Biology subjects

Loftus, M.

Publications and source records attributed to Loftus, M..

5 recordsLinked to original sources

bioRxiv2026

Biological signatures of history: Examination of composite biomes and Y chromosome analysis from da Vinci-associated cultural artifacts

Cultural heritage objects can accumulate DNA from materials, environments, and repeated human contact, but biomolecular profiling of such items is constrained by nondestructive sampling requirements, ultra-low biomass, and high contamination risk. Here we present a minimally invasive workflow that integrates gentle swab collection, low- input whole-metagenome sequencing, taxonomic profiling, and Y-chromosome analyses to recover "biological signatures of history" from Renaissance-era artwork and archival correspondence associated with ancestors of Leonardo da Vinci. Across artifacts, we recovered heterogeneous mixtures of microbial and eukaryotic DNA (including bacteria, fungi, plants, and viruses) consistent with composite "biomes" that reflect differences in substrate, storage, conservation treatments, and handling. Multivariate comparisons show reproducible sample-to-sample separations. In parallel, we assessed human Y-chromosome signal using a panel of [~]90,000 phylogenetically informative markers and partial Y-STR profiling where feasible. Across multiple independent swabs from Leonardo da Vinci-associated items, the obtained Y chromosome marker data suggested assignments withing the broader E1b1/E1b1b clade. However, the control samples also indicate mixed contributions consistent with modern handling and other sources. Together, these data demonstrate the feasibility as well as limitations of combining metagenomics and human DNA marker analysis for cultural heritage science, providing a baseline workflow for future conservation science studies and hypothesis-driven investigations of provenance, authentication and handling history.

genomics↗

bioRxiv2025

A global view of human centromere variation and evolution

Centromeres are essential for accurate chromosome segregation during cell division, yet their highly repetitive sequence has historically hindered their complete assembly and characterization. Consequently, the full spectrum of centromere diversity across individuals, populations, and evolutionary contexts remains largely unexplored. Here, we address this gap in knowledge by assembling and characterizing 2,110 complete human centromeres from a diverse cohort of individuals representing 5 continental and 28 population groups. By developing a novel suite of bioinformatic tools tailored for centromeric regions, we uncover previously unknown variation within centromeres, including 226 novel centromere haplotypes and 1,870 new -satellite higher-order repeat (HOR) variants. We find that mobile element insertions are present in 30% of centromeres, with chromosome 16 harboring Alu elements within the kinetochore site at an 11-fold higher frequency than expected. While most centromeres have a single kinetochore site, 6% of them have di-kinetochores, and <<1% have tri-kinetochores, which we confirm with long-read CENP-A CUT&RUN, DiMeLo-seq, and multi-generational inheritance. We further show that the position of the kinetochore is not random and is, instead, closely associated with the underlying sequence and structure of the centromere. To understand the nature of evolutionary change, we compared 2,110 complete human centromeres to 5,747 complete centromeres recently assembled from the Human Pangenome Reference Consortium. We show that centromeres have a >50-fold variation in mutation rate, with the most rapidly mutating centromeres on chromosome 1 and the slowest mutating centromeres on chromosome Y. Additionally, a subset of centromeres show evidence of introgression from archaic hominins, shaping their sequence, structure, and evolutionary history. We validate these centromere mutation rates in a four-generation family, spanning 28 family members and 483 accurately assembled centromeres, and show that the kinetochore site is the most rapidly mutating region in the centromere, with twofold more single-nucleotide variants than the rest of the centromeric -satellite HOR array on average. We propose a model that reveals an arms race between centromeric sequence and proteins, with frequent mutations within the site of the kinetochore that lead to changes in genetic and epigenetic landscapes and, ultimately, rapid evolution of these critically important regions.

genomics↗

bioRxiv2025

Genomic insights and breeding strategies for nixtamalization moisture content in hybrid maize

CORE IDEASO_LINixtamalization moisture content can be selected early in breeding programs using NIR spectroscopy. C_LIO_LIYield does not significantly correlate with nixtamalization moisture content in diverse or elite populations. C_LIO_LIAdditive and dominance gene action impact nixtamalization moisture content in hybrid maize. C_LIO_LIGenomic prediction can be used to assess nixtamalization moisture content early in hybrid maize breeding. C_LI Nixtamalization moisture content, a measure of the quantity of water absorbed during the nixtamalization of a grain such as maize, has a large impact on the end-quality of masa-based products. An application to predict nixtamalization moisture content from raw inbred and hybrid maize grain was recently developed, but its utility in a breeding context has not been assessed. Important breeding considerations for nixtamalization moisture content were assessed in diverse maize hybrids, modern commercial hybrids, and historically high-acreage hybrids grown in up to three environments across two years. This study demonstrated that nixtamalization moisture content is heavily influenced by growing conditions, but sufficient genetic variance is present to allow breeders to make gains from selection. Contrary to prior theory, there was no substantial correlation between nixtamalization moisture content and yield suggesting breeders can select for both traits without negatively impacting either trait. Both additive and dominant genetic action was observed and genomic prediction was able to predict nixtamalization moisture content in hybrids with an average Spearmans rank correlation coefficient greater than 0.441 and a root mean square error below 0.006. The findings here suggest that nixtamalization moisture content can be selected for early in breeding cycles, allowing breeders to develop improved food-grade maize germplasm without negatively impacting important traits such as yield. PLAIN LANGUAGE SUMMARYPlant breeders need to understand the biological mechanisms underlying a trait of interest to maximize the efficiency of their efforts. Nixtamalization moisture content is a highly complex trait that is determined by both genetic and environmental factors. In this study, nixtamalization moisture content was assessed in a diverse set of hybrid and inbred maize to understand the biological mechanisms underlying nixtamalization moisture content. The relationship between nixtamalization moisture content and yield was assessed, the genetic architecture and mode of gene action underlying nixtamalization moisture content were evaluated, and the efficacy of genomic prediction in assessing nixtamalization moisture content was determined. The findings of this study will allow breeders to create optimized breeding strategies for nixtamalization moisture content, thus improving the raw materials that are used to produce globally consumed products such as tortillas and tortilla chips.

plant biology↗

bioRxiv2024

Complex genetic variation in nearly complete human genomes

Diverse sets of complete human genomes are required to construct a pangenome reference and to understand the extent of complex structural variation. Here, we sequence 65 diverse human genomes and build 130 haplotype-resolved assemblies (130 Mbp median continuity), closing 92% of all previous assembly gaps1,2 and reaching telomere-to-telomere (T2T) status for 39% of the chromosomes. We highlight complete sequence continuity of complex loci, including the major histocompatibility complex (MHC), SMN1/SMN2, NBPF8, and AMY1/AMY2, and fully resolve 1,852 complex structural variants (SVs). In addition, we completely assemble and validate 1,246 human centromeres. We find up to 30-fold variation in -satellite high-order repeat (HOR) array length and characterize the pattern of mobile element insertions into -satellite HOR arrays. While most centromeres predict a single site of kinetochore attachment, epigenetic analysis suggests the presence of two hypomethylated regions for 7% of centromeres. Combining our data with the draft pangenome reference1 significantly enhances genotyping accuracy from short-read data, enabling whole-genome inference3 to a median quality value (QV) of 45. Using this approach, 26,115 SVs per sample are detected, substantially increasing the number of SVs now amenable to downstream disease association studies.

genomics↗

bioRxiv2022

Assembly of 43 diverse human Y chromosomes reveals extensive complexity and variation

The prevalence of highly repetitive sequences within the human Y chromosome has led to its incomplete assembly and systematic omission from genomic analyses. Here, we present long-read de novo assemblies of 43 diverse Y chromosomes spanning 180,000 years of human evolution, including two from deep-rooted African Y lineages, and report remarkable complexity and diversity in chromosome size and structure, in contrast with its low level of base substitution variation. The size of the Y chromosome assemblies varies extensively from 45.2 to 84.9 Mbp and include, on average, 81 kbp of novel sequence per Y chromosome. Half of the male-specific euchromatic region is subject to large inversions with a >2-fold higher recurrence rate compared to inversions in the rest of the human genome. Ampliconic sequences associated with these inversions further show differing mutation rates that are sequence context-dependent and some ampliconic genes show evidence for concerted evolution with the acquisition and purging of lineage-specific pseudogenes. The largest heterochromatic region in the human genome, the Yq12, is composed of alternating arrays of DYZ1 and DYZ2 repeat units that show extensive variation in the number, size and distribution of these arrays, but retain a 1:1 copy number ratio of the monomer repeats, consistent with the notion that functional or evolutionary forces are acting on this chromosomal region. Finally, our data suggests that the boundary between the recombining pseudoautosomal region 1 and the non-recombining portions of the X and Y chromosomes lies 500 kbp distal to the currently established boundary. The availability of sequence-resolved Y chromosomes from multiple individuals provides a unique opportunity for identifying new associations of specific traits with Y-chromosomal variants and garnering novel insights into the evolution and function of complex regions of the human genome.

genomics↗