Biology subjects

Turner, J. M. A.

Publications and source records attributed to Turner, J. M. A..

6 recordsLinked to original sources

bioRxiv2026

Genome editing of marsupial RSX reveals conserved and divergent principles in mammalian X-inactivation

X-chromosome inactivation balances X-gene dosage between the sexes in eutherians and marsupials. The lncRNA Xist mediates X-inactivation in eutherians but is absent from marsupials. An evolutionarily unrelated lncRNA, RSX, has been identified in marsupials, but its role in X-inactivation is unresolved because genome editing in these mammals has only recently become feasible. Using CRISPR-Cas9 in the opossum, we show that RSX is required for the initiation of X-inactivation in marsupial embryos. RSX deletion later, in differentiated cells, causes modest X-gene de-repression, with repressive chromatin marks H3K27me3 and H3K9me3 retained. H2AK119ub is not enriched on the opossum inactive X, revealing divergent Polycomb-mediated regulation in therians. Our findings reveal stage-specific roles of RSX in marsupial X-inactivation and identify conserved and divergent features of X-dosage compensation in mammals.

genomics↗

bioRxiv2025

Dissecting PADI6 function defines oocyte cytoplasmic lattices as regulatory hubs for fundamental cellular processes

Oocyte cytoplasmic lattices are critical for early embryo development but their composition and function are not fully understood. Mutations in PADI6, an essential component of cytoplasmic lattices, lead to early embryonic developmental arrest and female infertility. To investigate PADI6 function in mRNA storage, global protein levels, and lattice composition during early mammalian development we used single cell transcriptomics and proteomics methods to study two mouse models. Padi6 null mutation resulted in inhibition of embryonic genome activation, defective maternal mRNA degradation, and disruption to protein storage on the cytoplasmic lattices. Distinct developmental phenotypes were observed with a hypomorphic Padi6 mutation. By developing a powerful single cell proteomic fractionation method, we define the cytoplasmic lattice enriched proteome in which we find essential components of another major oocyte-specific compartment, the endolysosomal vesicular assembly (ELVA), suggesting previously unknown interconnections between them. Our findings highlight a critical scaffolding function of PADI6 and implicate cytoplasmic lattices as regulatory hubs for key processes in the oocyte and early embryo, including translation, respiration and protein degradation.

developmental biology↗

bioRxiv2024

Marsupial single-cell transcriptomics provides an atlas of developmental heterochrony

Single-cell transcriptomics has revealed conserved and divergent programmes of organogenesis in mammals, but existing studies have focused on eutherians. Marsupials exhibit short gestation and complete development externally, necessitating accelerated differentiation of anterior features required for locomotion and feeding. As such, they represent a unique outgroup with which to understand temporal shifts in development, known as heterochrony. Here, we generate the first single-cell transcriptomic atlas of gastrulation and early organogenesis in a marsupial, the opossum Monodelphis domestica. We find that anterior prioritisation is achieved by earlier initiation and shorter duration of transcriptional programmes relative to eutherians. The result is uncoupling of transcriptional and morphological progression, revealing unforeseen diversity in the order of developmental sequences in mammals. We uncover novel tissues for which heterochrony has not previously been documented. Our findings indicate that accelerated activation of transcriptional programmes facilitates the rapid growth needed for survival of the marsupial neonate.

developmental biology↗

bioRxiv2023

Four-Core Genotypes mice harbour a 3.2MB X-Y translocation that perturbs Tlr7 dosage

The Four Core Genotypes (FCG) is a mouse model system heavily used to disentangle the function of sex chromosomes and hormones. We report that a copy of a 3.2 MB region of the X chromosome has translocated to the YSry- chromosome and thus increased the expression of multiple genes including the auto-immune master regulator Tlr7. This previously-unreported X-Y translocation complicates the interpretation of studies reliant on FCG mice.

genetics↗

bioRxiv2020

Generating single-sex litters: development of CRISPR-Cas9 genetic tools to produce all-male offspring

Animals are extremely useful genetic tools in science and global resources in agriculture. However, a single sex is often required in surplus, and current genetic methods for producing all-female or all-male litters are inefficient. Using the mouse as a model, we developed a synthetic, two-part bicomponent strategy for generating all-male litters. We achieved this using CRISPR-Cas9 genome editing technology to generate large stable knock-ins on the autosomes and X chromosome. The bicomponent system functions via the sex-specific co-inheritance of a Cas9 transgene and an sgRNA transgene targeting the essential Topoisomerase 1 gene. This technology proved to be highly efficient in generating on-target mutations, resulting in embryonic lethality of the target sex. Our study is the first to successfully generate all-male mammalian litters using a CRISPR-Cas9 bicomponent system and provides great strides towards generating single-sex litters for laboratory or agricultural research.

genetics↗

bioRxiv2020

Frequent loss-of-heterozygosity in CRISPR-Cas9-edited early human embryos

CRISPR-Cas9 genome editing is a promising technique for clinical applications, such as the correction of disease-associated alleles in somatic cells. The use of this approach has also been discussed in the context of heritable editing of the human germline. However, studies assessing gene correction in early human embryos report low efficiency of mutation repair, high rates of mosaicism and the possibility of unintended editing outcomes that may have pathologic consequences. We developed computational pipelines to assess single-cell genomics and transcriptomics datasets from OCT4 (POU5F1) CRISPR-Cas9-targeted and control human preimplantation embryos. This allowed us to evaluate on-target mutations that would be missed by more conventional genotyping techniques. We observed loss-of-heterozygosity in edited cells that spanned regions beyond the POU5F1 on-target locus, as well as segmental loss and gain of chromosome 6, on which the POU5F1 gene is located. Unintended genome editing outcomes were present in approximately 16% of the human embryo cells analysed and spanned 4 to 20kb. Our observations are consistent with recent findings indicating complexity at on-target sites following CRISPR-Cas9 genome editing. Our work underscores the importance of further basic research to assess the safety of genome editing techniques in human embryos, which will inform debates about the potential clinical use of this technology.

developmental biology↗