Biology subjects

Harding, P.

Publications and source records attributed to Harding, P..

3 recordsLinked to original sources

bioRxiv2024

Human macula formation involves two waves of retinoic acid signaling suppression via CYP26A1 regulating cell cycle exit and cone specification

The human macula is a specialized, cone-rich region of the eye, critical for high-acuity vision, yet the pathways regulating its development remain poorly understood. RA-catabolizing enzyme CYP26A1 establishes the chick high-acuity area via upregulation of FGF8. However, detailed analysis of this pathway and its functions has not been performed in early human fetal tissue. Fluorescent in situ hybridization revealed striking biphasic CYP26A1 expression but little FGF8 in the presumptive macula region between post-conception weeks (PCW)6-17. Pharmacological RA signaling inhibition in human retinal organoids mimicking the two waves of CYP26A1 revealed early RA inhibition prompted early cell cycle exit and increased cone genesis, while late inhibition altered cone subtype specification. Conversely, recombinant FGF8 had no effect on photoreceptor fate. This work provides spatiotemporal examination of CYP26A1 across human macular development, as well as experimental evidence for the different roles of RA signaling inhibition in a human model of retinal development.

developmental biology↗

bioRxiv2022

Restoration of functional PAX6 in aniridia patient iPSC-derived ocular tissue models using repurposed nonsense suppression drugs

Aniridia is a rare, pan-ocular disease causing severe sight loss, with only symptomatic intervention offered to patients. Approximately 40% of aniridia patients present with heterozygous nonsense variants in PAX6, resulting in haploinsufficiency. Translational readthrough inducing compounds (TRIDs) have the ability to weaken the recognition of in-frame premature stop codons (PTCs), permitting full-length protein to be translated. We have established induced pluripotent stem cell (iPSC)-derived 3D optic cups and 2D limbal epithelial stem cell (LESC) models from an aniridia patient with a prevalent PAX6 nonsense mutation. Both in vitro models show reduced PAX6 protein levels, mimicking the disease. Repurposed TRIDs amlexanox and 2,6-diaminopurine (DAP), and positive control compounds ataluren and G418 were tested for their efficiency. Amlexanox was identified as the most promising TRID, increasing full-length PAX6 levels in both models, and rescuing the disease phenotype through normalization of VSX2 and cell proliferation in the optic cups and reduction of ABCG2 protein and SOX10 expression in LESC. This study highlights the significance of patient iPSC-derived cells as a new model system for aniridia and proposes amlexanox as a new putative treatment for nonsense-mediated aniridia.

genetics↗

bioRxiv2019

Lung, spleen and oesophagus tissue remains stable for scRNAseq in cold preservation

BackgroundThe Human Cell Atlas is a large international collaborative effort to map all cell types of the human body. Single cell RNA sequencing can generate high quality data for the delivery of such an atlas. However, delays between fresh sample collection and processing may lead to poor data and difficulties in experimental design. Despite this, there has not yet been a systematic assessment of the effect of cold storage time on the quality of scRNAseq\n\nResultsThis study assessed the effect of cold storage on fresh healthy spleen, oesophagus and lung from [≥]5 donors over 72 hours. We collected 240,000 high quality single cell transcriptomes with detailed cell type annotations and whole genome sequences of donors, enabling future eQTL studies. Our data provide a valuable resource for the study of these three organs and will allow cross-organ comparison of cell types.\n\nWe see little effect of cold ischaemic time on cell viability, yield, total number of reads per cell and other quality control metrics in any of the tissues within the first 24 hours. However, we observed higher percentage of mitochondrial reads, indicative of cellular stress, and increased contamination by background \"ambient RNA\" reads in the 72h samples in spleen, which is cell type specific.\n\nConclusionsIn conclusion, we present robust protocols for tissue preservation for up to 24 hours prior to scRNAseq analysis. This greatly facilitates the logistics of sample collection for Human Cell Atlas or clinical studies since it increases the time frames for sample processing.

genomics↗