Biology subjects

Healy, C.

Publications and source records attributed to Healy, C..

5 recordsLinked to original sources

bioRxiv2026

Non-canonical peptidoglycan cross-linking is essential for Mycobacterium tuberculosis acid resistance

Mycobacterium tuberculosis withstands acidic conditions to survive and replicate within macrophages. To define the genetic determinants of this adaptation, we performed a transposon screen in a lipid-rich, acidic medium that mimics the host environment and supports robust M. tuberculosis growth. This screen identified ldtB, encoding an L,D-transpeptidase, as essential for growth and survival under acid stress. Loss of LdtB decreased 3-3 peptidoglycan cross-linking, disrupted cell wall architecture, and impaired intrabacterial pH homeostasis, resulting in increased susceptibility to cell wall-active antibiotics. Notably, M. tuberculosis lacking LdtB displayed heightened sensitivity to meropenem within macrophages, suggesting that targeting this enzyme could potentiate {beta}-lactam efficacy during infection. These findings establish LdtB as a key mediator linking peptidoglycan homeostasis to acid stress resistance and underscores the importance of in vitro culture models that recapitulate the host microenvironment for uncovering new in vivo active therapeutic targets. TeaserDisabling a key peptidoglycan cross-linking enzyme compromises M. tuberculosis survival under acidic stress and antibiotic exposure.

microbiology↗

bioRxiv2025

Juvenile hormone degradation enzymes have shared and unique requirements in Drosophila development

Precise control of hormones is essential for animal development. Hormone bioavailability is regulated by their synthesis, transport, sequestration, natural turnover, and programmed degradation. Here, we use Drosophila melanogaster to investigate developmentally programmed degradation of the retinoid-like juvenile hormones (JHs). JHs promote juvenile growth and timely development by functionally opposing the steroid hormone, ecdysone. Despite well-characterized biochemistry, the developmental requirements for programmed JH degradation are poorly understood due to paralogue expansion. To close this knowledge gap, we generated double and triple knockout animals lacking one of two classes of JH degradation enzymes: JH esterases (JHEs) and JH epoxide hydrolases (JHEHs). We found that while both JHEs and JHEHs restrain JH signaling during Drosophila juvenile development, each has separate requirements in the regulation of developmental timing and growth. Strikingly, loss of all three JHEHs doubled the length of juvenile development, and the resulting pupae were smaller. Through targeted and genome-wide transcriptome analysis, measurements of hormone-producing glands, and rescue experiments, we uncovered both shared and unique dysregulated gene networks, some of which have established roles in the regulation of both body size and developmental timing. Our comparative analysis of both JH degradation pathways demonstrated that loss of JHEH, but not JHE, activates multiple levels of compensatory feedback to maintain homeostasis within JH and ecdysone axes. These data not only suggest that JHEH-mediated degradation is the dominant programmed JH degradation pathway in D. melanogaster development, but they also revealed new JH homeostatic mechanisms more generally. Together, this study provides new genetic tools and insights into programmed hormone degradation. Article summaryHormones control the timing of developmental transitions and growth. As such, multiple mechanisms ensure precise amounts of a hormone are available at the right time and place. Here, we investigated the poorly understood process of developmentally programmed hormone degradation using juvenile hormones (JHs) in Drosophila melanogaster as a model. We generated double and triple knockout strains to disrupt JH degradation and found an unexpected separation of requirements in regulating developmental growth and timing. Through phenotypic and transcriptomic analysis, this study provides insights into the mechanisms and complexities of programmed hormone degradation in animal development.

genetics↗

bioRxiv2023

The role of embryonic origins and suture proximity in repair of cranial bone

The cranial sutures are proposed to be a stem cell niche, harbouring skeletal stem cells (SSCs) that are directly involved in development, homeostasis, and healing. Like the craniofacial bones, the sutures are formed from both mesoderm and neural crest. During cranial repair, neural crest cells have been proposed to be key players; however, neural crest contributions to the sutures are not well defined, and the relative importance of suture proximity is unclear. Here, we combine calvarial wounding experiments with genetically labelled mouse models to demonstrate that suture proximity predicts the efficiency of cranial repair. Furthermore, we define the neural crest-mesoderm boundary within the sutures and demonstrate that Gli1+ and Axin2+ SSCs are present in all calvarial sutures examined. We propose that the position of the defect determines the availability of neural crest-derived progenitors, which appear to be a key element in the repair of calvarial defects. Summary statementThis study provides a new examination of the embryonic origins of cranial sutures in mouse. Using genetic lineage labelling, we identify specific contributions of neural crest cells and associated skeletal stem cells during repair of calvarial wounds. This is extremely relevant considering recent findings regarding the role of suture-residing stem cells.

developmental biology↗

bioRxiv2021

Genetic models of latent tuberculosis in mice reveal differential control by innate and adaptive immunity

Studying latent Mycobacterium tuberculosis (Mtb) infection has been limited by the lack of a suitable mouse model. We discovered that transient depletion of protein biotin ligase (BPL) and thioredoxin reductase (TrxB2) results in latent infections during which Mtb cannot be detected but that relapse in a subset of mice. The immune requirements for Mtb control during latency, and the frequency of relapse, were strikingly different depending on how latency was established. TrxB2 depletion resulted in a latent infection that required adaptive immunity for control and reactivated with high frequency, whereas latent infection after BPL depletion was independent of adaptive immunity and rarely reactivated. We identified immune signatures of T cells indicative of relapse and demonstrated that BCG vaccination failed to protect mice from TB relapse. These reproducible genetic latency models allow investigating the host immunological determinants that control the latent state and offer opportunities to evaluate therapeutic strategies in settings that mimic aspects of latency and TB relapse in humans.

microbiology↗

bioRxiv2019

Novel truncating mutations in CTNND1 cause a dominant craniofacial and cardiac syndrome

AbstractCTNND1 encodes the p120-catenin (p120) protein, which has a wide range of functions, including the maintenance of cell-cell junctions, regulation of the epithelial-mesenchymal transition and transcriptional signaling. Due to advances in next generation sequencing, CTNND1 has been implicated in human diseases including cleft palate and blepharocheilodontic syndrome (BCD) albeit only recently. In this study, we identify eight novel protein-truncating variants, six de novo, in thirteen participants presenting with craniofacial dysmorphisms including cleft palate and hypodontia, as well as congenital cardiac anomalies, limb dysmorphologies and neurodevelopmental disorders. Using conditional deletions in mice as well as CRISPR/Cas9 approaches to target CTNND1 in Xenopus, we identified a subset of phenotypes that can be linked to p120-catenin in epithelial integrity and turnover, and additional phenotypes that suggest mesenchymal roles of CTNND1. We propose that CTNND1 variants have a wider developmental role than previously described, and that variations in this gene underlie not only cleft palate and BCD but may be expanded to a broader velocardiofacial-like syndrome.

genetics↗