Biology subjects

Lathe, R.

Publications and source records attributed to Lathe, R..

7 recordsLinked to original sources

bioRxiv2026

mRNA editing of the Alzheimer's risk gene APOE

Variants in the human APOE gene govern the risk of Alzheimer's disease and other disorders. Three major APOE variants in humans reflect C to T replacements at two positions in a single exon: an upstream variant (AE4 site) that differs between the ancestral APOE epsilon 4 allele (APOE4) (C) and human-specific APOE2/E3 (T), and a downstream variant (AE2 site) that differentiates APOE3/E4 (C) from APOE2 (T). It has long been assumed that APOE allelotypes are genomically encoded, but here we report that multiple individuals express brain APOE C or U/T variant transcripts that differ from genomically templated versions. We demonstrate up to 10% C to U, or U to C nucleotide replacement at AE4 and AE2, but not at other sites, and with no corresponding changes in genomic DNA. Single-cell transcriptomic datasets from brain microglia revealed sporadic (up to ~8%) C to U replacement at AE2. We found 0.4 to 1.6% of brain transcripts in human APOE knock-in mice harbor selective C to U changes at either AE4 or AE2 sites. Transfection of HepG2 or Huh7 cells with either mouse or human APOBEC1 led to efficient (>90%) C to U editing of APOE4 mRNA at the AE4 but not AE2 site, with lower (<10%) C to T editing of genomic DNA at the AE4 site by mouse, but not human, APOBEC1. Furthermore, interrogation of proteomic datasets revealed up to 4% of non-genomically encoded APOE peptides in human plasma, indicating that the edited APOE transcripts are functional in vivo. These data suggest that APOE mRNA is subject to RNA editing that interconverts the different allelic forms of APOE.

genetics↗

bioRxiv2023

The remarkable complexity of the brain microbiome in health and disease

Microbes in human brain and their potential contribution to neurodegenerative conditions such as Alzheimers disease (AD) have long been debated. We recently developed a new method (the electronic tree of life, eToL) based on small subunit ribosomal RNA (rRNA) probes, further confirmed by large subunit rRNA analysis, to comprehensively address the spectrum of microorganisms in control and AD brain. We report a remarkable diversity of brain microbes in control brain. The most abundant are fungi, bacteria, and chloroplastida, and we report detailed identification of representative microbial species. The pattern is substantially conserved across different bilateran species from Drosophila to human. In terms of diversity, the human brain microbiome appears to be a subset (~20%) of the gut microbiome. Adenovirus type C was the major virus found in human brain; other viruses were not well represented. However, the spectrum of brain microbes differed between individuals as well as between brain regions examined from single individuals (amygdala, cingulate cortex, hippocampus, hypothalamus); of these four regions, the highest microbial burden was in cingulate cortex. There was evidence of spreading of pathogens between brain regions in single individuals. Some microbes are over-represented in AD brain according to two measures: (i) absolute number of microbes normalized to endogenous human transcripts, and (ii) the number of brain specimens showing overabundance versus control. Species over-represented in AD brain according to both measures notably include bacteria (Streptococcus, Staphylococcus/Bacillus, Sphingomonas/Ralstonia) and fungi (Acrocalymma/Altenaria/Aureobasidium of the Aspergillus group; Komagataella of the Candida group, Cortinarius of the Schizophyllum group, and Tausonia of the Cryptococcus group), that are all related to known human pathogens. In addition, an uncharacterized chloroplastida (algae-related) species was more abundant in AD brain samples. Although these findings point to diverse microbial species, indicative of multiple causation, similar absolute levels of bacteria and fungi in AD brain samples could suggest synergy between pathogens. However, it is important to stress that not all AD samples were positive for these microbes, but this could be because the affected brain region(s) was not examined. These findings support the contention that infection, perhaps associated with declining immunity with age, may contribute to AD development.

neuroscience↗

bioRxiv2022

Adjuvant effects of multifunctional transcription factor and BCG ‎target YB-1: exogenous YB-1 enhances specific antibody ‎production in vivo and protects mice against lethal E. coli ‎challenge

There is growing interest in the beneficial effects of immune system boosting through the administration of adjuvants, not only in acute infections such as COVID but also in chronic degenerative disorders that are potentially associated with infection. The best-known immunopotentiators are Freunds complete adjuvant (FCA) and its relative Bacille Calmete-Guerin (BCG), both based on Mycobacterium species. The key pathogen-associated molecular patterns (PAMPs) in both FCA and BCG are muramyl dipeptides (MDPs and glucosaminyl-MDP, GMDP). We previously identified the evolutionarily conserved protein Y-box factor YB-1/YBX1 as a primary target for MDP/GMDP. Unlike other host receptors for PAMPs, YB-1 is a diffusible molecule, and we therefore explored whether in vivo administration of YB-1, rather than its PAMP ligands, might enhance the immune response to a bacterial antigen and/or influence survival in the face of bacterial infection. We report that mice receiving YB-1 plus GMDP in vivo mount a significantly increased B cell response versus GMDP alone against a test antigen (Yersinia pestis V antigen), and that YB-1 administration alone significantly promotes survival in the face of lethal bacterial (Escherichia coli) challenge in vivo. Independent confirmation is warranted because recombinant YB-1 and its ligands could hold great promise both as adjuvants and as therapeutics.

immunology↗

bioRxiv2021

Evidence that nuclear receptors evolved from terpene synthases

Ligand-activated nuclear receptors (NRs) including steroid receptors orchestrate development, growth, and reproduction across all animal lifeforms - the Metazoa - but how NRs evolved remains mysterious. Given the universality of terpenoids - including steroids and retinoids - as activating NR ligands, we asked if NRs might have evolved from enzymes that catalyze terpene synthesis and metabolism. We provide evidence suggesting that NRs are a sub-branch of the terpene synthase (TS) enzyme superfamily. Based on over ten thousand 3D structural comparisons, backed up by multiple primary sequence alignments and mapping of ligand-contacting residues, we report that the NR ligand-binding domain and TS enzymes share a conserved core of seven -helical segments. Primary sequence comparisons reveal potential amino acid sequence similarities between NRs and the subfamily of cis-isoprene transferases, in particular dehydrodolichyl pyrophosphate synthase (DHDPPS) and its obligate partner, NUS1/NOGOB receptor. Our results suggest that a ligand-gated receptor may have arisen from an enzyme antecedent, and thus resolve the long-standing debate about whether the ancestral NR was unliganded. This would also explain aspects of NR ligand 'promiscuity', with implications for the development of pharmaceuticals targeting NRs and TS enzymes.

evolutionary biology↗

bioRxiv2019

The interoceptive hippocampus: mouse brain endocrine receptor expression highlights a dentate gyrus (DG)-cornu ammonis (CA) challenge-sufficiency axis

The primeval function of the mammalian hippocampus (HPC) remains uncertain. Implicated in learning and memory, spatial navigation, and neuropsychological disorders, evolutionary theory suggests that the HPC evolved from a primeval chemosensory epithelium. Internal sensing deficits in patients with HPC lesions argue that internal sensing may be conserved in higher vertebrates. We studied the expression of 250 endocrine receptors in mouse brain. Key findings are (i) the proportions and levels of endocrine receptor expression in the HPC are significantly higher than in all other comparable brain regions. (ii) Surprisingly, the distribution of endocrine receptor expression within mouse HPC was found to be highly structured: receptors signaling challenge are segregated in dentate gyrus (DG), whereas those signaling sufficiency are principally found in cornu ammonis (CA) regions. Selective expression of endocrine receptors in the HPC argues that internal sensing remains a core feature of hippocampal function. Further, we report that ligands of DG receptors predominantly inhibit both synaptic potentiation and neurogenesis, whereas CA receptor ligands conversely promote both synaptic potentiation and neurogenesis. These findings suggest that the hippocampus acts as an integrator of body status, extending its role in context-dependent memory encoding from where and when to how I feel. Implications for anxiety and depression are discussed.

neuroscience↗

bioRxiv2019

Possible origin of the scrapie genome in small endogenous RNAs; studies on eight candidate species in 263K scrapie infected hamster brain

The identity of the etiologic agent of the transmissible spongiform encephalopathies (TSEs), including bovine spongiform encephalopathy (BSE), scrapie and Creutzfeldt-Jakob disease (CJD), remains unknown. While much attention has been given to the hypothesis that the TSEs may be caused by a proteinaceous infectious agent or prion, there is considerable evidence to suggest that this hypothesis is incomplete. We have pursued an alternative contention: that the etiologic agent comprises in part a modified and replicating form of an endogenous nucleic acid, probably RNA. The endovirus hypothesis contends that the parental molecule is most likely to be a small and highly-structured cellular RNA that can convert to a replicating molecule by a finite number of nucleotide sequence changes. We have begun a systematic analysis of candidate molecular species present in hamster brain infected with scrapie strain 263K. Initial work focussed on the 7S group of small RNAs. Examination of 7-2, 7SK and 7SL failed to reveal differences in abundance and/or sequence between normal and scrapie (263K)-infected hamster brain. Inspection of other possible candidates, including U3, H1/8-2 and novel molecules KR1, nu1 and nu2, similarly failed to provide evidence for scrapie-specific molecular variants; alterations to the KR1 sequence failed to correlate with disease. We present sequences of hamster RNAs 7-2, 7SK, 7SL, H1/8-2, U3, nu1, nu2 and KR1. Together our data so far fail to contradict or confirm the hypothesis, while arguing that the major species of these 8 RNA molecules are unlikely to correspond to the etiologic agent of the TSEs.

neuroscience↗

bioRxiv2017

The promiscuous estrogen receptor: evolution of physiological estrogens and response to phytochemicals and endocrine disruptors

Many actions of estradiol (E2), the principal physiological estrogen in vertebrates, are mediated by estrogen receptor- (ER) and ER{beta}. An important physiological feature of vertebrate ERs is their promiscuous response to several physiological steroids, including estradiol (E2), {Delta}5-androstenediol, 5-androstanediol, and 27-hydroxycholesterol. A novel structural characteristic of {Delta}5-androstenediol, 5-androstanediol, and 27-hydroxycholesterol is the presence of a C19 methyl group, which precludes the presence of an aromatic A ring with a C3 phenolic group that is a defining property of E2. The structural diversity of these estrogens can explain the response of the ER to synthetic chemicals such as bisphenol A and DDT, which disrupt estrogen physiology in vertebrates, and the estrogenic activity of a variety of plant-derived chemicals such as genistein, coumestrol, and resveratrol. Diversity in the A ring of physiological estrogens also expands potential structures of industrial chemicals that can act as endocrine disruptors. Compared to E2, synthesis of 27-hydroxycholesterol and {Delta}5-androstenediol is simpler, leading us, based on parsimony, to propose that one or both of these steroids or a related metabolite was a physiological estrogen early in the evolution of the ER, with E2 assuming this role later as the canonical estrogen. In addition to the well-studied role of the ER in reproductive physiology, the ER also is an important transcription factor in non-reproductive tissues such as the cardiovascular system, kidney, bone, and brain. Some of these ER actions in non-reproductive tissues appeared early in vertebrate evolution, long before mammals evolved.

physiology↗