Biology subjects

Mallory, B.

Publications and source records attributed to Mallory, B..

5 recordsLinked to original sources

bioRxiv2025

Protamine lacunae preserve the paternal chromatin landscape in sperm

The transmission of the paternal genome requires extensive chromatin reorganization, in which nucleosomes are largely replaced by protamines that drive extreme condensation of the genome in the sperm head. Using Fiber-seq, we resolve patterns of paternal chromatin repackaging in sperm at single-molecule resolution, revealing the interplay between protamination and nucleosome retention. We find that nucleosome retention is probabilistic, with no locus universally occupied. Although promoters of spermatogenic genes preferentially harbor retained nucleosomes, the predominant carrier of paternal epigenetic information is protamine lacunae, accessible discontinuities in the protamine coat that preferentially mark critical regulatory elements. By contrast, centromere kinetochore binding regions robustly retain CENP-A mono-nucleosomes, providing a mechanism for the focal transmission of paternal centromeres. Finally, we find that paternal chromatin repackaging is altered in low-motility sperm. Together, these findings reveal distinct modes of paternal chromatin epigenetic inheritance with broad implications for development and infertility.

genomics↗

bioRxiv2025

Genetic diversity and regulatory features of human-specific NOTCH2NL duplications

NOTCH2NL (NOTCH2-N-terminus-like) genes arose from ape-specific chromosome 1 segmental duplications implicated in human brain cortical expansion, including an incomplete NOTCH2 gene. Genetic characterization of these loci and their regulation is complicated because they are embedded in large, nearly identical duplications that predispose to recurrent microdeletion syndromes. Using near-complete long-read assemblies generated from 70 human and 12 ape haploid genomes, we show independent recurrent duplication among apes with protein-coding copies emerging in humans 2.2-3.7 million years ago. We distinguish NOTCH2NL paralogs present in every human haplotype (NOTCH2NLA) from copy number variable ones. We also characterize large-scale structural variation, including gene conversion, for 28% of haplotypes leading to a previously undescribed paralog, NOTCH2tv. Finally, we apply Fiber-seq and long-read transcript sequencing to human dorsal forebrain organoids to characterize the regulatory landscape and find that the most fixed paralogs, NOTCH2 and NOTCH2NLA, harbor the greatest number of paralog-specific elements potentially driving their regulation.

genomics↗

bioRxiv2022

Single-molecule architecture and heterogeneity of human telomeric DNA and chromatin

Telomeres are essential for linear genomes, yet their repetitive DNA content and somatic variability has hindered attempts to delineate their chromatin architectures. We performed single-molecule chromatin fiber sequencing (Fiber-seq) on human cells with a fully resolved genome, enabling nucleotide-precise maps of the genetic and chromatin structure of all telomeres. Telomere fibers are predominantly comprised of three distinct chromatin domains that co-occupy individual DNA molecules - multi- kilobase telomeric caps, highly accessible telomeric-subtelomeric boundary elements, and subtelomeric heterochromatin. Extended G-rich telomere variant repeats (TVRs) punctuate nearly all telomeres, and telomere caps imprecisely bridge these degenerate repeats. Telomeres demonstrate pervasive somatic alterations in length, sequence, and chromatin composition, with TVRs and adjacent CTCF-bound promoters impacting their stability and composition. Our results detail the structure and function of human telomeres. One sentence summaryWe use single-molecule chromatin fiber sequencing to detail the structure and function of human telomeric DNA and chromatin.

genomics↗

bioRxiv2022

Evaluation of N6-adenine DNA-immunoprecipitation-based genomic profiling in eukaryotes

The detection of low-abundance DNA N6-methyladenine (DNA-m6A) remains challenging, limiting our understanding of this novel base in eukaryotes. To address this, we introduce an approach for systematically validating the selectivity and sensitivity of antibody-based DNA-m6A methods, revealing most commercial antibodies as poorly selective towards DNA-m6A. Finally, using a validated highly selective anti-DNA-m6A antibody we expose distinct patterns of DNA-m6A in C. reinhardtii, A. thaliana, and D. melanogaster.

genomics↗

bioRxiv2022

Inducible degradation of dosage compensation protein DPY-27 facilitates isolation of Caenorhabditis elegans males for molecular and biochemical analyses

Biological sex affects numerous aspects of biology, yet how sex influences different biological processes has not been extensively studied at the molecular level. Caenorhabditis elegans, with both hermaphrodites (functionally females as adults) and males, is an excellent system to uncover how sex influences physiology. Here, we describe a method to isolate large quantities of C. elegans males by conditionally degrading DPY-27, a component of the dosage compensation complex essential for hermaphrodite, but not male, development. We show that germ cells from males isolated following DPY-27 degradation undergo meiosis and spermiogenesis like wild type and are competent to mate and produce viable offspring. We demonstrate the efficacy of this system by analyzing gene expression and performing affinity pull-downs from male worm extracts.

genetics↗