photoreceptors

Mitochondrial Ca2+ regulates key cellular processes including cytosolic Ca2+ signals, energy production, and susceptibility to apoptosis. Photoreceptors are specialized neurons that have extraordinarily high energy demands and rely on cytosolic Ca2+ signals for light adaptation and neurotransmission. Here we show that unlike other neurons zebrafish cone photoreceptors express low levels of the mitochondrial Ca2+ uniporter (MCU), the channel that allows mitochondrial Ca2+ entry. To determine why MCU expression is kept low, we overexpressed MCU specifically in cones. This increases mitochondrial [Ca2+], causes faster cytosolic Ca2+ clearance, and accelerates photoresponse recovery. Moreover, flux through the citric acid cycle increases despite dramatic changes in mitochondrial ultrastructure and localization. Remarkably, cones survive this ongoing stress until late adulthood. Our findings demonstrate the importance of tuning mitochondrial Ca2+ influx to modulate physiological and metabolic processes and reveal a novel directed movement of abnormal mitochondria in photoreceptors.

cell biology↗