Biology subjects

Zethof, J.

Publications and source records attributed to Zethof, J..

4 recordsLinked to original sources

bioRxiv2026

Usherin in the pineal gland: altered sleep in zebrafish models of Usher syndrome type 2a

Usher syndrome type 2A (USH2a), the most common form of hereditary deaf-blindness, is frequently accompanied by fatigue and poor sleep quality. As these sleep problems occur independently of visual decline, it is hypothesized that the USH2A-encoded protein usherin regulates sleep and circadian rhythmicity via an extra-retinal mechanism. Ush2a knockout zebrafish models were utilized to investigate this hypothesis. Immunohistochemical analysis demonstrated usherin localisation in pineal gland photoreceptor cells in wild-type larvae, alongside the USH2 complex proteins Adgrv1 and Whrna. Cross-species transcriptomic and proteomic analyses confirmed USH2A expression in all mammalian pineal gland tissues studied. Circadian clock gene expression was measured over 24 h and showed preserved oscillatory patterns in wild-type and mutant zebrafish. Ex vivo superfusion of pineal glands revealed sustained circadian melatonin release with comparable phase and period to controls, although potential differences in absolute melatonin levels could not be excluded. Despite intact clock gene expression and melatonin release in ush2a mutants, behavioural classification over 24-h recordings revealed altered sleep-wake behaviour: ush2a mutants displayed elevated daytime sleep and significantly prolonged and more variable sleep latency. The dissociation between intact molecular rhythms and abnormal sleep behaviour likely implicates that usherin plays a role in sleep-wake regulation independent of the circadian pacemaker and melatonin synthesis. These findings suggest a novel role of usherin in the pineal gland and establish a mechanistic link between usherin dysfunction and sleep disturbances, providing a biological basis for the fatigue and sleep problems reported in USH2a patients.

animal behavior and cognition↗

bioRxiv2024

foxe1 mutant zebrafish show indications of a hypothyroid phenotype and increased sensitivity to ethanol for craniofacial malformations

FOXE1 mutations in humans are associated with Bamforth-Lazarus syndrome, characterized by cleft palate and hypothyroidism. Moreover, polymorphisms of FOXE1 are implicated in non-syndromic cleft palate. Much uncertainty still exists about the function of transcription factor FOXE1 in development. To address this, we have previously developed a foxe1 mutant zebrafish demonstrating mineralization defects in larvae. In the present study, we further investigate the thyroid status and skeletal phenotype of adult foxe1 mutants. Compared to wild type controls, mutant fish have increased expression of hypothalamic tsh{beta}, and hepatic dio1 and dio2. In plasma we found higher circulating Mg levels; together these findings are indicative of hypothyroidism. We further observed mineralization defects in scales, likely due to enhanced osteoclast activity as measured by increased expression levels of the markers tracp, ctsk and rankl. Gene-environment interactions in the etiology of FOXE1-related craniofacial abnormalities remain elusive, which prompts the need for models to investigate genotype-phenotype associations. We here investigated whether ethanol exposure increases the risk of developing craniofacial malformations in foxe1 mutant larvae that we compared to wild types. We found in ethanol-exposed mutants an increased incidence of developmental malformations and marked changes in gene expression patterns of cartilage markers (sox9a), apoptotic markers (casp3b), retinoic acid metabolism (cyp26c1), and tissue hypoxia markers (hifaa, hifab). Taken together, this study shows that the foxe1 mutant zebrafish recapitulates phenotypes associated with FOXE1 mutations in human patients and a clear foxe1-ethanol interaction.

developmental biology↗

bioRxiv2020

The transcriptome of regenerating zebrafish scales identifies genes involved in human bone disease

Zebrafish scales are mineralised plates that can regenerate involving de novo bone formation. This presents an opportunity to uncover genes and pathways relevant to human musculoskeletal disease relevant to impaired bone formation. To investigate this hypothesis, we defined transcriptomic profiles of ontogenetic and regenerating scales, and identified 604 differentially expressed genes (DEGs) that were enriched for extracellular matrix, ossification, and cell adhesion pathways. Next, we showed that human orthologues of DEGs were 2.8 times more likely to cause human monogenic skeletal diseases (P<8x10-11), and they showed enrichment for human orthologues associated with polygenetic disease traits including stature, bone density and osteoarthritis (P<0.005). Finally, zebrafish mutants of two human orthologues that were robustly associated with height and osteoarthritis (COL11A2) or bone density only (SPP1) developed skeletal abnormalities consistent with our genetic association studies. Col11a2Y228X/Y228X mutants showed endoskeletal features consistent with abnormal growth and osteoarthritis, whereas spp1P160X/P160X mutants had elevated bone density (P<0.05). In summary, we show that transcriptomic studies of regenerating zebrafish scales have potential to identify new genes and pathways relevant to human skeletal disease.

genetics↗

bioRxiv2019

Early life glucocorticoid exposure modulates immune function in zebrafish (Danio rerio) larvae

In this study we have assessed the effects of increased cortisol levels during early embryonic development on immune function in zebrafish (Danio rerio) larvae. Fertilized eggs were exposed to either a cortisol-containing, a dexamethasone-containing (to stimulate the glucocorticoid receptor selectively) or a control medium for 6 hours post-fertilisation (0-6 hpf). First, we measured baseline expression of a number of immune-related genes (socs3a, mpeg1.1, mpeg1.2 and irg1l) 5 days post-fertilisation (dpf) in larvae of the AB and TL strain to assess the effectiveness of our exposure procedure and potential strain differences. Cortisol and dexamethasone strongly up-regulated baseline expression of these genes independent of strain. The next series of experiments were therefore carried out in larvae of the AB strain only. We measured neutrophil/macrophage recruitment following tail fin amputation (performed at 3 dpf) and phenotypical changes as well as survival following LPS-induced sepsis (150 g/ml; 4-5 dpf). Dexamethasone, but not cortisol, exposure at 0-6 hpf enhanced neutrophil recruitment 4 hours post tail fin amputation. Cortisol and dexamethasone exposure at 0-6 hpf led to a milder phenotype (e.g. less tail fin damage) and enhanced survival following LPS challenge compared to control exposure. Gene-expression analysis showed accompanying differences in transcript abundance of tlr4bb, cxcr4a, myd88, il1{beta} and il10. These data show that early-life exposure to cortisol, which may be considered to be a model or proxy of maternal stress, induces an adaptive response to immune challenges, which seems mediated via the glucocorticoid receptor.

immunology↗