Biology subjects

Burr, S. E.

Publications and source records attributed to Burr, S. E..

6 recordsLinked to original sources

bioRxiv2026

Togaram Ensures Axial Alignment of the Sperm Neck

The sperm neck must remain mechanically stable to preserve a straight head-tail axis during spermiogenesis, yet the mechanisms that maintain this alignment after head-tail attachment forms are poorly understood. Here, using Drosophila, we identify Togaram (Toga), the ortholog of mammalian TOGARAM1, as a regulator of this maintenance phase. Toga localizes to the sperm neck and to a broader perinuclear microtubule scaffold that surrounds the nucleus, which we term the Sperm Microtubule Cage (SMC). Depletion of Toga causes a striking off-axis phenotype in which the centriole usually remains attached to the nucleus but fails to maintain a straight head-tail axis, whereas complete detachment is comparatively rare. Live imaging shows that this defect arises after initial attachment has formed, indicating a maintenance defect rather than a failure of head-tail assembly. Mechanistically, Toga is dispensable for initial formation of head and neck microtubules but is required for their stabilization during Canoe-stage remodeling. Loss of Toga increases microtubule turnover, strongly reduces acetylated tubulin in the manchette, SMC, and neck region, and leaves the sperm neck vulnerable to buckling. Off-axis spermatids are depleted at later stages, consistent with selective loss of mechanically compromised cells. Finally, Cep104 and CCDC66 associate with Toga in cultured cells and are likewise required for axial alignment, consistent with a conserved module analogous to the mammalian ciliary tip module. Together, these findings support a model in which Toga stabilizes sperm head and neck microtubules to preserve a straight head-tail axis during the maintenance phase of spermiogenesis.

cell biology↗

bioRxiv2023

Cellular Iron Deficiency Disrupts Thyroid Hormone Regulated Gene Expression in Developing Hippocampal Neurons

BackgroundDeveloping neurons have high thyroid hormone and iron requirements to support their metabolism and growth. Early-life iron and thyroid hormone deficiencies are prevalent, often coexist, and increase the risk of permanently impaired neurobehavioral function in children. Early-life dietary iron deficiency reduces thyroid hormone levels and impairs thyroid hormone-responsive gene expression in the neonatal rat brain. ObjectiveThis study determined whether neuronal-specific iron deficiency alters thyroid hormone-regulated gene expression in developing neurons. MethodsIron deficiency was induced in primary mouse embryonic hippocampal neuron cultures with the iron chelator deferoxamine (DFO) beginning at 3 days in vitro (DIV). At 11DIV and 18DIV, mRNA levels for thyroid hormone-regulated genes indexing thyroid hormone homeostasis (Hr, Crym, Dio2, Slco1c1, Slc16a2) and neurodevelopment (Nrgn, Pvalb, Klf9) were quantified. To assess the effect of iron repletion, DFO was removed at 14DIV from a subset of DFO-treated cultures and gene expression and ATP levels were quantified at 21DIV. ResultsAt 11DIV and 18DIV, neuronal iron deficiency decreased Nrgn, Pvalb, and Crym, and by 18DIV, Slc16a2, Slco1c1, Dio2, and Hr were increased; collectively suggesting cellular sensing of a functionally abnormal thyroid hormone state. Dimensionality reduction with Principal Component Analysis (PCA) reveals that thyroid hormone homeostatic genes strongly correlate with and predict iron status (Tfr1 mRNA). Iron repletion from 14-21DIV restored neurodevelopmental genes, but not all thyroid hormone homeostatic genes, and ATP concentrations remained significantly altered. PCA clustering suggests that cultures replete with iron maintain a gene expression signature indicative of previous iron deficiency. ConclusionsThese novel findings suggest there is an intracellular mechanism coordinating cellular iron/thyroid hormone activities. We speculate this is a part of homeostatic response to match neuronal energy production and growth signaling for these important metabolic regulators. However, iron deficiency may cause permanent deficits in thyroid hormone-dependent neurodevelopmental processes even after recovery from iron deficiency.

neuroscience↗

bioRxiv2019

Conjunctival microbiome-host responses are associated with impaired epithelial cell health in both early and late stages of trachoma

BackgroundTrachoma, a neglected tropical disease, is the leading infectious cause of blindness and visual impairment worldwide. Host responses to ocular chlamydial infection resulting in chronic inflammation and expansion of non-chlamydial bacteria are hypothesised risk factors for development of active trachoma and conjunctival scarring\n\nMethodsOcular swabs from trachoma endemic populations in The Gambia were selected from archived samples for 16S sequencing and host conjunctival gene expression. We recruited children with active trachoma and adults with conjunctival scarring, alongside corresponding matched controls.\n\nFindingsIn children, active trachoma was not associated with significant changes in the ocular microbiome. Haemophilus enrichment was associated with antimicrobial responses but not linked to active trachoma. Adults with scarring trachoma had a reduced ocular bacterial diversity compared to controls, with increased relative abundance of Corynebacterium. Increased abundance of Corynebacterium in scarring disease was associated with innate immune responses to the microbiota, dominated by altered mucin expression and increased matrix adhesion.\n\nInterpretationIn the absence of current C. trachomatis infection, changes in the ocular microbiome associate with antimicrobial and inflammatory responses that impair epithelial cell health. In scarring trachoma, expansion of non-pathogenic bacteria such as Corynebacterium and innate responses are coincident, warranting further investigation of this relationship. Comparisons between active and scarring trachoma supported the relative absence of type-1 interferon responses in scarring, whilst highlighting a common suppression of re-epithelialisation with altered epithelial and bacterial adhesion, likely contributing to development of scarring pathology.

microbiology↗

bioRxiv2018

Evaluation of a Chlamydia trachomatis-specific, commercial, real-time PCR for use with ocular swabs

BackgroundChlamydia trachomatis (Ct) is the most common bacterial sexually transmitted infection and the causative organism of trachoma, the leading infectious cause of blindness worldwide. Trachoma is diagnosed clinically by observation of conjunctival inflammation and/or scarring, however, there is evidence that monitoring Ct infection may be required for elimination programs. There are many commercial and in-house nucleic acid amplification tests for the detection of Ct DNA, but the vast majority have not been validated for use with ocular swabs. This study evaluated a commercial assay, the Fast-Track Vaginal swab kit, using conjunctival samples from two trachoma-endemic areas. An objective, biostatistical-based method for binary classification of continuous PCR data was also developed, to limit potential user-bias in diagnostic settings.\n\nResultsThe Fast-Track Vaginal swab assay was run on 210 ocular swab samples from Guinea-Bissau and Tanzania. Fit of individual amplification curves to exponential or sigmoid models, derivative and second derivative of the curves and final fluorescence value were examined for utility in thresholding for determining positivity. The results from the Fast-Track Vaginal swab assay were evaluated against a commercial test (Amplicor CT/NG) as well as a non-commercial test (in-house ddPCR) both of whose performance has previously been evaluated.\n\nSignificant evidence of exponential amplification (R2 > 0.99) and final fluorescence > 0.15 were combined for thresholding. This objective approach identified a population of positive samples, however there were a subset of samples that amplified towards the end of the cycling protocol (at or later than 35 cycles), which were less clearly defined. The Fast-Track Vaginal swab assay showed good sensitivity against the commercial (95.71) and non-commercial (97.18) tests. Specificity was lower against both tests (90.00 and 96.55 respectively).\n\nConclusionsThis study defined a simple, automated protocol for binary classification of continuous, real time qPCR data, for use in an end-point diagnostic test. This method identified a population of positive samples, however, as with manual thresholding, a subset of samples that amplified towards the end of the thermal cycling program were less easily classified. When used with ocular swabs, the Fast-Track Vaginal swab assay had good sensitivity but for Ct detection lower specificity than the commercial and non-commercial assays it was evaluated against, possibly leading to false positives.

molecular biology↗

bioRxiv2017

Population-based analysis of ocular Chlamydia trachomatis in trachoma-endemic West African communities identifies genomic markers of disease severity

Chlamydia trachomatis (Ct) is the most common infectious cause of blindness and bacterial sexually transmitted infection worldwide. Using Ct whole genome sequences obtained directly from conjunctival swabs, we studied Ct genomic diversity and associations between Ct genetic polymorphisms with ocular localization and disease severity in a treatment-naive trachoma-endemic population in Guinea Bissau, West Africa. All sequences fall within the T2 ocular clade phylogenetically. This is consistent with the presence of the characteristic deletion in trpA resulting in a truncated non-functional protein and the ocular tyrosine repeat regions present in tarP associated with ocular tissue localization. We have identified twenty-one Ct non-synonymous single nucleotide polymorphisms (SNPs) associated with ocular localization, including SNPs within pmpD (OR=4.07, p*=0.001) and tarP (OR=0.34, p*=0.009). Eight SNPs associated with disease severity were found in yjfH (rlmB) (OR=0.13, p*=0.037), CTA0273 (OR=0.12, p*=0.027), trmD (OR=0.12, p*=0.032), CTA0744 (OR=0.12, p*=0.041), glgA (OR=0.10, p*=0.026), alaS (OR=0.10, p*=0.032), pmpE (OR=0.08, p*=0.001) and the intergenic region CTA0744-CTA0745 (OR=0.13, p*=0.043). This study demonstrates the extent of genomic diversity within a naturally circulating population of ocular Ct, and the first to describe novel genomic associations with disease severity. These findings direct investigation of host-pathogen interactions that may be important in ocular Ct pathogenesis and disease transmission.

genomics↗

bioRxiv2017

Serology reflects a decline in the prevalence of trachoma in two regions of The Gambia

Trachoma is caused by Chlamydia trachomatis (Ct). It is targeted for global elimination as a public health problem. In 2014, a population-based cross-sectional study was performed in two previously trachoma-endemic areas of The Gambia. Participants of all ages from Lower River Region (LRR) (N = 1028) and Upper River Region (URR) (N = 840) underwent examination for trachoma and had blood collected for detection of antibodies against the Ct antigen Pgp3, by ELISA. Overall, 30 (1.6%) individuals had active trachoma; the prevalence in children aged 1-9 years was 3.4% (25/742) with no statistically significant difference in prevalence between the regions. There was a significant difference in overall seroprevalence by region: 26.2% in LRR and 17.1% in URR (p<0.0001). In children 1-9 years old, seroprevalence was 4.4% in LRR and 3.9% in URR. Reversible catalytic models using information on age-specific seroprevalence demonstrated a decrease in the transmission of Ct infection in both regions, possibly reflecting the impact of improved access to water, health and sanitation as well as mass drug administration campaigns. Serological testing for antibodies to Ct antigens is potentially useful for trachoma programmes, but consideration should be given to the coendemicity of sexually transmitted Ct infections.

epidemiology↗