Biology subjects

Canfield, V. A.

Publications and source records attributed to Canfield, V. A..

4 recordsLinked to original sources

bioRxiv2021

Effects of Hypopigmentation Alleles and Ancestry on Skin Color in the Kalinago of Dominica

Our interest in the genetic basis of skin color variation between populations led us to seek a Native American population with African admixture but low frequency of European light skin alleles. Analysis of 458 genomes from individuals residing in the Kalinago territory of the Commonwealth of Dominica showed approximately 55% Native American, 32% African, and 12% European ancestry, the highest Native American ancestry among Caribbean populations to date. Skin pigmentation ranged from 20 to 80 melanin units, averaging 46. Three albino individuals were determined to be homozygous for a causative multi-nucleotide polymorphism OCA2NW273KV contained within a haplotype of African origin; its allele frequency was 0.03 and single allele effect size was -8 melanin units. Derived allele frequencies of SLC24A5A111T and SLC45A2L374F were 0.14 and 0.06, with single allele effect sizes of -6 and -4, respectively. Native American ancestry by itself reduced pigmentation by more than 20 melanin units (range 24 - 29). The responsible hypopigmenting genetic variants remain to be identified, since none of the published polymorphisms predicted in prior literature to affect skin color in Native Americans caused detectable hypopigmentation in the Kalinago.

genetics↗

bioRxiv2021

Whole-organism 3D Quantitative Characterization of Zebrafish Melanin by Silver Deposition Micro-CT

Melanin-rich zebrafish melanophores are used to study pigment development, human skin color, and as a large-scale screening phenotype. To facilitate more detailed whole-body, computational analyses of melanin content and morphology, we have combined X-ray microtomography (micro-CT), a non-destructive, full-volume imaging modality, with a novel application of ionic silver staining to characterize melanin distribution in whole zebrafish larvae. Normalized micro-CT reconstructions of silver-stained fish consistently reproduced pigment patterns seen by light microscopy, and allowed direct quantitative comparisons of melanin content across wild-type and mutant samples, for both dramatic and subtle phenotypes not previously described. Silver staining of melanin for micro-CT provides proof-of-principle for whole-body, three-dimensional computational phenomic analysis of a particular cell type at cellular resolution, with potential applications in other model organisms and human melanoma biopsies. Whole-organism, high-resolution phenotyping is a challenging ideal, but provides superior context for functional studies of mutations, diseases, and environmental influences.

pathology↗

bioRxiv2021

Time-dependent pleiotropic phenotypes are caused by progressive DNA polymerase α deficiency in zebrafish

Pleiotropy caused by single-gene mutations is common and poorly understood. A zebrafish null mutant of DNA polymerase subunit B, huli hutu (hht), evolves a complex pleiotropy associated with DNA damage and S phase arrest across multiple organ systems over 5-7 days, including nuclear atypia, a common cellular feature in human cancers and pre-cancers, in gastrointestinal organs, and nuclear fragmentation in the eye and brain. The pleiotropic pattern of hht phenotypes is explained by progressive loss of wild-type maternal pola2 function in homozygous mutant embryos whose pola2 mRNA becomes undetectable by 24 hours post-fertilization (hpf). Inhibition of DNA synthesis by aphidicolin or hydroxyurea in wild-type embryos from 24 hpf phenocopied the pleiotropic pattern of hht. These results are consistent with a model in which time-sensitive, reduced capacity for DNA synthesis results in cell death in fast-replicating cells, and nuclear atypia in tissues with fewer and larger cells.

genetics↗

bioRxiv2018

Three-Dimensional Histology of Whole Zebrafish by Sub-Micron Synchrotron X-ray Micro-Tomography

Histological studies providing cellular insights into tissue architecture have been central to biological discovery and remain clinically invaluable today. Extending histology to three dimensions would be transformational for research and diagnostics. However, three-dimensional histology is impractical using current techniques. We have customized sample preparation, synchrotron X-ray tomographic parameters, and three-dimensional image analysis to allow for complete histological phenotyping using whole larval and juvenile zebrafish. The resulting digital zebrafish can be virtually sectioned and visualized in any plane. Whole-animal reconstructions at subcellular resolution also enable computational characterization of the zebrafish nervous system by region-specific detection of cell nuclei and quantitative assessment of individual phenotypic variation. Three-dimensional histological phenotyping has potential use in genetic and chemical screens, and in clinical and toxicological tissue diagnostics.\n\nOne Sentence SummarySynchrotron X-ray micro-tomography can be used to rapidly create 3-dimensional images of fixed and stained specimens without sectioning, enabling computational histological phenotyping at cellular resolution.

pathology↗