Biology subjects

Hill, P.

Publications and source records attributed to Hill, P..

3 recordsLinked to original sources

bioRxiv2026

Thermally driven sex reversal reveals divergent sex determination dynamics in wild viviparous reptile populations

Climate change can threaten population viability by disrupting sex ratios in species whose sex is influenced by temperature. While species with sex chromosomes were historically considered immune, in some species, temperatures can override genetic sex determination via sex reversal, leaving them vulnerable to climate-driven sex ratio shifts. The Tasmanian spotted snow skink (Carinacincus ocellatus), a viviparous reptile with an XX/XY system, provides a compelling case study. While laboratory studies demonstrated that extreme thermal conditions induce female-to-male sex reversal (XX males), its occurrence in the wild remains unexplored, limiting our understanding of actual climate impacts. Integrating 23 years of phenotypic and genetic sexing data across two climatically distinct populations, we provide the first evidence of sex reversal in a wild viviparous reptile. XX reversal occurred in both populations, affecting up to 23.5% of XX births in the warmer population, and was associated with colder minimum daily temperatures. Despite high birth rates in some years, sex-reversed adults were rare. We also identified putative XY females, suggesting bidirectional sex reversal and reinforcing the extreme plasticity of reptilian sex determination. Ultimately, sex reversal could act as an evolutionary trap, potentially compromising population viability as climate instability increases.

evolutionary biology↗

bioRxiv2023

Using a handful of transcriptomes to detect sex-linked markers in a lizard with homomorphic sex chromosomes

To understand the biology of a species it is often crucial to be able to differentiate males and females. Many species lack distinguishable sexually dimorphic traits, but in those that possess sex chromosomes, molecular sexing offers a good alternative. Designing molecular sexing assays is typically achieved through the comparison of male and female genomic sequences, often from reduced-representation sequencing. However, in many non-model species sex chromosomes are poorly differentiated, and identifying sex-limited sequences and developing PCR-based sexing assays is challenging without additional genomic resources. Here we highlight a simple procedure for detection of sex-linked markers based on transcriptomes that circumvents limitations of other approaches. We apply it to the spotted snow skink Carinascincus ocellatus, a lizard with homomorphic XY chromosomes that also experiences environmentally-induced sex reversal. With transcriptomes from 3 males and 3 females alone, we identify thousands of putative Y-linked sequences. We confirm linkage through alignment of assembled transcripts to a distantly related genome, and readily design PCR primers to sex C. ocellatus and related species. In addition to providing an important molecular sexing tool for these species, this approach also facilitated valuable comparisons of sex determining systems on a large taxonomic scale.

genetics↗

bioRxiv2019

Analysis of immunological resistance to primary Mycobacterium tuberculosis infection in humans

BackgroundDespite recent advances in diagnosis and treatment, tuberculosis (TB) remains a major infectious disease killer in resource-poor settings. Strategies to prevent Mycobacterium tuberculosis (Mtb) infection are urgently required. By characterising natural protective immunity to Mtb infection we aimed to identify correlates of protection to guide vaccine development and other immune based therapies. MethodsTwo groups of Mtb-exposed contacts of TB patients were recruited in The Gambia and assessed for Mtb infection status using either tuberculin skin test (TST) reactivity at baseline and 3 months or QuantiFERON (QFT) reactivity at baseline and 6 months. For both groups, converters were defined as having a negative test at baseline and a positive one at follow-up, while those with a negative test at both time-points were defined as non-converters (Mtb resisters). Participants were analysed using RNA-sequencing and plasma Mtb proteome IgA and IgG arrays. ResultsSeveral genes were found to be differentially expressed at baseline between the groups prior to any signs of infection by current tests. Modular analysis revealed a distinct B cell gene signature in TST non-converters compared to converters (at q < 10-6, AUC > 0.7), which was only present in the most highly exposed group. Interestingly, when infection status was defined by QFT, enrichment of Type I IFN and antiviral gene signatures was observed. Plasma IgG and IgA antibody reactivity across the entire Mtb proteome showed the best differentiation in individuals with the highest exposure. An AUC of 1.0 (q<10-3) was observed for IgA reactivity to Rv0134 and an AUC of 0.98 for IgA reactivity to both Rv0629c and Rv2188c (all lower in TST non-converters). IgG reactivity to Rv3223c resulted in an AUC of 0.96 (q < 10-4) and was again lower in TST non-converters. The highest AUC for those with lower Mtb exposure were 0.84 (Rv2411c) for IgA and 0.83 (Rv2131c) for IgG. ConclusionsThese data provide insight into the early protective response to Mtb infection and possible avenues for novel therapeutic strategies to prevent Mtb infection.

immunology↗