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Introductionmyo7aa, the homolog of the human Usher 1B syndrome pathogenic gene, myo7A, plays an important role in stereociliary development and maintenance, therefore, is critical for hearing and balance. However, the molecular mechanisms that myo7aa regulate hearing and balance still need to be studied.MethodsIn this study, we generated two independent zebrafish myo7aa knockout lines using CRISPR/Cas9 technology. To investigate the effects of myo7aa on hearing, YO-PRO-1 staining and startle response assay were used. To gain insight into the specific molecular mechanisms by which myo7aa affects hearing, transcriptome sequencing and bioinformatics analysis were employed.ResultsOur study showed that hair cells of myo7aa-/- zebrafish can not take up YO-PRO-1 fluorescent dye and are insensitive to acoustic stimulation in myo7aa-/- zebrafish compared to wild type. Genes related to the Rho GTPase signaling pathway, such as arhgap33, dab2ip, and arghef40, are significantly down-regulated in myo7aa-/- zebrafish embryos at 3 dpf. GTP and ATP compensation can partially rescue the hair cell defects in myo7aa knockout zebrafish.DiscussionOur findings suggest that zebrafish myo7aa affects congenital hearing by regulating Rho GTPase signaling, and loss of myo7aa leads to abnormal Rho GTPase signaling and impairs hair cell function. myo7aa, myo7A, arhgap33, dab2ip, arghef40 and myo7aa-/- fonts in the abstract are italicized. -/- is a superscript format.

Background:The COBLL1 gene has been implicated in human central obesity, fasting insulin levels, type 2 diabetes, and blood lipid profiles. However, its molecular mechanisms remain largely unexplored.Methods:In this study, we established cobll1a mutant lines using the CRISPR/Cas9-mediated gene knockout technique. To further dissect the molecular underpinnings of cobll1a during early development, transcriptome sequencing and bioinformatics analysis was employed.Results:Our study showed that compared to the control, cobll1a−/− zebrafish embryos exhibited impaired development of digestive organs, including the liver, intestine, and pancreas, at 4 days post-fertilization (dpf). Transcriptome sequencing and bioinformatics analysis results showed that in cobll1a knockout group, the expression level of genes in the Retinoic Acid (RA) signaling pathway was affected, and the expression level of lipid metabolism-related genes (fasn, scd, elovl2, elovl6, dgat1a, srebf1 and srebf2) were significantly changed (p < 0.01), leading to increased lipid synthesis and decreased lipid catabolism. The expression level of apolipoprotein genes (apoa1a, apoa1b, apoa2, apoa4a, apoa4b, and apoea) genes were downregulated.Conclusion:Our study suggest that the loss of cobll1a resulted in disrupted RA metabolism, reduced lipoprotein expression, and abnormal lipid transport, therefore contributing to lipid accumulation and deleterious effects on early liver development.