Biology subjects

Munasinghe, J.

Publications and source records attributed to Munasinghe, J..

5 recordsLinked to original sources

bioRxiv2024

Apolipoprotein-L1 G1 variant contributes to hydrocephalus but not to atherosclerosis in apolipoprotein-E knock-out mice

IntroductionIn USA, six million individuals with Sub-Saharan ancestry carry two APOL1 high-risk variants, which increase the risk for kidney diseases. Whether APOL1 high-risk variants are independent risk factors for cardiovascular diseases is unclear and requires further investigation. MethodsWe characterized a mouse model to investigate the role of APOL1 in dyslipidemia and cardiovascular diseases. Transgenic mice carrying APOL1 (G0 and G1 variants) on bacterial artificial chromosomes (BAC/APOL1 mice) were crossed with the ApoE knock-out (ApoE-KO) atherosclerosis mouse model. The compound transgenic mice were evaluated for the impact of APOL1 on systemic phenotypes. ResultsApoE-KO mice carrying APOL1-G0 and APOL1-G1 did not show differences in the extent of atherosclerotic lesions or aortic calcification, as evaluated by Sudan IV staining and radiographic examination, respectively. However, [~]20% of ApoE-KO; BAC/APOL1-G1 mice developed hydrocephalus and required euthanasia. The hydrocephalus was communicating and likely was due to excess cerebrospinal fluid produced by the choroid plexus, where epithelial cells expressed APOL1. Single-nuclear RNA-seq of choroid plexus identified solute transporter upregulation and mTORC2 pathway activation in APOL1-G1-expressing epithelial cells. Further, in the All of Us cohort, we found higher hydrocephalus prevalence among individuals with the APOL1-G1 variant in both recessive and dominant models, supporting the mouse findings. ConclusionWhile APOL1-G1 expression in ApoE-KO mice did not worsen cardiovascular disease phenotypes, we uncovered hydrocephalus as a novel APOL1 risk allele-mediated phenotype. These findings extend the spectrum of APOL1-associated pathologies.

molecular biology↗

bioRxiv2024

Band-selective IR PRESS for brain tumor spectroscopy allows robust detection of lactate

Lactate plays a critical role in the tumor microenvironment, driving tumor progression, metastasis, and immune evasion. Despite its importance, in vivo quantification of lactate using magnetic resonance spectroscopy (MRS) has faced challenges, primarily due to the overlapping lipid signal at 1.3 ppm. Current clinical practice employs a long echo time to exploit differences in T2 relaxation between lactate and lipids; however, this approach significantly suppresses signals from other metabolites. Lipid has a notably different T1 relaxation time than lactate and other metabolites, which may be exploited by an inversion recovery sequence to better distinguish them. However, this method has not found wide use because of the loss of signal in other metabolites. Here we introduce a selective inversion pulse with a short echo time MRS method (SPIR-PRESS), which mitigates this issue. In phantom experiments, SPIR-PRESS successfully suppressed lipid signals that could be misinterpreted as lactate in short TE PRESS spectra, while maintaining sensitivity to the full metabolite profile. SPIR-PRESS demonstrated superior performance in quantifying lactate compared to long echo time PRESS, with [~] 60 % increase in sensitivity for lactate detection compared to conventional PRESS with a 288 ms TE. In a mouse glioma model, SPIR-PRESS clearly detected lactate and other key tumor metabolites (choline, creatine, NAA) in the tumor, which were not detectable in conventional long TE PRESS. These findings highlight SPIR-PRESS as a promising technique for improved lactate quantification and comprehensive metabolite profiling in tumor environments.

biochemistry↗

bioRxiv2022

Ablation of Tmem65 Causes Lethal Mitochondrial Encephalomyopathy in Mouse

Transmembrane protein 65 (TMEM65) depletion in a patient carrying a homozygous variant in the Tmem65 splice site resulted in severe mitochondrial encephalomyopathy, indicating the clinical importance of TMEM65. However, the function of TMEM65 remains unknown. Here, we generated a TMEM65 reporter mouse as well as whole-body and tissue-specific Tmem65 knockout (KO) mice to investigate the localization and function of TMEM65. We show that TMEM65 is localized to mitochondria in heart, skeletal muscle, and throughout the brain. Both whole-body and nervous system-specific Tmem65 KO result in severe growth retardation and sudden death following seizures ~3 weeks after birth, indicating TMEM65 is indispensable for normal brain function. In addition, we find that skeletal muscle-specific Tmem65 KO leads to progressive, adult-onset myopathy preceded by elevated mitochondrial calcium levels despite unaltered expression of known mitochondrial or cellular calcium handling proteins. Consistently, we demonstrate that ablation of TMEM65 results in a loss of sodium-dependent mitochondrial calcium export. Finally, we show that blocking mitochondrial calcium entry through removal of the mitochondrial calcium uniporter (MCU) rescues the early lethality of whole-body TMEM65 ablation. Our data not only reveal the essential role of TMEM65 in mammalian physiology, but also suggest modulating mitochondrial calcium may offer a potential therapeutical approach to address defects associated with TMEM65 misexpression.

physiology↗

bioRxiv2019

Distinguishing Closely Related Pancreatic Cancer Subtypes In Vivo by 13C Glucose MRI without Hyperpolarization

Metabolic differences between patients and within the tumor itself can be an important determinant in cancer treatment outcome. However, methods for determining these differences non-invasively in vivo have been lacking. Using pancreatic ductal adenocarcinoma as a model, we demonstrate that tumor xenografts with a similar genetic background can be distinguished by their differing rates of metabolism, as detected by imaging of uniformly 13C labeled glucose tracers using a newly developed technique using tensor decomposition for noise suppression to bring the signal to a detectable level without hyperpolarization of the tracer. Using this method, cancer subtypes that appeared to exhibit similar metabolic profiles by other techniques that measured steady state metabolism can be distinguished.

cancer biology↗

bioRxiv2018

PET by MRI: Glucose Imaging by 13C-MRS without Dynamic Nuclear Polarization by Noise Suppression through Tensor Decomposition Rank Reduction

Metabolic reprogramming is one of the defining features of cancer and abnormal metabolism is associated with many other pathologies. Molecular imaging techniques capable of detecting such changes have become essential for cancer diagnosis, treatment planning, and surveillance. In particular, 18F-FDG (fluorodeoxyglucose) PET has emerged as an essential imaging modality for cancer because of its unique ability to detect a disturbed molecular pathway through measurements of glucose uptake. However, FDG-PET has limitations that restrict its usefulness in certain situations and the information gained is limited to glucose uptake only. 13C magnetic resonance spectroscopy theoretically has certain advantages over FDG-PET, but its inherent low sensitivity has restricted its use mostly to single voxel measurements. We show here a new method of imaging glucose metabolism in vivo that relies on a simple, but robust and efficient, post-processing procedure by the higher dimensional analog of singular value decomposition, tensor decomposition. Using this procedure, we achieve an order of magnitude increase in signal to noise in both dDNP and non-hyperpolarized non-localized experiments without sacrificing accuracy. In CSI experiments an approximately 30-fold increase was observed, enough that the glucose to lactate conversion indicative of the Warburg effect can be imaged without hyper-polarization with a time resolution of 12 s and an overall spatial resolution that compares favorably to 18F-FDG PET.

cancer biology↗