Selected Grantee Publications
A Germ-Free Humanized Mouse Model Shows the Contribution of Resident Microbiota to Human-Specific Pathogen Infection
Wahl et al., Nature Biotechnology. 2023.
https://www.nature.com/articles/s41587-023-01906-5
Germ-free (GF) mice are of limited value in the study of human-specific pathogens because they do not support their replication. In this report, investigators developed a GF humanized mouse model using the bone marrow–liver–thymus platform to provide a robust and flexible in vivo model that can be used to study the role of resident microbiota in human health and disease. They demonstrated that resident microbiota promote viral acquisition and pathogenesis by using two human-specific pathogens, Epstein–Barr virus and HIV. Supported by ORIP (P40OD010995), FIC, NIAID, NCI, and NIDDK.
Proteomic Profiling of Extracellular Vesicles Isolated From Plasma and Peritoneal Exudate in Mice Induced by Crotalus scutulatus scutulatus Crude Venom and Its Purified Cysteine-Rich Secretory Protein (Css-CRiSP)
Reyes et al., Toxins (Basel). 2023.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10467150/
Toxins in viperid snakes can induce clinically heterogeneous effects, but most viper venoms are composed of only 10 main protein families. Researchers investigated the proteome expression profile of extracellular vesicles isolated from biofluid samples from male and female mice after injection with crude venom and cysteine-rich secretory proteins. They reported changes in the expression of proteins involved in cell adhesion, cytoskeleton rearrangement, signal transduction, immune responses, and vesicle-mediated transports. This work could be applied in future efforts for early detection and assessment of local effects. Supported by ORIP (P40OD010960), NIGMS, and NHLBI.
Photoreceptor Disc Incisures Form as an Adaptive Mechanism Ensuring the Completion of Disc Enclosure
Lewis et al., eLife. 2023.
https://elifesciences.org/articles/89160
The first steps of vision take place within a stack of tightly packed disc-shaped membranes, or discs, located in the outer segment compartment of photoreceptor cells. In rod photoreceptors, discs are enclosed inside the outer segment and contain deep indentations in their rims called incisures. This presence of incisures has been documented in several species, yet their role remains elusive. This study demonstrated that incisures are formed only after discs become completely enclosed. At the earliest stage of their formation, discs are not round but rather are highly irregular in shape and resemble expanding lamellipodia. In genetically modified mice and frogs, researchers measuring outer segment protein abundances found that incisure size is determined by the molar ratio between peripherin-2, a disc rim protein critical for the process of disc enclosure, and rhodopsin, the major structural component of disc membranes. High perpherin-2-to-rhodopsin ratio causes an increase in incisure size and structural complexity; low ratio precludes incisure formation. They propose a model whereby normal rods express a modest excess of peripherin-2 over the amount required for complete disc enclosure to ensure that this important step of disc formation is accomplished. Once the disc is enclosed, the excess peripherin-2 incorporates into the rim to form an incisure. Supported by ORIP (P40OD010997, R24OD030008).
The Landscape of Tolerated Genetic Variation in Humans and Primates
Gao et al., Science. 2023.
Investigators created a whole-genome sequence database from 809 nonhuman primates (NHPs) of 233 species to test the hypothesis that gene variants that do not cause disease in NHPs would likely be benign also in humans. They found that 99% of the genetic variants that were benign in NHPs also were classified as benign in the human ClinVar database. In contrast, only 71% to 87% of genomic variants classified as benign in non-primate animals were benign in humans. Building on this approach, the authors reclassified more than 4 million human genetic variants of unknown health impact as likely being benign based on effects in NHPs. This work illustrates the power of comparative medicine approaches between NHPs and humans. Supported by ORIP (P40OD024628, P51OD011106) and NIGMS.
A Global Catalog of Whole-Genome Diversity from 233 Primate Species
Kuderna et al., Science. 2023.
https://pubmed.ncbi.nlm.nih.gov/37262161/
Researchers are interested in studying the remarkable diversity of morphology and behavior across primates to answer long‑standing questions in evolutionary and conservation biology. Using whole-genome sequencing, the investigators created a nuclear DNA phylogeny and reassessed evolutionary divergence times among primate clades. They found that intraspecies genetic diversity across families and geographic regions was associated with climate and sociality, but not with extinction risk. Furthermore, mutation rates differed among species, potentially influenced by effective population sizes. Lastly, they identified extensive recurrence of missense mutations that previously were thought to be human specific. Supported by ORIP (P40OD024628).
Early Detection of Pseudocapillaria tomentosa by qPCR in Four Lines of Zebrafish, Danio rerio (Hamilton 1882)
Schuster et al., Journal of Fish Diseases. 2023.
https://onlinelibrary.wiley.com/doi/10.1111/jfd.13773
The intestinal nematode Pseudocapillaria tomentosa in zebrafish (Danio rerio) causes profound intestinal lesions, emaciation, and death and is a promoter of a common intestinal cancer in zebrafish. This nematode has been detected in an estimated 15% of zebrafish laboratories. Adult worms are readily detected about 3 weeks after exposure by either histology or wet mount preparations of the intestine, and larval worms are inconsistently observed in fish before this time. A quantitative PCR (qPCR) test was recently developed to detect the worm in fish and water, and here the authors determined that the test on zebrafish intestines was effective for earlier detection. Supported by ORIP (R24OD010998, P40OD011021).
Giardia Hinders Growth by Disrupting Nutrient Metabolism Independent of Inflammatory Enteropathy
Giallourou et al., Nature Communications. 2023.
https://www.nature.com/articles/s41467-023-38363-2
Giardia lamblia is one of the most common intestinal pathogens among children in low- and middle-income countries. Investigators performed translational investigations using the Malnutrition and Enteric Diseases (MAL-ED) male and female cohort, as well as mice of both sexes, to identify mechanistic pathways that might explain Giardia-induced effects on early childhood growth. They identified signatures in the urinary metabolome of young children, suggesting that host growth restriction during infection is mediated by dysregulated amino acid metabolism. Supported by ORIP (P40OD010995), NIAID, and NIDDK.
Leukocyte Tyrosine Kinase (Ltk) Is the Mendelian Determinant of the Axolotl Melanoid Color Variant
Kabangu et al., Genes. 2023.
https://www.mdpi.com/2073-4425/14/4/904
The diversity of color patterns among amphibians is largely explained by the differentiation of a few pigment cell types during development. Mexican axolotls have a variety of color phenotypes, from leucistic to highly melanistic. The melanoid axolotl is a Mendelian variant characterized by large numbers of melanophores, fewer xanthophores, and no iridophores. Studies of melanoid were influential in developing the single-origin hypothesis of pigment cell development, proposing that all three pigment cell types derive from a common progenitor cell, with pigment metabolites playing potential roles in directing the development of organelles that define different pigment cell types. Xanthine dehydrogenase (XDH) activity was identified as a mechanism for the permissive differentiation of melanophores at the expense of xanthophores and iridophores. The authors used bulked segregant RNA-Seq (including a region on chromosome 14q) to screen the axolotl genome for melanoid candidate genes and identify the associated locus. The region 14q contains gephyrin (Gphn), an enzyme that catalyzes the synthesis of the molybdenum cofactor that is required for XDH activity, and Ltk, a cell surface signaling receptor required for iridophore differentiation in zebrafish. Wild-type Ltk crispants present similar pigment phenotypes to melanoid, strongly implicating Ltk as the melanoid locus. The results support the idea of direct fate specification of pigment cells, as well as the single-origin hypothesis of pigment cell development. Supported by ORIP (P40OD019794, R24OD010435, R24OD021479).
Effect of the Snake Venom Component Crotamine on Lymphatic Endothelial Cell Responses and Lymph Transport
Si et al., Microcirculation. 2023.
https://onlinelibrary.wiley.com/doi/10.1111/micc.12775
The pathology of snake envenomation is closely tied to the severity of edema in the tissue surrounding the area of the bite. This study focused on one of the most abundant venom components in North American viper venom, crotamine, and the effects it has on the cells and function of the lymphatic system. The authors found that genes that encode targets of crotamine are highly present in lymphatic tissues and cells and that there is a differential distribution of those genes that correlates with phasic contractile activity. They found that crotamine potentiates calcium flux in human dermal lymphatic endothelial cells in response to stimulation with histamine and shear stress—but not alone—and that it alters the production of nitric oxide in response to shear, as well as changes the level of F-actin polymerization of those same cells. Crotamine alters lymphatic transport of large molecular weight tracers to local lymph nodes and is deposited within the node, mostly in the immediate subcapsular region. Results suggest that snake venom components may have an impact on the function of the lymphatic system and provide new targets for improved therapeutics to treat snakebites. Supported by ORIP (P40OD010960).
A Live Dengue Virus Vaccine Carrying a Chimeric Envelope Glycoprotein Elicits Dual DENV2–DENV4 Serotype-Specific Immunity
Young et al., Nature Communications. 2023.
https://pubmed.ncbi.nlm.nih.gov/36914616/
Dengue vaccine development is challenging because some virus-specific antibodies are protective, whereas others are implicated in enhanced viral replication and more severe disease. Current dengue tetravalent vaccines contain four live attenuated serotypes formulated to induce balanced protective immunity. To simplify live-virus vaccine design, investigators identified co-evolutionary constraints inherent in flavivirus virion assembly. They found that the chimeric virus replicated efficiently in vitro and in vivo and that a single inoculation induced type-specific neutralizing antibodies in male macaques. These findings can be applied to the development of bivalent live dengue vaccines that induce independent immunity to multiple serotypes. Supported by ORIP (P40OD012217) and NIAID.