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TBC1D24 genetic variants are causally involved in the development of both autosomal recessive hearing loss and epilepsy syndromes, and autosomal dominant hearing loss (ADHL). So far, our group published four novel ADHL-causative TBC1D24 probably pathogenic variants by performing high-throughput genetic testing in families with ADHL, and more variants are yet to be revealed. In the light of current discoveries, variants in TBC1D24 emerge as a more significant cause of ADHL. The molecular mechanism behind the TBC1D24-associated ADHL is unknown. Using a zebrafish model, we investigated involvement of TBC1D24 in hearing and the functional effects of the associated ADHL-causing genetic variants. Different methodological approaches were used in the study, including (i) expression studies by whole mount in situ hybridization (WISH), qPCR on different developmental stages and cryosections, (ii) assessment of the zebrafish ear and neuromast hair cell morphology by high-resolution imaging and (iii) behavioral studies in a developed tbc1d24-deficient zebrafish models (by knock-down or knock-out of tbc1d24) and in overexpression and rescue tbc1d24 models. We show that the morpholino-mediated knockdown of Tbc1d24 resulted in defective ear kinocilia structure and reduced locomotor activity of the embryos. The observed phe-notypes were rescued by a wild-type TBC1D24 mRNA but not by a mutant mRNA carrying the ADHL-causing variant c.553G>A (p.Asp185Asn), supporting its pathogenic potential. CRISPR-Cas9-mediated knockout of tbc1d24 led to mechanosensory deficiency of lateral line neuromasts. Overexpression of TBC1D24 mRNA resulted in developmental abnormalities associated with ciliary dysfunction and mesen-dodermal mispatterning. We observed that the ADHL-causing TBC1D24 variants: c.553G>A (p.Asp185Asn); c.1460A>T (p.His487Leu), c.1461C>G (p.His487Gln) or a novel variant c.905T>G (p.Leu302Arg) alleviated the effect of overexpression, indicating that these variants disrupt the TBC1D24 function. Furthermore, the zebrafish phenotypes correspond to the severity of ADHL. Specific changes in ear structures upon TBC1D24 overexpression further highlighted its tissue-specific role in ciliary function and inner ear development. Our findings provide functional evidence for the pathogenic potential of the ADHL-causing TBC1D24 variants and lead to new insights into the function of TBC1D24 in cilia morphogenesis. [ABSTRACT FROM AUTHOR]

A subset of trunk neural crest cells form the metamerically organized dorsal root ganglia (DRG) which develop adjacent to the spinal cord. To investigate mechanisms underlying this specification event, we are characterizing mutations affecting DRG development in zebrafish. Disruption of shh signaling leads to interesting effects on DRG; most segments lack DRG neurons but some segments contain a large excess of neurons. These phenotypes are not due to effects on the initial establishment of neural crest since expression of foxd3, a premigratory neural crest marker, is normal. However, expression of neurogeninl, an early marker for DRG precursors, is missing in mutant embryos. To determine where shh signaling is required for normal DRG development, we have transplanted cells between wild-type and mutant embryos defective in the gli2 gene, which encodes a transcriptional effector of shh signaling. Normal DRG development is restored in a mutant background only when neurons originate from wild-type donors, indicating that shh directly affects DRG precursors. However, preliminary experiments suggest the excess neuron phenotype is a non-cell-autonomous defect. Treatment of embryos during somitogenesis with cyclopamine, an inhibitor of shh signaling, results in a temporal separation of the two DRG phenotypes. Taken together, our results suggest that shh has differential effects on distinct DRG precursors.

Classical experiments predict that factors secreted from the paraxial mesoderm are important for neural crest induction in overlying ectoderm. In contrast, more recent experiments indicate that interactions between neural and nonneural ectoderm are sufficient for neural crest induction. To investigate the role of mesoderm in neural crest induction in vivo, we have taken advantage of the genetic and embryological properties of zebra fish. In mutants that disrupt the Nodal signaling pathway (cyc;sqt, mzoep), mesoderm fails to involute during gastrulation and the resulting embryo has no head and trunk mesendoderm. By overexpressing the TGF-[Beta]-related signaling molecule Antivin, we can reproduce this phenotype. We observe that presumptive neural crest markers are expressed in nodal mutants and in Antivininjected embryos, which fail to express mesodermal markers. In addition, we examined whether dorsal mesoderm inhibits neural crest gene expression in the dorsalized swr/zbmp2b mutants. Neural crest gene expression was not rescued following overexpression of Antivin in this background. This result suggests that expanded dorsal mesoderm is not solely responsible for the lack of neural crest induction in swr mutants. Taken together, these results support a model in which ectodermal interactions requiring a functional BMP signaling pathway are sufficient for neural crest induction. However, differences in the A/P and D/V extent of neural crest gene expression domains suggest that mesoderm may be important for refining their spatial pattern.

Neural crest cells migrate from the neural tube to differentiate as neurons and glia in the peripheral nervous system, craniofacial cartilages, and pigment cells. Fate of the neural crest is, in part, determined by its premigratory location: i.e., neural crest cells from different regions of the embryos anterior-posterior axis form characteristic structures. We have identified a mutation, flat [top.sup.b369], that shows defects in derivatives formed by neural crest cells that migrate from a region between the ear and the first few somites. In mutant embryos homozygous for flat top, the posterior gill arch cartilages do not form. Wild-type cells transplanted into mutant embryos can form proper cartilages, demonstrating that environmental factors are still present to support this process. Early markers of neural crest formation, such as d1x2, or axial-specific neural crest markers like hoxa3 are apparently normal. Other arch-associated segmental structures not derived from neural crest are also normal. However, thymus formation is defective, heart valves are abnormal, and enteric neurons are drastically reduced. Molecular analysis of the flat top mutation may lead to better understanding of the complex tissue interactions involved in postotic neural crest specification.

We are interested in the mechanisms underlying specification of neural crest cells to form dorsal root ganglia (DRG). The DRG are neural crest-derived sensory ganglia that develop in a metameric pattern adjacent to the neural tube. Homozygous mutant sensory-[deprived.sup.w15] ([sdp.sup.w15]) embryos are completely missing DRG neurons. Aside from this loss of DRG neurons, embryos appear grossly normal until approximately 4 days post-fertilization (pf) when larvae develop severe edema around the eyes, heart and yolk sac and die. Staining with neuron-specific anti-Hu antibodies and anti-zn-5 antibodies reveals that DRG neurons are undetectable even at the earliest stages of development, whereas other structures of the PNS and CNS appear normal. Preliminary studies show that wildtype cells transplanted into [sdp.sup.w15] mutant gastrulae are capable of differentiating into DRG neurons suggesting that [sdp.sup.w15] acts cell-autonomously. We have mapped [sdp.sup.w15] to the distal arm of linkage group 24 and have shown that the mutation is a terminal deletion of approximately 1 cM. We are currently performing a complementation screen to identify ENU-induced point mutations that display the [sdp.sup.w15] DRG defect.

Abstract Background The sensory neurons and glia of the dorsal root ganglia (DRG) arise from neural crest cells in the developing vertebrate embryo. In mouse and chick, DRG formation is completed during embryogenesis. In contrast, zebrafish continue to add neurons and glia to the DRG into adulthood, long after neural crest migration is complete. The molecular and cellular regulation of late DRG growth in the zebrafish remains to be characterized. Results In the present study, we use transgenic zebrafish lines to examine neuronal addition during postembryonic DRG growth. Neuronal addition is continuous over the period of larval development. Fate-mapping experiments support the hypothesis that new neurons are added from a population of resident, neural crest-derived progenitor cells. Conditional inhibition of Notch signaling was used to assess the role of this signaling pathway in neuronal addition. An increase in the number of DRG neurons is seen when Notch signaling is inhibited during both early and late larval development. Conclusions Postembryonic growth of the zebrafish DRG comes about, in part, by addition of new neurons from a resident progenitor population, a process regulated by Notch signaling.

Abstract The meeting 'From sensory perception to motor output: genetic bases of behavior in the zebrafish embryo' was held at Minerve (South of France) on March 16–18, 2007. The meeting site was beautifully situated in the heart of the Minervois wine country, and its remoteness promoted conversations and interaction over the course of the program. The meeting covered neurogenesis and eye development on day 1, ear and lateral line development on day 2, and brain connectivity and behavior on day 3. Underlying all sessions, however, ran the growing importance of live imaging, an approach that takes full advantage of the transparency of fish embryos and early larvae, as illustrated by several movies and links in this report.

As genetic testing is increasingly integrated into nephrology practice there is a growing need for partnership with genetic experts. Genetic counselors are ideally suited to fill this role. The value of genetic counseling is born out of the clinical value of genetic test results against the backdrop of the complexity of genetic testing. Genetic counselors who specialize in nephrology are trained to understand and explain the potential effects of genes on kidney disease, which can enable patients to make informed decisions about proceeding with genetic testing, navigating variants of uncertain significance, educating on extrarenal features of hereditary kidney disease, facilitating cascade testing, providing post-test education about testing results, and assisting with family planning. Genetic counselors can partner with the nephrologist and provide the knowledge needed to maximize the use of genetic testing for patients for nephrology consultation. Genetic counseling is more than an element or extension of genetic testing; it is a dynamic, shared conversation between the patient and the genetic counselor where concerns, sentiments, information, and education are exchanged, and value-based decision making is facilitated., (© 2023 The Authors.)

Aims: To assess safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD) and immunogenicity of CNTO 7160, an anti-interleukin-33 receptor (IL-33R) monoclonal antibody, in healthy subjects and patients with asthma or atopic dermatitis (AD)., Methods: In Part 1 of this Phase I, randomized, double-blind, placebo-controlled study, healthy subjects (n = 68) received single ascending intravenous (IV) CNTO 7160 dose (0.001 to 10 mg/kg) or placebo. In Part 2, patients with mild asthma (n = 24) or mild AD (n = 15) received 3 biweekly IV CNTO 7160 doses (3 or 10 mg/kg) or placebo., Results: CNTO 7160 was generally well tolerated, with 1 serious adverse event of severe cellulitis reported (AD, CNTO 7160, 3 mg/kg). CNTO 7160 exhibited nonlinear PK (0.01-10 mg/kg). Mean clearance decreased with increasing dose (2.43 to 18.03 mL/d/kg). CNTO 7160 PK was similar between healthy subjects and patients with asthma or AD (3 or 10 mg/kg). Free sIL-33R suppression was rapid and dose dependent. Ex vivo inhibition of p38 phosphorylation of basophils was dose-dependent (1-10 mg/kg) and sustained inhibition (≥75%) was observed at higher doses (3 or 10 mg/kg). PK/PD modelling and simulation suggests that 1 mg/kg IV every 2 weeks provides adequate systemic drug exposure for sustained inhibition of p38 phosphorylation of basophils. Despite confirmation of target engagement, no apparent CNTO 7160 clinical activity was observed in patients (asthma or AD)., Conclusion: This first-in-human study provides PK, PD and safety data, supporting further clinical investigation of CNTO 7160 in patients with asthma and AD., (© 2020 The British Pharmacological Society.)